'^' \ (HIjp i. 1. Mill IGtbrarg Nortlj (Earolina ^tat? Hmoerfiitg SB808 P5P5 ^ENS. Date Due Je 5 - '3! WAY 2 1 1938 1938 Jir-9 '39 OCT 2 71$ ' 1 7088 w Digitized by tine Internet Arciiive in 2009 witii. funding from NCSU Libraries. littp://www.archive.org/details/peachleafcurlitsOOpier :/ Bulletin No. 20. V. l'. P. -72. U.S. Dl^PARTMEN'r OF A( iRICUL'I URl^:. DIVISION OF VEGETABLE PHYSIOLOGY AND PATHOLOGY. B. T. GALL-OWAY, Chief. F'EACH leaf CURL: ITS NATURE AND TREATMENT. BY NE^VTO]S^ B. -ELEnOE, In Charge of Pacific Coast Laboratory, Santa Ana, California, WASHINGTON: (JOVKRNMENT PRINTING OFFICE, 1000 DIVISION OF VEGETABLE THYSIOUKa AM) PATHOLOUY. SCIENTIFIC STAFF. B. T. Galloway, ('///(/ oj Division. Albert F. Woods, Assistant Chief. ASSOCIATES. Erwin F. Smith, . V. H. Dorsett, Merton B. Waite, Oscar Loew, Newton B. Pierce, Wm. A. Orton, Herbert J. AVebber, Ernst A. Bessey, M. A. Carleton, Flora W. Patterson, Marci's L. Floyd.* IN charge of laboratories. Albert F. Woods, J'huit Physiology. Erwin F. Smith, Plant Patltoh)(/y. Newton B. Pierce, Pacific Coast Lahoralory. Herbert J. Webber, Plant Breedimj. Oscar LoEW,t Plant Xutrition and Fcnncntalion. *Di'taik'cl ii.s tobacco expert, Divi.sion of Soils. +In charge of tobacco fermentation investigations, iJivisiun of Soils. LlHTIiR OF FRAXSMITTAL U. S. Department of A(;rk ultuhe. Division of Vegetable Physiology and Pathology, Washington, B. C, February W, 1900. Sir: I rospectfully transmit herewith a report on peach leaf curl, prepared by Mr. Newton B. Pierce, who has charge of the work of this Division on the Pacific coast, and recommend that it be published as Bulletin No. 20 of the Division. The report embodies the results of investigations and experiments carried on for a number of 3'ears, and shows conclusively that peach leaf curl can be controlled by com- paratively simple and inexpensive treatment. Respectfully, Hon. James Wilson, Secretary of Agriculture. B. T. Galloway, Chief (f Division. 3 LIHTER OF SURMITTAL Pacific Coast Laboratory, Santa Ajui^ Cal., Decemher 15^ 1899. Sir: I herewith .sul)init u report of investigations on the nature and treatment of peach leaf curl. The experiments described were con- ducted under the most varied conditions of soil, climate, etc., in all the leadinu- peach centers of the United vStates, and it is ])elieved that the recommendations for treatment here given are ecjually applicable wherever peaches are grown. Respectfully, Newton B. Piercp:, III Charge of PacljiG Coast Litlxiraton/. Mr. Vi. T. Galloway, Chief., Division Chapter II. ^Nature of Peach Leaf Curl 22 ~ ^ Physical conditions influencing the disease 22 The fungus causing the disease ?>\ H Relations of the fungus to the host 40 Chapter III. — ^History of the Treatment of Peach Leaf Ctrl 46 The European situation 4(3 ^ Development of the present methods of treatment 48 Chapter IV. — Plan of Preventive Spray Work Conducted hy the Depart- ment 67 Preliminary plans for the work 67 Sl)ray work conducted in 1894 70 Spray work conducted in 1 895 72 General consideration of sprays applied 75 Chapter Y. — Influence of' Sprays on the Vegetation of the Trees 77 +- Saving of foliage from injury by curl 77 Comparisons of weight and color of foliage from sprayed and unsprayed trees . 88 -\- Growth of branches and leaf buds on sprayed and unsprayed trees 91 The development of new fruit buds and fruit spurs for the year following an attack of curl 95 Chapter VI. — Influence of Sprays on the Fruiting of the Trees lO."! Thinning the fruit of sprayed trees lO;? Gathering fruit of sprayed and unsprayed trees 1 OH -V- Comparative quantity, quality, and cash value of fruit from sDrayed and unsprayed trees 112 Comparati-ve value of sprays in relation to fruit 115 "Y- Comparative size of fruit on sprayed and uns2)rayed trees II li Color of sprayed and unsprayed fruit 1 20 Method of thinning and cost of picking peaches 121 Thinning ])y hand and by curl 121 Cost of picking peaches 1 22 The local action of curl on foliage and fruit 122 -^- Records of trees sprayed on one siile 122 Chapter VII. — Preventive Spray Work Conducted by One iiakdists 126 General consideration of the auxiliary work 126 Notes on the auxiliary experiments in Michigan 127 Notes on the auxiliary experiments in Oregon 135 Notes on the auxiliary experiments in California 140 Notes on the auxiliary experiments in New York, Indi.xua, and other peach-growing States 144 7 8 CONTENTS. Page. Chapter VIII. — Preparation, Composition, and General ('iiaracter.s of THE Sprays Used 146 Preparation of the copper sprays 146 Copper sulphate solution '. 147 Bordeaux mixture 1 49 Eau eeleste ] 52 Modified eau celeste 1 53 Ainnioniacal copper carbonate 1 53 i^Prei)aration of the 8uli)hur sprays 154 Preparation of combined copper and sulphur sprays and iKites on other sprays tested 1 61 Bordeaux mixture and snli)hur s^jrays combined 161 Miscellaneous sprays 161 General characters of the sprays tested 162 The enduring qualities of the sprays 162 The corrosive action of the sprays 164 Advantages of discernible and indiscernilile sprays 165 \l Sprays adapted to use in wet and in dry localities . . 166 Chapter IX. — The Application of Sprays 167 General accessories for winter spraying 167 Nozzles suited to winter work 167 Hose and extension pipes 169 Protection of the sprayer 1 70 Pumps for various sized orchaiils 171 Spraying tanks 175 ^-Applying winter sprays for curl 175 . . The time for winter spraying 1 76 Y The manner of applying winter spi-ays 1 7() Si>raying where other diseases a.re present with curl 1 77 Prune rust on the peach {Puccinia pnmi Pers. ) 177 Mildew of the peach {Podosphveva uxyacanthx De B.) 1 78 Brown rot of the peach {Monilid frudigena Pers.) 178 Black spot of the peach {Chtdos^porium mrpoph'dmn Thi'im. ) 1 78 Winter blight of the peach and other spot and shot-hole diseases, such as Phylloxttda rircumsrissd 3erk., Ccrcospora clr(niiiifiriK.s(i Sacc., etc.. 179 Sooty mold of the ])each 1 79 Animal parasites of the peach tree ISO Chapter X. — Nature and Source of the Sprayin(; Materials Used 181 Copper sulphate 181 Copper carbonate 183 Ammonia 1 85 Sodium carbonate 187 Sulphur 190 Chapter XL — Peach Varieties and Nursery Stock in Relation to Cirl. 194 Comparison of peach varieties 194 H Treatment of nursery stock 200 Suminarv _ 202 ILLUSTRATIONS. PLATES. Page. Plate I. Curl-iiifcstod peach shoot from Biggs, Cal 11 II. MyreHuiii of KruitKCHft defonnan — the fungus causing peach leaf cui-l . 35 III. Fruiting stages of Exonscus deforniunts 36 IV. Germination of the ascospores of Eruascus deJoviiKWK. 38 V. Terminal peach twigs infested with peach leaf curl 42 VI. Sprayed and misprayed peach branches - 42 VII. Sprayed and unsprayed Crajvfords Late trees, Live Oak, Cal 77 VIII. Unsprayed trees in Lovell orchard. Biggs, Cal 89 IX. Lovell trees sprayed with Bordeaux mixture, Biggs, Cal 89 X. Fruit produced by row 15, experiment block. Biggs, Cal 107 XL Lovell trees sprayed with sulphur, lime, and salt. Biggs, Cal 112 XII. Lovell trees sprayed with sulphur and lime. Biggs, Cal 112 XIII. Lovell trees sprayed with Bordeaux mixture. Biggs, Cal 115 XIV. Lovell trees sprayed with eau celeste, Biggs, Cal 115 XV. Lovell trees sprayed with modified eau celeste, Biggs, Cal 115 ,.. wj TFig. 1, Manner of spraying trees on one side. Biggs, Cal \ ' iFig. 2, Action of curl on trees sprayed on one side, B>iggs, Cal ' 9'> XVII. Condition of trees sprayed on one side at maturity of fruit 124 XYIII. Fruit gathered from sprayed and unsprayed halves of tive 124 XIX. Showing fruitfulness of sprayed half of tree 124 XX. Sprayed and unsprayed Crawfords Late trees, Livi- Oak, C. 94. *Satlebeck, Dr. IL, Untersucli. ul)crdie I'ilzgattung Kxoascus, liaml mrg, 1SS4, p. 115. 14 PEACH lp:af curl: its nature and treatment. disease and its cause are Sadebeck,^ Winter,' De Bary,^ von Tavel,* Ha tig/ Zopf,'' Tubeuf/ Ludwig,* Sorauer,' Frank/« Kirchner," Fuckel/" and others. Winter says (1. c.) that the fungus of this malady causes great damage by early defoliation of the trees, and that it even kills the diseased trees by its repeated occurrence. In Great Britain peach leaf curl has been common for a great many years. In 1821 it was accurately described by an English gardener under the name of "'blight." He says:''* "Under this denomination [l)light] are frequently confounded two varieties of disease materially different in their appeanince, and which I shall distinguish by the appellation of hlister and curl. The former is generally confined to such peach trees as have glandular leaves, which are mostly subject to it in the months of April and May, and when attacked it is not until the latter part of the season, if at all, that they become healthy. The leaves so attacked are crisp, and assume a swollen, crumpled, and succulent appearance; the shoots themselves are affected by it in the saipe manner, and never produce either good blossom or healthy wood." Berkele}^ " has described the fungus causing this disease, and it has been mentioned by Bennett and Murray ^'' and many other English writers. (Consult a popular article on Peach Blister, by W. G. Smith, Gardeners' Chrmide., Vol. IV, pp. 36, 37.) ^Sadebeck, Dr. E., see locations cited; also Einige neue Beobachtungen und krit- ische Benierkungen liber die Exoascacepe, Bot. Ges., 1895, Band XIII, Heft fi. ^Winter, Dr. Georg, Die durch Pilze verursachten Krankheiten der Kulturge- wiichse, Leipzig, 1878, p. 47; also Rab. Kryjjt. Flora, 1885, II, p. 6. ^De Bary, Prof. A., Comparative Morphology and Biology of the, Fungi, ^lyceto- zoa, and Bacteria, English edition, Oxford, 1887, p. 265; see also in the same volmne various other references to the arrangement and position of the Exoascus group. * Tavel, Dr. F. von, Vergleichende Morphologie der Pilze, Jena, 1892, ^-p. 55, 56. ^Hartig, Dr. Robert, Lehrbuch der Baumkrankheiten, Berlin, 1889, p. 118; also the English edition, Text-book of the Diseases of Trees, London, 189-1, p. 132. ''Zopf, Dr. Wilhelm, Die Pilze in morphologischer, physiologischer, })iologischer, und systematischer Beziehung, Breslau, 1890, pp. 236, 282. 'Tubeuf, Dr. Karl Freiheer von, Pflanzenkrankheiten durch kryptogame Para- siten verursacht, Berlin, 1895, pp. 167-188. *Ludwig, Dr. Friedrich, Lehrbuch der Niedereu Kryptogamen, Stuttgart, 1892, p. 205. ^Sorauer, Dr. Paul, Handbuch der Pflanzenkrankheiten, Zweiter Theil, Die para- sitilren Krankheiten, Berlin, 1886, p. 278. 1° Frank, Dr. A. B., Die Krankheiten der Pflauzen, Band II, Die Pilzparasitilren Krankheiten, Breslau, 1896, pp. 249,250. Edition of 1880-81, Vol. II, p. 526. '^Kirchner, Dr. Oskar, Die Krankheiten und Beschiidigungen unserer landwirt- schaftlichen Kulturpflanzen, Stuttgart, 1890, pp. 324, 407. '^ Fuckel, L., Symbolte mycologicse, 1869, p. 252. '^ See quotation in Report of Michigan Pomological Society for 1873, pp. 16, 17. '* Berkeley, M. J., Introduction to Cryptogamic Botany, 1857, p. 284, and Outlines of British Fungology, London, 1860, pp. 376, 444, tab. 1, fig. 6. '^Bennett, A. W., and Murray, George, A Handbook of Cryptogamic Botany, London, 1889, p. 379. GEOGRArHlC DISTRIBUTION. 15 Tulasne/ Prillicnix," iiiul others (Coins coinplcto (rajrriculturc, T. XV, p. 255, art. IYh-Ium-) have studied this disease more or. less care- fully iu France, where it often develops in a scM'ious form. In June, 181>0, the writer saw the peach trees near th(> Mediterranean, particu- larly about Montpellier, in anything but a healthy condition. On the Hd of June leaf curl was l)ad, and the ends of ])ranches were seen to he dying- in some cases. In Italy Briosi and Cavara,-' Berlese/ and Comes ^ are among those who have described this malady. The dis- ease varies in its prevalence through Italy in accordance with its habits elsewhere. The trees of northern Italy appeared more iiealth- ful than in the south of France during the \isit of the Avriter in 18tM), but considerable gummosis, perhaps due to the same cause, was observed in both regions. In western Sicily, near Palermo, leaf curl was again encountered in severe form. The situation in Spain and Portugal is not known, but in the more humid coast regions it should not be materially different from the condition found in Itah\ In Greece, as stated })y Prof. P. Genardius,'' the disease rarely causea. any damage of importance, ])ecause of the dryness of the climate, and for this reason, he states, no treatment has becMi tried. In Austria- Hungarj^ the situation respecting leaf curl is nuich the same as in Italy. Dr. Johann Bolle, director of the Institute of Experimental Agricultural Chemistry, at Gorizia, writing from the island of Cherso, under date of Octol)er 25, 1897, states that in rainy weather the disease appears some years with great intensity and causes great damage. In Roumania the situation is much the same. Prof. Wilhelm Knechtel, of the Agricultural School of Herestrau, states in a letter dated Bucha.rest, October IT, 1897, that in that country leaf curl of the peach is also a troublesome and destructive disease to which the trees are subject in many years. He states that Roumania has in the region of the lower Danube almost a steppe climate — in sunuuer very hot and dr}', in winter cold, with very abrupt temperature changes, so that the variations of temperature within twenty-four hours not infre- quently amount to from 10° to 15° R. (22.50° to 33.75° F.). When such changes of temperature occur in the spring at the time of leaf development the disease is certain to appear. The growth of the \'egetation, which has been favored through the preceding warm days, is checked during succeeding days of lowered temperature, when 'Tulasne, L. R., Ann. d. Sci. Nat., 1866, ser. 5, T. V, p. 128. ■' Prillieux, Ed., Bull, de la Soc. Bot. de France, 1872, T. XIX, pp. 227-2.30; Compt. Rend, li; also Maladies des Mantes Agricoles, Paris, 189.5, T. I, pp. 894-400. ^Briosi, G., and Cavara, F., Fungi Parassiti d. Piante Coltiv. od Utili, essice., delin. e descr., 1891, fasc. 5, No. 104. ^Berlese, A. N., I Parassiti Vegetali d. I'ianto Coltiv. <> I'tili. Milano, 189.5, ])p. 124-126. "Comes, O., Crittoganiia Agraria, NajMjli, 1891, i)p. Ui'-i, 165-167, 549. "Letter dated Athens, Sept. 12, 1895. 16 PEACH LEAF CUKL*. IT8 NATl'KE AND TREATMENT. the development of the fungus ])egin.s, .so that in June all leaves at the ends of the young l)ranchos are curled and deformed and perhaps all the blossom ])uds fall oH'. If the more developed leaves at the base of the young shoots prove more resistant to the fungous action, then fresh shoots are formed in June, even if not in normal condition, but yet somewhat healthy, so that the tree remains intact. Tn the more pro- tected hill regions of the vineyards, at the foothills of the Carpathian Mountains, this disease is also troublesome, but less intense tlian in other parts of the country. Peach leaf curl exists in South Africa, and prolmbly also throughout Algeria and other peach-growing portions of the continent. Professor MacOwan, of the department of agriculture of Cape Colony, has written of the disease in South Africa, giving his views as to the j)roper manner of treating the same. ^ He also writes that it is "a great plague at the Cape."'" A peach grower of Drysdale, Frere, Natal, in writing to the C'ape Colony agricultural department under date of October 81, 1S98, says that he has a good many peach trees of the yellow, white, and St. Helena varieties, and that they are all affected with the discolored and curled-up leaves characteristic of this disease; that several of his neigh- bors are complaining that their peach trees are suffering like his; and that the disease seems to be spreading. The young trees were simi- larlv affected. ^ Perhaps no foreign country has suffered more from peach leaf curl than New Zealand. Mr. W. M. Maskell, of Wellington, writes as follows : * " The curly l)light has ])een for many years prevalent in this country — so much so that whereas in the earh' days peaches were exi-eed- ingly luxuriant and fine, they have dwindled to comparativel}^ very small and poor trees and in many parts of the colony almost died out. In the last two or three years the people have been advised to emploj'' remedies, and have done so to some extent, so that there is a marked improvement in the peach orchards. * * '^'' I can myself recollect, early in the sixties, when the most splendid peaches used to gi-ow wild in the warm northern districts, where now scarcely a tree is seen; and the curly blighthas been a dreadful curse all over the colon}'." Australians report peach leaf curl among their serious plant dis- eases. In South Australia it ""has been known quite twent}- 3^ears,'"' and probably longer, and occasions considerable losses in seasons favoring it. The situation is much the same in New South Wales. ' MacOwan, Prof. P., Agricultural Journal, published by the department of agriculture of Cape Colony, 1892, Vol. V, pp. 252, 253. . -Letterdated Cape Town, Oct. 26, 1895. •■'Agricultural Journal, Cape Colmiy, Vol. YI, No. 23, p. 451. •* Letter dated Wellington, New Zealand, Deceml)er24, 1895. ^Observations of ]\Ir. A. Molineux, general secretary for the agricultural hurcau of South Australia, letter dated Adelaide, February 11, 1895. GEOGRAPHIC DISTRIBUTION. 17 Prof. N. A. Co])l),' i){ithologist for the agriculturiil department of that colony, bus deserilxHl the malady (^uite fully, and althouj^h he fails to specify particular localities, it is pro))al)le that his descriptions arc drawn from observations made in the colony for which he writes. He says that in the most severe eases of the disease '" the fruit falls about three weeks after setting, and not a peach is h'ft to ripen. This oeeurs on trees on which the disease is chronic and severe. * * * Such trees are worthless, nay, worse than worthless; they are a constant menace to the peacli trees in the neigh))orhood. The sooner they are cut down and burned, and thus utterly destroyed, the better it will be for the peaeh industry. "■ "■ ■" I have now describedthe disease in its worst form, a form in which it is not common. The milder forms of the disease are much more frequent." Peach leaf curl also prevails in Victoria, where it has ])een placed,- according to Mr. D. McAlpine,' pathologist for Victoria, among the specified diseases in the vegetable diseases bill, recently passed in that colon^^ ]\Ir. ]\Ic Alpine also says that according to Mr. George Neilson, chief inspector luider the vegetation diseases act, it has been known in Victoria since 1856, and affected peach trees were just as bad then as now. INlr. ]\IcAlpine adds: "The disease is distributed all over the colony. In the cooler districts it is generally more severe than in the northern and warmer districts, and it is generally more prevalent in a moist and cool spring than in a dry, warm one." The situation in Japan has been learned through the obliging and careful inquiries of Prof. K. Miyabe,^ of the Sapporo Agricultural College. He writes that Exoascas deformans is at present a serious pest to the peach trees at Sapporo, north island, and states that his attention was first called to its presence in that place some three or four years since, but that there is no doubt of its existence from the time of the first introduction of American peach trees, about twenty- three years ago. The Japanese flowering (double red) peach trees and nectarines were introduced at Sapporo by a florist about six or seven years ago from Echigo Province in the northern part of the main island or Honsiu. These varieties were found to be attacked to some extent during these few years. American varieties are now most seriouslj'^ affected, and man}' persons have been obliged to cut down their trees on account of the disease. Respecting the distribution throughout Japan, Professor Miyabe says: "As to the rest of Hokkaido [the northern island] I found the fungus in 1890 at Mombetsu, a farming village on Volcano Bay, settled about twenty-seven years ago by the people from Sendai. I could not tell whether the pe^ach trees culti- vated there were of American or Japanese origin. In Honsiu, or ^Cobb, Prof. N. A., paper in the Agricultural Gazette, 1892, Vol. Ill, pp. 1001-1004. ■''Letters dated Melbourne, Australia, July 14, 1896, and Oct. 12, 1897. * Letter dated Sapporo, Hokkaido, Japan, Nov. 22, 1897. 19093— No. 20 2 18 PEACH LEAF CUKL*. ITS NATURE AND TREATMENT. Main Ishmd, the peach curl seems to be prevalent only in the northern provinces. * * * I sent letters of in(iuiry relating- to this (Question to the graduates of our college, who studied especially al)out the parasitic fungi in our laljoratory, and whose opinions I can trust. From ]Mr. Y. Tukahashi, at Morioka, in Rikuchu Province, I received the following an.swer : 'Peach curl is very prevalent in this town. Almost every tree is more or less attacked by the fungus. I saw some trees entirely attacked. At the end of summer [spring?] all the dis- eased leaves fell to the ground and new leaves were produced.''' In the southern island, Kumamoto, a correspondent reported to Professor Mij^abe that the disease had not been seen there by him. From Tokyo Professor Shirai, of the College of Agriculture, reports that he has not yet found the disease in that section of the main island. In China, as the writer is informed, peach leaf curl prevails to a very large extent, and the losses are probalily considerable from this cause. ^ ORIGIN OF THE DISEASE. The country of origin of peach leaf curl is not positively known. It was hoped that the inquiry as to distribution would develop posi- tive information respecting this point, but such has not been the case. That seedling peaches are remarkably susceptible to the disease, and that the Chinese Saucer peach is among those most subject to it, appears to indicate that the home of the peach is the source of the disease, and that the two may have come to us together from a com- mon point of origin. Recent studies have been constantly tending to reduce the number of species of plants once thought to be subject to curl. At present it is believed that it is confined almost wholly to the peach or its derivatives, as the nectarine and peach-almond. The exceptions to this, where the disease has been noted on the plum, almond, etc., are rare, and not sufficiently numerous or general to mate- rially affect the evidence that the peach is the natural host of the fungus. Thus far, however, it has been impossible to learn if the peach in the interior of China, its supposed home, is affected by this trouble, though in the coast regions it is said to prevail extensively. Such information as has been obtained from Japan indicates the recent introduction of the disease in that country, and that the United States is probably its source rather than the near-by continental coast. I'n Australia, how- ever, this may properly be questioned, for, as already mentioned, Mr. ^ Letter from Augustus White, Esq., forwarded April 3, 1896, through the kindness of Mr. Eufus S. Eastlack, then U. S. Deputy Consul-General at Shanghai, China. Mr. White says, in conckiding his statements, that the Chinese, ignorant of the use of the knife in pruning, trust solely to an annual inspection of the trees at the time the blossoms set, when they carefully pick off all excess of fruit, and with it all diseased leaves, etc., but allow these to fall to the ground and remain under the trees to rot or reproduce the plague, as nature thinks best. LOSSES FROM TIIK DISK ASK. 19 Gcorg'O Nc'ilsoii, chict" inspector iiiulcr tlif \'co-cttitioii diseases act of that colony, states that ju^ach h'af curl has hiMMi known in Victoria since 185t). This dates thi> })resence of the disease in Australia hack to a time when its inn)ortation from Amei'ica to that country would he douhtful. Its FiUro])ean origin, however, may not he im|)i-()hal>lc. The severity of the disease in the gardens of C'iiina and the fact that the peach probably reached Europe and America fiom the East make it still desirable to learn if the trouble is ])revalent amono- the wild or escaped peach trees in the intcMior of the Chinese Kmpir(\ It may be pertinent to state, in view of the fact that Dai'win holds the peach to be derivcnl from the almond, that none of the many widely cultivated varieties of the almond in California, either of local or for- eign origin, arc subject to peach leaf curl, even wIkmi growing beside peach orchards denuded by it. Trees which are api)arently the result of almond and peach crosses are somewhat ati'ected, however, and sev- eral of the nectarines, which are derived from the peach, are quite subject to it. Seedling peacht\s, as stated, arc very commonly attacked, but of some forty to tift}^ varieties of seedling almonds examined by the writer none has thus far shown the disease. LOSSES FROM THE DISEASE. The direct annual losses to the peach interests of the United States from peach leaf curl are very large, and arc usually much greater than is suspected by the growers themselves, as the nature and action of the disease are misunderstood by them, and its effects frequentl}'^ attributed to other causes. In case an orchard is so affected that it fails to hold the crop, or sets but a partial crop, the grower has but little ground for an opinion as to what the jdeld would have been had curl not prevailed, hence the estimates of losses made by growers are frequently very unsatisfactory. In case curl occurs after a severe cold spell in spring, as is quite commonly the case, the orchardist is apt to charge the loss of fruit to the low temperature rather than to the disease. The preventive spray work conducted by the Depart- ment has shown, also, that the loss estimates are nearly always too low. By preventing the disease upon a portion of the trees of an orch- ard the amount of injury sustained by the untreated trees has been determined most accurately by direct comparison. Such comparative work has now been conducted for several years in many of the leading peach-growing centers of the country, and these tests enable the writer to state that the losses sustained l)y the peach industry are probably not overdrawn in the following estimates: Of a large num- ber of peach growers who replied to a circular letter sent them in 1893, there were 251, living in 35 peach-growing States and Terri- tories, who stated whether or not their orchards were affected by curl. 20 PEACH LEAF CUKL: ITS NATUKE AND TREATMENT. '^Sixty-three per cent of -t hcac (158 growers) reported thtU their orohiirds were affected, and 37 per cent (93 growers) reported that their trees had not been troubled by it. Of the 158 whose trees were affected, 60 per cent (104 growers), or about 42 per cent of the 251 orchardists reporting on this disease, reported more or less loss. The growers who reported loss were residents of 21 States, and were scattered from the Atlantic to the Pacific. The losses sustained varied from a small amount of fruit to the entire crop, and in some instances many of the young trees were killed. Of the entire number of reports received as to the presence or absence of curl in the orchard of the grower, 93 came from States or sections of the country where little leaf curl prevails, as Texas, Delaware, Florida, Kansas, etc., so that the data should be strictly representative of the peach-growing coun- try as a whole. The- replies received were from Alabama, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Geor- gia, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Nebraska, New Jer- sey, New Mexico, New York, North Carolina, Tennessee, Texas, Virginia, Washington, and West Virginia. The amount of loss sustained by the 42 per cent of the growers reporting losses is given in the replies in various ways. Some growers have reduced their loss to dollars and cents; others have indi- cated the loss in percentage of crop; while still others have used some term, such as '\slight" loss, '\smair' loss, etc., as a reply to the inquiry. In estimating the true loss sustained by these growers a uniform system has been adopted. Where the loss has been stated in dollars the amount has l^een recorded as given. Where the loss is given in percentage of crop the cash loss has been determined from the basis used by the United States Census Bureau in determining the ^'alue of peach crops for the Eleventh Census. A full peach crop was valued at 1150 per acre, and all portions of a crop at the same rate. Where the report of the grower was indefinite, the statement being that the loss was small, it has been placed at $2.50 per acre, which amounts to about 2i cents per tree as usually planted. It is probable that this is nmch below the average loss in such cases, as a loss so small as this would usually escape notice. In all the calculations in these esti- mates an effort is made not to overrate the loss. These calculations gave a loss to the growers averaging $10.95 per acre for the acreage reported as suffering from the disease, or 42 per cent of the full area. This IS equivalent to about |4.60 per acre for the entire acreage, or about 4 cents per tree. At first thought this may seem high, but this is more apparent than real. If one 10-acre orchard loses its crop from curl, valued at $150 per acre, the loss amounts to $1,500. There may be 32 other orchards of 10 acres each all al)out this orchard where not a peach is lost, yet the average for such ti district is the same as that stated. This is perhaps a clearer manner of putting the matter than LOSSES FROM THE DISEASE. 21 by phu'iiiy; ;iii iivonigc l<^ss foi- all orchards. The loss may ho viewed in still another manner. If an orchardist has grown peaches for 32 years and lost only oni^ crop dnrino- that time from leaf curl his loss for the third of a century will average as high as here calculated. There are large sections of the country where curl is scarcely known, as in portions of Texas. For such regions the preceding estimates may appear high. On the other hand, there are other prominent sections of the country devoted to peach culture where these estimated losses will certainly ])e far too low. If the preceding calculations and statements are accepted as fairly representing the situation throughout the country, the annual losses fi"om curl in the United States may be approximated. The P^leventh Census reports the orchards of peach trees in the United States at that time (1889-90) as 507,736 acres, and from replies to our circular we are led to believe that curl was present in 63 per cent of these orchards and that 42 per cent sustained some loss from the disease. Most of the orchards included in the 42 per cent sustained only a slight loss, but a very small percentage sustained a heavy loss, some- times amounting to the entire crop. The average loss for the 42 per cent of the orchards is found to amount to $10.95 per acre, or about 10 cents per tree, averaging the trees at 108 per acre. The total acreage of the country being 507,736, the loss should be calculated upon 42 per cent of this, or 213,249 acres, which gives a total esti- mated annual loss from peach leaf curl of $2, 335. 07(5. In this estimate no account has been taken of the great injury to the growth of trees, the injury to nursery stock, the death of young orchard trees, nor the loss to succeeding crops from the reduced ninnber or quality of fruit buds on affected trees. There is also the loss arising from the culti- vation and pruning of unproductive orchards, which, if it could be determined, would probably bring the entire annual loss to the country up to $3,000,000 or more. Since 1893, when the investigation of this disease was undertaken by the writer, a very large amount of correspondence has been con- ducted with peach growers in all parts of the Union who have sus- tained losses from curl, and this correspondence has resulted in the accunuilation of a large number of facts respecting these losses. These data, however, have not been drawn upon in the above esti- mates, as it might be claimed that they were from growers only who have suffered from the disease, and consequently would not fairly represent the industry as a whole — a claim which can not be made against the circular letter, the basis of the estimates, which was addressed to peach growers in general in all parts of the United States. In fact there appears to have been a larger percentage of replies received from sections of the country where curl is scarce than from the more affected portions. CHAPTER IT. NATURE OF PEACH LEAF CURL. The study of the nature of ])hint diseases is intimately linked with the stud}^ of plant physiology, and the true science of vegetable pathology is largely, as Ward has defined it, the study of abnormal physiology. (Introduction to Hartig's Text-book of the Diseases of Trees.) These facts become evident when studying the etiology of peach leaf curl and the conditions attendant upon its widespread development. The direct cause of peach leaf curl has long been known as a parasitic fungus, Exoascus deformans (Berk.) Fuckel, but it is evident from a careful study of the disease that the injurious development of the fungus is distinctly correlated with special physi- ological phenomena of the peach tree itself. These conditions of the tree are in turn dependent upon such external influences as tem- perature, the humidity of the soil and atmosphere, and others. Such facts were foreshadowed by the theories advanced by peach growers as to the cause of the disease. Many growers have considered peach leaf curl as the direct result of excessive moisture and low tem- perature or sudden changes, and as these physical conditions cer- tainly have an important bearing upon the injurious development of the disease, they are considered together with the direct relations of the parasite to its host. However, too much stress can not be placed upon the fact that the fungus alone is responsible for the injury to the tree. Without the parasite not a leaf would curl nor a peach fall on account of this malady — in fact, no such disease would exist. This is shown by the work hereafter detailed. It is fortunate that the direct cause of peach leaf curl is a parasitic fungus rather than unfavorable atmospheric conditions, for the latter could not be controlled, while the control of the fungus has been found practicable, simple, and inex- pensive. IMIYSICAL CONDITIONS INFLUENCINd THE DISEASE. The influences of temperature, humidity, situation , soil, etc. , upon leaf curl are often so well marked that they have frequently and in fact quite generally l)een mistaken for the active cause of the disease. Indeed a very large percentage of peach growers have maintained, to within the past ten or fifteen years, that sudden changes of temperature occurring in conjunction with wet weather ari^ the sole cause of the curling and 22 PHYSICAL CONDITIONS INFLUENC1N(} THE DISEASE. 28 loss of foliag-0. Notwithstaiulino- the iiuihIh'i- of known facts lo the contrary, there are even now many lirowcrs who rctiiin this i(U'ii to the utter and needless loss of their crops. Th(> wi-iter lias met men wiio so firmly believe that leaf curl is due to unoontroUahh' climatic inlhieiiccs that they would not consider other explanations. IxMny- unwillino- to visit the orchard, though the crop was beinji- lost throitoh curl and by so doing- future crops might have ))een saved. To gather the experience of peach growers in general respecting the conditions under which leaf curl develops most severely, a circular of incjuiry was addressed to several hundred orchardists in November, 18iK>. The replies to some of the (juestions are presented. Among the iiKpiiries the growers were recjuested to state if they iiad o])served the disease to be more prevalent after a cold spell in the spring. To this (juestion 97 replies were received, 89 affirmative, 6 negative, and 2 growers said they had o])served no difference, which shows that the orchardists are almost unanimous in holding that a cold spell in the spring favors the development of curl. To the second question, as to whether the trees were most affected by curl in a wet or drA^ season, there were 104 replies. Of these, 78 stated that peach trees were most affected in wet seasons, 8 that they were most affected in dry seasons, and 18 that there was no diffei'ence. Here again is seen a marked agreement in the replies, a great majority of the growers recognizing that wet years favor the disease. • The above-considered conditions — a cold spell in the spring and wet weather — may be explained by stating that such conditions favor, on the one hand, the serious development of the fungus causing the dis- ease, and, on the other, they result in a nuich greater susceptibility of the tissues of the peach leaves to the attacks of the parasite. Where both cold and rain occur together in the spring, about the tinu^ the leaves are pushing, the disease is liable to develop seriously and few varieties can then resist it. The action of wet, cold weather upon the tissues of the peach, making them much more subject to curl than they otherwise would be, has been considered in relation to other plants in a paper by Prof. H. Marshall Ward,* who says that vr/zt/^ thecomhined effect fi of tlie physical enviTOiiine)it are unfavorxible to the host, hut not so oi^ are even faiforalde to the lyarasite, we find the disease a.^.su//t hi r/ a more (yr less jyvonounced epidemic character. He is not here spetdcing of curl, but the statement holds perfectly true for that disease. A cold, wet spell succeeding warm spring weather, has a tendency to saturate and soften the tissues of the i)each, as in the case of other plants. The sudden checking of active transpiration, due to lowered temperature and saturated atmosphere, soon results in the tissues of th(> plant being suffused with water. ''The stomata," as Ward puts it, "are nearl}' ^Wanl, Prof. II. IVIarshall, The Relations between Host and Parasite in Certain Diseases of Plant^J, Crooiiian Ltctiiic, I'mc Ixoy. Soc, Vol. XlyN'II, No. I'DO. 24 PEACH LEAF CURL: ITS NATURE AND TREATMENT. closed, the cell walls hounding the intercellular passages and the air in the passages themselves are thoroughly saturated with water and aqueous vapor, respectively, and the movements of gases must be retarded accordingly; turgescence is promoted, and the water contents accunuilate to a maximum, owing to the disturbance of equilibrium between the amounts absorbed by the active roots in the relatively warm soil and those passing oft' into the cold, damp air; much more water is absorbed by the roots in the relatively warm soil than passes ofl' as vapor in equal periods of time." Further than this. Ward states that ""thc^ low temperature, feeble light, and partially ))locked ven- tilation system have for a consequence a depression of respiratory activity and the. absorption of oxygen genei'ally." This must give a lowered vitality and an accumulation of organic acids. The reduced light also leads to a decided reduction in the assimilative power of the leaves. ''The turgid condition of the cells, and the diminished inten sity of the light," Ward sa}\s, ""will favor growth." If this takes place, "the tendency will be for the very watery cell walls to become relatively thinner than usual, as well as watery, because the ill-nourished protophism does not add to tlie substance of the walls in proportion. This being so, we have the case of thinner, more watery cell walls acting as the onlv mechanical protection between a possible fungus and the cell contents." It is generally known that the conditions of moisture and shade, which are above shown as making the tissues of a host plant more tender and watery (more svibject to fungous attacks), are also the conditions most favorable to the development of fungi. This holds equally as good for Exoasciis deformans as for other forms. In speak- ing of these conditions in relation to a fungus known as Botrytis^ Pro- fessor Ward gives some generalizations equall}" applical)le to Exoascus def(yrmans in its relation to curl. He says that just those external climatic conditions which are disturbing the well-being of the green host plant are either favorable to the fungi considered or, at awy rate, not in the least inimical to their development. "Thus," he sa3\s, "the oxA^gen respiration of the fungus goes on at all temperatures from 0° C. to 30'-' C. and higher, and although we still want information as to details, experiments have show^n that the m3^celia flourish at tempera- tures consideralily below the optimum for higher plants. Moreover, light, so indispensable for the carbon assimilation of the green host, is absolutel}' unnecessary for the development of the fungus. Then, again, the dull, damp weather and saturated atmosphere, so injurious to higher vegetation, if prolonged, because they entail interference with the normal performance of various correlated functions, as we have seen, and render the plant tender in all respects, are distinctly favorable to the development of these fungi; consequently the very set of external circumstances which make the host plant least able to PHYSICAL CONDITIONS INKLUP^NOINO THE DISEASE. 25 withstand the cntiT aiul (li'vasUition of a parasitic fungu.s liki; Jioliu/fls^ at tlio same tiiiio favor the dovolopiiiont of the fiino-us itself." The writer thinks, as the result of ol)servatioiis in the field, that JExoasciu'i di^forz/nnhs is favored in both its entrance and spread within its host by the conditions which have just been considered. It is a widelv observed fact that leaf curl usualh^ develops sparingly in a uniformly warm and dry spring, and it is also noticed that where infection has occurred a return of wariii, dry weather, or even the occurrence of a hot, dry wind, will check the development of the fungus within the tissues. An infected leaf may fail to develop the spores of the fungus under such circumstances. The thin, satu- rated cell walls and the moist intercellular spaces thus appear to be closely correlated with the active vegetation of the fungus. The growth and consequent tenderness of the tissues is also important in this connection. Where soil, elevation of orchard, and atmospheric conditions are unfavorable to a Saturated condition of the plant paren- chyma, the disease is not likel}' to run more than a short and feeble course. Soil and elevation are here considered with atmospheric con-" ditions, for it is found that on the same farm a difl'erence of elevation or soil moisture may determine the degree of virulence of the disease. The influence of elevation may be of onh" secondary nature — that of maintaining a higher temperature — but its action on the disease is fre- quently well marked. Of 92 orchardists who expressed their views as to whether trees are affected b}^ curl most on high or on low land, 48 sa}^ that trees suffer most on low land, 14 on high land, and 30 think there is no difference. While the majority claiming that trees on lovv' land are most affected is not as large as some of the majorities obtained in replies to other questions, it represents over one-half the replies received to the question under consideration and is more than three times as great as the number who lielieve trees to be most affected on high land, hence is sufficient to estal)lish confidence in its reliabilit}', even if it were not indorsed bv many published statements to the same effect. Mr. Thomas A. Sharpe, superintendent of the experiment farm at Agassiz, British Columbia, has made several comparative reports on the action of peach leaf curl on trees planted in the valley and upon the more elevated bench lands of the farm. A few brief statements from these reports should be of value in connection with the above statements.^ In 1892, Mr. Sharpe says, the peach trees suffered from a severe attack of leaf curl. ''Only 5 varieties of those planted in the valley escaped" the disease. ''The trees planted on the bench lands did not suffer so much, and appeared to recover much more rapidly than those in the valley" (1. c, p. 278). In 1893, it is said, ' See report;^ f)f experimental farms, Ottawa, Canada, for the years indicated. 26 PEACH LEAF CURL: ITS NATURE AND TREATMENT. the curl leaf in the pencil unci iiecturine trees was worse than it had ever been before, the Malta l)eing the only variety that was entirely healthy on level land. The varieties received from Eng-laiid and planted on the level land were just as badl}^ affected as the otliers. The first and second bench orchards suffered alike with those on the level j:;r()und, but the orchard hig-hest up, at an elevation of 800 feet, had no curl in any case, and the trees appeared to have suffered less from cold than those lower down (1. c, p. 342). Mr. Sharpe says that in 1896, "as heretofore, the trees on the upper benches, both nectarine and peach, escaped the curl leaf entirelv" (1. c., p. -MO). Again, it is said that "the peach crop on the level land this year [in 1898] was almost an entire failure. The curl leaf was ver}" prevalent, nearly every tree being seriously affected by it.'" Relating to the orchard on the bench lands, it is stated that "curl leaf did not affect the foliage there; in fact, it has never injured the foliage on either peach or nectarine trees on the })enches over 300 feet above the valley" (1. c, p. -lOS). These facts have an especial interest and value in that they were recorded by a single observer on one farm and during successive years and epidemics of curl, and thej^ are in perfect harmony with the experience of a majority of the growers whose views are presented above. The soil ma}^ exert its influence by abundantly or feebly supplying the transpiration stream, in accordance with the degree of accessibility of the moisture it contains, to the root hairs of the tree. It may he said, however, that as leaf curl commonly develops at the beginning of spring growth or at the close of the winter's rains, the soil will rarely be found so deficient in moisture as to greatly retard the devel- opment of the disease where other conditions are fa^'orable. It is prob- ably equally true that the excess of water usually found in the soil in the spring is favorable to the special development of the disease at that season in its worst form. Besides the influence of temporary excessive humidity of the atmos- phere upon leaf curl, which has already l)een considered, there are other atmospheric influences and relations of importance, which depend upon the local or general geographic, topographic, and climatic fea- tui'es of country. Some of theso more prominent atmospheric influences nui}' here be briefly considered, together with their most probable causes. Proximity to large l)odies of water, whether salt or fresh, greatly favors the development of curl. The cause for this clearly rests in the resulting greater humidity and lower temperature of the atmosphere. Plants growing in a constantly humid atmosphere have normally more succulent and tiMider tissues than those growing in a drier region. The reasons for this have already been alluded to for special cases of extreme atmospheric humidity and lowered temperature. Near large PHYSICAL CONDITI<>NS TNKLUENCINO TITK DISEASE. 27 l)()(li('s ot^ water si)riiio- t"()<^s coinmonly occur, and those lead to the increase of the atmospheric huinidity at a time whiMi th(^ t'oliat>-e is tender and orowiny- rapidly, thus stimulating- a development of curl almost amuiall}' and over wide stretciu's of country. lnde[)en(lent of fogs, the atmosphere about large bodies of water is also nuicli more huiuid than in an inland i-egion. Instances of th(> influence of large l)odies of water on the general prevalence and fre(pient occurrence^ of curl in a region are found in western New York, near the shoi-e of Lak(^ Ontario; in Ontario. Canada, near Lakes Erie and Ontario; in Michi- gan along the shore of Lake jNlichigan; in Oaliforida about the )»ay of San Francisco and at other points along the Pacilic coast: in ^Vashing- ton and British Columl)ia a])out Puget Sound; and in many similar situations in all portions of the world where the pcnich is grow' n. The writer believes, however, that the influence of large ])odies of water upon the development of curl depends in part upon the normal spring temperature of the region, and likewise upon the source of the prevail- ing winds. Where the prevailing spring winds are from a dry, inland region instead of from the water, the atmosphere does not feel the influences of the latter. Moreover, where the spring temperature is high, transpiration may proceed normal!}^ even in the neighborhood of large bodies of water, and curl may not commonly prevail. In contrast to the influences of large ])odies of water are those of neighboring dry and atid plains or desert regions. In the midst of such influences peach leaf curl can rarely attain to an epiphytotic development, and then only under special favoring seasonal condi- tions. The atmosphere is normally too dry in such situations to exert a predisposing action upon the host, and it certainly does not favor the serious development of the parasite. Exemplifying these condi- tions are large areas in Arizona, New Mexico, Nevada, Utah, Colorado, Texas, Kansas, and California. Little or no curl is reported from the more arid portions of these sections of the country, its absence being due, at least in part, to the influences here considered. Another of the broader influences afi'ecting the general and perma- nent prevalence of curl over extensive regions is the normal amuial rainfall. Comparisons of this kind must be made, howe\'er, between regions of approximately similar temperatur(\ Under such condi- tions it may be said that the general amuial prevalence of leaf curl increases with the increase of normal annual precipitation. Compari- sons of this kind can hardly be justly drawn in the ^Mississippi Valley or on the Atlantic coast, as the temperature conditions vary too greatly in those regions from north to south. On the Pacitic coast, however, owing to the modifying influence of the Pacific Ocean, the temperature prevailing from Lower California to British Cohunbia, a distance of about one thousand three hundred miles, presents no such o-reat variations as are found in a like distance from south to 28 PEACH LEAF CURL: ITS NATURE AND TREATMENT. north on the Atlantic coast, ,so that the relations of annual rainfall to the constant prevalence of curl ma}^ be more fairly decided. In the following remarks on this subject I have left out of consid- eration the temporary influence of exceptional seasons and, as far as possible, the special influence of local features. The subject should be viewed from the liroad field above pointed out. In southern Cali- fornia leaf curl is not recognized as a generally prevalent and serious trouble, but there is evidence which shows that its prevalence increases from San Diego northward to the San Bernardino Mountains. The average annual rainfall varies from about 10 inches at the former place to 10 inches at Los Angeles, which is not far from the mountains. In the San Joaquin Valley the prevalence of curl increases as a whole from the south central portion toward Sacramento and the north. The average annual rainfall, which is 7 inches at Tulare, 9 inches at Fresno, 11 inches at Merced, and 14 inches at Stockton, reaches 20 inches at Sacramento, about which center curl is quite prevalent. The average rainfall at Oaldand is 23 inches, and curl is quite troublesome there. In the Sacramento Valley curl is frequently quite prevalent, and the rainfall \aries from 20 inches at Sacramento and Chico to 34 inches at Kedding. About Ashland, in southern Oregon, the rainfall is 23 inches, and the disease is about as in the Sacramento Valley. Farther north in Oregon curl becomes decidedly more prevalent and injurious at the west of the Cascade Mountains, and increases as Portland is approached. The rainfall is 35 inches at Roseburg, 4() inches at Albany, and 49 inches at Portland. From Albany to Portland the peach industry' has been greatly injured bj- curl, and on its account many growers in this region have considered peach culture a failure. Curl, it seems, was introduced into the central ])art of the Willamette Valley, Marion County, nearly half a century ago. Prior to that time the peach was successfully grown in that region in spite of the humidity of the climate. In the Patent Office Report for 1855, p. 298, there is a statement of the situation in Polk and Marion counties from 1852 to 1855. This statement was from Mr. Amos Harry, of Farm Valley, Polk County, Oreg., and is of special interest in this connection. Mr. Harrj- says: "The peach in this county has been afiected with a disease known as the 'curled leaf.' which threatens to destroy the trees. It made its appearance at Mill Creek, in Marion County, in 1852, and extended considerably on that side of the river (Willamette River) in 1853, but had reached most parts of the valley in 1854-55. Some trees seem to escape it nuich more than others, but if the malady increases for two years to come as it has for two past, I fear we shall come entirely short of this delicious fruit. Some think it is owing to cold, wet weather, and recommend shortening all the limbs as a remedy, and some experiments seem to favor this idea. Others think it is produced by an insect, and that no remedy will save the trees unless it can be applied to the ivhole surface of the leaves." PHYSICAL (M»NDIT1(>NS I ni<'lup:ncin(^ thk diskask. 2U 'V\w r;iiii1":ill at rortliiiid, as already said, is-ll> iiiclu's, atid curl iscoin- moiily prevalt'iit and sovcnv. At llinatilla, cast of the Cascade Moun- tains. l)ut al»()ut the same distance north as Portland, the rainfall is only 1<> inches, while on that side of tlic mountains the peach industry i>; extiMisive and everywhere prospiM'ous, leaf curl liein*"' much less prevalent and of secondary importance. This shows that it is not the distance north and the consecjuent lower temperature which makes curl more severe at Portland than at Los Angeles for insttince, l)ut that it is the excess of rainfall, for at the east of the mountains, near Umatilla, the temperature goes equally as low or lower than at Portland, and curl is of little importance there. In the Pu^-et Sound i-eoion peach culture has never developed extensively, the general prevalence of curl and its injurious action being one of the chief reasons. The rainfall is 50 inches at Seattle and 5(5 inches at Olympia. It is only T inches at Kennewick and !> inches at Ellensburg, on the east side of the Cas- cade Range. The peach orchards of North Yakima and .neighboring sections on the east side of the Cascades and near Ellens) )urg, where this rainfall is taken, are noted for their extent, thrift, and general health, and curl is not a serious trouble. This case is parallel with that of Portland, already considered. The rainfall at the west of the mountains is 50 to 50 inches or more, while at the east it is only 7 to 9 inches. In the former region peach growing is not listed ])y the Washington Board of Horticulture as one of the horticultural indus- tries, but in the latter region the peach is a leading fruit, lieing extensively and successfully grown. The winter temperature east of the mountains should range fully as low where the peaches are grown as at the west of the range. The contrast in peach culture in the two situations results from the difference of rainfall, and the heavy rain- fall at the west of the Cascades results in a developnuMit of curl almost prohibitive to peach growing.' In replying to a circular letter sent to the peach growers of Mary- land, November, 1893, Mr. T. C. Stayton, of Queen Amie, makes some statements which bear directh' on the matter here considered and are of nmch interest as resulting from personal observation. After speak- ing of the conditions in Maryland, Mr. ' Stayton savs: "I was in Washington State during the months of April, May, June, etc., this year, and I find they can not grow peach trees west of the Cascade Mountains or in western Washington, as that part of the State is called, as that is a A'ery wet part of our country." He adds that this was especially true in 1893, and continues: '"About all the young trees that had been planted in that pai-t of the State died fi'om curl leaf, or so nearly so that they were worthless, ])ut over in eastern ^^'ashiIlgton I did not notice any curl leaf, the climate being dry." ^ For a full and accurate account of the rainfall conditions prevailing on the Pacific coast, see Report of the Rainfall on ttie Pacific Slope for from Two to Forty Years, AVashington, 1889; also other reports of the Weather Bureau. 30 I'KAOH lp:af curl: its nature and treatment. Peach l(>af curl appears to ])e more prevalent in late tlian in earh'' springs. This is pro))al)ly due to the lower temperature and greater rainfall usually accompanying the former. Of 80 growers who gave their experience in relation to this matter, 43 stated that curl affects trees most in late springs, 23 believed it affects them most in early springs, and l-i had noticed no difference. The question as to whether peach leaf curl affects trees most after a cold or warm winter was submitted to the growers, and of the 67 who replied, 27 stated that trees were most affected after a cold winter, 21 that they were most affected after a warm winter, and id growers had observtnl no difference. The ([uestion of the influence of heav}' dews on curl was also sub- mitted to the orchardists, and the views expressed in their replies exlii])it a remarkable agreement, 47 out of the 58 expressions of opinion received stating that the disease is no worse after a series of heavy dews. To the writer it appears probable that these answers are in perfect accord with the facts. Heavy dews can exert l)ut slight influence upon the tissues of the peach, as they occur at night, when , transpiration from the leaf is largely checked by the reduced light and lowered temperature of the atmosphere, resulting in the stomata being nearly closed. With the return of light and warmth the dew evapo- rates with the resumption of transpiration, and can have but little influence upon the tissues of the leaf. It might seem that dew would have a direct action on the germination of the spores of the fungus and in that way lead to a serious development of the disease after one or more heavy dews. This view, however, is not supported by observa- tions either in the field or in the laboratory. In regions having little cloudy weather, with exceptionally clear sky, as in many portions of the Southwest, the heat of the soil radiates rapidly after sunset. In such sections of the country the days are hot and the nights cool or cold in comparison, the range of temperature between night and day being often considerable. In such regions dew is conmion and often heavy, but it is here that least curl occurs. Relative to the action of dew on the germination of the spores of ExoasiCKs dcformam^ it may be said that something more than dew is required for such germination. The writer has tested this matter most thoroughly, not only with dew, but with many forms of culture media at various temperatures and with varying supplies of oxygen. Bi-cfeld has also shown that moisture alone is not sufficient for germi- nation, behaving utterly failed to induce germination in a single instance after months of work with culture media in liquid form. Budding of the spores is eas}^ to obtain in all liquids, and is more abundant and continuous in sidtable nourishing cultures than in dew or rain water. Fiftv-eight growers replied to an inquiry on this subject, 47 stating that the disease is no worse after a series of heav}^ dews, 7 that it is worse, and 4 that no difference was observed. THE DIRECT CAUSE (»K I'EACJI LEAK (MIRL. 31 THE EINIRIS CAi;siN(! THE DISEASE. The fungus i-:uisiiiu- peach leaf curl, now known as Krixisciisdrforimiiis (Bork.) Fuckol, is a incuihor of the subfamily of fuii««i known as Ki't)((f. The /i'/v>^^s•aY^ arc low or simple Aacomycetc.s^in' funt>-i hear- ino- their spores in cases or usci. The classification of the Enxm-i'iv which now lavs o"reatest claim to seientihc permanence is that outlined in the recent writings of Sade- beck, who has given careful study to these forms. ^ Of the five genera which he recognizes, only the last directlv concerns us at this time, as it is to this genus {Exodseui^) that the peach curl fungus belongs, as well as numerous other species injurious to horti- culture. In considering this genus Sadebeck ~ has grouped thirty of its species according to certain characters of development. He recog- nizes the following characters of the genus : ExoAscrs Fuckel. A. The myceliimi is perennial in the inner tissues of the axial organs. a. The development of the hymenium occurs only in the floral leaves of the host plant. Eight species. h. The development of the hymenium occurs only in tlic foliage leaves of the host plant. Seven species, including E. deformaiif:.^ (-. The development of the hymenium occurs upon the leaves as well as uiion the fruits. One species. B. The mycelium is perennial in the buds of the host plant and de\-elops only subcuticularly in the leaves. ^Sadebeck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1.S93, ]>. 43. Sadebeck recognizes five genera in the Exoasceeol)achtungen und kritische Bemerkungen iiber die Exoascacese, pp. 277, 27S, reprint from den Ber. d. deutsch. ])ot. Ges., 1895, Bd. XIII. *Dr. von Derschau has described the occasional fruiting of E.ioftsciis deformans in the blossoms of the peach. The ligures given by this author do not show the nor- mal development of ascogenous cells \n the l)lossoms which are so common in the leaf blade of the peach. His figures show the asci as arising from lateral branches of a continuous mycelial liyi)ha, and this mycelium is situated beneath the epidermal cells instead of between the cuticle and ei)idermis (Landw. Jahrb., Berlin, 1897, pp. 897-901, and Table XLI) . 32 PEACH LEAF CURL: ITS NATURE AND TREATMENT. ii. The development of the liyiiu'iiinni occurs only in tlie floral U-aves of tluOiost plant. Three species. h. The development of the hyineninni occurs only upon the foliage leaves. Ten species. V. The resting mycelium extends intercellularly in the deformations of the leaves. One species. It may be seen under A h of thi.s arrangenient that Exomcvs defor- mans is said to possess perennial mycelium, inhabiting the inner tis- sues of the axial organs, and that the development of the hymenium oeeurs only in the foliage leaves of the host plant. As will be seen in another part of this ))ulletin, it is perhaps a perennial nature of the mycelium of E. dfforvums which makes it difficult to thoroughly rid an orchard of curl l)y means of spray treatment, but this matter requires further careful consideration. The sjnionymy of Exoancm defonnans (Berk.) Fuckel has been given by numerous writers. Sadebeck^ gives it as follows: Ascoim/ces deformanfi Berk. Intro, to Cryptogamic Botany, 1857, p. 284. Ascoaporhun deformans Berk. Outlines, 1860, p. 449. Taphriim deformnni^ Tul. Ann. Sci. Nat., 1866, V. S^r., t. 5., p. 128. Exonttrna defoniicnis Fuckel. (o) Perm-tc Fuck. 8yml)ol;« Micolog., 1869, p. 252. This fungus has been very commonl}- observed and frequently described by ))otaiiists since Berkeley called attention to it in 1857. It has thus l)een known as the cause of curl for a little less than half a century. The peculiar l)ehavior of peach foliage under its action has been observed l)v horticulturists, however, for a much longer time. The disease was well descrilied in England in the early part of the present century. In spite of tlie A'cry common appearance of Exoasats deformans upon peach foliage in peach-growing countries, the descriptive litera- ture relating to its life history is not free from conflicting statements. Several species of Exoascew have been confounded with this species in* some instances, and subsequent writers have perpetuat(xl the confusion. Some earlier writers l)elieved this species inhabits a considerable number of host plants, thus resulting in the description and distribu- tion of several distinct species as Exoascus deformans. To avoid such confusion it would be best to confine remarks upon this species to the fungus as it develops upon the peach {Prunus persica L.), which if not its onl}^ host, is certainly its most com-mon one. At least two modes of infection of the peach tree by Exoascus deformans are said to exist — (1) by means of perennial mj^celium, and (2) by means of the spores of the f luigus. Sadebeck^ is authority for the statement that the mycelium winters over in the 5''oungest portions of the one-year-old branches of the host ' Radebeck, Dr. E,., Die parasitischen Exoasceen, Ham1)urg, 1893, y>. 53. •■'Idem. 1. c. THE INFECTION OF THE HOST. 33 ])hmt. unci iiuiy hv seen in the priniary oortox. in the lut'diilla. and in the niedullary I'ays of the first shoots of each period of veo-ctation, but has not l)oen observed in the soft bast. With the be^innin^- of the new season of growth the luyeeliuni, aceording to Sadebeck, extends into the leaves of the young shoots, penetrates first the inner tissue of the halves, and finally i)r()gresses to the deveh)pinent of the subeutieular hymeniuni. From what foundation of experimentation Sadebeck has arrived at these views respecting this particular species, I :un unabl(> to state, but lie has giviMi th(> outlines of his investigations upon other species.' The facts given by De liarv ' can not be cited- here, for this work was done upon the Exoascus infesting the cherry tree, and which is now considered to be distinct from J^J. deformans. The general acceptance of the view that spring infection of the peach foliage is largely due to the extension of the internal perennial myce- lium into the new shoots and leaves from the shoots of the previous sunnner, has probably considerably retarded the progress of prevent- ive treatment. Pathologists have thought it improbable that an}^ considerable amount of disease could be prevented after a tree was once generally affected, as the perennial mycelium, being internal, could not be readily reached by external sprays. Prillieux,'' writing in 1872, advises the gathering of the diseased leaves and the cutting away and burning of the diseased branches. Frank * has made like reconnnendations in both editions of his work on plant diseases. Assuming the mycelium to be perennial, he says that the curing of the disease might be aimed at through cutting back of the diseased branches and the prevention through quick removal of the diseased leaves. Winter' suggests a somewhat similar line of treatment, with the additional recommendation that the trees be protected from rain during the unfolding of the leaves. Dr. Cobb/' as late as 1892, after speaking of the perennial mycelium of this fungus, discusses pre- ventive and curative measures, such as the destruction of diseased leaves, prunings, etc., while in the more severe cases he says the sooner the trees are cut down and Inirned the better it will be for the peach industry. ^ Sadebeck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1893, pp. 24-28. — Das perennirende Mycel der Exoapcus-Arten. '■'De Bary, A., Com. Mor. and Biol, of the Fun• * Frank, Dr. A. B., Die Krankheiten der Pflanzen, lireslau, 1881, Part 11, p. 526; second edition, 1896, Vol. II, p. 250. ^Winter, Dr. Georg, Die durch Pilze verursachten Kranklicilcu der Kultiirj,'e- wiichse, Leipzig, 1878, p. 47. "Cobb, Dr. N. A., The Agricultural (iazette, Sydney, New South Wales, IS92, Vol, III, pp. 1001-1004. 19093— No. 20 3 34 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Relative to the use of fungicides the same writer says: "These treatments are of doubtful value as far as the curl is concerned, and were it not that they arc useful in other waj'S I would not mention them." It is evident that these views are the result of Dr. Cobb's belief that the perennial mycelium is responsible for the major portion of the spring infection of the tree. The writings of others to the same effect could be cited, but the views of the workers already named are sufficient to show that their recommendations for treatment have been based upon the hypothesis that the spring infection could not be prevented by treatment with fungicides, as it arose mainly from in- ternal mycelium rather than from the germination of external spores. That this view has held l)ack the preventi^•e treatment of the disease, as already claimed, can not be doubted, and that a perennial mycelium is not responsible for more than a very small percentage of the spring infections seems evident from the results of the present experi- ments; in fact it may even be questioned if such infection takes place except under exceptionally favorable conditions. Our experiments have demonstrated that as high as 98 per cent of infections may be prevented by a single thorough application of a suitable fungicide. This is as high a percentage of control as is often obtained in the treatment of fungous diseases where no perennial mycelium exists, and it seems probable that the infections by this means ma}' not com- monly exceed 5 per cent of each spring's infections. Were this not the case we would be forced to assume that the spray has a direct effect upon the hibernating mycelium, which certainly would be unusual and scarceh' to be expected. The second mode of spring infection — that by means of spores — is probably much more general and important in this disease than has been supposed. That 90 to 98 per cent of the infections of the tree are prevented l)y a single spraying suggests that at least such percent- age of the infections is by means of spores. The m3a'elium of Ji'xonsci/s dtfornxinx as found in the peach, shows great differences in the form and appearance of its hyphiv. These differences depend upon the stage of development of the fungus and the various functions of the mycelium. The writer recognizes three types of hyphie, which may be termed vegetative, distributive, and fruiting. The vegetative hypha? are found most commonly in the leaf paren- chyma, l)ut are also met with in the leaf stalk and cortical parenchyma of badly diseased and distorted liranches. Thes(> hypha> may be most distinctly seen, and are most highly developed, in infested leaves which have not yet formed the hymenium of ascogcnous cells, but in which the parasite has been present a sufficient time to entirely alter the character of the palisade tissue and cause the loss of the chlorophyll. In the leaf blade the palisade tissue tirst shows the serious action of BULL. 20, DIV. VEQ. PHYS. & PATH, U. S. DEPT. AGRICULTURE. PLATE II. MYCELIUM OF EXOASCUS DEFORMANS, THE FUNGUS CAUSING PEACH LEAF CURL. A.H<,eii«. (•o.l.iih.Bailiitu.r. DESCRIPTION OF PLATE 11. Mycelium of Exoascus deformans (600/1) . Figs. 1 and 2, normal vegetative hyphfe, as found in the leaf parenchyma, showing characteristic septation, modes of branch- ing, etc. ; figs. 3, 4, and 5, usual type of distrilmtive hyph;e found in swollen branches in the cortical parenchyma and medulla; figs. 6, 7, 8, and 9, fruiting hyphie, show- ing successive stages in the development of ascogenous cells from the su})cuticular mycelium (6) to the half-formed ascogenous cells (9). (See PI. Ill for further stages in the development of the ascogenous cells and asci.) THE MYCELIUM OF THE FUNGUS. 35 tlio vegetative hyphpe, which are usually found somewhat later among tiu> cells of the spongy pariMichyma, below the vascular network. The loss of chlorophyll from the two classes of leaf parenchyma couunonly jn-eserves the order here given. The form of the vegetative hyphjc is very irregular, and their elements, or cell members, are often of dif- ferent size, length, and shape. The cells vary greatly in diameter from one end to the other, are frequently much curved and twisted, and oftentimes appear triangular in cross section. The branches n..iy arise froui greatly enlarged triangular bifurcations, or in other instances directly from the sides of the cells. These vegetative hyphiB are all intercellular so far as observed, but are commonly found adher- ing closely to the cell walls of the host, frequently wrapping about the parenchyma cells. The walls of the hyphee are semitransparent but tirm, couunonly having a slight yellowish cast. The septa present peculiar characters. Two adjoining cells of a hypha have the appear- ance of being separately closed at the end and united with each other l)y means of an intervening plate, which if it should be dissolved or lost would leave the cells separated but closed. These peculiar septa are remarkably refractive and characteristic. They are well shown in the drawings of Sadebeck (Die parasitischen Exoasceen, Haml)urg, 1893, Tab. II, tigs. 7, 8). The predominating characters of the vegetative hyphffi are shown in PI. II, tigs. 1 and 2, of this bulletin. The hyphse there shown were carefully sepai-ated from the leaf parenchyma and drawn under the camera. The vegetative hypha3 of the ))ranch are nuich like those of the leaf, and have been seen most commonly among the looser parenchyma cells of the cortex just exterior to the bast fiber bundles. Thus far they have never been found by the writer in the cambial tissues. Sadebeck states that the mycelium has been found in the pith and medullary rays. The distributive hyphse are shown in PI. II, tigs. 3, 4, and 5. They have been found by the writer in the tissue lying close beneath the epidermal cells of diseased peach twigs, and in great al)undance in the pith. They are occasionally found in groups of several hyphffi but slightly separated from each other and following a course parallel to the longitudinal axis of the shoot. The cells composing these hyphte are much longer than either the vegetative or the fruiting forms, while they are nearh' straight and of more uniform diameter. The septa are characteristic of those found in the other forms of the mycelium of this fungus. Such distributive hyphie have been follow^ed for some little distance in the swollen portions of the peach twig, and the name has been given them from their apparent function of spreading the fungus in the branch. Such hyphie ])ranch l)y })ifurcation, the branches commonly assuming a course parallel to the parent hypha and the direction of the peach limb. 36 PEACH LEAF CUEL: ITS NATURE AND TREATMENT. The fruiting hypha? have been seen to arise in Exoascus deformmis from the vegetative hyphte after the latter have become well developed in the parenchj^ma of the leaf. Large, well-nourished vegetative hj'phse commonly develop just below the epidermal cells of the upper leaf surface/ From these hyphre arise branches which penetrate between the cells of the epidermis, and press themselves between the epidermis and the cuticle. Such hyphas may be seen both in section and surface view. These subcuticular hyphje now branch freely, and follow with more or less regularity the triangular space formed by the juncture of two adjoining and somewhat rounded epidermal cells with the cuticle. This is presumably the line of least resistance to the advance of the hyph^. By opening and following these channels the mycelium assumes the outlines of a quite uniform network beneath the cuticle. While this manner of following the line of juncture of adjoin- ing epidermal cells with the cuticle is common, it is not invariably the practice of the fungus, cases occurring where apparently no such agreement exists. Series of straight and parallel hyphse, at regular distances apart, are sometimes met with beneath the cuticle as the precursors of the hymenial layer. These send off lateral branches on either side, which hy enlarging, l)ranching, and curving eventually occupy most of the surface of the epidermis between the main hyphre. It is probable that the path followed b}' the first subcuticular hyphse depends largely upon the firmness with which the cuticle is attached to the epidermal cells, and which may largely depend upon the amount of water in the tissues and upon the age and rapidity of their growth. With the leaf tissues full of water and making a rapid growth, the hyphfc could naturally pursue a more direct course beneath the cuti- cle than under contrary conditions. After the establishment of a much-branched filamentous network of subcuticular h3^pha% the cells of which are usually slender, of medium length, thin-walled, and of comparatively uniform diameter (PI. II, fig. 6), these cells begin to distend, and are shortened by the formation of new transverse septa (PI. II, fig. 7, and PL III, fig. 22). A])out this time all septa become nuich more distinct. At a later stage the cells become still more distended and subspherical (PI. II, fig. 8). As these enlarged cells ^ Miss E. L. Knowles (Bot. Gaz., Vol. XII, No. 9, p. 217) has called atten- tion to the fact that Winter's statement that "the asci break through the lower side of the leaf" does not hold good for the peach (Kryp. Flora, Asco., p. 6, and Krank. Kultur-Gewiichse, Leipzig, 1878, p. 47) . Winter is not alone in stating that the asci of E. deformans arise on the under surface of the leaves. Robinson says: " The asci are borne on both sides of the leaf, but in greater numbers upon the lower sur- face" (Robinson, B. L., Notes on the Genus Taphrina, Ann. Bot., Nov., 1887, Vol. I, No. 11, p. 168) . Atkinson also says: "The asci are developed on both surfaces of the leaf" (Atkinson, Geo. F., Leaf Curl and Plum Pockets, Cornell Agr. Exp. Sta. Bull. No. 73, 1894, p. 325) . These and other like statements have probably arisen from a study of other foliage than that of the peach, and of other species of Exoascus, and qave been perpetuated through insufficient reference to nature. I DESCRIPTION OF PLATE III. Fruitinii s^ta.ijri'.'; of Exoascns deformans. Figs. 1 to 13 (600/1), various stages and conditions of tlie asci and ascospores of tlie fungus. Fig. 14, section of peach leaf, showing subepidermal and subcuticular mycelium, the latter already partially dif- ferentiated into ascogenous cell.s. Fig. 15, section of peach leaf showing three suc- cessive stages in the formation of the asci from the ascogenous cells: a, the pushing of the ascogenous cells; b, the ascus nearly full-formed, but with the contents still connected with the ascogenous cell; c, the asci separated by ivsei^tum from the ascog- enous cell, which now forms the stalk cell of the ascus. Figs. 16 to 20 (600/1) , thi* first stages in the formation of the asci from the ascogenous cells, the latter being ruptured above and the asci pushing upward. " i\, the pr.shing of a forming ascus through the leaf cuticle (600/1). Figs. 22' ^600/1), v^arious stages in the formation of ascogenous cells from subcuticular j um. (For several early stages in this process see PI. II, figs. 6 to 9). Figs. 28 * (600/1) show fully developed ascogenous cells as seen from above. • ^ "^ ^1 i ,r at BULL. 20, DIV. VEQ. PHYS. & PATH., U. S. DEPT. AQRJCULTURE. FRUITING STAGES OF EXOASCUS DEFORMANS. A.Hu«n A-O..Litl.. K«iliinonr. THE B^RtriTlNG HABITS OK THE FUNGUS. 37 spread out Ix'twccii the cpidcnnal cells of the leal" and the cuti- cle they are nuich distorted, curved, and lohed, the branches and lobes eventually tillint>\ in a ((uite uniform and continuous manner, the entire space between the elevated cuticii^ and epidermis, so tliat a more or less perfect and continuous hymenial layer of ascogenous cells is formed (PI. II. t\g. t»: PI. Ill, %s. 23, 24, 25, 2<;, and 27). At tliis time the cells become well rounded and heavy-walled, and they may or may not become loosened and separated from each other (PI. III. iij>s. 28-30). These are now the fully developed ascog-c- nous cells of the hymenium, and they are fully stored with nutritive materials for the development of the asci. In their compact, continu- ous, and rounded condition they resemble, when viewed from the sur- face, the stones in the pavement of an old Roman highway. The various phases of the development of the hymenium of ascog- enous cells may often be observed at one time in a single infected leaf. The center of a swollen spot frequently shows the fully devel- oped h3'meniuni, while at the margin of the spot the first filamentous hyphtv are just spreading beneath the cuticle. In such instances nearly all stages in the development of the ascogenous cells ma}^ be studied in a single well-prepared specimen. The development of a subcuticular hymenium has been observed in the petiole as well as in the ])ladt^ of th(> leaf. The formation of the asci from the fully developed ascogenous cells has bt^en carefully followed in the stud}^ of a large number of prepara- tions. Thus far no sexual phenomena have been observed in connec- tion with the formation of the ascogenous cells or with the develop- ment of the asci. As already said, the walls of the ascogenous cells are heav}'. The earh' steps in the development of the asci from these cells (the development of a papilla-like elevation on the upper surface of the cells) cause the rupture or dissolution of the heavy wall where the elevation occurs. The phenomenon is that of the germination of a heavy-walled spore, or, perhaps, more properly, the outgrowth or prolongation of an endospore through the rupture of the epispore (PI. Ill, tigs. 17. 18. etc.). The fact to be noted is the perfect rest- ing condition into which the ascogenous cells may pass before the development of the ascus, as shown by the marked delimitation between the thin wall of the forming ascus and the heavy wall of the ascogenous cell. The entire isolation of single ascogenous cells or groups of cells from all sources of vegetiitive supply indicates that the ascus is entirely dependent for its nourishiuent upon the stored materials of the cell from which it arises. The ])ushing of the ascus after the com- plete development of the ascogenous cell instead of in direct con- tinuation of the development of the latter, also ])oints to a probal)le cessation and renewal of the reproductive activity of the ascogenous cell. 38 PEACH LEAF CURL: ITS NATURE AND TREATMENT. J II view of these facts, it seems possil^le that the asoogenous cells may be capable of enduring, under especially favorable conditions, a resting period of considerable time. Such resting ascogenous cells have ])een sought for upon the swollen branches of the peach, how- ever, without success. Further research along this line is desirable. As the fungus is already known to fruit upon the blade and petiole of the leaf and upon the blossom, and a vegetative mycelium is found growing thriftily in the swollen branches, there seems to be no good reason why the parasite may not fruit upon the infected twigs. The perpendicular growth of the developing asci in the leaf soon rup- tures or pierces the cuticle, and where large numbers of asci develop at the same time the cuticle is lifted, torn, and lost, the asci forming a more or less continuous plush-like surface growth. Isolated asci press through the cuticle so as to form separate perforations (PI. Ill, fig. 21). The contents of the forming ascus are finely granular, and as the ascus elongates these contents crowd into the upper portion and a septum is formed across the basal part in such a manner as to cut off the now emptied ascogenous cell as a stalk cell for the ascus (PI. Ill, fig. 15). When fully developed the asci are usually broader at the top than at the base, and often somewhat clavato in form. A series of asci measured varied in length from 34 to -11: yw, the average being 38 // ; the width of the asci ranged from 10 to 12 yu, and the height of the stalk cells varied from S to 13 yw, the average being slightly over 10 fi (PI. Ill, figs. 1-13). The formation of the ascospores in Exoascus deformans has not ])een carefully studied ])y the writer. Sadebeck has shown, however, for 7i'. turgidus^ that mitotic nuclear division occurs in the ascus in connec- tion with spore formation (Untersuch. iiber die Pilzgattung Exoas- cus, Hamburg, 1881, PI. Ill, fig. 20). The ascospores developed in the asci of E. defonaanx vary in numl^er from 3 to 8, the latter being the full and typical number. When mature they are surrounded by a moderately firm cellulose wall, which is rather inconspicuous, owing to its transparency. The spores are usually somewhat oval in foriu, being longer than broad, l)ut occasionally some are seen which appear nearly or quite spherical. Fresh ascospores sometimes show distinct nuclear phenomena. This has been observed with spores still within the ascus, as well as in many which have escaped. The nucleated appearance seems less common in budding or germinating ascospores than in those in a resting condition (PL IV, figs. 1, 2, 3, 4, and 10). The average length of the ascospores measured was Tjy yw, the length varying from 6 to 9 yw, and the average width was (iyV A*- varying from 5 to 7 yu. The ascospores escape from the ascus through an apical rup- ture of the latter. Germination of the ascospores has been observed by the writer to proceed in two ways: (1) By means of })udding oi- conidia formation; (2) by means of stocky germ tubes, often one branched and reseml)ling promycelia. DESCRIPTION OF PLATE IV. Germination of the ascospores and conidia of Exoaseus deformans. Figs. 1 to 12 (about 800/1) , ascospores, of which five show nuclear phenomena and several are budding. Figs. 13 to 21 (800/1) , thin-walled conidia, several of which are producing buds; the remaining spores, unnumbered, show various modes of promycelium formation or mycelial germination. BULL. 20, DIV. VEG. PHYS. & PATH., U. S. DEPT. AGRICULTURE. PLATE IV. Nevffoii H. Ileicr Hfl Tial ()n| GERMINATION OF THE SPORES OF EXOASCUS DEFORMANS. A.lloeii lb t'M. Uth. Bulli>i,>ir<.. GERMINATION OF THE SPORES. 39 Budding- of the ascospores occurs either before or after the escape of the spores from the ascus. In the formation of the bud conidia the process may take place from the ascospore direct, one conidium after another being produced, or the contents of the ascospore may pass into a thin-walled conidium nearly or (^uite equal in size to the ascospore, this large conidium then assuming the function of Inid production. Ordinarily the ascospore buds at one point only, but ))ud formation at two points has been seen. Budding occurs most commonly at one end of the ascospore, but occasionally lateral buds are observed. In the early stages of Inidding the ascospore sometimes shows a nipple-like swelling at one end, reminding one of the germinating end of the sporangium in the Peronosporece. The successive primary conidia bud- ding from an ascospore may become loosened and turned to one side by the following conidium, which swells from the same germ pore of the ascospore. In other cases several conidia may remain united with each other, but when this condition is observed it is frequently the result of the secondary or tertiary budding of the primary conidium, several orders or generations of buds remaining united. When the process of primary conidial budding- can no longer take place the empty ascospore may or may not become separated from the last primary conidium. With the exception of the case above referred to, the dif- ferent orders or series of conidia (primary, secondary, tertiary, etc.) when grown in pure water, are each smaller than the preceding, and the conidia are considerably elongated in form, sometimes almost cylindrical. The walls of the conidia are more delicate than those of the parent spore. In a suitable nourishing fluid, as the extract of malt, the conidia take up nourishment and increase in size, thus enabling them to continue the budding process for considerable periods of time, as in the yeasts (Saccharomyces). Whether the conidia of Exoascus deftmnans are able to induce an alcoholic fermentation through their growth in saccharine culture media is not known, but Sadebeck states that the conidia of other species of this genus certainly possess this fermenting power. The second method of germination of the ascospore of Exoascus deformans, that is, the pushing of germ tubes, is rarely met with except upon the host plant itself. Such mode of germination is shown in PI. IV. The germ tu]>e produced from the ascospore is usuallv much swollen near the spore and tapers considerably toward the extremity, though not infrequently considerable constrictions occur at one or more points in its course. It seems probable that this tube is in many cases capable of directly infecting the host, probably through a stoma, as observed by Sadebeck in Exoamus tosquinetii^ and that its function is not wholly the abjointing of sporidia. Such separation of sporidia, in fact, has not thus far been observed. The germ tube, or promycelium, is connected with the spore by a very narrow and short tube, with straight and })arallel walls. The same mode of con- nection is also observable in the formation of the bud conidia, and 40 PEACH LEAF OFRL: ITS NATURE AND TREATMENT. " reminds one of the sterigmata bearing the sporangia of PhytophtJiora mfeatans. Thus far efforts to induce filamentous germination of the liud conidia or of the ascospores of Exoaseits deformans in culture media have proved unsuccessful. Brefeld has worked with this problem for months, and the writer has frequently attempted to obtain this form of germination. ' Budding occurs, as already indicated, quite readily in various nutrient solutions, and short promycelia from the ascospores have l)een found in some cultures. In nearly if not all cases, however, the ascospores showing promycelia or short mycelial germination have shown that this germination occurred under natural conditions upon the peach leaf, the germinated spores l^eing transferred from the leaf to the culture in preparing the latter. It may be added here that the bud conidia are also formed in vast numbers upon the surface of the infested leaf after the maturing of the ascospores. It is largely these conidia which give the infested leaf the marked white appearance conmionly observed at the height of the disease. The leaf appears as if covered with flour or a heavy white bloom. RELATIONS OF THE FUNGUS TO THE HOST. Under a previous heading in this chapter the physical condition? which influence the serious development of peach leaf curl have ])een considered in accordance with the light which we now have relative to such influences, and there remain to l>e taken up at this time the more intimate and direct relations of the host and parasite. These relations include the action of the fungus upon the cell contents, the cell walls, and the cellular tissues of the host: the probable mode of infection and the spread of the parasite within the tissues; the wintering of the fungus upon the tree; etc. 'A very considerable number of cultural experiments have been tried. The cul- tures of ascospores and conidia have been subjected to temperatures much below the freezing point and to various degrees of heat in the thermostat. Sudden changes of temperature have been tried. Increased antl diminished amounts of oxygen, as con- trasted with that of the normal atmosphere, have been tested. Even a chamber filled with nearly pure oxygen has produced no apparent effect. Water from various sources, such as rain water, dew, ice water, distilled water, tap water, etc., has been tested. Solutions of the various sugars, malt extract, sterilized beer, plum extract, etc., were tried. Hanging drop cultures of various nutrient media and plate cultures of potato-peptone-sugar gelatin have not shown germination. Drops of variou- nutrient solutions placed upon newly forming leaves dissected from unopened peach buds and these held in moist chambers have given only negative results. The same is true for peach pits brought near to germination and the cotyledons treated with a weak solution of diastase, the spores ])laced between them and held at various tem- peratures in uioist chambers. Sections of such cotyledons with spores placed upon them were also prepared in moist chambers. A brief treatment of the spores with ether was tested without bringing about germination. Prillieux states that attempts to artificially infect the leaves or shoots have not thus far succeeded (Mai. d. Piantes Agr., Vol. I, p. 399). RELATION!^ OK THE FLTN(Jrs To TlIK HOST, 41 As already i ndicatct I. ( he writ crs work wit li sprays seemed to show t lial not more than a small i)ereeiitaiie of each yeai's iiit'eetioiis ordiiiai-ily arise from a perennial mycelium. In the LoncII oichaid. where the personally eondueted work w;is can-ied out. it would appeal- that not to exceed 2 to 3 per cent of tiie infections could have arisen from that cause. On the other hand it would seen) that at least t>5 per c«Mit of the infections arose from spores, for, as already stated, 95 to !>8 per cent of the spring infections could be pn>vented ))y a sinole spraying-, and this was actually accomplished where the spra^'ing- was done with sufficient thoroughness. It is believed by the writer, howev(M-. that these percentages will vary within mod(M'at(» limits in diti'erent locali- ties, with different varieties, and in different seasons. Tiie following observations will explain these views. The mycelium of diseased leaves is found to l)e connected through the leaf petiole with the mycelium of the infected limb. From the writings of Sadebeck and man}" others it might be supposed that the leaves were infected from the perennial mycelium in a majority of eases, and that the mycelium met with in the petiole of the leaf origi- nated from the perennial mycelium of the branch. That such spring infection really occurs from the wintering- myc(dium of the ])ranch should perhaps be admitted, but that such is the connnon mode of infection of the leaves is certainly doubtful. The writer's studies have shown that the mycelium in the branch close to a clustcn- of infected leaves diminishes in amount as it passes upward or downward in the branch from such leaves. This fact is as obvious from microscopic studies of the infested tissues as from the external hypertrophies observable to the eye. A macroscopic examination of diseased and swollen branches will show that the enlarged parts may extend upward or downward along the branch from the base of th(^ petioles of the leaves, which seem to represent the center of infection. In a majorit}' of cases these swollen ridges terminate before reaching another leaf bud, though in some instances they are seen to extend along the branch throughout the entire length of one or more internodes, and in such cases it is fair to suppose that the mycelium ma^^ have infected the young leaA'es of a second or third bud in its course. It should be remembered, however, that this mycelium, in a great majority of instances, indicates no connection with a previous year's mycelial growth, but has evidently just entered the l)ranch from one or more infected leaves. The microscopic evidence supports these conclusions, which are, to some extent, in harmony with Benton's observations, to be hereinafter consid(M-ed, l)ut th(^ writer is scarcely prepared to admit the large percentage of spring infections arising from now mycelium entering the branch which the observations of that writin- seem to imply.* The microscope shows that the hj'pha? which })ass away from 'Pacific Kural I'rcss, Auir. L', iSitO, p. SS. 42 PEACH LEAF CURL: ITS NATURE AND TREATMENT. the Inisc nH the k'uf petiole i^mdiialh" decrease in numbers as they recede from the leaves, and they appear to l)e wholly lost at a short distance from the point of entrance into the shoot. As a rule, little or no mycelium has been found extendinjj- more than 1 or 2 inches 1)eyond a point where external macroscopic evidence of disease exists. The preceding facts lead to the 'oelief that where mycelial infection of f<)liag(; takes place from the branch it is usually done in the spring from hyphte arising from spore-infected leaves of the same season, and that this occurs only in comparatively few instances or in bad cases of disease. The}^ also indicate that living perennial nwcelium which succeeds in accomplishing spring infection, is comparatively rare. Badly infested and swollen branches are apt to die and dry out, thus att'ording no living tissue for the support of the infesting myce- lium. Such l)ranches, even if living until the following spring, are not apt to produce much growth, and frequently produce none what- ever. Furthermore, the badly swollen mycelium-infested branches are comparatively few, and it is believed that the infested winter buds of these branches very rarely exceed 2 to 3 per cent of the total mmi- ber of buds upon the tree. Most branches appear to sutler from the disease only in an indirect manner, that is, by the fall of affected foliage. It seems probable to the writer, therefore, that the swollen branches, in which the swelling is apparent to the eye, constitute the true and almost exclusive home of the perennial mycelium, and there- fore supply the only possible source of spring infection by the win- tering h^'phjp, and conseqitentlv the only source of infection not controllable by spraj's. This is in harmony with the results of wide- spread orchard treatment. All but 2 to 3 per cent of infections have been prevented by a single spraying. (See the results of work on half-spraj'^ed trees.) That such spraying did not prevent the spread of the mycelium in the inner tissues of the host is shown by the fact that when it is delayed until the leaves have fairly started and have become infested, the treatment is ineffective and the disease will con- tinue to develop and both foliage and crop may be lost. It is not the checking of the spread of the mycelium from the branch to the new leaves, therefore, that results from spraying, but the prevention of the early spore infections from withotit; and as all but 2 to 3 per cent of the 3^ear's infections may be thus prevented, all of such infections must be considered as arising from spores. The limitation of the perennial mycelium of Exoasciis deformanx: io the swollen branches or branch parts, as here held, is in harmony with observed facts respecting other species of Exoascece. It is not under- stood, for instance, that trees developing witches' brooms are infested in all their branches, but that the branch-infesting mycelium is limited in its distribution to those centers which develop the abnormal nudti- plication of shoots, the swellings and other external manifestations of disease. (See Pis. I, V, and VI, and descriptions, in connection with DESCRIPTION OF PLATE V. Terminal peach twigs badly affected by curl. The mycelium of the fungus has entered the growing end of these shoots, and the conditions being favorable, it has developed to such an extent as to prevent further elongation of the twig, thus form- ing a compact head, with greatly shortened internodes. It is in shoots of this char- acter that the mycelium is found, and its extent is nearly coincident, so far as observed, with the swollen portions of the branch. Such swollen branches consti- tute a striking feature of the disease, but rarely involve more than 2 to 3 per cent of the buds of a tree. Specimens were collected at Santa Ana in the spring of 1899 and photographed natural size. (Compare with Pis. I and VI.) Bull 20, Div, Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate V. Peach Twigs and Leaves Affected by Curl. The (li.stril)Utivu niyceliuin of the I'uii^riis is I'dunil in such swulleu tinmclies. DESCRIPTION OF PLATE Xl. Sprayed and iinsprayed branches of Lovell peach trees in the experiment ]>lock at Biggs, as they appeared in 1895. The sprayed branches at the left show the large amount of fruit and healthy foliage on the s])rayed trees; the unsprayed branches at the right have lost most of their foliage and all the fruit from curl. These unsprayed Ijranches show the typical ami common effects of curl. Hypertrophy of the branch is not shown, and it is probal)le that these branches carry little if any perennial mycelium. Thorough winter treatment of such branches with proper fungicides will prevent 98 per cent of the spring infections and conduce to the development of foliage and fruit, as shown on the branches at the left. All these trees were equally infected by the fungus in 1893, when the orchard suffered severely from curl, and had the l^rancrhes at the left not been sprayed before the leaf buds opened in the spring of 1895, they would have been in the same condition as those at the right nf the j.lat*". (Compare with Pis. I, V, and VII.) Buil. 20. Div. Veg. Phys. &i Path., U. S. Dept. at Agriculture. Plate VI. CONCLUSIONS REGARDING SPRING INFECTIONS. 43 tlu^ l)rosont ivniarks on intVsttMl and noiiinfostod hnuichcs, ) It soonis [)r()lnil)lo, thorot'oro, (1) that most of thespriiio- intVctioiisof the pcju-h oc't'ur from spores which have wintered on th(> tre(>andal)out the lu^wly formed buds; (2) that most of the infectinl halves fall off without infectinj»- the l)raneh whieh bears them; (3) that the mycelium of badly diseased leaves sometimes infects the branch throujrh the leaf petiole; (-1) that such mycelium after entering- the branch may pass upward or downward, and in some instances may follow the branch foi- the length of one or at most a few internodes, and possibly infect one or two adjoining buds; (5) that badly infested branches usually die during- the year; while in comparatively few instances they may sup- port a living- mycelium capable of inducing spring- infection of opening l)ucls; ((>) that uiost infected branches show by external hypertrophy the presence of the parasite, which may commonly be removed by pruning- ott' the hypertrophied parts at a point a few inches below the swelling; (7) that seasons, atmospheric conditions, localities, and varieties ma}^ have a limited bearing on the extension of the mycelium in the branch and upon the amount of mycelium wintering in an active state, although the results of spraying- in many parts of the country, continued for several years, have shown the variation in these respects to be confined within comparativelv narrow limits. The direct infection of the peach leaf by means of the spores of Exoaseus deformans has not been seen. The efforts made to observe the germination and penetration of the fungus have already been touched upon. One thing seems certain, viz, that under ordinary conditions this form of infection occurs at a very early period in the development of the leaf, but evidently not before the opening of the leaf buds. Veiy young leaves are found to be already infected, but spraying just before the buds expand will prevent this infection, i. e., infection may be prevented by the treatment of closed buds, which would scarcely be true if a perennial mycelium were within. If we may judge by analogy, the germ tube of the fungus enters the leaf through a stoma. Sadebeck reports that such was his ol)servati()n in Kroascus tosquinetii^ in which species the germ tube creeps for a short distance on the leaf surface, and then enters a stoma, much as in the germination of the conidium of PIn/tojtIithora omnivora. The major portion of the spring infection of foliage occurs while the latter is young and tender, but it is observed that new infections may take place for a considerable time if the various inlluencing con- ditions continue favorable to the fungus. These conditions act chieHy in suddenly retarding the transpiration of the host, and some of them have already been discussed. On the other hand, a short period of spore infection may be expected when external influences are such that transpiration is rapid and normal. The longer or shorter course of the disease in spring- may be said to depend largely, therefore, upon the greater or less susceptibility of the tissues of the host, mostly 44 PEACH LEAF CURL*. ITri NATURE AND TREATMENT. resulting'- from utmosplioric iiiliiuMic-cs. The injuiy wliicli tlic fungus may do after infection is also dependent, where development of the fungus has not progressed too far, upon a verj^ nice bahince of the atniosplieric conditions. Newly infected leaves may be greatly distorted and fall at an early date, or they may be only slightly injured ])y the fungus, according to the atmospheric conditions prevail- ing and their influence toward softening or hardening the tissues and moistening the intercellular spaces of the host. A few days favorable to the drying and toughening of the parenchyma of the infested Leaf may entirely check the spread of the fungus. The action of the mycelium of E. deformaiis upon the tissues of the leaf and branch of the peach has ])een widely remarked. The hypertrophies of peach branches, due to this parasite, are as striking and characteristic as are the witches' brooms caused on other hosts by various ExoascecB. In the case of the peach, however, there is rarely if ever any increase noted in the number of shoots, as upon the cherry, the hypertrophy manifesting Itself in enlargements and twistings of the infested branch. There is often a great reduction in the length of the infested portion of the shoot and a shortening of the internodes, so that the approximated and enlarged leaves give a tufted or plumed appearance to the shoot. An examination of transverse sections of such enlarged shoots shows that the enlargement is due to a great increase in the number of cells of the cortical parenchyma, and frequently an entire separation of such cells into a network or series of chainlike cells. The structure of the infested parenchyma is altered, the cells being- enlarged and much more angular than normally, while the thickness of the tissue from the bast libers to the epidermis is frequently eight or ten times as great as usual. The parenchyma cells lose the chloro- phyll and all matter which the eye can detect, becoming quite trans- parent. The cell walls vary much more in thickness than normally, some of them being heavier and others lighter than in healthy cells. Transverse and longitudinal sections of swollen peach twigs show that the pith cells are greatly injured along the course of the infesting mycelium. The location of the mycelium ma}^ often be detected by treating transverse sections with Bisuiark brown, the infested medul- lary tissue taking less stain than that not harl^oring the fungus. The walls of the healthy cells of the medulla become reddish brown, while those of the infested tissue assume scarcely more than a light yellow or yellowish brown. The cells of the infested tissue are also much more angular and irregular than those in which the mycelium does not exist, while in some instances the cells collapse. The action of E. deformans on the tissues of the peach leaf has been considered by different writers, as Prillieux,^ Knowles,^ and others. iPrillieux, Ed., Mai. d. Plantes Agr., Vol. II, pp. 394-400; also Bull, de la Soc. But. de France, 1872, T. XIX, Comp. Rend. d'Sci., 3, pp. 227-230, ^Knowlcs, EttaL., Bot. Gaz., 1887, Vol. XII, pp. 216-218, with piau^ ACTION OF THE FUNGUS ON THE LEAF TISSUES. 45 The l)adly intVstcd Icavos hci'oinc groatly inc roused in thickiie.s.s uud breadth and the weij^'ht is often much increased above the normal, the tissiu>s l)ec()me stifi'ened in a coriaceous or cartihiginous manner, tiie cell walls become j^reatly thickened, and the cells becomes more com- l^ressed. The cells of the palisade tissue are increased in size and number, and suft'ei- an entires loss of chloi'opiiyll, as in the case of the cortical parenchyma of the l)ranch. The walls of the epidermal cells become considerably thickened and the nuiltiplication of the paren- chyma cells on either side of the midri)) causes a pronounced gather- ing- and distortion of these tissues. As the midrib docs not elongate in proportion to the increased extent of the parenchyma, it acts as a gathering string passing through the leaf from end to end, and the })arenchyma becomes folded upon itself. The increase in the number of cells occurs more extensively among the palisade tissue of the upper half of the leaf than among the cells of the spongy parenchyma of the under leaf surface; hence the majority of badly diseased leaves are convex above and concave below, though this appearance is often lost sight of, owing to the number and varietv of folds which the leaf l)lade assumes. CHAPTER III. HISTORY OF THE TREATMENT OF PEACH LEAF CURL. THE EUROPEAN SITUATION. That the present outline of the gradual development of methods for the treatment of peach leaf curl in the United States may be properly appreciated, it is desirable to first show the conditions prevailing in Europe as presented hj some of the leading European writers on plant diseases. Prillieux, in an interesting paper on peach leaf curl, pre- pared in 1872, describes the fungus Exoascus deforiuans and its action on the tissues of its host.^ He states that the fruiting fungus should be looked upon as the center of infection, and that it is desirable to remove the diseased leaves as thoroughly as possible and to destroy them. He also states that this work should be supplemented by the cutting ofi' and burning of diseased branches. In 1878 Winter'^ stated that the only wa^^ to prevent this disease is to destroy the fungus by caref ulh- removing the affected leaves, and by protecting the trees from rain during the unfolding of the leaves, as rain favors the spread of the parasite. The same year Felix von Thiimen wrote of Exoascus ])rxm{^ the fungus causing plum pockets and closely related to Exomcim defor- nuins of the peach, ^ but made no recommendations for its treatment. In 1885, however, he again spoke of the plum pocket disease and pointed out that it can not be removed except by severe cutting back of the new and old wood of the affected trees.* In 1880-81 Frank, in the second volume of the first edition of his work on plant diseases, rec- ommends the cutting back of the twigs as a cure for leaf curl, and the quick removal of the diseased leaves for prevention.'^ In 1886 the well-known work of Sorauer on plant diseases^ appeared. The treatment recommended by this author is somewhat similar to that recommended by Frank. He says, in speaking in a general way ^Prillieux, Ed., Bull, de la Soc. Bot. de France, 1872, T. XIX, pp. 227-230. - Winter, Dr. Georg, Krankheiten der Kulturgewiu-hse, Leipzig, 1878, p. 47. ^Thiimen, Felix von. Die Pilze und Pocken auf Wein und Obst, Berlin, 1878, III, Fungi Pomicoli, pp. 88, 89. ^Thiimen, Felix von, Diebekanipfungder Pilzkrankheiten unsererKulturgewiichse, Vienna, 1886, p. 71. ■^ Frank, Dr. A. B., Die Krankheiten der PHanzen, Breslau, 1880-81, Theil II, p. 526. " Sorauer, Dr. Paul, Handbuch der Pflanzenkrankheiten, second edition, Theil II, p. 281. 46 HISTORY OF TREATMENT. 47 of the Ex<)iif Imds, and he roconnnends the removal of isohited slijrhtly diseased leaves soon after the first appearance of the blister-like swellings. When through the attaek of a majority of the leaves of a branch it is shown that the mycelium is already present in the axial organs, it is advised that all of the young wood of the affected })ranches be cut off. Hartig de- scribed peach leaf curl in 1889,^ and again in the Englisii edition of his work published in 181>4,'' but he leaves the su])ject without makimr any suggestions as to treatment. In 1890 Dr. Kirchner published a work on plant diseases," in which he recommends the cutting off of diseased l)ranches for the control of the disease. In 1891. Dr. Comes, in writing of this disease, states that no direct means for combating the parasite -exists. He discusses the gathering and burning of dis- eased and fall(>n leaves, the cutting back of inf(>cted branches, and the application of cultural methods in their influence on the disease.* A most excellent work on plant diseases by Dr. Tubeuf appeared in 1895. ' This writer groups the diseases caused b}^ the ExoaacfH' among those maladies Avhich should be combated by the removal of the diseased living plants and plant parts (pp. 86, 87). The second edition of Frank's work on plant diseases appeared in 1896, fifteen vears after the publication of the first edition, but the same recommenda- tions for the treatment of curl are again made, word for word." In all the preceding works there is no recognition of the methods of treat- ment l)eing adopted and discussed in the United States and in Aus- tralia. The recommendations for cutting away the diseased branches so generally presented are the same as advanced by P^hrenfels nearly a century before for the control of mildew of the peach." It is hardly necessary to say here what most orchardists have learncHl by experience, that is, that it is impossible to eliminate the diseas«> by ordinary cutting back of the branches, and that in tlxc orchai'd it is equally impracticable to prevent the disease by the early removal of the diseased leaves. About this time the work l)eing done on this disease appears to have attracted the attention of Europeans. In 1894, in his work on vege- table parasites, Berlese recommends for this disease in Italy the use 'Hartig, Dr. Robert, Lehrlmch der Baumkraiikheiten, Berlin, 1889, pp. lis. Hit. -Idem, The Diseases of Trees, London, 1894, pp. 132, 13.3. ^Kirchner, Dr. Oscar, Die Krankheiten nnd Besehiidiguiijren niisercr laiidwirl- schaftlichen Kulturpflanzen, Stuttgart, 1890, p. 324. ♦Comes, Dr. 0., Crittogamia Agraria, Naples, 1891, Vol. I, pp. 167,168. ^Tubeuf, Dr. Karl Freiherr von, Pflanzenkrankheiten dnrch kryptngamc I'ara- siten verursacht, Berlin, 1895, pp. 86, 87, and 184. ^Frank, Dr. A. B., Die Krankheiten der Pflan/en, secoinl edition, I'.rfsian, 1896, Bd. II, pp. 249, 250. "Ehrenfels, J. ]\I. Ritter von, Ueber die Krankheiten und Verietzungen der Frucht- oder Gartenbaume, Breslau, 1795, p. 225. 48 PEACH LEAF CURL: ITS NATURE AND TREATMENT. of Bordeaux mixture in the .spring, although he adds, as if doubting its utility, that the mycelium of the parasite winters over under the cortex of the branches/ In France, in 1895, Prillieux published the first volume of a work on plant diseases, devoting several pages to the consideration of peach leaf curl.' In this work the recommendations for treatment appear- ing in his paper in 1872 are not given, but instead it is stated that treatuionts with the salts of copper seem sometimes to produce good results in preventing the multiplication by spores; but, as in the case of Berlese, he adds, as if in doubt of the value of such treatments, that they are without effect upon the perennial mycelium hidden in the tissues. By the year 1898 the true idea of the preventive treatment of curl had been grasped in Germany. Professor Weisz, in his paper on plant diseases,^ published that year, cites the present method of con- trolling curl. After renewing the older recommendations to cut off and burn the affected twigs, he says that the trees should be sprayed with copper-soda or copper-lime solution (eau celeste or Bordeaux mixture), the first time hefore the buds open. That these recom- mendations are not the results of work done by Weisz, however, appears probable, for his description of the disease is evidently quoted, as he falls into the error of Winter, Frank, Kirchner, and other writers in stating* that the bloom produced by the fruiting of the fungus appears upon the under surface of the leaves. Had he worked upon this disease in the field he would not have been apt to follow the above authors in their erroneous description of the fruiting habits of the parasite. DEVELOPMENT OF THE PRESENT METHODS OF TREATMENT. The successful treatment of peach leaf curl dates from the time when fungicides were first applied to dormant peach trees. So far as learned, this treatment was first practiced in California, being intro- duced by the winter application of sprays for the destruction of the San Jose scale {^AspldiotuH: 'pernlciosus). This insect was first discov- ered in the Santa Clara Valle}^ about 18T0, Init some time had elapsed between the date of its introduction and the use of the stronger winter sprays for its control. Caustic soda and potash were early tested against this insect, and afterwards sulphur was added, the sulphides of potassium and sodium being used by many growers. Somewhat later whale oil soap and sul- ' Berlese, A. N., I Parassiti Yegetali delle Piante Coltivate o Utili, preface dated 1S94, pp. 124-126. '■^Prillieux, Ed., Mai. d. Plantes Agr., Paris, 1895-97, pp. 394-400. ^ Weisz, J. E., Die schiidlichsteii Krankheiten unserer Feld-, Obst-, Gemuse- und. Ciarten-Gewachse, ]SIiinchen, 1898, p. 45. HISTORY OF TREATMENT. 4'.) phur were eoinbineil hy l)oiliiio-. and still hittT a fau>tic >\)Vi\.y contaiii- ino- lime was tested. AH the ahove cheinicals. cvfii the milk of !im<\ wore applied to dormant trees, and they are all known to possess sutK- cient funoieidal aetion to control peaeh leaf curl to a lar«i-o extent if applied to the trees shortly befpre they bloom. While many growers were using these etiustie and sulphide sprays, another spray eontaining nuieh larger (juantities of sul})hur was being used, and proved of nuich greater power, both as a fungicide and insecti- cide. This was a spray containing sulphur and lime, or a sulphide of calcium, and the history of its introduction is of special interest and is inseparable from the early hi.story of the treatment of lurl. Mr. Alex- ander Craw, quarantine officer of the California State Board of Horti- culture, has published an account of the introduction of this spray in a recent number of the Pacific Rural Press,' but the following facts were gleaned froiu those who were the tirst to use and introduce the spraA'.'" !Mr. A. T. Covell, who tirst applied this spray to dormant peach trees, near Fresno, Cal.. does not supph' exact dates relative to the work, but Mr. N. W. Motheral, of Hanford. and Mr. I. H. Thomas, of Visalia, agree in placing its iirst use as a spray in the year 1880 or 1881. The writer is informed by Mr. Motheral that the lime, sulphur, and salt solution was originally used as a sheep dip in Aus- tralia, where it was known as the ''Victoria lime-and-sulphur-dip" for scab. He states that it was recommended I)y a Dr. Rowe, and offi- cially indorsed for a sheep dip in that country. This dip. it is also said, was introduced in California by Mr. Charles Hobler. of Hanford. and Mr. Hobler claims to have first recommended it to ^Mr. Covell. then living near Fresno, for the treatment of his infested peach trees. Mr. Covell disputes this claim, but holds that he (Covell) first used this solution as a spray upon his trees with success in the control of the San Jose scale. As soon as this spray was found to be a practical suc- cess, ]Mr. Covell, ]Mr. Thomas, and Mr. Motheral worked for its gen- eral adoption in the treatment of scale. Mr. Thomas states that he sprayed his own orchard the winter after seeing the action of the spray on Mr. Covell's trees, and about this time the facts were given to the press. Mr. Thomas writes that thi.s spraj' was in general use in and about Visalia as earlv as 1883, 1884, and 1885, and in Mr. Motheral's .section, near Hanford, at the same time. It may here 1)0 stated, however, that lime and sulphur had l)oen united by boiling in water and used as early as lS'y2, at least in hothouses, for controlling the dis- eases of plants. (See Revue Horticole, 1852, p. 168, and Gardeners' Chronicle, 1852, p. 419.) 'Pacific Rural Press, July 29, 1S99, p. 6S. ^Letters from I. II. Thomas, Visalia, Cal., Sept. 6, 18W; X. \V. Motlieral, Han- ford, Cal., Sept. 6, 1899; and A. T. Covell, Woodbridge, Cal., Oct. \:i, 1899. 19093— No. 20 4 50 PEACH LEAF CURL: ITS NATURE AND TREATMENT. It will be seen hy the preceding outline that jstrong fungicidal spraj^s were in general winter use upon peach trees throughout much of Cali- fornia in the years 1880 to 1885, during which time the peach or- chards of many portions of the State were Ijadly affected by curl. In a report by Mr. W. G. Klee. who inspected the orchards in man}- counties of California from July to September, 1886, it is stated that in Alameda County the cultivation of peaches must be confined to such varieties as are very little subject to leaf curl ; in Santa Cruz County, that ' ' peaches, of course, are subject to curly leaf, and can not, as a general thing, be considered prolital)le;" and that in the Santa Rosa Valley the peach is "of course subject to curh" leaf.''^ As peach leaf curl was quite prevalent throughout California in 1880-85, and as a large number of peach growers treated their dor- mant trees with fungicidal sprays during that period, it is not strange that they soon learned that the winter sprays prevented curl. Mr. I. H. Thomas, of Visalia, informed the writer^ that it was about the year 1885 that he noticed that the orchards sprayed with the lime, sulphur, and salt solution were entirely free from leaf curl, while orchards con- tiguous were affected so badly that all the foliage fell off". In 1886 Mr. ^\. G. Klee said.^ when speaking of an inspection he made of the orchard of Mr. A. Block, of Santa Clara, Cal. : "A treat- ment of peaches affected with curly leaf attracted my attention. Trees not subjected to this treatment were in verv poor condition, while the others, favored with it, were in fine, healthy bearing.'* Mr. Block says respecting this work* that he was making experiments for the destruc- tion of scale insects when he detected a perceptible difference in the amount of curl on the treated and the untreated trees. He thinks this was one or two years before Mr. Klee had seen his trees in 1886. After having noticed the action of the sprays applied for scale in the prevention of curl, he went to work to ascertain what particular ingredient caused the prevention of the fungous disease. These direct experiments, Mr. Block states, were carried out on a row of 23 trees in his orchard. Among the chemicals tested were caustic soda, caustic potash, carbolic acid, tobacco, and sal soda, all more or less coml)ined with whale oil. Among the numerous sprays used, Mr. Block thinks that a strong solution of caustic soda gave the best results. All these sprays were applied while the trees were dormant.^ The stronger ^Klee, W. G., Reports and Papers Ijy the Inspector of Fruit Pests, read at Sacra- mento, November, 1886, Kept. Cal. State Bd. Hort., 1885-86, pp. 344, 347, 349, 350. 2 Letter dated Visalia, Cal., Sept. 6, 1899. •^L. c, p. 347. * Letters dated Santa Clara, Cal., Sept. 1 and 10, 1899. ^ It may be noted that whale oil soap was thus used by Mr. Block with success against ciirl in 1885 and 1886. Prof. L. R. Taft, in a letter dated Agricultural College, Mich., Aug. 31, 1899, says that he had good results in the treatment of curl with limewater, lye, and whale oil soap. (See also records of experiments by the writer with milk of lime, etc.) Mr. F. M. Webster reports satisfactory results with whale HISTORY OF TREATMENT. 51 caustic spra}' recommended by Mr. Block consisted of I pound of ;>8 per cent caustic soda to 6 or T gallons of water. The same year. 1n8(j, Mr. Sol. Runyon. of C'ourtland. Cal., reported that he had met with success incontroUino- a ■"1)lii;ht" of peach trees, the name of the dis- ease not ])eing known to hini. This })light had })r('\iously caused all the leaves to fall from every tree he had. especially the youiit-- ones. He used a caustic spray on the dormant tree, as did Mr. Block, and states that the trees which he treated were not atiected by th(> blig-ht at all. while the untreated trees, right l)eside the treated ones, were badly atiected.^ There is little dou))t that Mr. Runyon was treating curl, as it is a xevy serious trouble in that section of the State. After the leaves had fallen in the autumn of 1886 and during- the winter of 1886-87, ]Mr. Runyon sprayed many of his peach trees with a spra}' composed of 2 gallons fish oil, 10 pounds of caustic soda (98 per cent), and 5 pounds of copper sulphate to 100 gallons of water. This spray, as applied, was certainly a preventive of curl, and as a portion of his peach trees were left untreated the contrast should have been marked. Unfortunately, however, 1 have been unable to get further details of this early work with copper sulphate, as Mr. Runyon is no longer living.^ In November, 1888, Mr. W. G. Klee stated at the Chico meeting of the California State Board of Horticulture, that an experienced and suc- cessful fruit grower in San Jose had used successfully for the purpose of killing scale insects, the so-called sal soda and whale oil wash, and that he maintained that ever since he had been using that wash he had been free from leaf curl in his orchard.^ Mr. Joseph Hale, of Stock- ton, Cal., reports * that he sprayed his peach trees, while dormant, in the years 1888. 1889, and 1890. as well as in subsequent years, and that as a result he sustained no loss from curl during these j'ears. He used the lime, sulphur, and salt spray. ^Ir. G. W. Ramsey, of Lotus, Cal., states that he began spraying his orchard with lime, sulphur, and salt in 1890 or possibh' in 1891, In 1895, in writing of his past spray work, he states that his trees had not been affected in the least bv leaf curl since he had ])een using the above wash. He says: "It completely exterminated the scale the first two years I used it, but I continue to apply it to my trees once a year to prevent leaf curl." He further states that this wash nuist be applied when the ])uds are dor- mant, and that it is generally applied in February in his section. oil soap (South AiL«tralian J^nirnal of Agriculture, Marcli, 1899, Vol. II, No. 8, p. 630) ; see also the results reported by Henry Rofkar and W. V. Latham &. Son, of Catawba Island, Ohio, as reported by A. D. Selby, Bull. No. 104, pp. 208, 209. Ohio Agr. Exp. Sta., March, 1899. 'Rept. Cal. State Bd. Hort., 188.3-86, p. 221. -Il)id., 1887-88, p. 93. "Rept. Cal. State Bd. Hort., 1889, p. 172. * Reply to circular letter of Nov. 25, 1893. 52 PEACH LEAF CURL! ITS MATURE AND TREATMENT. As earl}' as 1890 the efl'ectiveness of lime, sulphur, and salt against curl appears to have been observed in Oregon. Mr. J. D. Whitman, of Medford, Oreg., who was horticultural commissioner for the third district of that State, wrote under date of January 27, 1S!>4, that four 3^ears' observation as commissioner had demonstrated beyond a doubt that a spray of lime, .sulphur, and salt is an effectual remedy for leaf curl. He states that the application in ever}^ instance w^as made for the purpo.se of destroying the San Jose or pernicious scale, and gener- alh' on only a portion of the orchard, the other portion showing the curl as usual. The lirst practical experiments with copper sprays on dormant trees for the control of curl, after the sprays applied by Mr. Sol. Runyon in 1886 and 1887, were conducted, so far as learned, in the 3'ear 1890. The siunmer use of these sprays had been tested in Australia, and proba))ly elsewhere, for several years, but with slight success in the control of curl. About the 1st of Deceml^er, 1889, Mr. L. E. Benton, then of Berke- ley, Cal., wrote to the United States Department of Agriculture for information relative to the nature and treatment of curl. These inqui- ries were answered at length, the literature on Kroascus deformans being quite fully cited. No method of controlling this disease was then known at Washington, and as winter spra}" ing had not yet reached its present importance, the reco'mmendations for treatment were nec- essarily inadequate, and were based upon the then accepted views respecting the strict perennial nature of the mycelium of the fungus, and the consequent difficult}' of controlling the parasite by sprays. After gathering such information as he desired, Mr. Benton insti- tuted a series of spraying experiments in the university orchard at Berkeley in the spring of 1890. The work done by ]Mr. Benton, although limited in extent, was of the utmost practical importance, as well as of great theoretical interest. A summar}' of his results was published in August, 1890.^ Three copper ,spra^^s were tested, the annnoniacal copper carbonate, basic copper acetate solution, and Bor- deaux mixture. The ammoniacal copper carbonate was applied on February 28, 1890, before the opening of the buds. All three of the sprays mentioned were also tested soon after the leaves started. The results demonstrated that winter treatment of the trees with the salts of copper will effectivel}' control the disease, but that summer treat- ment Avill not control it, and also that infection of the spring growth b}' perennial un^celium was the exception and not the rule with this disease — facts of the utmost practical importance for the orchardist. Mr. Benton's studies likewise led him to the view that the m^'celium, passing from infected leaves to the stem, is able to infect new foliage 1 Pacific Rural Press, Aug. 2, 1890. HISTORY OF TREATMENT. 58 by following- close ))ohind the growing point of tho stem. His o])serva- tions seemed to point to this young niyoeliuni. ivsulting from tlic iirst spring infections, as the source of the later infections through the branches rather than tiie perennial mycelium of the previous year. He says that not only does the fungus live in the leaf of the peach, but it at once pushes its way into the young growing stem, following the growing point as fast as it lengthens und passing into the leaves as fast as they appear. On this account he concludes that no external appli- cations can stop such a fungous growth, and spraying after the buds burst and the fungus has become estal)lished will have little effect. It ma}' be added that several 3'ears' ol)servation in large Ijlocks of trees sprayed after the foliage had started lias shown the writer that the dis- ease can not thus l)e controlled, and that ]Mr. Benton's conclusions are correct. Whether this failure is due to the causes pointed out by ]\Ir. Benton, however, or simply to the lack of the prevention of the infec- tion by spores, or to both sources of infection, should be giA'en further study. Mr. Benton states that in the spring of 1890. the time his experiments were undertaken, '"no remedy was known; since, some practical growers have found successful means of comliating it. and these experiments now deserve no further credit than that they were intentional and not a matter of chance." It is now known that curl had been controlled l)y numerous growers in widely separated regions in California through the use of various sprays many years prior to 1890. Mr. Benton says he was unaware of tliese facts when he began his work, and his experiments are worthy of full credit, not alone for the enterprise shown in undertaking them. ])ut for the results of unquestioned A'alue to which they led. In 1891 the copper treatment for peach leaf curl was independently discovered and clearly demonstrated in Australia. The successful results of this work were observed in November and Deceml)er. 1891, and were published in the South Australian Register of March 80. 189*2. At a meeting of the Nuriootpa branch of the South Australian Agri- cultural Bureau, held in Angaston during November. 1890, the sub- ject of fungous diseases atiecting fruit trees was discussed and the appointment of a committee to conduct preventive experiments was considered. At a subsequent meeting Messrs. F. C. Smith. W. Sage, and A. B. Robin were selected for this work. During the interval before spraying, Mr. Smith corresponded with those in charge of the pathological departments in Australia. England. California, and Wash- ington. The report in the South Australian Register says that among the replies received was a series of valuable reports from Professor Galloway, showing that up to 1889 modified can celeste, annnoniacal copper carbonate, and Bordeaux mixture had proved most successful in the United States. "These were therefore selected by the commit- tee for their experiments." Mr. Smith, of this committee, informed 54 PEACH LEAF CURL! ITS NATURE AND TREATMENT. the writer that their work was based largely upon that of Prof. E. S. Goff on Fusicladium.^ The spray work was begun in July, before the trees leafed out, the main object being to control apple scab and the shot-hole fungus on the apricot. The sprayed apricot trees belonged to Mr. Trescowthick, and were treated with Bordeaux mixture. In the block was one peach tree, which was sprayed when the apricots were treated. This tree had suffered severel}^ from curl, so much so, in fact, that it had not borne for four or five years, but after spraying it yielded eight cases of fruit of 50 pounds each, or -iOO pounds, the curl being almost entirely prevented. Mr. Smith writes, respecting this work, that when apph'ing Bordeaux mixture from July to October, 1891, for the various diseases with which they w^ere coping he had not the slightest idea that this or any of the fungicides would have anj^ effect whatever on curl leaf, and the members of the committee were the more sur- prised to see its marvelous effects in January and February. ' ' It was the most conclusive of all our tests," it was stated." The work was continued the following season, and some contrasts obtained on the place of Messrs. Sidney Smith & Son, of Yalumba, are of interest in this connection. In an article published at that time it is stated that the effects of spraying with Bordeaux mixture upon both peaches and apricots were very noticeable. On one side of the fence was seen a healthy set of trees, well clothed with fruit and dark green foliage, and with no curled leaves, while on the other side, where spra}'- ing had not been done, was a block of apricots, among which were a few peach trees very badl}'^ attacked by leaf curl. At this time the orchard of Mr. A. B. Robin, of Nuriootpa, secretar}^ of the committee for experiments, was inspected b}^ Mr. Molineaux, general secretary of the South Australia Agricultural Bureau, and by several prominent horticulturists, and was found to have a splendid crop of fruit, nearly all the apricot and peach trees having been sprayed. One peach tree had been sprayed on only one side with the Bordeaux mixture, and on this side the foliage was clean and health}^, while on the unsprayed side it was curled. "Here again," says the reporter of this examination, "was absolutely conclusive evidence of the preventive effect of spray- ing for curl leaf." In the United States, in 1892, the use of both the sulphur and copper sprays on dormant trees was much more common. The control of curl was a new discovery to several growers who had not heard of the published experiments. Mr. George Woolsey, of lone, Cal., had been considerably troubled by a shot-hole fungus affecting peach twigs — a conunon trouble in the northern portion of the State. A bundle of the affected twigs was sent to Professor Woodworth, of Berkelev, who 'Letter dated Angaston, South Australia, Feb. 11, 1895. ^Letter dated Angaston, South Australia, Apr. 6, 1895. HISTORY OF TREATMENT. 55 advised the use of Bordeaux mixture; but us this fungus i.s active in the spring before the trees leaf out, Mr. Woolsey spraj'ed the trees while dormant. He says, in relation to his results, that ho found Bordeaux mixture corrected the trouble with the twigs, and at the same time acted as a specific for the leaf curl. ^ His work for the control of curl in the following year was strikingly conclusive as to the effectiveness of this spray. Mr. D. W. Sj'lvester, of Gej'serville, Cal., conducted some spraying experiments in 1892 with the direct object of controlling curl. His spray was composed of 12 pounds of copper sulphate and 20 pounds of lime to 100 gallons of water, and was applied to the dormant trees. Mr. Sylvester states that having formed the opinion that the disease was of fungous nature, and knowing of the value of copper sulphate as a fungicide, he determined to test it against curl. He believed better results would be obtained by killing the "germ" than by waiting until the disease appeared, and this, he says, induced him to make the appli- cation to the dormant trees. For the experiment he selected a row of 10 trees, spraying 5 and leaving 5 unspraved for comparison. He states that the 5 sprayed trees held their leaves and fruit and bore a crop, but the others shed every leaf and every peach, and for more than a month looked as if a fire had gone over them. In spite of this experience, Mr. Sylvester neglected to spra}' in 1S03, when, he states, the trees shed all their leaves and nearly all their fruit through curl, ^ and adds that the best time to spray is just as the buds begin to swell. A portion of the peach trees on the Rio Bonito ranch at Biggs, Cal., were sprayed with the lime, sulphur, and salt spray in 1892, the spray being applied to the dormant trees as elsewhere. The contrast that season between the sprayed and unsprayed trees was well marked, the unspraj'ed trees l)eing much affected by curl, while those treated were practically free from it. These observations were made at the time by Mr. McDonald, the foreman, and by others on the ranch. The preceding examples could be greatly extended if necessary, as winter spraying was a common practice in California after 1885. By 1892 the San Jose scale had also become more widely distributed in Oregon, and was being quite general!}' treated by ^vinter sprays in that State. Mr. A. H. Carson, of Grants Pass, Oreg. , began spraj'ing his orchard about this time. In reply to a communication sent to him November 25, 1893, Mr. Carson saj's that his knowledge as to the lime, sulphur, and salt remedy for leaf curl was gained by observing that trees on which this remed}- was used to destroy the San Jose scale were not affected by curl, although they were varieties much subject to the disease. On the other hand, he states that unsprayed trees, with the same conditions as to exposure, altitude, etc., were badly affected. Mr. J. H. Stewart, of Medford, Oreg. , writes that he spra^'ed his peach ^ Letter dated lone, Cal., Aug. 26, 1899. 2 Letters dated Geyserville, Cal., Nov., 1893, and Sept. 18, 1899. 56 PEACH LEAF CUKLI ITS NATURE AND TREATMENT. trees in 1892. ^ He saj's he used a spray in 1892, 1893, and 1894, which was effectual against scale and most fungi. This spra}" was composed of lime, sulphur, and sulphate of copper, and was applied in the winter. In the East, about this time, mildew, brown rot, black spot, rust, and curl were attracting the attention of peach growers and causing serious losses in some sections, and a good many growers were trying- summer sprays for the control of one or more of them. Mr. F. P. Herr, of Ridgely, i\Id., writes^ that for three successive years prior to 1895 he sprayed with limewater, Bordeaux mixture, and arsenical mixtures, and that everything he used produced aljsolutely negative results, except the arsenites, which injured both foliage and fruit. It would appear probable from these results that the sprays were applied too late to be effective against curl. Mr. L. B. Geiger, of Hoffman, Pa., writes^ that he was formerly troubled with leaf curl in his orchard, but has had verj^ little of late years. The reason of this, he thinks, is the fact that he has sprayed his peach trees with Bor- deaux mixture several times each 3^ear since 1892. He states that at least To per cent of the crop of one variety was thus saved. Whether the spray work was done in the winter, or whether, owing to the number of applications made, the summer spray persisted in its action through the following winter, is not known. It was in 1892 that Prof. L. R. Taft, of the ^Michigan Agricultural Experiment Station, first obtained the idea that peach leaf curl could be controlled l)y the application of winter sprays. This gentleman has supplied the leading facts respecting his work.* He says: "In 1892 I was making a series of experiments with Bordeaux mixture and solutions of copper sulphate to learn the strength that could be used upon various plants and trees without injury. These materials were applied at different times, the sprayings being at intervals of about four weeks, from April to July, and while some trees received but one application, others were sprayed two, three, and four times. It was noticed, the trees sprayed in April with either copper sulphate or Bordeaux mixture had no curled leaves, while unspra^'ed trees and those that were not sprayed until June or July were seriousl}' injured by leaf curl. "From the marked difference in the injury from the leaf curl to the spra3'ed and unsprayed trees, I felt ver}- confident that the disease could be held in check to a large extent b}^ the use of fungicides, and in writing Bulletin 92, in December, 1892 (published in March, 1893), I make the statement that ' it is quite certain that the disease can be, to some extent, held in check bj' their use,' in referring to the effect 1 Letters dated Medford, Oreg., Dec. 14, 1894. ''Letter dated Ridgely, Md., Feb. 15, 1895. ^Letter dated Hoffman, Pa., Mar. 18, 1895. ^Letter dated Agricultural College, Mich., Aug. 31, 1899. HISTORY OF TREATMENT. 57 of fungicides in preventing- the development of leaf curl on peach trees." It would seem that the work in Australia, as well as that of the pre- ceding ten 3'ears in California, had not come under the notice of Pro- fessor Taft at the time of his observations in 1892. and that the same was true at the close of the succeeding year's experiuK^nts. In his article on curl, published in the American Agriculturist for February, 1894, he says,^ in speaking of the treatment of curl prior to his work in 1893: ''Although there were some vague suggestions as to the possible value of some of the fungicides as remedies for this dis- ease, nothing was reallv knoAvn until the past season."" jNIay 20, 181»3, while working on plant diseases at Yul)a City, Cal., in company with Mr. R, C. Kells. then horticultural commissioner of Sutter County, that gentleman told the writer of a peach orchard in the vicinity where peach leaf curl had been controlled hy the previous winter's sprays. The orchard was that of Mr. W. H. Campbell, of Yuba City, and was at once examined by the writer in company with Mr. Kells. The trees were of the Orange Cling variety, and had l)een sprayed with lime, sulphur, and salt up to the base of the smaller liranches of the main limbs, for the purpose of killing the San Jose scale upon the older wood, the spraying of the tops of the trees not being necessary. The result of this treatment was to protect the lower half of the trees from the attack of curl, while the tops were left unprotected. Curl developed seriously in the Sacramento Valley that spring, and as a consequence these trees were badly diseased and stripped of foliage down to the line where the limbs had been sprayed for San Jose scale. The resulting appearance was most striking, and showed the advantages of spraying in a marked degree. The lower half of the trees was well supplied with normal green foliage, while the upper half was either bare or the leaves present were yellow and Ijadl}' curled. Photographs of these trees were taken on May 21. 1893. Ma}' 22, 1898. the writer visited the Riviera orchard, at Live Oak, Cal. This orchard is situated on the Feather River bottom and is under the management of Mr. A. D. Cutts, of Live Oak, one of the proprietors. In this orchard was found a most striking case of the pre- vention of cull by the use of winter sprays. In the winter of 1892-93 one block of trees was thoroughly' sprayed for San Jose scale with lime, sulphur, and salt. After this work was completed the weather became unfavorable for further spraying. The soil was so wet from rains that a 40-acre block of Crawf ords Late trees could not l)e sprayed, and it was so late in the winter before the work could be done that Mr. Cutts feared it might injure the fruit buds if he sprayed the trees entire. He therefore had the trees in this block examined, and rags were tied upon the limbs of those which appeared to most need a thorough ^The Curl of the Peach, American Agriculturist, Feb., 1894, pp. 71, 72. 58 PEACH LEAF CURL*. ITS NATUEE AND TREATMENT. spraying for scale. These marked trees were scattered, here and there one, throughout the entire 40-aere block. In February the marked trees were very thoroughly sprayed over all parts, as much as two gallons of spray being applied to each tree. After this work was completed the entire block, with the exception of the trees already treated, was sprayed as high as the forks of the main limbs, thus avoiding any injury to swelling buds. As before stated, curl devel- oped seriously in the Sacramento Valley in the spring of 1893, and the result was that the unsprayed trees, as well as those sprayed only on the main limbs, ^ere nearly denuded by the disease, while the scattered trees which had been spraj^ed throughout were in full and vigorous foliage and growth. In the writer's notes upon the examination of this orchard on May 22, 1893, it is stated that the trees fully treated in this block were loaded with fruit and in full leaf, while the trees sprayed only to the forks of the limbs were nearly bare and almost wholly destitute of fruit on the unsprayed parts. Such fruit as was found on the unspraj^ed branches was inferior in size and quality. It is further stated that the absence of fruit on the untreated branches as compared with the abundant yield of the treated branches gives such a striking contrast as to be almost beyond belief. ^ Mr. William N. Runyon, of Courtland, Cal., treated a large acreage of peach trees with lime, sulphur, and salt in the winter of 1892-93. He states that the trees sprayed once while dormant were practically free from curl, while trees of the same variety not sprayed were badly affected.^ He also gives an observation of interest in connection with the habits of the fungus, and one since indorsed by the writer, that is, that the disease ""will not spread from an unsprayed to a sprayed tree." In letters from Mr. Runyon^ relative to this work, he remarks that although he had heard that a mixture of lime, sulphur, and salt was benelicial in controlling curl, he had no idea that the result would be so nearly a complete prevention. He says that it was only when curl leaf had become quite prevalent on unsprayed trees that he noticed its almost total absence on those that had been spraj^ed. The most striking instance, he states, was where about 50 three j-ear old nectarine trees stood in rows adjoining about a dozen full-grown trees of the same variety that had shown curl for years. The young trees, not having shown any scale, were left unsprayed, and were a mass of curl, while the old trees, which were given the regular treat- ment, were almost entirel}' free. In this orchard about 60 acres of peach trees were also sprayed, the work being done about the 1st of ^ For further notes and tabulated records of some of this work of the spring of 1893 the reader is referred to Chapter VII under Notes on the Auxiliary Experi- ments in California. ^ Answer to circular letter of Nov. 25, 1893. 3 Letters dated Courtland, Cal., Jan. 31, and Mar. 8, 1894. HISTORY OF TREATMENT. 59 February, aud 40 acres of young trees left unsprayed. In the Santa Clara Valley the sulphur sprays were in general use by the leading growers in 1893. Mr. A. B. Elder, of Santa Clara, writes, in reply to a circular letter of November 25 of that year, that this spray is giving good satisfaction for the control of curl and "is used by large growers of peaches." Mr. John Rock, of Niles, Alameda County, Cal., writes, under date of December 28, 1893, that a mixture of lime, sulphur, and salt is a preventive of curl if applied before the flower buds expand. Bordeaux mixture was used in the winter of 1892-93, in the Carmel Valley, near Old Monterey, with the express purpose of controlling curl, Mr. Daniel Snively, of Gubserville, Cal.. writes^ that his brother used Bordeaux mixture for the control of this disease, and that its action is " so certain that any twig not touched is sure to curl."' Mr, George Woolsey, of lone, Amador County, Cal., sprayed his orchard with Bordeaux mixture in the winter of 1892-93, for the express purpose of controlling curl, and as a result of his experiments in the winter of 1891-92, to which reference has already been made. Relative to his work in the spring of 1893, ]Mr. Woolsey says^ that he sprayed all of his apricot trees, but as time pressed he found that he would not be able to spray all of his peach trees, so ho sprayed the most valuable portion, i. e., the young lower growth, and left the top unsprayed. He states that the season of 1893 was damp, and leaf curl very prevalent in his neighbors'' orchards, but on his place all the trees and parts of trees sprayed w^re exempt, all the others being badly affected by curl and the crop on them almost a failure. A healthy growth on the lower sprayed part of the trees, and the branches denuded of foliage on the upper unsprayed part, formed "a most striking object lesson,"' and, Mr. Woolsey adds, has made him "an enthusiast on Bordeaux mixture.'' A few demonstrations such as he obtained in the season of 1893, he remarks, would convince the growers of the profitableness of the work. ^Nlany peach orchards were sprayed in Oregon in the winter of 1892-93. A favorite spray was a combination of the sulphur spray with copper sulphate, although the former was used separately by some growers. The object of the combined spray was to unite, as far as possible, the insecticidal qualities of the sulphur spray with the fungicidal qualities of the copper salts.'' The winter application of aumioniacal copper carbonate was tested in Oregon also, by ]\Ir. M. O. Lownsdale, of Lafayette. In repl}^ to the circular letter dated Nov- ember 25, 1893, Mr. Lownsdale says he had fair success in prevent- ing curl with lime, sulphur, and salt applied in the winter, followed ' Reply to circular letter of Nov. 25, 1893. 2 Letter dated lone, Cal., Mar. 26, 1894. • ' See results of the tests of combined sprays made liy the writer, pp. 84, 86, 117, liS. 60 PEACH LEAF CURL: ITS NATURE AND TREATMENT. by three applications of ammoniacal copper carbonate after the appear- ance of the foliage. He had better success, however, from ammoniacal copper carbonate applied in late winter, before the swelling of the buds, followed by three applications of a weaker solution upon the foliage. "This.'' he says, "was a complete success." In Michigan the work in 1893 was very satisfactory. ]Mr. Charles Youngreen, of Whitehall, sprayed one row of peach trees before the}' leafed out in the spring. He states ^ that not one of the sprayed trees showed curl, while the unsprayed trees were all affected. The follow- ing year he sprayed the entire orchard and not a tree suffered from the disease. At Shelby. Oceana County, several growers sprayed with Bordeaux mixture with good success. Mr. K. Morrill, of Benton Harbor, stated at a meeting of the Michigan Horticultural Society held at Shelby. June 14 and 15. 1893. that he found there, in four or five cases, that men had sprayed peach trees with Bordeaux mixture, and the effect in decrease of leaf curl was plain to be seen." jNIr. Morrill fails to state, however, whether the lirst spraying was done while the trees were dormant. The effects of curl at Shelby at that time were marked, the same gentleman remarking that in one morning he had seen enough damage done by it to pay for spraying all the orchards within five miles. Professor Taft reports his work in 1893 as follows:^ "In order to secure definite knowledge upon the subject [treatment of curl], I arranged for a series of experiments, and in the fall of 1892 had a number of peach trees sprayed with a solution of copper sulphate (1 pound in 25 gallons), and in a similar experiment at South Haven Bordeaux mixture was used as soon as the leaves dropped in Novem- ber, 1892. During the tirst half of April, 1893. the same trees were again sprayed with similar mixtures, and other trees were treated that had not been sprayed in the fall of 1892. The result was that where fully 50 per cent of the leaves and all of the fruit di'opped from the unsprayed trees, there was little injurv to the same varieties that were treated in both fall and spring or that were sprayed only once, in April; but where the}' were not sprayed until after the leaves had come out only a slight benefit was secured. The results were given in Bulletins 103 and 104 of the Station. On June 14, 1893. I gave the results, up to that time, at the meeting of the State Horticultural Societj'. '' The orchards of the Michigan Agricultural Experiment Station at South Haven, in charge of JNIr. T. T. Lyon, had suffered severely from curl in 1890, 1891, and 1892.* Mr. Lyon says, respecting the spraj'^ 1 Letter dated Whitehall, Mich., Sept. 6, 1899. =^ Kept. Mich. State Hort. Soc, 1893, p. 68. * Letter dated Agricultural College, Mich., Aug. 30, 1899. *See Repts. Mich. Hort. Soc, 1890, p. 144; 1891, p. 228; 1892, pp. 160, 161. HISTORY OF TREATMENT. 61 work done in the winter of 1892-93,^ that as the apparent result of the fall and spring- sprayings, there was; almost a total absence of leaf curl, although it had usuall\^ been quite prevalent there in early spring, and was present in 1893 in neighboring orchards, causing many of the leaves and fruits to drop. He says'" further, that to him "the effect of the spra}" upon leaf curl in particular was a revelation." The work of Professor Taft in this orchard in 1893 was reported on several occa- sions during 1893 and 1894.^ The work of the writer began in Michigan by the publication, in the fruit belt of that State, in the latter part of July. 1893, of notices of the work done in California.* and of requests for the names of peach growers who had sustained losses from this disease. In August, plans for experiments at Shelby and Ludington were in progress, and in November a circular letter, stating that leaf curl had been successfully prevented in California, was addressed to the peach growers of all the leading peach centers of the country. In this circular it was stated that "It is proposed to carry on during the coming season some work in different parts of the United States." The circular reached many of the leading peach growers of Michi- gan. During the winter, that of 1893-94, plans for the testing of winter sprays for the control of curl were undertaken by growers, at the request of this Department, at Whitehall. Albion. Ganges. Beulah, Riverside, Benton Harbor, St. Joseph, Kalamazoo, Covert. Hawk- head, South Haven, Ludington, Shelby, Douglas, Millgrove. Custer, Amber, Mears, Hart, Gobleville. Ortonville, Monterey. Fenville, Saugatuck, Allegan, Wayland, Bradley, Peach Belt, etc. During the winter of 189-1-95 the above list was greatly extended. Within these two 3'ears over 400 ^lichigan peach growers were sent full instruc- tions for controlling curl. Each grower was requested to make his tests according to an experiment sheet sent him, leaving unsprayed trees for comparison. In this way man}- striking object lessons were obtained, aiding materially in the early and widespread introduction of the methods of treatment recommended. Reports of a few of these experiments are given in a subsequent chapter. The Department's tests in Ohio were instituted through a circular letter in November, 1893, announcing to a large number of peach growers in that State the successful treatment of curl in California, and stating that experiments would be undertaken in the East. As a result of replies to this circular, full instructions for controlling curl iMich. Exp. Sta. Bull. Xo. 104, pub. Feb., 1894, pp. 64, 65. ^ Letter dateil South Haven, Mich., Dec. 16, 1897. ^ Paper read at Shelby, June 14, 1893, Kept. Mich. Hort. Soc, 189:1, pj.. 66, 67, and 79; article in Allegan Gazette, July 1, 1893; Mich. Exp. Sta. Bull. No. Hi4. p. 64; pul). Feb., 1894; American Agriculturist, Feb., 1894, pp. 71, 72. * Ludington (Mich.) Appeal, issue of July 20, 1S93, quoted by Shelby Sentinel, etc. 62 PEACH LEAF CURL: ITS NATURE AND TREATMENT. ■were sent to a number of orchardists in the peach-growing centers of Ohio in the winter of 1893-94. During this and the succeedino- winter over tiftj orchardists, located in twentj'-five different peach- growing centers of the State, received carefully prepared instructions for winter spraying for curl. The instructions for both winters were planned in the usual manner of experimental work, a number of unsprayed or control trees being left for comparison with the trees to be treated with each spray to be tested. The ol>ject in thus planning the work was the same as for that in Michigan and elsewhere— that is, to obtain such striking contrasts between sprayed and unsprayed trees that they would form long-remembered object lessons for all who should chance to see them. The spray work of the Ohio Agricultural Experiment Station after 1890 was quite extensive: but the treatment of peach leaf curl is not mentioned in the bulletins on orchard spraying published b}' that station in December, 1891, and February, 1893,^ although in the latter (Bui. No. -18. p. 12) the spraying of peach trees for other diseases is considered. In the spring of 1893, however. Prof. W. J. Green sprayed a considerable number of young peach trees, just planted, the object being ""to determine the truthfulness of the statements that had been made concerning the effect of spraying upon peach trees." In relation to curl. Professor Green says that he "did not see any effect until the season of 1894." during which and in 1895 "there was some effect noticeable."" He saj'S further, in this connec- tion: "I am aware that other work in this direction had been done before I commenced, because I received my suggestions from some other source, but I can not now recall the particular case."' (Letter dated September 30, 1899.) Upon these results obtained by Professor Green, and supported by the work of Benton in California and Taft in ]Michigan, were based the subsequent experiments of Prof. A. D. Selby in the orchard of "William Miller, of Gypsum, Ohio." These experiments were begun, according to Professor Selby, in April, 1895/ but no results with leaf curl were obtained until 1896.* as in 1895 there was no difference between sprayed and unsprayed trees in the amount of curl developing, it being so insignificant as to be without evident eff'ect. The curl which developed in 1896 enabled iSIr. Selby to obtain some contrasts between sprayed and unspra3^ed trees, but these contrasts were not as ^ Green, W. J., The Spraying of Orchards, Ohio Agr. Exp. Sta. Bui. No. 9, Dec, 1891, Vol. IV, second series; Bui. No. 48, Feb., 1893, p. 12; and a letter from Pro- fessor Green, dated "Wooster, Ohio, Sept. 30, 1899. 'Letter from Prof. A. D. Selby, dated Wooster, Ohio, Sept. 13, 1899. ='L. c; also Ohio Agr. Exp. Sta. Bui. No. 92, JNIarch, 1898, pp. 237-245. *Ohio Agr. Exp. Sta. Bui. No. 92, March, 1898 p. 245; also Thirtieth Ann. Kept. Ohio State Hort. Soc, pp. 87. HISTORY OF TREATMENT. 63 marked as they would have been had the disease developed seriously.^ As it was light in 18i>5 and 181H), no gain in fruit was shown by sprayed over unsprayed trees these years. In 1897 the work was con- tinued, and owing to the serious development of curl the desired contrasts in foliage were obtained. Unfortunately, however, the fruit buds had been killed by cold and no fruit records were obtainable. The first contrasts in fruit on sprayed and unsprayed trees in ]\Ir. Miller's orchard were reported to Mr. Selby in 18U8, and they are both valuable and conclusive.' The announcement of the Department's work on leaf curl was sent to the growers of peaches in Illinois, Indiana, and Pennsylvania at the same time that it was sent into Ohio and other States of the East, viz, in November, 1893 : and during the winters of 1893-9-1 and 1894-95, 135 peach growers in Pennsylvania, 81 in Indiana, and 36 in Illinois were requested to spray for th6 control of curl and report to the Department. A complete plan for these tests, control trees being provided for in every case, was sent to each of the growers. So far as reported, where instructions were followed, the results of this work were satisfactory in all cases where curl developed and where frost did not prevent the obtaining of results. "Winter spraying for the control of curl began in New York, so far as known to the writer, in the winter of 1893-94, during which and the following winter over seventy peach growers of the State received from the writer full instructions for the treatment. These instruc- tions were sent out through personal correspondence with orchardists in over twenty of the peach-growing centers, and by means of care- fully prepared circulars. Among others, Mr. W. T. Mann, of Barkers, undertook sprav work for the Department in the winter of 1893-94. Carefulh^ planned experiments were carried out by him in his young orchard, the spraying being done on April 9, and before growth started, and alternate rows being left untreated for comparison. Mr. Mann reported the results of this work as satisfactory, and thev are elsewhere given in this bulletin. Mr. James A. Staples, of Marl- boro, also conducted spray work for the Department in 1894, 1895, and 1896, and where the instructions were carried out respecting the time of first spraying his results were fully satisfactory. Prof. L. H. Bailev^ reported the work of Mr. Henry Lutts, of Youngstown, for the spring of 1894; and Mr. A. D. Tripp, of North Ridgewa}', reports excellent results from his work. 'Ohio Agr. Exp. Sta. Bull. No. 92, pp. 246,247. ^Ohio Agr. Exp. Sta. Bull. Xo. 104, March, 1899, p. 210; also Rept. Ohio State Hort. Soc, 1898, p. 13. ^Bailey, L. H., Impre!=i=ion.« of the Peach Industry in Western New York, Cor- uell Agr." Exp. Sta. Bull. No. 74, Oct., 1894, pp. 382, 383. 64 PEACH LEAF CURL: ITS NATURE AND TREATMENT. A bulletin of the Cornell Agricultural Experiment Station, by Georo-e F. Atkinson,^ which appeared in September. 1894, treats of leaf curl and plum pockets. Respecting the treatment of leaf curl, Mr. Atkinson says that some experiments had been made in various places by spra^'ing the trees with Bordeaux mixture for the prevention of the disease. Some of the experimenters regard it as certain, he states, chat the disease can to some extent be checked by this method, and adds; ** It is quite likely that, in some cases at least, another disease is confused with leaf curl, and this fact might account in those instances for the results claimed." The doubts here expressed as to the results of the work in New York do not appear to have been supported bvany held work of the station , and may have arisen from Mr. Atkinson's under- standing of the perennial habits of the fungus causing the disease. There seems to have been no winter spraying for curl by the Cornell Station before the spring of 1898, and the results then obtained are in perfect accord with those obtained in 1894 by growers cooperating with the Department. In the spring of 1898 several experiments were instituted and carried out by B. M. Duggar and H. P. Gould. The results of this work are given in a bulletin by Mr. Duggar, published in February. 1899.^ The efforts to control peach leaf curl by winter sprays in Canada, so far as concerns the work of the Canadian Government, appear to have begun nearly simultaneously in Ontario and British Columbia. At the experiment farm at Agassiz, British Columbia, the peach orchard had suffered severely from curl prior to the introduction of winter spraying. The su]:)erintendent, Mr. Thomas A. Sharpe, reported for 1892 that of the large number of peach varieties at that time on the farm — about 116 — onlv 5 escaped leaf curl, and the attack was severe.^ In the report for 1893 it is said that leaf curl was worse that year than ever before. Of about 129 varieties on the farm the Malta was the only variety on the level land that was entirely free.* In the spring of 1894 the trees were sprayed with strong Bordeaux mix- ture when the leaves were partly expanded, but no leaf curl developed that year, even the unsp rayed orchards not being troubled by it.' It should be stated here, however, that the work done was too late to have given good results had curl developed, and that it did not properly constitute a preventive spraying. Whether this late sprajdng was owing to the nature of the season, or whether it was supposed that such treatment w^ould control the disease, is not known to the writer. 1 Atkinson, Geo. F., Leaf Curl and Plum Pockets, Cornell Agr. Exp. Sta. Bull. No. 73, Sept., 1894, pp. 324-326. '^Duggar, B. M., Peach Leaf Curl, etc., Cornell Agr. Exp. tr^ta. Bull. No. 164, Feb., 1899, pp. 377-384. » Kept. Exp. Farms, 1892, p. 278. * Kept. Exp. Farms, 1893, pp. 342, 343. /Kept. Exp. Farms, 1894, p. 404. HISTORY OF TREATMENT. 65 In 1895 Mr. Sharpo reports that the peach trees at Agassiz were sprayed with Bordeaux mixture before leafing out, and again when the leaves were nearly full grown. He states that the sprayed trees had very little curl, and made a very strong and healthy gi'owth, while on a few unsprayed trees of several varieties the leaves were nearly all destroyed by curl, and the trees themselves made a very feeble growth.^ This treatment, so far as known, is the first successful experiment for the control of curl by the Canadian Government. Leaving con- trol trees for comparison added greatly to the value of the work, which was also strengthened by the results at Agassiz the following 3"ear, 1890.^ The writer regrets to add, however, that unfavorable results attended the spray work at Agassiz in 1898.^ The reasons for this failure are not apparent. In Ontario the early results were not so satisfactory as at Agassiz, owing to the nondevelopment of the disease in Ontario. Mr. John Craig, horticulturist of the Central Experimental Farm, at Ottawa, planned the Ontario work. He states that the work on peaches in 189'± was planned to prevent the rotting of fruit and injury from insects, and that the first spraying was not given until May 1.* Mr. Craig's work on leaf curl began in 1895, by the application of winter spraj's,'' but owing to the absence of the disease that 3'ear no con- clusive results were obtained. Later work, I am informed by Mr. Craig, has given more conclusive and satisfactory results.* The vari- able results reported in Bulletin No. 1, second series, leads the writer to wonder, however, if the early spray work was done with sufficient thoroughness. Mr. W. M. Orr, of Fruitland, Ontario, met with verj^ convincing and satisfactory results from winter spraving in 1898.^ The same is true for the experiments of Mr. A. H. Pettit, of Grimsby, Ontario, who carried on work in 1898 and 1899, the results of the latter year, when one row of trees was left untreated for comparison, being very striking. The work of this Department in extending the use of sprays for the control of curl on the Pacific coast began in the spring of 1893. In the fall of that year a circular letter on the subject was addressed to many Pacific coast growers, and this was closely followed by requests that growers undertake preventive spray work in the winter of ^ Kept. Exp. Farms, 1895, p. 396. 2 Kept. Exp. FariiiP, 1896, p. 449. 'Eept. Exp. Farms, 1898, p. 403. *Rept. Exp. Farms, 1894, pp. 110, 111. ^ Peach Culture in Canada, Bull. No. 1, second series, pj). 35-37; Central Exp. Farm, Dept. of Agr., Ottawa, Canada, Sept., 1898. ^Letter dated Ottawa, Oct. 7, 1897. 'Canadian Horticulturist, Jan., 1899, pp. 18-20. 19093— No. 20 5 66 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 1803-94. During the winters of 1893-94 and 1894-95 the writer sent full instructions for preventing curl by winter sprays to over two hundred and seventy California peach growers, and requests to carry on spraying experiments, with similar instructions, to more than one hundred growers in Oregon, and to many in Washington. In all of this work for the extension of spraying an effort was made to intro- duce it in as large a number of leading peach-growing centers as pos- sible, especially in those sections of the coast where leaf curl had been most prevalent. The results of some of these experiments are given in Chapter VII, and the facts gathered and experiments conducted under the direct charge of the writer in 1893, 1894, and 1895 are detailed in full in other portions of this bulletin, and require no discussion here. CHAPTER IV. PLAN OF PREVENTIVE SPRAY WORK CONDUCTED BY THE DEPARTMENT. PRELIMINARY PLANS FOR THE WORK. The partial control of peach leaf curl in the spring of 1893, in a few orchards of the Sacramento Valle}^ in which the trees had received a winter spraying for the control of the San Jose scale {A> After locating unci iiunilH'ring eacli of the 3(S expcrinient.s tt) be tested the block was carefully examined to determine if any of the trees were missing or so injured as not to represent entire trees. The results of this examination are also embodied in the plat. Where trees were missing the fact is shown l)y a cipher (0) in the place of the West. 3 5G 55 54 §53 52 51 50 49 48 47 46 45 44 ii 42 41 40 39 38 37 36 35 34 33 32 31 30 S 7 6 5 4 -Tree numbers.- Nortli. 3 2 1 10 9 8 South. -Truo nmiibers.- 24§ East. ♦Sprayed in 1894 and 1895, except where noted. "^Unsprayed in 1894 and 189.5. § Sprayed in 1894 and left unsprayed in 1895. tree, but it was found that only two trees, both from row 39, were wanting in the block. The cross (+) in row 35 represents a nectarine tree, omitted in results of work. In cases where main limbs had been broken off or the tree otherwise injured, the proportion of the tree remaining is expressed in numerals, i. e., 8 in the place of a tree indi- cates that the tree was eight-tenths perfect, 5 that it was live-tenths 70 PEACH LEAF CURL: ITS NATURE AND TREATMENT. perfect, etc. As will be seen, however, there were very few imperfect trees. In all the following calculations of fruit, etc., these few discrepan- cies in the number of trees are carefully taken into account in arriv- ing at results intended for comparison with other rows. The amounts produced by the trees of each row are first divided by the number of trees actually in the row to obtain the average per tree, and this amount is multiplied by 10 to obtain the amount a full row would yield at the given average. By reference to the plat it may be seen that the trees and parts of trees missing amount to but 5.8 equivalent trees for the entire block, that 51 of the 58 rows have the whole com- plement of 10 perfect trees, and that the missing trees or parts of trees are divided among the remaining 7 rows. SPRAY WORK CONDUCTED IN 1894. The spray tests conducted in the Rio Bonito orchard in 1894 included the application of sprays prepared according to 3S different formulae, making 38 distinct experiments. Each experiment included two adjoining rows of 10 trees each, one sprayed and the other unsprayed for comparison. Of these 38 experiments 11 involved two sprayings of the trees treated and 27 a single treatment. All treat- ments were made during the dormant period of the trees and varied in date from February 1 to March 6. The consideration of the preparation of sprays for this work will be discussed in a subsequent chapter devoted to that subject, as will also the methods of applica- tion, which will be given for use in both small and large orchards. The table which follows is prepared to show as concisely as possible the arrangements adopted for the experiments of 1894. The rows of trees once treated and those twice treated are shown, the date or dates of treatment and the formula or formulae used in each case. Table 1. — Showing the formula of the sprays applied in 1894, dates of application, and rows treated. Row No. Date of spraying, Formulse for 45 gallons of spray. Feb. 20 Feb. 24 /Feb. 16 lFeb. 28 Feb. 23 Feb. 24 Feb. 23 /Feb. 20 \Mar. 3 Feb. 24 Feb. 13 Feb. 13 /Feb. 26 \Mar. 6 15 lbs. sulphur, 30 lbs. lime, 10 lbs. salt. Control row. 10 lbs. sulphur, 20 lbs. lime, 7 lbs. salt. 10 lbs. sulphur, 20 lbs. lime, 7 lbs. salt. 5 lbs. sulphur, 10 lbs. lime, 3 lbs. salt. Control row. 5 lbs. sulphur, 10 lbs. lime, 3 lbs. salt. 15 lbs. .sulphur, 30 lbs. lime. Control row. 10 lbs. sulphur, 20 lbs. lime. 10 lbs. sulphur, 20 lbs. lime. 5 lbs. sulphur, 10 lbs. lime. Control row. 5 lbs. sulphur, 10 lbs. lime. 20 lbs. lime, 20 lbs. salt. Control row. 20 lbs. lime. 45 lbs. salt (hot). 46 lbs. salt (hot). SPRAY WORK OF 1894. 71 Table 1. — Shon>inf/ the formu/ir of the Hprayn applied In 1S94, dates of application, and rows treated — Continued. Row No. Date of spraying Formuke for 46 gallons of spray. 17 18 Feb. 26 19 Feb. 27 •20 21 /Feb. it; \Feb. 20 Feb. 21 22 23 24 fFeb. 6 \Mar. 1 Feb. 23 25 26 27 /Feb. 6 \Mar. 1 Feb. 26 28 29 30 Feb. 2 31 32 Feb. 2 /...do... \Mar. 2 34 35 Mar. 3 36 Feb. 27 37 38 Feb. 26 39 /Feb. 1 \Feb. 28 40 41 Feb. 23 42 /Feb. 14 \Mar. 3 43 44 . .. Feb. 24 45 Feb 27 46 47 /Feb. 14 48 iMar. 3 /Feb. 14 49 50 Feb. 14 51 Mar. 3 52 53 /Feb. 14 \Mar. 6 Feb. 27 54 55 56 Mar. 6 .57 ....do .. 58 Control row. 3 lbs. copper !4 made it possible when the work was resumed in 1895 to ascertain if the 72 PEACH LEAF CURL: ITS NATURE AND TREATMENT. effects of one year's treatment extended to the crop or foliage of the second year. While peach leaf curl did not develop seriously in the Sacramento Valley in 1894, it prevailed quite extensively in other portions of the United States. This resulted in acquiring facts bearing on the experi- ments for 1895 in the Rio Bonito orchard. The experiments planned by the Department and carried out by growers in the East and in the north Pacific States, where leaf curl developed, showed that one thorough spraying during the dormant period of the tree was sufficient. The experiments of 1895 were consequently modified from those of 1894 in respect to the number of applications made, as well as in other respects found to be advisable. SPRAY WORK CONDUCTED IN 1895. In the spray work in the Rio Bonito orchard during the winter and spring of 1895, the same block of Lovell peach trees was selected as that treated the previous year, and in each case the same unsprayed or control rows were left as in 1894. In 1895 the number of experiments made in this block was 38, as in the previous year, but three of the 38 rows were not sprayed, being left without treatment for the purpose of observing the action of sprays applied in 1894 upon the crop and foliage of 1895. These three rows were numbers 4, 24, and 53, each of which had received two treatments in 1894. The facts thus learned are considered farther on. The spray work of 1895 included but a single spraying of each row designed for treatment. As already indi- cated, each experiment included one treated and one untreated row, each row having 10 immediately adjoining trees. By treating one row on either side of each control row the latter served as a contrast row for both sprayed rows. By referring to the plat of the block, p. 69, this arrangement may be seen. Row 1 is sprayed; row 2, unsprayed; row 3, sprayed. These three rows make two experiments — rows 1 and 2 compared make the first experiment, while rows 3 and 2 com- pared make the second experiment. In like manner rows 4 and 5 and 5 and 6 make two experiments. These illustrations will be sufficient, as the entire block, with the exception of the three rows already noted, was treated according to the same general plan. In considering the application of sprays in the experiments of 1895, the nature of the sprays used, the formulae according to which they were prepared, the location of the rows treated, and the dates of appli- cation, as well as the location of the control rows for comparison, are set forth in the table which follows. That the reader may better grasp the nature of all treatments which each row had received the previous year, the formula? for the sprays applied in 1894 are placed at the left of the treatment given the same rows in 1895. SPRAY WORK OF 1895. 73 o3 o ■^— s;^) nw •-'«-□ a; o CI - a> a> a a a.§ .9 • ■' • ' -« ^^ 1— < ^ X5 s— -^ o .o ^ n :,• O CO > !M bo*: c .-'- : - 3 fc. 3 i: •- ~ c ~ X — x; ,.-"". 1 fT ftg o. ■a c — ci. c ^ ?.G?r >-. cs X n S C V.' . o • Ji^B o. 0^:^0^ (3 lO o lOrt rH 3 3 s a i a ■~; ^^ n '-' XiXi x> X! 3 Xi lOiO lO lO lO 0) 5^ 3 - - S c K c S X o o II 1) ft-P ft ft s. coppe Control s. coppe Control . copper 1 Control s. coppe s. coppe Control . copper C 3 O 3 o o o o o rrO ft rrO X! 3 ^ £ £ 5 § ^ £5 o ^ CO ■* (N (N CO CO -S>CO 110 c c f^s Sp^ PS, a~ a a o £5 ' oo" X ;5£J CO ^ " _ ^ o a; sa to CO £5 oo aa| M W W ■°-^£ iC lO lO oT iT a," a ai <:^ Q^ I ft ft ft ■ ft ft ft 0)0 aaa £££ a> oTaT ■5 — -c O-ftft, a> o '""—'' — " " = — jQjQ ££5 £££ £££ £~;3££^££ § ~" ~" M -^ -f CO C4 IC u; -r -f CO CO CO M C4 c< -m CI •* co in 01 O - ,3J2 S X5£ ,3 ^,3 t-iC^CO -^ lOtOl-^CCOS O i-KNCO-^iC -.S 1-X310 —• N N c^ cj CI 'OJ eot^ CO o (N . o . Hf. ,3 fn :s SfJH f^ O r^ OOOOrHCI CO 04 c) cj e^ CO CO CO CO 3S§ 74 PEACH LEAF CURL! ITS NATURE AND TREATMENT. iC iC iC iC lO lO GENERAL CONSIDERATION OF SPRAYS APPLIED. 75 The methods of preparing and applying the sprays used in 1895 are considorod in sub.se(|iient chapters. In each case an effort was made to do thorough work in applying the sprays, l)ut, as is true with all such work in the Held, more or less variable results could not be avoided owing to the weather conditions and other influences. The treatment was given the 85 rows during the ten days immediately preceding the general opening of the flowers, that is, at the close of the dormant period of the trees, or from February ^i) to IVlarch 5. In a few of the more forward trees a small percentage of the flowers had. opened before the completion of the work. GENERAL CONSIDERATION OF SPRAYS APPLIED. Several distinct types of sprays were tested in the preventive work on curl in 1895, and these were prepared in many forms and propor- tions. The two fungicidal bases, copper and sulphur, which are now recognized in all countries as most valuable for this class of work, enter into the composition of a large proportion of the sprays used, in one form or another. In testing sprays considerable weight was given to the fact that the peach tree is subject to the attacks of certain serious insect pests, prominent among which is the San Jose scale, and that a spray com- bining both fungicidal and insecticidal properties would often prove of greater value than one the action of which was solely fungicidal. Having these facts in mind, and knowing the demonstrated value of the sulphur, lime, and salt spray as an effective remedy for the San Jose scale, this spray, together with various modifications, was tested and compared (rows 1, 3, and 6). Besides quantitative modifications of the spray, tests of its constituents were made to acquire such facts respecting their value as were obtainable. The sulphur and lime united were tested in several proportions without salt (rows 7, 9, 10, 12, 16, 51, and 57). The lime and salt were tested together (row 13), and the lime was tested separately (row 44). The trial of a strong salt solution was made the previous year (row 16), but as it injured the foliage somewhat it was omitted in 1895. Other modifications of the sulphur spray were prepared by adding ditterent fungicides, with the hope of increasing its fungicidal action without detracting from its effectiveness as an insecticide. Sulphate of copper was added in different proportions (rows 18, 19, and 36), and the addition of iron sulphate was also tried (row 56). The copper sprays tested for leaf curl were numerous and were variously prepared and combined. As alread}' said, copper sulphate was added to the sulphur sprays, but it was most extensively used in the preparation of the Bordeaux mixture, in which form it was applied in many experiments and of various strengths (rows 15, 21, 22, 25, 28, 33, 41, 45, and 54). Copper sulphate with ammonia (eau celeste) was 76 PEACH LEAF CURL: ITS NATURE AND TREATMENT. tested (rows 27 and 80), as was the modified eau celeste, composed of copper sulphiate, sal soda, and ammonia (rows 35 and 39). Two experi- ments were also conducted with ammoniacal copper carbonate (rows 32 and 38). The action of sulphide of potassium was tested (row 47), as well as sulphide of potassium combined with milk of lime (rows 42 and 48). Iron sulphate in connection with lime was applied in one experiment (row 50), and, as already stated, was also used in connection with sulphur and lime (row 56). Of the three rows left unsprayed in 1895 (rows 4, 24, and 53), one (row 4) had received two applications of the sulphur, lime, and salt spray in 1894; another (row 24) had been twice sprayed in 1894 with Bordeaux mixture; and the third (row 53) had received two spray- ings in 1894 with a hot saponilied solution of sulphide of potassium. Bull. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate VII _1 Si < bjD > 1 en LU rr :j \- a S IT i- 2 I < - q: s O £ UJ s I- _ < '- UJ r H --^ z 3 S " bo Q - UJ ;:: I- S < a UJ a H -2 DESCRIPTION OF PLATE VII. Sprayeil and unsprayed C'rawfords Late trees in the orcliard of Mr. .\. D. C'ntts, Live Oak, Cal. The tree seen at the right was sprayed with hnie, sulphur, and salt in February, 1893; that at the left was unsi)rayed and was denuded of foliage and fruit l)y eurl. (See records of fruit of sprayed and unsprayed trees in this orchard, p. 141.) The trees were photographed in May, after most of the curled leaves had fallen from the unsprayed tree. (Compare witli I'l. XX.) chaptp:k v. INFLUENCE OF SPRAYS ON THE VEGETATION OF THE TREES. SAVINC OF FOLIAGE FROM INJURY IJY CURL. (PI. VII.) The effeotivenoss of the winter .sprays diseussed in the previous chap- ter in saving the foliage of peaeh trees from injurv )»y peach leaf curl has been carefully considered. The relative importance of this matter appears from the fact that it is the injury from the loss of foliage which is responsible for the ultimate loss of the fruit. The spray work already mentioned was completed, in 1895, about the close of the first week in March. From this time on the flowers ()p. — Comparatire jwrccntnge of diseased foliage an sprayed and imspraijed trees April 22 and 23 and May 9, 1895. Trees examined. April 22 and 23, 1895. May 9, 1895. Avemge per cent of disease on the trees of all control rows 83.fi 26.2 82.0 86.9 Average (ler cent of disease nn the trees of all siiraved rows 21 2 Average jier cent of disease on the trees of the three rows sprayed in 1894, but left unspra ved in 1895 87 Those comparisons show 3.3 per cent more diseased foliage on the control trees Ma}^ than April '2)1. The percentage of foliage of the spniyed trees showing disease^ had decreased, howi^-er, 5 per cent. Of the total foliage of the trees sprayed in 1894. l)ut left unsprayed in ISito. T) per cent more was diseased at the second date than at the first. These figures indicate that the divergence in the percentage of disease on sprayed and unsprayed trees was still increasing just prior to the second estimate. The second estimate may thus be considered as taken before any of the trees had begun to recover from the efiects of the disease. The time of maximum contrast was the true time to make the estimates, and it is believed the date of this second estimate was certainly not too late to fully comply with this requirement. This belief was substantiated b\' a third partial estimate made a week later, which gave in general very similar results to those obtained Ma}' 9. It siiould also be said that the decrease in the percentage of disease on the sprayed trees between the dates of the first and second estimates did not indicate that the second estimate was made too late, or after the trees had begun to recover, but mereh' that the leaf buds had not fully pushed at the time of the first estimate. This is further shown by the fact that the percentage of disease was still increasing on unsprayed trees up to that time. Before considering the action of individual sprays in saving the foliage from curl, the following comparisons are given of the action of the classes of sprays used: Table 7. — Percentage of healthy foliage on trees differently .sprayed. Percentages of healthy foliage .shown by trees sprayed with diflfercnt cla-sses of spravs. P2stimated April 23 and Mav 9, 1895. Average of 30 trees sprayed with siilphnr, lime, and .salt Average of 70 trees sprayed with snipluirand lime Average of 100 trees sprayed with the two preceding sulphur sprays A verage of 90 trees sprayed with Bordeaux mixture .\ verage of 20 trees si>rayed with eau celeste Average of 20 trees sprayed with modified eau celeste Average of 130 trees sprayed with the three preceding copper .sprays Average of 20 trees sprayed with ammoniacal copper car- bonate 19093— No. 20 6 ercentage of healthy foli- age Apr. 22 and 23, 1895. ercentage of healthy foli- age May 9, 1895. ain in per cent of foliage from Apr. 23 to May 9, 1895. PU C^ o 71.4 84.6 13.2 69.3 80.0 10.7 70.3 82.3 12.0 86.2 89.6 3.4 83.3 91.7 8.4 83.0 87.6 4.6 84.2 89.6 5.4 09.8 01.4 eyes'" 9^ ^ .00 O S3 t.rH O-O^ >. •« CSS 36"- So 8.4 82 PEACH LEAF CURL: ITS NATURE AND TREATMENT. T.\BLE 7. — Percentage of It ecdthy foliage on treea differently sprayed — Continued. Percentages of healthy foliage shown by trees sprayed with different classes of sprays. Estimated April 23 and May 9, 1895. Percentage of healthy foli- age Apr. 22 and 23, 1895. Percentage of healthy foli- age May 9, 1895. Gain in percent of foliage from Apr. 23 to May 9, 1895. 76.3 59.2 79.2 32.0 54.3 73.5 54.5 82.0 57.0 75.8 38.8 49.8 58.8 79.5 5.7 6.8 25.0 'csio Average of and lime Average of Average of lime Average of Average of lime Average of Average of 30 trees sprayed with copper sulphate, sulphur, (a) 10 trees sprayed with iron sulphate and lime 10 trees sprayed with iron sulphate, sulphur, and 10 trees sprayed with sulphide of potassium 20 trees sprayed with sulphide of potassium and 10 trees sprayed with milk of lime 10 trees sprayed with milk of lime and salt. 2.2 3.4 4.5 14.7 o Compare text. The table shows the average of healthy foliage on the trees sprayed ■with the sulphur sprays (sulphur, lime, and salt, 30 trees; sulphur and lime, 70 trees) to haye been 82.3 per cent May 9. The average on the trees sprayed with the leading copper sprays (Bordeaux mixture, 90 trees; eau celeste, 20 trees; modified eau celeste, 20 trees) was 89.6 per cent. The average amount of healthy foliage saved on trees sprayed with a combination of these two leading classes of sprays (Bordeaux mixture added to the sulphur and lime sprays, 30 trees) was no greater than the average saved by all sulphur and lime .spra3's alone, being 82 per cent as against 82.3 per cent for the sulphur sprays. This result was a surprise, but by carefully looking into the reason it would seem that the low average in the case of the combined sprays was due to the low average of the single row 36, while the high average of the sulphur sprays arose from including in the average the results of those sprays which contained much more sulphur than was used in the combined sprays. Notes on the spray applied to row 36 show that considerable sulphur was precipitated in cooking, probabl}^ through overheating, and for this reason it would be as well to omit this row in determining the average saving of the combined spraj's. The two remaining rows, 18 and 19, sprayed with combined sprays, showed 84.7 and 83.2 per cent of healthy foliage, respectively — an average of 83.9 per cent. The formula for each of these experiments contained 5 pounds of sulphur. In the experiments with uncombined sulphur sprays there were four formulfe containing 5 pounds of sul- phur each. The average per cent of saving of these four experiments was 75. 3. These facts show that when the amount of sulphur was equal there was an average gain of 8.6 per cent in healthy foliage resulting from the addition of Bordeaux mixture to the sulphur spra3^s. The average percentage of foliage saved by the use of the ammo- niacal copper carbonate (20 trees) was. May 9, 61.4. As the ammoniacal SAVING OF FOLIAGE. 83 copper carbonate sprays used contained niueh less basic copper car- bonate than the other copper sprays applied, their comparativeh^ low effectiveness against ciirl is fully accounted for, and for this I'eason they were not included when (calculating the average action of the copper spra3^s in general. The}^ were outclassed by the amount of copper used in the other sprays. The foliage saved by the use of iron sulphate and lime (10 trees) was but 57 per cent May 9. This shows a much less satisfa(!tory action than either the copper or the sulphur sprays. The iron sulphate com- bined with the sulphur and lime sprays showed a saving of foliage Ma}^ d of 75.8 per cent. While this is a good showing, the beneficial action was evidently due to the sulphur of the spray and not to the iron, and the result was even below the average obtained bj' the sulphur sprays alone, or equal to those having the same amount of sulphur. One experiment (10 trees) was made with sulphide of potassium, but the average percentage of foliage saved by this spray was, May 9, only 38.8. Sulphide of potassium combined with milk of lime (20 trees) showed a greater saving of leaves, being 49.8 per cent, but as the sulphide alone gave a saving 11 per cent lower, and as milk of lime saved as high as 58.8 per cent, it is questionable if the lime was not the more active agent in the combination. As already stated, the milk of lime applied as a spray (10 trees) showed a saving of 58.8 per cent of the leaves, which was quite satisfactory for a spray con- taining none of the standard fungicides. The spray prepared from lime and salt (10 trees) gave a high record, the healthy foliage May 9 being 79.5 per cent. While it is possible that the fungicidal action of this spray may be somewhat higher than that of milk of lime alone, it is perhaps more probable that the results noted arose from another influence. It was learned in the previous year's work that a solution of salt injured the new growth and tender leaves, and it is thought likely that in the present case the earliest growth and that which first showed disease was destroj'^ed by the spray, and that the foliage estimated was a new and somewhat later growth, showing much less disease than the first foliage would have shown. It would be well, however, to repeat this test. Some interesting facts are brought out by the preceding table in relation to the continued action of the fungicides used. By comparing the first column, the percentages of healthy foliage taken April 22 and 23, with the second column, the percentages taken May 9, it will be seen that the percentage of healthy foliage on all trees spraA^ed with the sulphur or copper sprays increased decidedly between the two dates of estimate, as shown in the third column. On the other hand, the action of the weaker sprays was overcome b}" the disease, and the percentage of healthy foliage May 9 was much less than April 23, as shown in the fourth eohunn. These weaker sprays checked the 84 PEACH LEAF CURL I ITS NATURE AND TREATMENT. action of the fungus at lirst, but were not sufficiently active or per- sistent to prevent its gradual increase upon the trees. An apparent exception to this in the case of the sulphide of potassium appears to arise from the fact that the disease was never greatly ch(>cked by this fungicide, the amount of health}^ foliage being only 32 per cent April 23. Another and more marked exception is seen in the trees spra\'ed with lime and salt in solution. It is thought, however, that the tru(> explanation of this exception is that given in the preceding paragraph. What has been stated will be sufficient to indicate the comparative value of the main classes of sprays used in these experiments. It is shown that the highest degree of (effectiveness in saving foliage is possessed by the copper sprays, that the sulphur sprays also possess a high degree of fungicidal activity, and that where Bordeaux mixture is added to the sulphur sprays the effectiveness of the latter is some- what increased. It is also made clear that sulphide of potassium, sulphate of iron, and several other sprays, as tested, are of secondary value in this work. It should be noted that the average saving obtained from the use of the sulphur sprays is sufficiently high to well warrant the use of these sprays, either in combination with Bordeaux mixture or alone, in cases where it is desired to use a spray having both fungicidal and insecticidal qualities. It will now be advantageous to briefly consider the h>ading indi- vidual sprays composing the classes of sprays already discussed, in respect to their action on peach foliage and peach leaf curl. The fol- lowing table gives a compact presentation of the number and nature of these sprays, as well as their action in controlling curl: Table S. — Nature and courjionilion of spraijs applied. Row No. ('lasses and formula; of sprays applied. Sulphur, lime, and salt : 1.5 lbs. sulphur, 30 lbs. lime, 10 lbs. salt , 10 lbs. sulphur, 20 lbs. lime, 5 lbs. .salt .'■> lbs. sulphur, 10 lbs. lime, 3 lbs. salt , Sulphur and lime : 15 lbs. sulphur, 30 lbs. lime 10 lbs. sulphur, 20 lbs. lime 10 lbs. sulphur, 8 lbs. lime 6 lbs. sulphur, 4 lbs. lime 5 lbs. sulphur, 15 lbs. lime 5 lbs sulphur, 10 lbs. lime 5 lbs. sulphur, 5 lbs. lime Bordeaux mixture and sulphur sprays combined : 3 lbs. copper sulphate, 10 lbs. sulphur, 20 lbs. lime 3 lbs copper sulphate, 5 lbs. sulphur, 10 lbs. lime 2 lbs. copper sulphate, 5 lbs. sulphur, 10 lbs. lime Bordeaux mixture : lbs. copper sulphate, 15 lbs. lime CD Oj < 92.3 S4.7 76.8 85.4 83.1 85.4 82.0 74.8 81. 68.5 78.2 84.7 83.2 S.C: Ki 607 549 488 554 536 554 528 473 520 424 499 549 637 80 60 60 60 60 60 80 60 60 60 70 80 80 100 SAVING OF FOLIAGE. 85 Taule 8. — yi>lif O .S r; sea 03 w « O o-S- 3 lbs. copper snlphato, I'l lbs. lime 5 lbs. copper sulplmto, Id lbs. lime 3 lbs. eopjier sulphati', 10 lbs. lime 3 lbs. copper sulphate, 10 ll)s. lime 5 lbs. copper sulphate, h lbs. lime 4 lbs. copjier sulphate, h lbs. lime 3 lbs. copper sulphate, •') lbs. lime 2 lbs. copper sulphate, ."> lbs. lime Eau celeste : 4 lbs. copper sulphate, 3 pints ammonia 2 ll)s. copper sulphate, 3 pints amm'oniii Modified eau celeste: 4 lbs. copper suliihato, ,"i lbs. sal soda, 3 pints ammonia. 2 lbs. copper sulph.ite. :'. lbs. sal soda,2 pints ammonia. Ammoniacal rdjijicr carbunate: 6 ounces ((ijiiier carbonate, 3 pints ammonia Soiuices CI ijiper carbonate, 2 pints ammonia Iron sulphate and lime : 6 lbs. iron snliihate, 10 lbs. lime Iron sulphate, suljihur, and lime : .5 lbs. iron sul]iliate, .t lbs. sulphur, 10 Dis. lime Potassium sulphide .solution : 8 pints ]Mitassinm suljihide .solution 1'ota.s.siinu sulphide .solution and lime: 12 pints potas.sium sulphide solution, 10 lbs. lime 8 pints potassium sulphide solution, 5 lbs. lime Lime and salt : 20 lbs. .ime, 20 lbs. salt Lime : 20 lbs. lime *91. 87. Sh. 82. 95. 94. 89. 89. 91. t92. 91 83. 70. .51 *604 6t)6 556 529 634 624 588 584 598 1606 603 539 438 302 336 480 197 344 219 509 350 80 100 90 80 100 100 80 80 SO tioo 80 80 80 60 40 40 40 50 40 60 50 * Exceptional, see p. 87. t Outside row, next to driveway. The above table is planned to trive for each experiment the t'ollowing- facts: (1) The number of the row to which <^he spray was applied; (2) the nature and amount of the ingreditMits used in each cas«»; (8) the average per cent of healthy foliage shown by the trees of the row May !•, 1805; (4) net gain in healthy foliage iil)ove the average per cent of health}' foliage produced b}' all of the control trees of the block (200 unsprayed trees), and which is expressed in })er cent; (5) thrift of uninfected leaves in color, texture, and .size. The figur(\s under the foui'th head were obtained in the following mtuiner: The a\'erage percentage of healthy foliage of all the ti"(M\sof each control row was first jisctn-tained. These amounts Avere added together and divided l)y the number of rows (20) to obtain the ax'crage percentage of healthy foliage of all control trees of the block. This axcrage was 13.06. From the average percentage of each sprayed row was then su])tracted the average of all control trees to ol)tain the g:un in hetUthy foliage of each sprayed row. This net gain was then di\ ided by the 13. OH per cent of th(> .-ontrol trees to obtain tiie net gain per cent of each sprayed row. For example, take row 1 : !t2.3 7; 13.06 % =Ti>.24 % gain; 79.24 % ^13.06 % .shows the net gain to be 'fftJ = 60T% of the 86 PEACH LEAF CURL". ITS NATURE AND TREATMENT. average amount of healthy foliage of the control trees. The fifth sub- ject, thrif tiness of leaves, is discussed in the next general head of this chapter. In considering the saving of foliage induced through the use of the sulphur, lime, and salt sprays (rows 1, 3, and 6) in comparison with the average saving of sprays containing an equal amount of sulphur but no salt (rows 7, 9, 10, 16, 57, 12, and 51), there appears to be a slight gain in favor of the former sprays. The average saving from both classes, taken together or separately, is in proportion to the amount of sulphur contained in the spray. With 15 pounds of sul- phur the average net gain in healthy foliage was 580 per cent; with 10 pounds, 517 per cent; with 6 pounds, 528 per cent; and with 5 pounds, 480 per cent. In considering the combined sulphur and copper sprays (rows 18, 19, and 36), it is well to omit comparisons of row 36, on account of the injury caused to the effectiveness of the sprav applied to it through the precipitation of a portion of the sulphur in boiling, as has already been noted. Rows 18 and 19, containing 3 pounds and 2 pounds of copper sulphate, respectively, and each containing 5 pounds of sulphur and 10 pounds of lime, show a gain in healthy foliage of 519 per cent and 537 per cent, or an average gain of 513 per cent. The average gain from the sulphur sprays, which contained the same amount of sulphur but no copper, was, as already stated, 180 per cent. This shows the advantage of adding the copper to the sulphur sprays. In the table the experiments with the Bordeaux mixture are arranged according to the amount of copper and lime used in each. The results obtained in the 9 experiments bring out some valuable facts respecting the most desirable proportions of copper and lime to be used. Of the 9 experiments with Bordeaux mixture, 2 formula? contained 15 pounds of lime each, 3 formuhe 10 pounds each, and 4 formulae 5 pounds each. By comparing rows 15 (6 pounds copper sulphate, 15 pounds lime), 41 (5 pounds copper sulj)hate, 10 pounds lime), and 21 (5 pounds cop- per sulphate, 5 pounds lime), it will be seen that there was a gain in healthy foliage of 589 per cent, 566 per cent, and 634 per cent, respec- tively. Dividing these gains by the number of pounds of copper in the respective formulae, which may be fairly done, owing to the nearly equal amounts of copper contained in each, the following results will .be obtained: Per cent. Row 15 (6 pounds copper sulphate, 15 pounds lime^l pound copper to 2.5 pounds lime) shows a gain of foliage per pound of copper sulphate of 98 Row 41 (5 pounds copper sulphate, 10 pounds lime = 1 pound copper to 2 pounds lime) shows a gain of foliage per pound of copper sulphate of 113 Row 21 (5 pounds copper sulphate, 5 pounds lime = 1 pound copper to 1 pound lime) shows a gain of foliage per pound of copper sulphate of 127 SAVING OF FOLIAGE. 87 These comparisons indicate a decided increase in activity of the spraj's as the percentuoc of lime is lessoned — the total amount of cop- per remaining the same, at least to that point where the number of pounds of copper sulphate and lime are eciual. The formula) contain- ing 8 pounds of copper sulphate can not all be compared as justly as the above formuUe have been, owing to a difference in the make of copper sulphate used on row 33. However, rows 45 and 54, each hav- ing been sprayed with a formula containing 3 pounds copper sulphate and 10 pounds lime, may be compared with row 25, which was treated with 3 pounds of copper sidphate and 5 pounds of lime. The average saving of foliage per pound of copper sulphate in the former two experiments (10 pounds lime) was 180 per cent. The saving per pound of copper sulphate in the latter experiment (5 pounds lime) was 196 per cent. These comparisons also show most gain in foliage per pound of copper sulphate where least lime was used. That no misconception may be formed from the preceding com- parisons, it is w^ell to consider that the sprays were applied in these cases immediatel}' before the opening of the buds, so that prompt action of the copper was of greater importance than the enduring qualities of the sprays. As will be elsewhere shown, however, the endurance of sprays upon the trees is largely increased with the increase of the amount of lime they contain. A large increase of lime above the absolute requirements for the Bordeaux mixture is not necessary when the spray is applied so near the date of the opening of the buds that its action can not be delayed without loss in effectiveness. On the other hand, if the spray is applied at an earlier date, so that it is required to withstand weathering for a longer period, a considerable increase in the amount of lime may be an advantage in increasing its enduring quality. The amount of copper sulphate used in the preparation of the Bor- deaux mixture varied from 2 to pounds for 45 gallons of spra3\ Of the nine formulae tested, that containing 5 pounds of copper sulphate and 5 pounds of lime (row 21) gave the highest gain in foliage over the average healthy foliage of the control trees, or 634 per cent. There was an actual average saving of 95.9 per cent of the spring foliage of the 10 trees sprayed, consequently the average loss of foliage in this experiment was only 4.1 per cent. The next best results were obtained with the spray containing 4 pounds copper sulphate and 5 pounds lime (row 22). This spray gave a gain in foliage above the average produced by the control rows of 624 per cent. The average amount of foliage saved on the 10 trees was 94.5 per cent, showing that all but 5.5 per cent of disease had been prevented. While row 33 shows the next highest saving in foliage, these results, as already indicated, are exceptional, as shown by comparison. The yield of fruit which this row produced also shows the foliage records to be exceptional, and they may properly be omitted in these comparisons. 88 PEACH LEAF CURL: ITS NATURE AKD TREATMENT. The results obtained by the use of eau celeste and modilied eau celeste were very satisfactory, but in no case was as high a percentage of foliage saved by them as in the better tests with Boi'deaux mixture. The exceptionally high percentage of foliage saved on row 30 with but 2 pounds of copper sulphate may be in part due to the fact that the row was an exterior one of the Ijlock and next to a driveway, where the trees may have been better nourished than those of interior rows. By comparing the formula used on row 27 with that used on row 35 (each containing 4 pounds of copper sulphate) it will be seen that the saving of foliage was about equal with eau celeste and modified eau celeste. Comparison of these results with those shown by row 22, which was sprayed with Bordeaux mixture containing the same amount of copper, will show that the latter saved the highest percentage of foliage. Ammoniacal coppei carbonate gave less satisfactory results than the preceding sprays, probably owing to insufficient copper. The various results given by the other sprays tal)ulated require no special comment. Another fact is made evident by the preceding table. Of two formula3 of the same class, as the Bordeaux mixtures, one containing more of the fungicide than the other, the percentage of foliage saved for each pound of fungicide will be the greater in the weaker spray. Each of the Bordeaux mixtures used in spraying rows 21, 22, 25, and 28 contained 5 pounds of lime, but the amounts of copper sulphate used were 5, 4, 3, and 2 pounds, respectively. The total net amount of foliage saved by these sprays and the net saving per pound of copper sulphate each contained may be thus shown. Row 21: 5-poun(l formula, (3;)4 per cent saved; per pound of copper sulphate, 127 per cent. Row 22: 4-poun(l formula, 624 per cent saved; ])er pound of copper sulphate, 156 per cent. Row 25: 3-pound formula, 588 per cent saved; per pound of copjier sulphate, 196 per cent. Row 28: 2-pound formula, 584 per cent saved; per pound of copper sulphate, 292 per cent. These figures show a gradual decrease of the total per cent of foliage saved as the amount of the fungicide is decreased, but a decided increase in the percentage of foliage saved per pound of fungicide. COMPARISONS OF WEIGHT AND COLOR OF FOLIAGE FROM SPRAYED AND UNSPRAYED TREES. Besides the direct loss of leaves through infection by Exoasem defor- mans^ there is an indirect loss through the retarding of growth of such foliage as has not been directly infected by the fungus. A limited examination of this matter was made May 17 and 18, 1895. Two typical trees were selected in adjoining rows, one of which had been 20, Div, Veg. Phys & Patn., U. S. Dept of Agriculture. Plate VIII. 6 ■= DESCRIPTION OF PLATE VIII. Experiments at Biggs, Cal. (Unsprayed.) Looking north through the Lovell trees from row 28 of the experiment block, sliowing the nnsjirayed trees on l)oth sides as they appeared IVIay 15, 1895, in the unsprayed orcliard. These should be contrasted with the two sprayed rows, 21 and 22, shown in PI. IX. Bull 20, Div. Veg^ Phys. & Path., U. S, Dept. of Agriculture. Plate IX. DESCRIPTION OF PLATE IX. Experiments at Biggs, Cal. (Bordeaux mixture.) Looking east between rows 21 and 22, May 15, 1895. Row 21 was treated before blooming with 5 pounds copper sulphate, 5 pounds lime, and 45 gallons of water, and row 22 with 4 pounds copper sulphate, 5 pounds lime, and 45 gallons of water. Row 21 matured 4,443 pounds of fruit, and row 22, 4,421 pounds, while row 20, unsprayed, just south of row 21, matured only 648 pounds, and row 2,3, unsprayed, just north of row 22, matured only 712 pounds. Row 21 set 22,164 peaches, and row 22 set 21,478, while row 20 set only 1,911, and row 23 only 2,127; or, in other words, row 21 set eleven times as many peaches as row 20, and row 22 ten times as many as row 23 (p. Ill) . (Com- pare with PI. VIII.) COMPARATIVE WEIGHT AND COLOR OF FOLIAGE. 89 sprayed and tho othor not. Those were trees No. 10 of rows 20 and 21. Tree No. 10 of row 21 was sprayed the first week in Marcli, 1895, with Bordeaux mixture (5 pounds copper sulphate, 5 pounds lime). Tree No. 10 of row 20 had not been sprayed. From each of these trees was gathered 2 pounds of hoalthy folia<*'e. Careful measurements wore made of the length of the branches of 1894 o-rowth necessary to yield this weight of healthy leaves, and it was found that on tho unsprayod tree it required 18H foot 2 inches, while on the sprayed tree it reijuired only -49 feet 4 inches. The work was done as similarly as possible on both trees. The 2 pounds of foliage from the sprayed tree contained 2,428 leaves, and tho 2 pounds from the unsprayed tree 2,546. In other words, 118 more healthy leaves were required from the unsprayed tree than from the sprayed tree to equal 2 pounds in weight, or 59 more leaves per pound. This result is due to the indi- rect rather than the direct action of tho disease. The leaves from the unsprayed trees, being healthy, should average as great in weight as those from the sprayed trees, were it not for tho retarding and impoverishing action of the disease upon tho general growth of the tree. In comparing diseased with healthy loaves, however, this ratio would be reversed. Tho number of diseased leaves required for a given weight would be much less than the number of healthy leaves required. The diseased leaves are greatly curled and distorted through the irritation or stimulative action of tho fungus present in tho tissues, and in many instances thoy also become enormously increased in width, thickness, and weight. The contrast observed in the color and general appearance of the leaves of the sprayed and unsprayed trees was very marked. The foliage of tho trees treated with the stronger copper sprays, especially tho Bordeaux mixtures, presented the finest appearance. On May 8, 1895, t^vo months after tho spray work was completed, and at the height of the disease, the foliage on trees thus sprayed presented the greatest perfection. It was so abundant and so dense as to throw very dark shadows beneath the trees, making it difficult to obtain good photographs among them. This dense foliage existed upon both the lower and the upper ))ranches. The leaves were of a very dark and rich green color, long, soft, and beautiful. Upon the unsprayed trees comparatively few leaves presented the appearance of full health, and much of the diseased foliage had already fallen, leaving many trees nearly bare. The color of much of the remaining foli- age was vellow and sickly. Many of the uncurled leaves were small and light colored on both tho lower and the upper limbs. What growth these trees had made up to that date was largely terminal, very little healthy or comparatively healthy growth being apparent from lateral buds. (Compare Pis. VIII and IX.) 90 PEACH LEAF CURL: ITS NATURE AND TREATMENT. The influence of the various sprays on the thriftiness of the leaves was especially examined. This examination was conlincd to such foliage as was free from infection by the fungus, but was extended to sprayed and unsprayed trees alike, and to all rows of the block. In recording the comparative thrift of uninfected foliage, attention was given to the depth of the green color, to the softness of texture, and to the size of the leaves. These features of the foliage were considered collectively and recorded on the scale of 100; for instance, the most thrifty foliage was recorded at 100 per cent of thrift, and the less thrifty at a lower percentage. This method enables one to distinguish at a glance those spra^^s giving the l^est results in color, texture, and size of leaves — in other words, in functional ability. The records for each row and formula are given in the general table under the preceding head of this chapter, to which the reader is referred. It will there be seen that the trees of 5 rows produced foliage of the highest quality in spite of the presence of disease. These rows were all sprayed with the copper sprays, and all but one with Bordeaux mixture. Owing to the fact that row 30, showing lirst-quality foliage, was an outside row, it may be well to omit it in comparisons. The remaining -1 rows, Nos. 15, 41, 21. and 22, were all spraved Avith Bordeaux mixture, containing 6 pounds, 5 pounds, 5 pounds, and 4 pounds of copper sulphate, respectively. Smaller amounts of copper sulphate did not give equally high results. The average results shown by the different classes of sprays are as follows: Per cent. Sulphur, lime, and salt (3 rows) 67 Sulphur and lime (7 rows) 63 Bordeaux, sulphur, and lime combined (3 rows) 77 Bordeaux (9 rows) 90 Bordeaux, 4, 5, and 6 pound formulfe (4 rows) 100 Eau celeste (2 rows) 90 Modified eau celeste (2 rows) 80 Ammoniacal copper carbonate (2 rows) 70 Iron sulphate and lime (1 row) 40 Iron sulphate, sulphur, and lime (1 row) 40 Potassium sulphide (1 row) 40 Potassium sulphide and lime (2 rows) 45 Lime and salt (1 row) 60 ^ Lime (1 row) 50 Trees sprayed in 1894, but not in 1895 (3 rows) 20 Control trees (19 rows) 20 - The Bordeaux mixture is here shown to give the best average results as to thrift of foliage. The excellence of texture, color, and size of the leaves on rows sprayed with the stronger Bordeaux mixtures would be hard to surpass. ^ First leaves probably injured by spray. ^One exceptional row, showing 40 per cent, omitted; perhaps benefited by wind- bome spray. INFLUENCE OF SPRAYS ON THE VEGETATION OF THE TREES. 91 GROWTH OF URANCHES AND LEAF liUDS ON iSl'HAYEI) AND UNSPRAYED TREES. Besides knowing the action of the disease and of the sprays upon foliage, it is desirable to ascertain their action on leaf buds and the growth of branches. Two months after growth started — from May 10-1-ir, 1895 — a study was made of the growth of 20 trees in the experi- ment block, 10 sprayed and 10 unsprayed. The rows selected for this work were Nos. 20 (unsprayed) and 21 (sprayed). These rows were types of the injurious action of the disease and of the beneficial action of the spra}' applied, which was 5 pounds of copper sulphate and 5 pounds of lime. Much time Avas given to making measurements of the new growth and recording the results, the time being equalh' divided between the 10 sprayed and the 10 unsprayed trees. Typical limbs were nieasured^upon both the lower and upper portions oT the tre^g7 and the lenp-th ni^cprnpTraTivp henlth of the new growth^ was recorded. The length of 1S*J1 growth and that which was older was first ascer- tained, and was followed by careful measurements of all spring growth of 1895 arising from wood of 1891 or from that which was older. The results of this work are shown in the following table: Table 9. — Records of nieanurements of. healtlni and diseased wood on unsprayed and sprai/ed trees, taken May 10-14, 1895. 1 •2 3 4 5 6 7 8 9 10 Total Row 20, unsprayed trees. .^^ In. 1,422 1,614 1,364 1,304 1,576 1,8«6 1.366 1,7.T« 1.986 1,912 16,188 Length of spring growth of 1895— On wood of 1894. In. 492 .570 301 .5.57 499 298 .527 686 977 670 In. 249 229 251 304 326 2.57 230 516 550 582 5,577 3,494 On wood more than 1 year old! Row 21, sprayed trees. Ooo In. 76 219 83 I 234 ; 85 1 182 18 53 120 56 1,126 91 134 22 29 41 41 32 In. 674 664 592 666 702 976 998 1,068 938 982 8,260 Length of spring groAVth of 1895— On wood of 1894. In. 1,189 908 768 1,.580 1,100 1,2.59 1,348 2, 751 2,100 1,869 In. 14,872 40 On wood more than 1 year old. In. 194 494 46 330 45 325 183 195 84 220 In. 2,116 From the footings in the preceding ta])le it appears that the total length of 1894 wood measured upon the unsprayed trees was nearly twice as great as that measured on the spray ed trees. This arose from the scarcity oF liew growth on this unsprayed woo5, hence an equal time given to taking measurements upon each tree included more old wood upon unsprayed than upon sprayed trees. 92 PEACH LEAF CURL: ITS NATURE AND TREATMENT. On the unsprayed trees, prior to the middle of May, the total amount of new growth on 10,188 inches of 189-1: wood, including the older wood from which this arose, was 10,599 inches. On the sprayed trees the new growth amounted to 17,045 inches during the same time (two months) on 8.260 inches of 189-4 growth, including the older growth from which the latter arose. JThis was a net gain of 215 per cent, length of o ld wood consid ered, over the growth produced by the unsprayed trees. Otherwise^tatocl. the unspra^'i^d trees had tneragecl a new spring growtli oF7 85 inches \)ov running foot of 1M*4 wood and older, while the sprayed trees had produced a growth of 2-1.75 inches per foot of 1891 wood and older during the same time. This shows a' gain in growth on the sprayed trees during these two months of 16.90 inches per foot of old wood. The importance of this matter will appeal' to all growers who have peach orchards situated where the spring growth represents the major part of that of the season, as is true in man}'' peach-growing regions. In such orchards this would frequently represent a reduction of 25 per cent in the annual growth. In the peach, the growing wood of one year is the bearing wood of the next, hence the amount of wood produced would have added sig- nificance. Considering the total growth of the spring of 1895 from wood grown prior to 1894 — the pushing of dormant or quiescent buds — an analysis of the table shows a net gain by the old wood of sprayed trees of 173 per cent above the growth produced from like wood of unspra3^ed trees. This action of spray enables the grower to renew bearing wood on the lower portions of his trees, which is an advantage where trees are old or close set and tending to grow upward, or where curl or other causes have tended to denude the lower limbs of 3^oung and productive wood. This tendency of Bordeaux mixture to aid in the forcing and active growth of dormant l)uds was especially well marked in the case of a tree sprayed very thoroughh^ on one side (6 pounds copper sul phate, 1 pounds quicklime, 45 gallons of water) and left unsprayed on the other. From the base of the main liml)s on the spraj'ed side there arose 13 shoots from dormant buds during the first two months of spring growth, while the unsprayed limbs produced practically none. The 13 shoots on the sprayed side had made the following growth to Ma}^ 17, growth beginning about the close of the first week in March: Shoots. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Total. Length in inches 36 44 29 37 46 21 36 36 36 46 22 21 23 36 feet 1 inch. As shown by the table, the growth coming from 13 dormant buds at the base of the main limbs of the spraj^ed side of the tree during the first two mouths of spring growth amounts to 36 feet and 1 inch, COMPARATIVE GROWTH OF BRANCHES AND LEAF BUDS. 93 or an axeraov ot" ovrr ;>;> inclu's tor the lo shoots. That this astonish- ing pushing of new ))asal buds was not due to injur}^ of the top by the spray was shown by the immense amount of dark grcM'n foliage the sprayed half of the tree produced and from the amount and perfec- tion of the fruit it bore. It was evidently an aided or stimulated basal growth. In talde U is shown the comparative health or disease of the spi-ing wood measured. Wiiere shoots liad sult'ered from disease to such an extent that they were enlarged, crooked, or otherwise dis- torted or injured l)y the disease, they were classed as diseased ; when not so injun^d, they were classed as healthy. In respect to this classi- iication the tal)le gives the following facts: On the unsprayed trees the new shoots nieasun^d on growth of 1894 or older amounted to 10,599 inches, of which 0.703 inches was of healthy wood and 3,896 inches of diseased wood, or, in other words, 63 per cent of the wood was healthy and 37 per cent diseased. On the sprayed trees the total length of new shoots measured on 1891 growth or older was 17,015 inches; of this, 16,988 inches was of healthy wood and only 17 inches of diseased wood, or 991 per cent was healthy and i per cent diseased.^ Man}^ peach orchards- are cultivated under conditions of moisture and nourishment that enable the trees to grow throughout the entire sum- mer. In such situations trees badly diseased in the spring are apt to so far recover l^f ore frost that there is little apparent difference between them and the trees saved from curl by the use of sprays. That this recovery is not entire, however, is shown by actual comparisons. In the Riviera orchard. Live Oak, Cal. , were obtained the following records, in February, 1894, f ron 10 sprayed and 10 unsprayed Crawf ords Late peach trees. The trees are fully described under the following heading of this ^ These comparative records of the length of healthy and diseased 1)ranches upon sprayed and unsprayed trees fully serve the purpose of comparison for which they are here intended. There is another phase of the matter, however, which should not be overlooked or misunderstood at this time. A branch classed as diseased does not mean that it was diseased or swollen throughout its entire length, but that external signs of a diseased or injured condition were noted at some point in its course. If it be supposed that one-third of the injuries noted were dead ends or other imperfections not due to the infecting of the branch by the fungus, but indi- rect injuries arising from the loss of foliage, there remain two-thirds of the injuries which may l)e properly assumed to be due to the infection of l)ranches by means of mycelium coming from diseased leaves. There would then api)ear to l^e 25 per cent of tiie cases which might be classed as diseased from mycelium infection. As already indicated, however, this does not mean that these l)ranches are infected throughout their entire length, Init show one or more points of infection at the buds. It is thought by the writer that not more than 1 bud in 10 is actually infected in these diseased branches. If this estimate is approximately correct, the number of infected buds on the unsprayed trees would be represented by one-tenth of 25 per cent, or 2.5 per cent of the buds on the tree. In brief, it is believed that it is rare for more than 3 per cent of the buds of a badly disea.>^ed tree to become infected by the mycelium from diseased leaves — in other wonls, that rarely more than this jjercentage of buds of one year carry a perennial mycelium to the next spring. 94 PEACH LEAF CURL: ITS NATURE AND TREATMENT. chapter, and it will here be sufficient to state that the growth on the sprayed and unsprayed trees could be fairly compared. The sprayed trees were treated with the sulphur, lime, and salt spraj" in the winter of 1892-93. Leaf curl developed seriously in the orchard in the spring of 1893. The sprayed trees saved their foliage and bore a full crop of fruit in 1893, while the unsprayed trees, everywhere surrounding those that were sprayed, lost the spring foliage and most of the fruit. All trees stood upon moist, deep, rich river bottom land, where growth could continue throughout the season. In the fall of 1893 the unspraj^ed trees had apparently largely overtaken the sprayed trees in growth, as the former had carried little crop, while those that were sprayed had matured a full crop. That the unsprayed trees were not, however, fully abreast of the sprayed trees when growth ceased in 1893, is shown by the measurements recorded in February, 1891: (table 11). These measurements were made on various sides of each tree, and on lower and upper limbs, and as a week was devoted to the work, the measurements are believed to bo sufficiently extensive to give reliable results. Table 10. — Gain in number of lateral shoots and spurs Jruin. old vjood on sprayed trees. Records. Trees. Sprayed. Unsprayed. Length of old wood, measured in inches, on sprayed and unsprayed trees — Number of lateral shoots and spurs that pushed from old wood in 1893 8,255 2,922 0. 3539 13 7,363 2,300 0. 3124 Gain in favor of sprayed trees per cent. . The above table shows that 13 per cent more buds had pushed into shoots and spurs on the spra^^ed trees, in the summer of 1893, than on the unsprayed trees. All represented new growth from old wood. The following table shows that the length of the new growth for the entire season of 1893 on the sprayed trees was 6.4 per cent more than that produced on the unsprayed trees. This was in spite of the facts that the unsprayed trees were so situated that growth could continue until frost and that they had not carried a crop of fruit as had the sprayed trees: Table 1L — Gain in length ofiww growth in favor of sprayed trees. Records. Trees. • Sprayed. Unsprayed. Length of old wood, measured in inches, on sprayed and unsprayed trees — 8, 255 7,363 18, 174 2,692 16,390 1,100 20,866 1 17.490 Inches of new growth per inch of old wood Gain in new growth in favor of sprayed trees per cent. 2.527 6.4 COMPARATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS, 95 The nuinbiM- of leaf buds })roduc'ecl on the spniyed and iinsprayed trees per lineal inch or foot of old wood did not greatlj'^ diifer. There was, however, a gain of 1 per cent in favor of the sprayed trees, as shown below: Table 12. — (t'o(», in number of leaf buds iv furor of sprayed IreeSy/^""'^ Rofords. Length of old wood, measured in inches, on sprayed and iinsprayed trees. . Number of leaf buds Average number of leaf buds to inch of wood Gain in favor of sprayed trees per cent The tendency of the new growth to send out lateral branches and spurs was much more marked upon the sprayed than upon the unsprayed trees, the gain in this case being 101) per cent. This is a decided advantage, for the tree is thus enabled to bear a heavier and more equall}' distributed crop than where such laterals are few. Tablk 13. — Gam ia number of lateral xlioots and up itrs front new wood on sprayed trees. Records. Trees. Sprayed. Unsprayed. Length of new wood, measured in inches, on sprayed and unsprayed trees... Number of lateral shoots and spurs froni new wood 18, 174 &40 0.0a52 109 16,390 276 0.0168 Gain in favor of spraved trees per cent. . A complete tabular presentation of the data from which the four preceding tables have been drawn will be found under the following heading. THE DEVELOPMENT OF NEW FRUIT BUDS AND FRUIT SPURS FOR THE YEAR FOLLOW'INCx AN ATTACK OF CURL. In February, ISD-l, while the action of the sulphur sprays was being considered in the Riviera orchard, the question arose as to the rela- tive abilit}" of sprayed and unsprayed trees to produce fruit buds and fruit spurs for the year following a severe attack of curl. Many trees in this orchard had been spraved with the sulphur sprat's in the winter of 1892-93 for the d(^st ruction of the San Jose scale [Asjndio- tua jperniciosU'^. The manner in which this work was done furnished an excellent opportunity to ascertain the facts desired respecting the development of fruit l)uds. It was noted during the early part of the winter that individual trees, scattered through a 40-acre block of 4-year- old Crawfords Late, had become infested with San Jose scale. A careful examination of this part of the orchard was then made, and each tree found to be infested with the scale was marked for spraying. 96 PEACH LEAF CURL! ITS NATURE AND TREATMENT. Later in the winter Mr. A. D. Cutts, one of the proprietors and the superintendent of the orchard, had these marked trees thoroughly sprayed with sulphur, lime, and salt, the formula used being as fol- lows: Sulphur 15 pounds, lime 30 pounds, salt 10 pounds, water 60 gallons. While this spray was known to be effective against San Jose scale, it also proved very effective against curl, which developed seriously in the orchard in the spring of 1893. The result of the spraying was to produce a most striking effect. When the disease developed, the unspraj^ed trees, which i-epresented the major portion of this 40-acre orchard, were almost wholly denuded of foliage and largely of fruit, while the spraved trees, scattered through the block, were in full foliage and fruit. This orchard was selected as a very suitable place in which to study the relative thrift and number of fruit ])uds and spurs pro- duced on sprayed and unsprayed trees for the year following, and for this purpose 20 trees were selected from this block in February, 189-1. Ten of these trees had been spra3'ed in the winter of 1892-93, and had thus escaped serious injury from curl in the spring of 1893, while 10 of them had not been sprayed and had suffered considerably from the disease. These 20 trees were all Crawfords Late, 6 years old in the winter of 1893-91, and similar in other respects, the soil, situation, etc., being the sariie. The work of counting and grading buds upon these sprayed and unsprayed trees was begun about the middle of February, 1894, and continued for a week, an equal amount of time being given to each tree. To make all records as representative as possible of all portions of the trees studied, the limbs were measured and the buds counted and classi- ffcd upon different sides of each tree and upon both lower and upper limbs. In the selection and measurement of limbs, as well as in the counting and classification of the buds, an effort was made to correctly represent the conditions existing in all parts of each tree, and of all trees alike. After the selection of a limb for study, all wood grown prior to 1893 was measured and the length recorded. Following this all the shoots and spurs of 1893 growth, and arising from the old wood measured, were counted and the number set down. All these new shoots, with the exception of fruit spurs 4 inches or less in length, were then measured. Records were kept of the length of the new shoots, the number of well-developed fruit buds, the number of poorly developed fruit buds, and the nimiber of leaf buds they bore. A record of the number of lateral shoots and fruit spurs from the growth of 1893 was also preserved. The results of this work are brought together in the two tables which follow: DESCRIPTION OF PLATE XXX. Views of the right and left sides of the Gunnis power sprayer of San Diego, Cal. Tliis sjirayer is one of the liglitest, most compact, and most practical power sprayers in use for general orchard work. It supplies 2 or 4 lines of hose, as may be desired. A tender is commonly used to carry the spraying materials to the orchard, where an extra rotary pump, worked by the same power as the spray pump, rapidly transfers the spray to tlie tank of the spray wagon. Such an outfit is adapted to extensive orchard work. Mr. II. R. Gunnis, San Diego, Cal., is the ownerand operator of this machine. Bull. 20, Div. Veg. Phys. 8c Path., U. S. Dept. of Agriculture. Plate XXX. Right and Left Views of Power Sprayer, San Diego, Cal. COMPARATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. *J7 ^ "-I "ts^ ?!. •(saqout ui mSuai) pooM pio ■s-)oons ji) joquin^^ « ti 52 X o -1 3; OS to 00 • ■*tooo?i aioooO'j'iNOc^coA'^ •s^ooqs JO J3qnin>j •sands jo aaqamM •spnq jt!,)[ JO joqranfj ■pado -I3A8P Aiaooj ■p3doi3Aapn9AV ■(saqDni ui qjSn3[) pooAv'Avaf^ -^iOcotot^t^»-"ooaot-< «;t^t~00'*00 ioooaix*-rooOi-<-r ^OOtOiOOi>30'-CXl^ "^ X ^1 C^l X t^ t^ a: rH '^ XaiOST-HOSr-iiOi— <>— II— ( •sjooqs JO jaqrann 's[BaajBi ■sands jo aaqtnn*j •spnq J-B31 joaaqran*^ •pado -laAap Xiaooj •padoiaAap nsAV C-J T-( C^ iC CO C^I o ^ -.0 C^) T-;cJc^05eot^-*5om« IN i-HrHCvl r-lrHIN 0£JifflT)<5CrHXX«t^ eOi-IC-lC^C-li-li-KNC^rt ccnx"^coxo^anco CCC^COCOC-li— ICOCJC^CO CC iC ■^ T »C *T -T 'i: "^ to •(saqani ni qjSnai) pooAi 'Ava^ •sjooqs joaaqinnu 'siBaajBq •sands jo aaqran^ OTt>O-5 CDlCXtOt^iCX'-OXX t-^COCOOCO -'^iC-TX ;o r*. X OT o 19093— No. 20- 98 PEACH LEAF CURL: ITS NATURE AND TREATMENT. • (sotjoui III qjSuai) pooAv pio re iC -f CO O^ -^ >C '-D l^ O CO O lO i-l t-H Ol on~ C^ o C'l CO -^ O CO" -^ -^ lO t^ iC sjooqs JO joqiuUiSI •sjTids JO jaqniuH • (s9qDui lit q^Suai) pooAi pio •sjooqs JO aaqiiin>i y3^i— t OKOooiN'^^coo^ai i^ o lO 00 (M -* a i-l(Mi-lrH ■* tHC-ICOOCCiHOOOOO^O lOOiCiOOOSTjiOiHOO iHC^C^rHOOOCOC'10 I— (COCC^C^i— IOO^:Ot-h C^C^COOl-^C^'TCOC^CO •pado -IsAa p A[jo0(i OS ».t CC O -J^ CO Xi CC' iC r-t «:■ I^ C^D (M i-l O -t< iC n" C^l COCO'I'-^C^CO^CX'IOCO •p3dO[3A0pn8A\. OOOCOCOiCt~COC-)«-1" ^COi-OC»CCCOrHl^CO-f • (saqoui lu qiSuaO poo'.vv 'avos^i O) t^ Ol -f* '-0 --O CC O 1^ rH Gc a:' o CO o -+ cC' --C CO i spnq juai jo jaqnitiN COlOCDt^iCt^t^COCO^ i-H iH OJ T-H r •pado - 1 a A a p A|jooj 'XS-ft^COGO-^Oit^t^-l^ (N(MC^l-1aiOrHOiO i-HC^lCO'MCOCO-Ji'^-t*'^ • (saqaui ui qjSuai) pooAY Avajj iCOil^iOCOOOeOCOOitN •sjooqs JO jaquinu 'siBiajBi i^rHO -OSCO '-JOCOiC •sands jo aaqutiiN: 1-1 Ol CO -f lO O t^ 00 Oi o COMPARATIVE DEVELOPMENT OK FRUIT BUDS AND SPURS. 99 In the preceding tables, the number of shoots and spins of 1893, which arose from wood of 189:2 or earlier (old wood), as well as the length of the old wood itself, are classed under the general head of new growth from old wood. The measurements of the growth of 1893, and the number of lateral shoots and fruit spurs, as well as the number of fruit and leaf buds the new growth produced, are classed under the head of new wood. The buds were counted in a uniform manner upon all growth measured, except the buds borne by fruit spurs, w^hicli are estimated at 3 buds per spur in the tal)ulated calcula- tions which follow. The fruit buds have been divided into two classes — well developed and poorly developed. In considering the information given in the preceding tables, only those facts having a direct bearing on the fruit buds of the sprayed and unsprayed trees will be taken up under this heading. Those relating to length of new growth, number of new shoots, and number of leaf buds have already been considered under the preceding head- ing of this chapter. The following digest from the general tables shows that 23,879 fruit buds of all kinds were produced by the new growth arising from 8,255 linear inches of old wood on 10 sprayed trees in 1893 — an average of 2.892 buds per inch of old wood. The average number of buds per inch of old wood on the 10 unsprayed trees, obtained in a similar man- ner, was 2.686. These figures show that the sprayed trees produced 7f per cent more fruit buds of all kinds in the summer of 1893 than were produced by the unsprayed trees. These were fruit buds for the crop of 1894, and upon trees bearing a full crop in 1893, while the contrasted unsprayed trees bore very little. Table 16. — Gain in total number of fruit buds on sprayed trees. Trees. Records. Length of old wood, measured in inches, on sprayed and unsprayed trees . TotaJ number of fruit buds of all kinds Average number of same to inch Gain in favor of sprayed trees j.per cent.. The percentage of gain in the gross number of fruit buds shown by the spra3'ed trees is considerable, but it represents only partially the advantages derived from the spray. P^xaminations of the unsprayed trees showed that a large percentage of the fruit buds they had pro- duced in 1893 were imperfect, many of them being so poorly developed that fruit could not be expected from them. The following table shows the average number of imperfectly developed fruit buds on the spra3''ed trees to be 0.944 per linear inch of old wood, while on the unsprayed trees the average jxt inch of old wood was 1.24l>. This shows 32 per cent more imperfect fruit buds on the unsprayed than upon the sprayed trees at the close of the growing season of 1893. 100 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Table 17. — Excess of imperfectly developed fruit buds on unsprayed trees. Records. Trees. Sprayed. Unsprayed. Length of old wood, measured in inches, on sprayed and unsprayed trees 8,255 7,792 0.944 7,363 9,200 1.249 32 Average number of imperfectly developed fruit buds to inch of wood In comparing the number of well-developed fruit buds which were produced in ls'.);5 by the sprsiyed and un.spraycd troos. independent of the number of spur l)uds, it was learned that the number upon the spra3'ed_ti::£es^was 20 per cent greater, as shown in the following table, than the nuraber produced by the unspraj^ed trees. Table 18.^ — Gain in icell-develojied fruit buds, exclusive of spars, on sprayed over unsprayed trees. Records. Trees. Sprayed. Unsprayed. Length of old wood, measured in inches, on sprayed and unsprayed trees 8,255 7,363 12,049 8,927 1. 459 1. 212 Gain in favor of sprayed trees per cent. . 20 Taking the aggregate of all well-developed fruit buds, including the spurs, at an average of 3 buds each, the sprayed trees make a still better showing when contrasted with the unsprayed. The average number of all well-developed buds on the sprayed trees was 1.949 per linear inch of old wood, and on the unsprayed trees 1.437 per inch of old wood. This shows a gain of 35 per cent in well-developed fruit buds in favor of the sprayed trees. These facts are shown in tabular form as follows: Table 19. — Gain in spur buds and other well-developed fruit buds on sprayed over wisprayed trees. Records. Length of old wood, measured in inches, on sprayed and unsprayed trees Aggregate of spur buds and of other well-developed fruit buds Average number of same to inch Gain in favor of sprayed trees per cent. . One of the most striking contrasts shown by the data obtained in these field studies is that existing between the number of fruit spurs and spur buds produced b}^ the sprayed and unsprayed trees in 1893. There was a net gain in the number of fruit spurs and spur buds on the sprayed trees of 118 per cent above the number produced b}^ the unsprayed trees, a fact that should certainly appeal directl}^ to the business faculties of every grower of peaches. It should also be remembered that these sprayed trees had carried a crop while pro- COMPAEATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. 101 ducing these fruit spurs for the following year, while the unsprayed trees had borne but few peaches. The facts here discussed are shown in the table that follows. Tahle 20. — Gain in number of spur buds on sprayed over unsprayed trees. Trees. Rofords. Lengtli of old wood, measured in inches, on sprayed and unsprayed trees Total number of spurs NumbiT of spur buds, estimated at 3 buds per spur Average number of spurs per inch Average number of spur buds per inch Gain in favor of sprayed trees per cent. . Besides comparing the number of fruit buds produced in 1893 by the sprayed and unsprayed trees, it is desirable to contrast the bud- producing abilities of the upper and lower portions of these trees. It is generally conceded as desirable that the crop of a peach tree should be borne as largely as possible upon the lower limbs, and anything tending to this result may prove of value. Peach leaf curl, being due to a fungous parasite, has a tendency to do more injury to the lower than to the upper portions of the trees affected. The atmospheric con- ditions are more favorable for the germination of spores and to fungous growth in the lower and more shaded portions of the tree, and the lower branches accumulate greater numbers of fungous spores than the upper branches. In the following table it is shown that the total number of fruit buds produced b}^ the lower limbs of the sprayed trees was 7 per cent greater than the number produced by the upper limbs, com- paring equal lengths of new wood in each case. On the unsprayed trees, however, the upper limbs produced 5 per cent more fruit buds per linear unit of new wood than the lower limbs. This shows a difference of 12 per cent in favor of the sprayed trees. The tabulated figures are as follows: Tablk 21. — -Gain in total number of fruit buds on lower limbs of sprayed trees over those of unsprayed trees, as compared with upper limbs of each, respectively. Records. Trees. Sprayed. Un.sprayed. Length- of new wood, measured in inches, on upper limbs 10,964 1,358 9,770 Length of spurs, estimated at 2 inches per spur . . 554 Total length of new wood on upper limbs 12, 322 10,324 7,210 1,334 6 6''0 Length of spurs, estimated at 2 inches per spur 546 Total length of new wood on lower limbs 8,544 7,166 Total number of fruit buds on upper limbs 13, 724 10, 155 1.114 1.189 7 11,901 7,876 1 1.53 1.099 Gain in favor of lower linilis on sjirityed trees per cent.. 5 Difference in favor of sprayed trees '. do 12 102 PEACH LEAF CURL: ITS NATURE ANr> TREATMENT. By contrasting only the well-developed and spur fruit buds it is learned that there was 14 per cent in the number of buds in favor of the lower limbs on the sprayed trees and 4 per cent in favor of the upper limbs on the unsprayed trees. This showed a difference of 18 per cent in favor of the lower limbs of the sprayed trees. The entire comparison is given in the table which follows: Table 22. — Gain in number of well-developed and spur fruit buds on the lover limbs of sprayed over unsprayed trees, as compared with upper limbs of each, respectively. Records. Trees. Sprayed. Unsprayed. 10,964 1,358 9,770 554 Total length of new wood on upper limbs 12, 322 10,324 Length of new wood, measured in inches, on lower limbs . Length of spurs, estimated at 2 inches per spur Total length of new wood on lower limbs . 7,210 1,334 8,544 Number of well-developed and spur fruit buds on upper limbs Number of same on lower limbs Average number of same per inch on upper limbs Average number of same per inch on lower limbs Gain in favor of lower limljs driv'e, or twenty in all, and an extra man was assigned as superintendent of the twenty pickers, to see tliat all instruc- tions were carefully carried out. Every man was instructed to leave all fruit h(^ pickinl ])eneath the tree from which it was gathered, pick- ing boxes having been previousl}^ distributed for this purpose. The work of picking began at the south end of the experiment block. AYhen the fruit which was sufficiently matured had been gathered and placed in the boxes ])eneath a tree, the picker proceeded to the next tree north, thus following the same north-and-south row until he had passed entirely through the block, and when each man had thus completed his north-and-south row the entire block had been picked over, the fruit being beneath the trees from which it came. The first and second pickings were conducted in this manner, but the second was not begun until after the first was completed and the gathered fruit had been removed from beneath the trees. The process of collecting the fruit of the first picking l)egan as soon as the pickers had completed an east-and-west row and had proceeded to the next row toward the north. Four men were employed to collect and weigh the peaches — two to collect the fruit in the orchard and two to weigh, count, and keep the records. The fruit was brought from the east and from the west to the central driveway on a low plat- form wagon drawn b}^ one horse. The boxes of fruit gathered from the 10 trees of each experiment row were piled at the side of the driveway, close to the last tree of the row. The boxes of fruit from each tree were also distinguished by means of cards bearing the number of the tree from under which the boxes were taken (PI. X). The weighing began as soon as the fruit from the 10 trees of an experiment row had been piled at the side of the central drive. Plat- form scales were placed on a level base close to the fruit boxes, and the fruit from each tree of the row was weighed separately. The gross weight was recorded for each tree, as well as the immber of picking boxes. The average weight of the picking boxes used was afterwards carefully determined, and from these data the net weight of fruit was ascertained and tabulated for each tree of each row of the block. After the weight of fruit for each tree of an experiment row was thus learned, 100 pounds of peaches were weighed out from tjqjical boxes of several trees of the row. The number of peaches in this lOO pounds of fruit was then ascertained by counting, the number ))eing recorded with the other data for the row. The fruit of all the experiment rows was weighed and the average size of the peaches determin(nl ])y count- ing, as here indicated. Following close after the weighers came five or six sorters. These men graded the fruit, according to the requirements already outlined, into three classes — one for an Oakland canner}", one for a Chico can- nerv, and a third class for drvinijf. These three classes constituted 108 PEACH LEAF CURL: ITS NATURE AND TREATMENT. really but two qualities of fruit — a first quality for canning, and a second quality for drying. After the fruit of a row was graded a careful count of the number of picking boxes of each class of fruit was made, and the numbers recorded. From these figures were deter- mined the proportions of the total yield of the row which belonged to the different classes of fruit. The same process of picking, collecting, weighing, counting, grading, and recording was followed for the second picking as for the first. In the following table are shown the net weights of fruit gathered at the first picking from each tree of the entire block of 58 experi- ment rows, with the total weight for each row. Table 25. — Weight of peaches of first incking from the Lovell trees of the experiment block of the Rio Bonito orchard, gathered in the fall of 1895. Row No. Weight of fruit, in pounds, gathered at first picldng from trees Nos. — Total net weight of fruit in row. Number of trees in row. Average weight 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. per tree. 1 75 51 164 69 42 190 88 93 259 216 109 89 121 71 74 75 267 29 271 ?75 142 122 140 129 36 193 139 22 162 332 30 111 200 114 538 303 55 322 365 110 470 539 88 65 386 71 438 573 98 237 127 132 159 94 237 129 69 140 330 65 274 128 108 246 296 64 139 137 61 214 277 126 62 449 97 314 277 99 207 137 147 31 56 175 169 11 202 89 86 191 70 109 253 87 52 242 144 109 405 267 54 48 180 16 116 298 64 258 134 252 401 53 'iii' 27 166 147 54 157 57 73 228 181 39 218 219 83 304 161 47 474 298 88 341 331 32 498 544 62 43 426 19 166 400 60 323 149 315 250 107 563 188 198 273 118 111 179 120 140 97 183 151 248 240 107 154 203 114 474 216 119 233 364 27 431 556 95 52 424 62 425 489 90 219 179 218 373 148 491 354 84 234 384 49 200 145 45 164 324 56 116 79 60 120 207 ■ 84 63 421 153 181 282 195 262 90 289 87 159 212 180 115 233 249 114 247 209 91 573 451 58 296 245 32 617 469 75 48 565 109 513 489 33 296 111 209 428 79 597 365 127 284 439 53 410 223 97 139 413 42 105 182 86 118 251 25 44 392 137 244 313 83 190 140 241 74 100 212 222 39 234 297 41 168 187 114 340 235 89 144 201 22 252 324 38 56 459 96 290 379 95 318 199 298 429 133 590 365 163 341 461 47 305 119 28 231 363 73 169 142 41 229 193 63 73 408 67 381 399 46 180 165 200 69 64 237 169 53 153 467 166 240 145 47 453 291 44 288 189 23 343 332 105 24 140 48 49 34 66 204 110 16 121 169 70 147 77 32 273 198 21 119 180 59 427 346 53 96 Pounds. 1,570 1,007 1,687 741 810 1,813 1,708 568 2, 101 2,553 833 1,957 1,676 844 4, 227 2,348 715 2,609 2,594 574 4,307 4,275 672 547 3,771 658 3,116 4,126 576 2,615 1,552 2,282 3,189 1,102 4,034 2,681 1, 125 2,4.52 2,804 936 3,464 1,924 655 1,742 3,288 727 1,572 1,347 695 2,114 2,641 1,067 753 3,797 1,024 3,298 3,412 859 10 9.5 10 9.8 10 10 10 10 10 10 10 9.4 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 9.8 10 8.6 10 10 10 8 10 10 10 10 10 10 10 10 10 10 10 10 10 9.6 10 10 9.5 10 10 Pounds. 157 2 106 3. 168.7 4 5 6. 75.6 81 181.3 170.8 8. 56.8 9 10 210.1 2.55. 3 11 65 1 71 229 166 83.3 12 208.2 13 14 232 121 492 157 133 383 251 61 426 384 22 65 380 70 345 313 29 188 71 177 283 87 192 55 357 112 56 241 324 99 438 524 80 50 236 121 400 385 36 198 152 139 271 128 167.6 84.4 15 16 17 18... 422.7 2:34.8 71.5 260.9 19 2.59.4 20 57.4 21 22 430.7 427.5 23 24. 67.2 54.7 25 285 1 430 377.1 26 27 28 49 206 421 25 45 217 379 46 65.8 311.6 412.6 29 57.6 30 236 342 261.5 31 215 299 387 127 424 315 138 274 339 114 314 299 52 182 326 215 243 208 146 448 310 143 403 414 222 400 211 84 226 9«fi 155.2 32 228.2 33 34 325.4 110.2 35 393 291 298 213 80 ' ?tfi 469 36 268.1 37 112.5 38 246 283 135 412 287 92 171 328 52 130 97 77 250 264 162 140 337 93 336 330 91 91 154 123 268 176 85 150 220 87 149 155 91 284 330 99 68 457 166 361 400 64 245.2 39 350.5 40 59 451 157 32 163 222 107 118 106 95 147 263 135 105 443 80 415 359 92 69 430 179 32 70 510 90 228 117 78 107 247 147 54 311 45 294 254 86 93.6 41 346.4 42 192.4 43 65.5 44 174. 2 45 328.8 46 103 ! 53 190 i 958 72.7 47 157.2 48 151 74 295 299 94 90 294 92 268 397 181 32 350 310 132 54 285 94 504 471 134.7 49 69.5 50 211.4 51 264.1 52 106. 7 53 78.4 54 379.7 55 102.4 56 347.1 57 341.2 58 51 1 •'^'' 85.9 „_ GATHERING FKUIT OF SPRAYED AND UNSPRAYED TREES. 109 At the side of the total colunm in the preceding- table is given a col- umn showing the number of trees in each row. The total amount of fruit gathered at the first picking from each row has been divided by the number of trees in the row, giving the average aniount of fridt picked per tree for each row of the block. This average is shown in the right-hand column. In the table which follows is given the net weight of fruit gathered at the second picking from each tree of the block not picked clean at the tir.st picking. Table 26. — Weight of peaches uf second picking from the Lovell trees of the experiment block of the Rio Bonito orchard, gathered in the fall of 1895. Row No. Weight of fruit, in pounds, gathered at second picking from trees Nos. — 121 6 124 13 21 6 6 18 11 18 11 28 18 1 295 33 150 212 62 63 119 23 24 10 26 10 13 28 13 16 Total net weight of fruit in row. Pounds. 1,242 343 1,109 255 236 452 517 107 357 415 136 146 184 84 124 152 43 91 118 74 136 146 40 52 217 14 100 137 26 2,526 786 1,136 1,082 222 840 393 245 424 439 173 566 198 84 265 203 47 102 92 61 55 91 64 47 266 75 92 91 43 Number of trees in row. 10 9.5 10 9.8 10 10 10 10 10 10 10 9.4 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 9.8 10 8.6 10 10 10 8 10 10 10 10 10 10 10 10 10 10 10 10 10 9.6 10 10 9.5 10 10 Average weight per tree. Pounds. 124.2 36.1 110.9 26 23.6 45.2 51.7 10.7 35. 7 41.5 36.6 15.5 18.4 8.4 12.4 15.2 4.3 9.1 11.8 7.4 13.6 14.6 4 5.2 21.7 1.4 10 13.7 2.6 252. 6 78.6 113.6 110.4 22.2 97.6 39.3 24.5 42.4 54.8 17.3 56.6 19.8 8.4 26.5 20.3 4.7 10.2 9.2 6.1 5.5 9.1 6.4 4.9 26.6 7.5 9.7 9.1 4.3 110 PEACH LEAF CURL: ITS NATURE AND TREATMENT. The total 5deld of the trees and rows of the experiment block is shown in the following- table, which was compiled from the preceding records of fruit gathered at the first and second pickings. Table 27. — Total weight of peaches' of first and second pickings gathered from the Lovell trees of the experiment block of the Rio Bonito orchard in the fall of 1895. (a) Row No. Total weight in pounds of fruit gathered at first and second pickings from trees Nos. — 1. I. 3. 4. 230 183 340 9.'> 134 236 2Ah 173 298 71 173 70 74 49 146 83 253 197 276 238 197 89 30 11 2«7 188 216 285 357 105 76 35 97 178 111 191 205 221 70 61 114 117 363 556 253 12;^ 321 87 56 66 52 251 322 256 330 381 144 102 125 109 446 483 410 552 558 257 80 88 67 56 65 48 247 414 180 121 71 16 409 446 116 404 573 298 39 99 64 ;«9 532 525 259 160 219 284 282 333 463 371 527 190 156 53 542 300 288 248 186 127 69 82 153 220 243 •^96 438 95 155 m 371 423 499 249 151 157 85 117 46 168 306 206 236 314 222 99 64 107 160 148 118 155 155 136 91 78 105 284 214 161 330 288 288 99 135 141 68 72 114 478 541 460 170 108 96 361 346 442 418 277 359 64 99 92 5. 5. 7. 8. 245 394 302 111 115 181 267 315 403 165 91 100 152 159 100 117 321 222 183 211 222 151 142 52 248 315 234 327 325 297 107 145 69 167 288 168 203 244 187 114 99 127 474 580 340 216 462 263 119 63 89 2;S3 296 144 364 259 212 27 36 22 431 629 252 556 469 324 95 82 38 52 53 74 424 589 488 62 115 96 425 , 513 306 489 489 379 102 33 95 418 434 459 282 138 222 331 316 328 477 442 448 148 92 139 543 632 684 369 365 437 111 135 187 261 308 341 451 462 475 74 53 47 262 425 326 183 236 124 58 104 40 205 154 240 341 430 389 63 44 82 148 111 178 94 182 154 73 95 43 130 118 239 220 251 203 96 43 66 75 44 82 476 402 426 171 137 93 198 244 381 312 313 425 195 109 52 10. Total. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38 39. 40. 41 42. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 129 76 243 81 42 239 148 104 290 245 72 240 2-55 140 525 177 144 406 261 68 438 395 28 71 403 75 345 313 29 458 111 377 396 95 482 304 92 269 309 150 459 308 99 187 347 55 140 108 82 254 276 162 147 356 93 339 331 91 259 54 308 57 134 311 301 39 314 238 83 304 184 47 474 298 88 341 362 54 498 544 62 43 458 19 166 417 65 524 176 325 253 107 593 199 242 336 69 430 179 32 70 534 90 228 117 78 107 247 147 54 311 45 294 254 422 232 308 103 87 275 199 71 179 530 184 255 159 59 475 297 51 302 202 28 396 340 107 28 285 52 222 460 25 675 408 389 468 141 570 315 138 305 369 114 335 299 52 213 359 103 215 157 79 306 314 100 90 328 92 281 327 62 308 116 236 85 103 247 250 36 187 259 101 201 132 50 311 256 30 149 197 77 460 426 65 109 500 45 268 441 51 727 363 453 426 203 528 363 187 440 443 245 500 236 106 258 319 67 228 181 32 356 315 142 54 285 94 504 487 52 2,812 1,350 2,796 996 1,046 2,265 2,225 '675 2,458 2,968 969 2,103 1,860 928 4,351 2,500 758 2,700 2,712 648 4,443 4,421 712 599 3,988 672 3,216 4,263 602 5,141 2,338 3,418 4, 271 1,324 4,874 3,074 1,370 2,876 3,243 1,109 4,030 2, 122 739 2,007 3,491 774 1,674 1,439 756 2, 169 2,732 1,131 800 4,063 1,099 3,390 3,503 902 a For plat of orchard see p. 69; for sprays applied see p. 73. As already said, after the weight of fruit for each tree of a row had been asc-ertained and recorded, the number of peaches in 1<>0 pounds of this fruit was determined by counting. From several picking- boxes of fruit, coming from different trees of the row, was weighed out 100 pounds of peaches fairly representing the fruit of the row. The peaches of this 100 pounds were then carefully counted and the number recorded. This was done both foi the first and second pick- GATHERING FRUIT OB^ SPRAYED AND UNSPRAYED TREES. Ill ings aiul for the sprayed and imspniyiMl row.s. Whore less than loo pounds of fruit was oathcrod tho iHiinh(>r of peaches ])er 100 pounds was (h'terinined by countini;- a h'ss weioht of fruit, usually .')(» pounds. The foUowin^i' table gives the results of this work for both (ii-st and second pickings: Table 28. — Xiuiihcr of peaches per 100 pomtds; wcujlil uf fruit gulheral; and inimhcr of peaches thinned, gathered, and set by the trees of each row in the experiment block of Ihr I Ho Bonito orchard in 1895. (a) Number of peaches in 100 pounds. 03 Pounds of fruit — Number of peaches gath- ered at — Number of peaches— -o 2 a o 'm O OQ fe 1,242 4,066 343 2,971 1,109 4, SOS 255 2, 223 236 2, 4.54 4.52 5,040 517 4, 7S2 107 1, 602 357 6, 051 415 7,199 136 2,432 146 5, 538 184 4,911 84 2, .583 124 13, 061 152 6,903 43 2,116 91 7,827 118 7,496 74 1, 665 136 13, 266 146 13, 6S0 40 1,989 52 1,597 217 10,710 14 1,S12 100 8.600 137 12, om 26 1,596 2,526 7,636 786 4,718 1,136 6,709 1,082 9,280 222 3,196 840 13,111 393 7, 641 245 3,173 424 6, 915 439 8, 104 173 2,808 .566 9, 838 198 b,mo 84 1,919 265 .5,383 203 10,160 47 2,203 102 4, .543 92 4,149 61 2,029 55 6,067 91 7,897 64 3,233 47 2,259 266 11,619 75 3,021 92 9,663 91 10,168 43 2,422 o^ P OJ Eh Average number of peaehes set per tree. 259 295 285 300 303 278 280 282 288 282 292 283 293 ' 306 309 294 296 300 289 290 308 320 296 292 284 280 I 276 : 291 I 277 j 292 I 304 , 294 i 291 290 I 325 285 I 282 282 289 • 300 284 303 293 309 309 303 289 308 292 287 299 303 300 306 295 293 298 282 288 317 310 335 323 324 326 322 323 313 316 321 312 6 324 362 317 6 327 6 339 6 340 6 332 6 314 6 362 6 344 6 3.56 6 368 6 3.54 6 360 6 370 6 360 313 326 311 335 330 345 332 330 330 328 312 339 335 6 304 337 346 6 330 3.56 6 324 6 312 6 3(!(; 6 3.56 6 336 6 325 6 3.52 6 334 6 384 6 370 6 360 1,570 1,007 1,687 741 810 1,813 1,708 568 2,101 2, .5.53 833 1, 9.57 1,676 844 4, 227 2,348 715 2, 609 2, .594 .574 4,307 4,275 672 .547 3,771 658 3,116 4, 126 576 2, 615 1, .5.52 2, 282 3, 189 1,102 4,034 2,681 1,125 2,4.52 2,804 936 3,464 1,924 6.55 1,742 3,2*8 727 1,.572 1,347 695 2,114 I 2,641 I 1,067 I 7.53 I 3,797 : 1,024 3, 298 3, 412 ,S.59 3, .577 1,087 3,438 8.54 762 1,4(H 1,68.^, 345 1, 153 1,299 430 469 574 272 449 482 140 308 401 246 427 529 138 185 799 50 360 507 94 7,906 2,562 3,533 3, 625 733 2,898 1,305 809 1,399 1,440 .540 1,919 663 2.55 893 702 155 363 298 190 201 324 215 153 936 250 3.53 3:i7 1.55 7,643 4, 058 8, 246 3,077 3,216 6,504 6,467 1,947 7, 204 8,498 2,862 6,007 5, 485 2, 855 13, .510 ■ 7, 385 2, 2.56 8, 135 7,897 1,911 13,693 14,209 2, 127 1,782 11,. 509 1,892 8,960 12, .513 1,690 15, 542 7, 280 10,242 12, 905 3,929 16,009 8,946 3, 982 8,314 9,544 3,348 11,757 0,493 2,174 6,276 10,862 2,3.58 4, 90C) 4,447 2,219 6,268 8,221 3,448 2,412 12, .555 3,271 10, 016 10, .505 2, .577 5,442 '4,'829 2, 3.52 2, 265 3,863 4, 3.52 2,730 1,841 7,762 2, 401 3, 024 3,616 8,470 7, 269 5, 128 5, 742 10,208 3,269 7,360 9,730 4,896 3,318 5,821 5,953 773 3, 951 675 2,985 5, .568 5, 659 5, 2.51 13,085 4, 0.58 13, 075 3,077 3,216 8, 8.56 8, 732 1,947 11,067 12, 8.50 2, 862 8,737 7, 326 2. 8.55 21,272 9,786 2. 2.56 11,1.59 11,. 513 1,911 22, 163 21,478 2, 127 1,7.82 17,2.56 1,892 14, 088 18, 2.55 1,690 25, 7.50 7, 2.S0 13, .511 20, 26.^ 3, 929 25, 739 13, .841' 3, 982 11,632 15, 365 3, 348 17,710 6, 493 2,174 7,049 14,813 2, 3.58 4,906 5,122 2,219 6, 268 11,206 3, 448 2,412 18, 123 3,271 1.5,675 15, 7.5(i 2, .577 10 9.5 10 9.8 10 10 10 10 10 10 10 9.4 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 9.8 10 8.6 10 10 10 8 10 10 10 10 10 10 10 10 10 10 10 10 10 9.6 10 10 9.5 10 10 1,308 i',m 886 873 1,107 1,285 929 733 2,127 979 1,116 1,1.51 2,216 2,148 1,726 1,409 1,825 2, .575 1,351 2,068 2,993 1,384 1,163 1,921 1,771 649 705 1,481 491 512 627 1,120 1,812 1,6.50 1,576 a For plat of orchard see p. 09; for sprays applied see p. 73. 6 Number calculated from a less weight than 100 pounds, usually from 50 pounds 112 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Following the lig-ures in the above table which .show the number of peaches in 100 pounds of fruit are those giving the number of pounds of fruit gathered at the first and second pickings. From these four columns of figures has been calculated the number of peaches gathered from the trees of each row of the block for both the first and second pickings. By adding these numbers the total number of peaches matured bv the trees of each row was quite accurately determined. To this amount is now added the number of peaches thinned from the trees, where thinning was required, the grand total representing the number of peaches firmly set by the trees of each row. By dividing this grand total by the immber of trees in a row it has been possible to show the average number of peaches set per tree on both sprayed and unsprayed trees, and for ever}^ row in the experiment block. COMPARATIVE QUANTITY, QUALITY, AND CASH VALUE OF FKUIT FROM SPRAYED AND UNSPRAYED TREES. (Pis. XI ami XII.) The actual yield in pounds of peaches, the qualit}", and the cash value of the fruit produced by the sprayed and unsprayed trees of the experiment rows of the Rio Bonito orchard in the season of 1895 are full}'^ and accurately shown in the table which follows. This table gives a full record of the yield as it was taken in the orchard, and the results are of the greatest value from a practical standpoint, convey- ing an accurate idea of the cash gain resulting from this spray work. If the reader will compare the average value of the fruit produced by the sprayed trees of row 21, for example, with that of the fruit pro- duced by the unsprayed trees of row 20, some conception of the possible gains resulting from thorough spraying may be obtained. In studying this table, it should be remembered that the results shown were obtained from the use of 35 different f ormulte and spra3^s. Some of the sprays were of little value, others of medium value, etc., hence the gains shown for the entire block are far below what they would have been had the trees of each of the rows been sprayed with such sprays as those used upon rows 21, 22, or others of the better-yielding rows of the block. DESCRIPTION OF PLATE XI. Experiments at Biggs, Cal. (Siili)hur, lime, and salt.) Looking west between rows 2 and 3, May 14, 1895. Row 2 was unsprayed; row 3 was sprayed before blooming with 15 pounds sulphur, 20 pounds lime, 5 jiounds salt, and 45 gallons of water. The average value of fruit matured jjer tree in row 2 was $1.96 and in row 3 i5i3.90. The spray used showed a net gain from the treatment, as determined by the compar- ative value of the peaches set by the trees of both rows, of 216 per cent (p. 117) . Bull. 20, Div. Veg. Pnyi. 8c Patn., U. S. Dept. of Agiicultuie. Plate Xi. DESCRIPTION OF PLATE XII. Experiments at Biggs, Cal. (Sulplinr and lime.) Looking west between rows 9 and 10, INIay 14, 1895. Both rows were sprayed before l)looming. Row 9 was treated with 10 pounds sulphnr, 20 pounds lime, and 45 gallons of water, and row 10 with 10 pounds sulphur, 8 pounds lime, and 45 gallons of water. Row 8, adjoining row 9 at the south, and row 11, adjoining row 10 at the north, were untreated. The aver- age value of fruit matured i^er tree on row 9 was $3.35, and on row 8 only 91 cents. The average value of fruit matured per tree on row 10 was $3.90, and on row 11, $1.35. As determined by the comparative value of the peaches set by the trees, the spray used on row 9 showed a net gain over row 8 of 457 per cent, and that used on row 10 showed a net gain over row 11 of 337 per cent (p. 117) . It may be seen that the lower limbs are not as thickly covered with foliage where the sulphur sprays are used as where the copper sprays are used. This is especially true where the former is applied too late or too strong. (See PI. XI.) Bull. 20, Div. Veg. Pnys. & Path , U. S. Dept. of Agriculture. Plate XII. COMPARATIVE QUANTITY, QUALITY, AND VALUE OF ERUIT. 113 ■sasjj po.vvadsn^i <5a •Baajl paXBadg i-2 :g ■-0 •ccSi THiA CC CC • CO CO • CO c^ 8:? 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ITS NATURE AND TREATMENT. to'— o^.-t-^ict^oc-JC4 C^C^ r-i^H C^i— I !N ocooit^^rr^ccr :d^:r:i>xt^r-4t^^Oinr^un; ,,• X ?T =;. --o in — i^ ut in i~ -.o i.; -o x —■ -o o -o r-: s 31 X 3i c> m t^ -o in en rH -■ ■= " 1 c-j t^ ro ^ in « Sut.Up JOJ jinj^ ^ T r- rH in^ t^ ci o oi in -o o X c-i in — t^ i-i o ci o Oi o o '^ ci o in -^ yininOwX^oo'-oco-rt^ci-^xc^irHr^w-^-^t^cc^r^in-^oai ^xcO'.r^i-(inr:c^c^cCF^incOT-Hooi>T-(C^c^t-i-.5--^c^^t^c^i5-T5*r^ •Aioj jad spunod ut jinjj jo piajA *^ CO r^ L^ c-j t^ t^ i^ i^ -r o CO' c-i TO o OS t^ t^ cc in 'w cc. ?c o o OS oi o o T-ico-TO^coxocoxiNr-co^t-o-ri>tCTrt^.-Hr~,-iXOOcoinoi in''cfco''Tj<"r-r'^"eo''r-rc4'co'"r-r'^'"(N' cTrO rHt-^' -M'c-fr-T TaT^-cCCO ■saajj pajJBJdsufi X CO ?5 o CO 1-t 05 1" -o in •rt CO ■saaj; paXBjdg XX I>^ o^ o c^ r-rH ^a> r-in ■-0 t^ t^in ?c1 OCT. 52 CO xco •.DO in in coco •Avoj ui saaji jo jaqran^ JXOOOXOOOOOOOOOOOOOC-. 00 3-. oo 1 -3 •saaj} paiSBjdsufi •saajj pajiBjdg X • ^ ; o • -1 ; S-. ' r-O _^ i-H • t> ■ o " : " : '^ : "^ '"' 2t= sg lOCO XCJ •OrH ill S3 ■~Z CO • ■3 o ill CC "^ -^ CO C4M |-^(N • c^co «rt MO) • ■* • coco •5at5iDid pnoo8S •Sui2[0id :jsjij: iC C-) CI Ci ri -T 1-1 ut: CI -TT -^ i-iiCX'XOCCX'Mu^OcO !iS lO CJ 1— I I— I O — 1— I T X Oi cf T— " cf CC i-T '^ cf i-T cf cT ; cj lO -^ X CI r- *r C-. r-t T --Cur: ci ci Oi 1-H lO T-tCC t-(r-i ) Cl»-i CCt-iCOOO OrHC^CO'^iO'^r-XClO'— 'C^CCrfiC'— r»XOOi-HC4C CO CO CO CO CO CCCC CO CO CO "^ ■^ -rf iC iC lO iC iQ iC vQ L Bull. 20, Div, Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate XIII. DESCRIPTION OF PLATE XIII. Experiments at Bigg^i, Cal. (Bordeaux mixture.) Looking west between row's 20 and 21, May 11, 1895. Row 20 was unsprayed ; row 21 was sprayed l)eiore bloom- ing witli 5 pounds copper sulphate, 5 pounds lime, and 45 gallons of water. 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CO C-. 01 1^ o -^ =-. i-o -^ o X ^) :~i -r c^ 05 1^ o ^^m' -ir Tj^ x' d d x' -T r^ co' x' d -r d t-^ -r oi ci lO 1-^ t~^ ■* co — ' o d oi lO i-irHr-l(MT-iT— r- — Ol r-rt?) •.Cr-::^C5r^f*OM'— oxcit^rsuoxxict^ioc^coooj-^ociic •J5 3--coxoauooii: — oic:oxtxu;c-. ocouot^:-)XCico-^Tr ^0icO»lO)OJ'HT?o;i-!04iC 'r-ir-'— ^COCOrHTjlOrHCOCOr^ •pajniBm uaqAv ?injj puBiijBO JO 5qSiaAV pajBtnijsa ibjox X o ■•^ c^ 01 oi ic X t^ t^ o X c. 01 cr- X X -.c — ^ oi X 01 uo ic o -^ 'o t^ -T CO — X cc X cc 01 1^ M r — r X — X -c — .i ^. — X t^ o — 01 X -^ c] M :-- ■-; X CO -^ X ^. t^ M r- CO o 1.0 cc -^ o 01 CO -r -^ -^ X to o o CO •jinij pxiBiiiBO oj pa -ppB jqgiaAV juao aad \i t^^Jr--T-Or-X01 — t^Cnt^LCt^OlX'-D-T^X'TXt^X- C^Ol 05-~0 X CO-O X 02I>— rHCOOiOC — - - T-^ M 01 C^ O^ rl — i CO r^ r^ OJ •pajaqjBS u a q Av A'aau -UBO pUBl^lBO th X CO ic w »-^ r^ — --c o ^- ' :if;T— fxsio — locooo-i- ■i^t^ooiojiccoxoicr^r , _, , _ , _ , _ _■ CO i^ 3^ OJ oi oi ^ 01 — CO ^' rH o '^ irt ic r^ — — i^ c^ c o CO CI 01 CO ;o c^ OJ OJ CO :c -T- lit T X ut CO '~5— ToJ^OJ" Oj'Ol" rHrn' 01' 1-"' Oj" !->' 01" T-'i-T •-■ijauuBO oaiqo •SUTAId cocsr^-i'T-'rHCOr^OjcoC5cocot^xt^r-r^c;Oi0^uoor;or--x i ^o lO '-C ir^ tC lO i> -^ iC :^ X -f 'w o — cc t 4 X c: Ci ir: t~ ■— uo Ci — OJ ic ■— OJ -^ ' ; X .- -J' t CO " I :xoJco-rxoJOJi^cOt— i/rco — ' . 1.0 r^ OJ o c: uo — o X OJ i-o -^ f o OJ — * o o '-T: n o li^ ^ ./ ifc o — X T-* c; o --C CO — i^ r: -T X 1 T— — -^ -r -ri^ CO tc r^ uo -r w c^ ^ CO -^ '-c rH lO cC' OJ OJ CO ^ lO CO — CO t^ r- OJ OJ rH ^ -r OJ — i^ 01 ^ ^ r-i •AVOJ JO saajj Aq jas saqoBad jo jaqninu [bjox ■I no c^ C-. OJ OJ 01 i-O X o CO -r 31 CO X -^ OJ C-. X -^ X 01 CO ^ i-O -^ t^ " OJ CO -T X cc -^ — r- C-. t^ -r — lO o 01 — -^ = — r- 01 1^ I^ uO t^ r". t^ X Ci — 00 CO x^ -r •— o X CO o^ ^ 01 o) 01 -r — --^ OJ '-c i> i^ co~ d" CO*" lo" co" co' 1— lo' co" r^ d" oj'^i^ -r" oj" ^^ ic" OJ d' ^ co~ Oj" x" co" lo'uo*" of a S3 •AiOJ JO saajj Xq pajn}Bi\[ c OJ i-O 35 C5 -.c OJ -r -r X t~ CO -T -^ 01 X o r~ 31 X — X 01 1-0 —. -^ lO i> x-rooJO-rX' ^ — i03ir^t^*wL0o-r'— -^OJ^ — LOt^i— oi> OJOJCio^oCiCscouocoi^Tr-— oixco^i-rojOJOJ-r-TiiOOJOLrriC r-^ d" oj" co" d" x" CO* xT id co" r4" d" oT d" d" o j' ■^" -t" oT d' xT CO of of co" d' d" Oj" •A\oj JO saajj niOJj pauuiqx irfic" rHMecriO'Cr^x— . 3— <0JC0^i/0cCt~xa»O oseoeowcccocococ ^TT^^^iOiClTOiC INFLUENCE OF SPRAYS ON THE FRUITING OF THE TREES. 119 COMPARATIVE SIZE OF FRUIT ON SPRAYED AND UNSPRAYED TREES. Owing to the fullness of the records obtained relative to the weight and number of peaches gathered from the sprayed and unspraved trees in the present experiments, it is possible to learn the compara- tive average weight of the fruit produced on treated and untreated trees. It might seem that the unspraved trees, having to mature on an average 291.3 peaches per tree, would jield larger fruit than the sprayed trees, which had to mature 949.2 peaches per tree; in other words, that the increased number of peaches upon sprayed over uusprayed trees would, to a considerable extent, be counterbalanced by an increase in the size of the fruit on the lightly loaded unspraj^ed trees. It has been found, however, that w^here the conditions for vig- orous growth of a tree are present, and where the fruit upon a tree is so thinned that the tree is not overloaded, the peaches of the full- bearing tree are practically as large when mature as are those of the tree which has lost much of the crop from curl. The following table has been compiled from the facts in hand upon this matter. It is shown in this table that the fruit from the sprayed trees averaged for the whole block (315.3 trees) 299.0311: peaches per 100 pounds, and the fruit from the unsprayed trees averaged for the whole block (228.9 trees) 299.0312 peaches per 100 pounds. This shows that the gain in size of peaches on unsprayed trees over those on sprayed trees, as determined by the average number of peaches to 100 pounds, is foVoiTTF per cent, or only about ^oVsj of 1 per cent. This amounts to nothing from a practical standpoint. Table 31. — Size of fruit on sprayed and unsprayed trees as determined by the average number of peaches per 100 pounds. Num- ber of trees in block Fruit produced 1 by all trees I of block. Average production per tree. First pick- ing. Sec- ond I)ick- ing. First pick- ing. Sec- ond pick- ing. Average number of peaches — Per 100 pounds. First pick- ing. Sec- ond pick- ing. Per tree. Proportion-I ate percentage I yield | of trees, i Average per- centage of gain in size of fruit First pick- ing. Sec- ond pick- ing. First pick- ing. Sec- ond pick- ing. Aver- age num- ber of peachesi ,„ „„ per luu I „r,_„,,p^ Dounds *P™>ea ^ \:zr trees over per tree. that of sprayed trees. Sprayed Unsprayed 315.3 9.5,094 ib.s. LU. 228.9 19,035 14,504 3,257 Lhz. 275.4 83.2 Lbs. 42 293.2 293.6 337.4 330.8 807.6 244.3 13.2 14.6 299.0344 299.0312 It should not be understood by the above that a crop of 950 peaches draws no more heavily upon a tree than a crop of 3()0 peaches when other conditions are equal. All observation tends to show that such is not the case. A tree too heavily loaded will often produce 120 PEACH LEAF CURL: ITS NATURE AND TREATMENT. much smaller fruit than a properl}' thinned tree, even upon exceed- ingly rich soil. The facts given in both the preceding text and table show clearly, however, that the severe attaclc of curl in the spring of 1895 drew upon the vitality of the unsprayed trees as heavily as did the excess of 65;) peaches each on the sprayed trees. Otherwise stated, the trees averaging -300 peaches were drawn upon as heavily by the attack of curl, combined with the maturing of 300 peaches, as were the sprayed trees in maturing 950 peaches. If this had not been the case, the unsprayed trees would have better nourished their crop, and would have produced larger and heavier fruit than those which were sprayed. These facts should receive the attention of all thoughtful growers, as no one can afford to have his trees drawn upon to the extent of two-thirds of a crop of peaches without return, even when frost or other causes would not have allowed him a crop on sprayed trees. To permit trees thus to suffer from curl even in such a year would be equivalent to draining them of much vitality, even though the}^ failed to show this drain in the reduction of wood or fruit liuds for the ensuing year. But it has already been shown that a marked reduction in the number and quality of fruit l>uds is a result of a spring attack of curl. The soil is also certain to sustain an unnec- essary drain upon its resources. Another phase of this subject is made clearer by the above table. There are very manj" varieties of peaches so resistant to leaf curl that the fruit does not drop, even when a large percentage of the leaves are lost. Man}- growers leave such varieties unsprayed, thinking that the saving of the fruit is the all-important point, and that the loss of the spring foliage alone does not warrant the spraying of such varie- ties. The above facts will show the error of such deductions. When the loss of the foliage upon the Lovell is equal to the drain upon the tree brought about in maturing two-thirds of a crop, the loss of the foliage upon a semiresistant variety must be approximatel}" the same. This drain will be apt to show also in the size and weight of the fruit, if not in the number of peaches. Certainly no grower is warranted in leaving any varietj" unspraj^ed simpl}' because that variety holds its fruit in spite of the loss of foliage. The trees have suffered in such a case, and the orchardist can scarcely avoid feeling the loss in the reduced vigor of his trees, the reduced weight and size of his fruit, and the added drain upon his soil. COLOR OF SPRAYED AND UNSPRAYED FRUIT. The Lovell peach is normally a fruit of fine color, but under the action of certain of the sprays used its color was greatly heightened. In observing this action of the spra3\s no color scale was used, but the marked brightening on certain sprayed rows was too distinct to be mistaken b}'^ the most careless observer. This heightening of color METHOD OF THINNING AND COST OF PICKING PEACHES. 121 was not due to excess or lack of crop, for it was distinct on l)oth heavily and lightly loaded trees, where the fruit was of medium size and where it was exceptionally large. l)ut was due to the use of the copper sprays, especially of the stronger Bordeaux mixtures applied. Here is another advantage in the use of the copper salts. This increase in color would certainly mean dollars to the grower where the fruit was placed on the market in competition with unsprayed fruit, even of the same variety. The writer regrets that a color scale could not have been used in this connection, so that the true heightening of color could be stated, but the contrast between sprayed and unsprayed fruit, where the spraying was done with the Bordeaux mixture, was observed and discussed by many who had this fruit to handle. METHOD OF THINNING AND COST OF PICKING PEACHES. THIXXIXG BY HAND AND BY Cl'RL. An argument advanced bv certain peach growers and requiring con- sideration is that a moderate spraying under ordinary conditions is sufficient. By avoiding too thorough work enough curl is allowed to develop to cause the dropping of one-fourth to one-half of the peaches being set by the tree. If soil conditions are favorable it is thought the trees will still retain a sufficient crop, and the expense of thinning will be avoided. At first thought the plan here suggested might seem the easiest and cheapest waj' of thinning fruit. A consideration of all points involved will show, however, the faults of this method. To do effective pre ventive spraying against curl the spray must be applied to the dormant tree, and to judge of the severity of a coming attack of curl before growth begins is too uncertain a method to warrant the indorsement of practical growers. All influencing conditions may appear to favor a light attack of curl till after the spraying is completed, when a sudden change of temperature or a cold rain may develop a severe attack within the course of a few days. Under such conditions, incomplete or light spray work may cost the grower the major portion of his crop. In case the severitv of curl is about as presupposed, the numl^er of peaches remaining on the tree being about what the tree should carry, it is still very probable that the grower has sustained a loss in the stoppage of growth of wood and fruit and in the fall of foliage equal to or above the expense of thinning. There is also a difference between hand-thinned trees and those thinned by curl. This disease is local in its action, not general. If one branch in the midst of dis- eased branches is thoroughly spraved it will hold its fruit, while the peaches will fall from those not sprayed. This will show that the peaches of a diseased tree are not thinned evenly, as the disease is fre- quently not uniformly distributed over all branches of the tree. Then 122 PEACH LEAF CUKL". ITS NATURE AND TREATMENT. the fruit is for the most part nourished by the foliage of the branch which bears it, and hence if the disease is not equally distributed the foliage will be unequally distributed and the fruit unequally nourished. One portion of a tree may have an excess of fruit, even to the break- ing of limbs, while another portion shows a deficiency. Besides the unequal thinning of fruit on different portions of a tree, arising from the unequal action of curl over the tree as a whole, there will also appear an unequal thinning of the fruit of individual branches. In this respect, one of the prime objects of hand thinning, the equalizing of the fruit distribution upon the branches, is lost when the thinning is caused by curl. Such fruit as remains upon the curl-thinned branches is apt to be largely toward the ends of the limbs. The statements here made respecting the local action of the disease and the local nourishing of the fruit upon a limb or portion of a tree, are known to be correct, and have been established by a series of care- fully conducted experiments on sprayed halves of trees. The details and results of this work are given in the concluding section of this chapter. COST OF PICKING PEACHES. When considering the picking and sorting of peaches from sprayed and unsprayed trees a marked difference is noted in cost in favor of those sprayed. In the Rio Bonito orchard, where our experimental work was prosecuted, it has cost the proprietors '^1 per ton to pick fruit from fully loaded sprayed trees. In contrast to this the cost of picking and sorting the fruit of the unsprayed trees just north of the experiment block, in the summer of 1S9.5, was $3 per ton. This was on account of the scattered condition of the fruit on these trees, which were affected by curl in the spring like the control trees of the experiment block. This cost per ton was calculated with wages at Bl per day, the men boarding themselves, and where one sorter to five pickers was employed. We have here a difference of $2 per ton in the cost of picking and sorting fruit from sprayed and unsprayed trees. This added expense on unsprayed trees arises, of course, through the necessity of picking over a greater expanse of tree and orchard surface to obtain a given amount of fruit. It is l^elieved that in this single item of picking the fruit enough is saved to more than cover the expense of spraying the trees and thinning the fruit. THE LOCAL ACTION OF CURL ON FOLIAGE AND FRUIT. RECORDS OF TREES SPRAYED ON ONE SIDE. The study of the habits of Exomcus defor/nans and its influence upon its host led to the following investigation into the localization of the parasite upon the tree and its local rather than general effects. Bull. 20, DIv. Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate XVI. DESCRIPTION OF PLATE XVI. Fig. 1 shows the condition of the trees sjirayed on one side (considered in the text, p. 123). The right side of the tree shown was sprayed with Bordeaux mixture, the left side was unsprayed. (Compare with Pis. XVII, XVIII, and XIX.) Fig. 2 shows the condition of the tree sprayed on one side after, curl had largely denuded the unsprayed half at the left. LOCAL ACTION OF CURL ON FOLIAGE AND FRUIT. 123 Just north of the experiment block, in the continuation of the same orchard, was selected a row of 6 trees for treatment on one side. The spray used on half of each of the first three trees from the east was the standard Bordeaux mixture recommended 1)y the Department, viz, 6 pounds copper sulphate, 4 pounds (quicklime, and 45 gallons of water. The spray used on the following three trees was lime and sulphur, con- sisting of 10 pounds sulphur, 2(» pounds lime, and -15 gallons of water. In doing this spraying an effort was made to treat only one-half of each tree. Each tree was first examined, and, in some instances at least, a large canvas stretched through it in such a manner as to divide it as nearly as possible into two equal parts. All the branches on one side were thoroughly sprayed, the canvas preventing any of the spray reaching the limbs of the other half. In this way the half of each of three trees was spraj^ed with each of the above-mentionel sprays. A photograph showing the appearance of one of these trees shortly after treatment is shown in PL XVI. ]Mav 10 and 18, 1895, when curl had reached its highest development, careful estimates of the loss of foliage were made for the sprayed and unspra3'ed sides of the 6 trees used in the experiment. The following table shows the results of these estimates: Table 32. — Foliage lost from sprayed and unsprayed halves of trees. Percentage of leaves which fell from- Sprayed half . . Unsprayed hal- Trees tres ted Trees treated with Bordeaux with sulphur mixture. (a) spray. (6) Tree No.— Tree Xo.— 1. 2. 3. 4. 5. 6. 4 6 18 15 15 92 92 90 85 85 85 a Foliage estimated May 18, 1S95. h Foliage estimated May 10, 1S95. On May 8 the trees were examined, and the notes made at that time state that the sprayed and unsprayed sides presented a .striking con- trast. It is said that "the foliage on the sprayed half of the trees is perfection itself in almo.st all cases. It is very dense and abundant, l)oth below on the limbs and above. The leaves are of a ver}' dark, rich green, and are long, soft, and beautiful. The growth is very thriftv, in fact, unusually so. There are pro))ably not more than 2 to ;> per cent of the leaves curled at all on the sprayed half, and these are confined to points at the top of the branches not properly sprayed. On the unsprayed half of these trees there is very little healthy growth. Probably 95 per cent of the leaves are curled, and most of them badly curled and distorted. Probably not less than 90 per cent of those produced thus far this spring will drop. The color of the foliage is yellow and sickly. Such leaves as are not curled are small and light in color. The foliage upon both lower and upper limbs is badly affected. 124 PEACH LEAF CURL: ITS TSTATURE AND TREATMENT. What little growth there is which is thus far free from curl is termi- nal — very little healthy or comparatively healthy growth is seen from lateral buds. As to fruit, I may say that much is dropping from the curled side and little from the other." (Pis. XYI and XYII.) The work of thinning the fruit from the sprayed halves of these trees was not conducted at the time the sprayed trees of the general experiment block were thinned. The writer believes that the records of the fruit thinned from these trees were not kept except for one tree sprayed on one side with Bordeaux mixture. The fruit on the sprayed half of this tree was thinned May 8, 1895, and amounted to 1,145 peaches, which weighed 23 pounds, or very nearly 50 peaches to the pound. These peaches were very uniform in size and stuck tightly to the limbs. If they could have grown to the usual size when picked in the fall they would have given 381 pounds of fruit. No peaches were thinned from the unsprayed half of this tree. The yield of the 6 trees was carefully determined by weighing and counting the fruit from the sprayed and unsprayed sides of each tree separately. The results of this work are shown in the following table: Table 33. — Yield of sprayed and wisprayed halves of trees. Bordeaux mixture, tree No. — Sulphur sprav, tree No.— ■ Pounds of fruit gathered from — Sprayed half Unsprayed half Number of peaches gathered from Sprayed half , Unsprayed half 2.S4.S 14.3 361. 6 50.6 1,064 147 286. T 25.3 836 74 112.2 48.6 303 132 189.3 80.4 450 220 64.6 35.3 172 94 By the preceding table it is shown that the sprayed half of tree 1 bore 718 peaches, weighing 284.8 pounds, while the unsprayed half bore onl}" 40 peaches, weighing- 14.3 pounds. In this case, as in the case of the other trees of this series, the localized position and action of the fungus of curl upon a tree is shown. The unsprayed half of the tree suffered so severely from the disease that it lost 92 per cent of its foliage and all but 14.3 pounds of fruit. This severe attack on one side of the tree appeared to have no influence whatever over the sprayed limbs of the other side, as the fruit on the spraved half was thinned of 1,145 peaches, lost but 2 per cent of its foliage, and bore 284.8 pounds of as fine peaches as any in the orchard. On the other hand, the full and healthy covering of foliage on the sprayed side of the tree appears to have had no beneficial influence over the diseased side. Had it had any well-marked beneficial influence the fruit of the unsprayed half would have been retained, which was not the case. The same local action of the disease, and the same local nourishing influence due to the assimilative action of the healthy foliage may be DKSCKirTION OF PLATK XVTI. This plate shows the condition of one of the treeH sprayed on one side at the time of pii-king the fruit. The leaves have been cut away with pruning shears to enal)le the photograph to show the fruit upon the sprayed half (right side) of the tree, and the absence of fruit upon the unsprayed half (left side) . The sprayed half matured 284.8 pounds of the finest peaches; the unsprayed half matured only 14.3 pounds. Over 1,100 peaches were thinned from the sprayed half of this tree to enable the limbs to l)ear the crop, while the unsprayed half was nnthinned except by curl. (For rei'ords of this and other trees sprayed on one side see Chapter YI, also comi)are with Pis. XYI, XVIII, and XIX.) DESCRIPTION OF PLATE XVITI. Peaches gath eredjrom the tree sprayed oudnc side shown in the precedmg plate. The fruit shown on the two dryingltraysat the h'ft, together with that in the lower conipartment of the tray at the right, was gathered from the sprayed half of this tree. Tlie peaches shown in the uj>per right-hand eonqiartinent were all that mature^ on the unsprayed half of the same tree. The s])rayed half bore 718 peaches, weigliiiig 2S4.S ])ounds; the nnsprayed half hore only 40 peaches, weighing" 1-J. 8 i)OUiids. (Compare with Pis. XAT, XVn, and XTX.) ' ■-— — — - Bull. 20, Div. Veg. Phys, & Path., U. S. Dept. of Agriculture. Plate XVIII. >v/^^^\>'^vV -^ i- <, 1^ < k. '.^:-:v-.,-! ,\\'j: ■ 1- DESCKIPTION OF PLATE XTX. This is a photograph of a hmb of the sprayed haU' of the tree shown in Pis. XVI and XVII, after the removal of the leaves with pruning shears. A good idea of the size and perfection of this fruit may be obtained from the plate. The color was strikingly high and rich. The size of the fruit is further shown by the fact that the l)eaches averaged 252 per 100 pounds. (See note on this work at the close of Chap- ter VI, p. 122; also refer to Pis. XVI, XVII, and XVIII.) Bull. 20, Div. Veg. Phys & Path., U. S. Dept. of Agriculture. Plate XIX. LOCAL ACTION OF CURL ON FOLIAGE AND FRUIT. 125 seen in the condition of the foliage and crop on the sprayed and nnsprayed sides of the other trees inchided in these experiments. It even appears likely, both from observation of the trees and from the general laws of use and disuse and supply and growth, that the influence of the sprayed upon the unsprayod ix)rtions of the tree, in the presence of an attack of curl, is detrimental rather than ])eneiicial. It is probable that the half of the tree in full foliage, instead of lend- ing material aid to the defoliated side, tends to further rob that side, at least of the crude sap coming from the roots. For the purpose of showing the reader the striking results obtained from these trees, several photographs were made at the time the crop was matured. In order that the fruit might be seen upon the tree the foliage was carefully cut away and a screen placed behind the tree (PI. XVII). A single limb was also photographed, as shown in PI. XIX. The fruit gathered from the sprayed and unsprayed halves of tree 1 is likewise shown in PI. XVIII. The unusual size and brightness of color of the fruit from the sprayed half of this tree was very marked. The peaches averaged 252 per 100 pounds. The aver- age of peaches for the large experiment block was, as before stated, 299 per 100 pounds. There was thus a gain of 18.66 per cent in size of fruit on the sprayed half of this tree over the average for the block. CHAPTER VII. PREVENTIVE SPRAY WORK CONDUCTED BY ORCHARDISTS. GENERAL CONSIDERATION OF THE AUXILIARY WORK. While planning the experiments already detailed it seemed desirable to set on foot a similar line of work among peach orchardists in gen- eral. It was thought that several advantages could be attained from such auxiliary and coincident work: (1) It would indicate the effective ness or noneff'ectiveness of the sprays recommended, in controlling curl under the various conditions of variety, situation, soil, temperature, atmospheric humidity, seasonal variations, etc., existing in the many peach-growing sections of the country. (2) It would eliminate the personal element of the other experiments being conducted, and would introduce various new conditions of orchard work, thus point- ing out the efficiency or needs of the general grower and indicating what features of the work should receive special attention in offering final recommendations. (3) It would introduce the methods of treat- ment in many peach-growing centers, and by means of the object lessons thus set up, it would effect a much more rapid and general adoption of such spra34ng methods than could be hoped for otherwise. In advance of the inauguration of this work, which was begun in the fall of 1893, correspondence was opened with over 1,600 peach growers in all peach-growing centers of the United States. To each of these growers was sent a circular describing the nature and cause of peach leaf curl, outlining a series of spraying tests which it was desirable to have conducted for its prevention, and supplying the spraj^ formulae known to have given good results in California. Each grower was given the facts necessary to enable him to carry out the work, and was requested to furnish the Department with the results of his experiments. A very large number of growers expressed their willingness and desire to assist in conducting these experiments, and a very consider- able number have done so in many of the peach-grovring centers. It ma.j also be said that the number of growers who have adopted annual spraying methods as a result of this introductory experimental work is large and is constantly increasing. In fact, the spraying of peach trees for curl has become very general in many of the peach-growing centers of the United States where the disease prevails. 126 AUXILIARY WORK. 127 Of the reports which have been received of work conducted by the growers, it is thought best to inchide a few from those regions where curl is most common. The reports given are of nuich vakie, and in numerous cases they show that the experiments were carefully carried out. Representative reports will l)e given from the lake shore fruit belt of Michigan, from the Willamette Valley, Oregon, where peach culture has been greatly checked by curl, and from several growers in California and elsewhere. An effort has ])een made to present these reports, which have been carefully tal)ulated, in as compact form as possible. NOTES ox THE AUXILIARY EXPERIMENTS IN MICHIGAN. A very considerable number of peach growers in the more northern portion of the Michigan fruit belt received from the Department a request to undertake spraying experiments in the winter of 1893-94 for the prevention of peach leaf curl. Among these orchardists was Mr. Smith Hawle}', of Ludington. This gentleman, as well as several other growers of Mason and Oceana counties, entered heartily into the work, the result being that at present a veiy large number of orchardists are annually spraying for curl in that region. The work conducted by Mr. Hawley involved the testing of a number of spraJ^s in early and late winter with one and two applications. It was very carefully carried out, and as the disease developed quite seriously in that region in the spring of 1894 his results are most interesting and valuable. The data supplied by his report are presented in the fol- lowing table and notes: 128 PEACH LEAF CURL*. ITS NATURE AND TREATMENT. •saajj paXBidsnii ■saaji paABJdg fig's ■saajj paA-Bjdsu.i 0=10 o •S99JJ paXBjdg •Sai.iBJds puooas •SniiBjds JSJIJ ■paABadsuii •paiiBadg la ^>■. CO g'53 f- is iso OJ 03 ^ ow g-sa- !s.5 5-S^ fe OS o-s a & t- ^ C. ^- -^ m t- o .S "^ <1> P.«. 0.5 vC. O -. 1— 'COr^--OiOiCTr'^'M , cj ^ — ~' — -^ >:? ^ tn o 5 ■* ■^- ;S K ^ K ;S K ^ o .S ^ lO»0'^'-HCOrHy^^C<)r-l CO iClO "V •^catauadxa jo ■o^^ paB Bihnuo} jo lajjai ^O) ^ CO t^ ^,03 AUXILIARY WORK. 129 TIk^ prcH'odinj^ t{il)le o-ivo.s the details of eij^ht of Mr. Hawley's cxpcrinnMits. The oxpci'lnioiits arc distiiij>-uished by MUin])er.s (1-8), and tlio formula' usihI hy letters (A, B, and C). Mr. Hawley's notes on these experiments were written chiefly on two dates, the first imnuMliately after the estimates of foliao-e wei-e mad(> and the second shortly after the fruit was gathered. His statements in general are yiven in the foUowino- notes: Experiment i: June 23, 1894. — Tliis experiment was made under rather unfavorable circnm- stam'es, as the wind came up quite strong after I had commenced, and consequently I could not do the work as thoroughly as I wished, but the results now promi.se to be entirely satisfactory. The foliage is perfectly fresh and green, and apparently the peaches are going to hang on. Another thing that now appears to be well estab- lished is that the earlier spraying is the better. [See notes under experiment 2.] There is now (juite a perceptible difference to be noticed between early and late spraying as regards the foliage. October'], 189-1:. — This experiment has demonstrated the effectiveness of the spray used. While the crop was not large, owing to the unhealthy state of the trees from leaf curl last year, yet it was about three times as lavge on the sprayed as on the unsprayed trees. The fruit was much nicer. I could easily pick out the baskets of fruit from the sprayed trees. Experiment 2: June 2,3, 1894. — This experiment has given entire satisfaction so far, as the foliage of the trees is perfect and the fruit is hanging on well. This experiment, taken in (H)nnection with the others, indicates that the blue vitriol solution, C, acts quicker than the sulphur solution. The winter sprayings seem fully as effective with the sul- phur solution as with the blue vitriol, but the spring spraying is not (juite as good. October!, 1894. — While the difference in the amount of fruit gathered from the sprayed and unsprayed trees is not as great as in some of the other experiments, j'et the effect is fully as apparent, for these trees were not nearly as badly affected last year as some others, and consequently they all had a fair load of fruit. There was a far greater difference noted in the foliage than in the fruit. Experiment S: The first spraying of this experiment was on January 19, and was followed by a heavy rain storm, which lasted twenty-ff>ur hours, and will undoubtedly prevent the full benefit of the work from being realized, but the work was very thoroughly done and may be effective. June 23, 1894. — The second spraying was well done, and at this date the effect .«eems to show (1) that formula B is not strong enough to have the desired effect; and (2) that two sprayings are not much better than one, provided the work is thoroughly done with one spraying, and provided, aLso, the spraying is followed by good weather. .October 1, 1894. — This experiment has given greater satisfactif»n than anticipated. The proportion of sprayed to unsprayed fruit is better than expected at the time of the estimate on the loss of foliage. Experiment 4-' June 23, 1894. — The contrast between the sprayed and unsprayed trees at tliis date is very decided in this experiment. The first s})raying was on the .«ame date as experiment 3, and followed by rain. The last was done April 12 with formula C, and was well done, and the trees now look fine. 19093— No. 20 9 130 PEA.CH LEAF CUEL: ITS NATURE AND TREATMENT. October 1, 1894. — The results of this experiment are rather disappointing, as I was led to believe when I made the estimate of the loss of foliage in June that the results would be more satisfactorj' than with experiment 3. Whether the solutions used had the effect of neutralizing each other, or whether formula B, having Ijeen first applied, prevented any benefit from formula C, I can not tell. Experiment 5: June 23, 1894. — The first spraying of this lot w^as followed by ten hours' rain, the last spraying by good weather. The treated trees present a fine appearance, but the con- trast is not so great as in some other experiments, for the control trees are an outside row and apparently not as badly affected as those farther in the orchard. I do not anticipate a very large difference in the fruit yield. October 1, 1894. — This experiment has turned out just as I thought it would. The difference in the amount of fruit from the sprayed and unsprayed trees is not great, yet it is quite satisfactory considering the conditions. Experiment 6: June 23, 1894. — This experiment was thoroughly made, but was unfortunately followed by twenty-four hours of w'arm rain, commencing ten hours after the spray- ing, so that the result is not as satisfactory as desired, but the effect is so noticeable that the difference can be seen half a mile away. October 1, 1894. — The results of this experiment are entirely satisfactory. In spite of the fact that the spraying was followed by rain and then by very cold weather, the yield of fruit was one-third more on the treated trees than on the untreated trees, but what pleases me most is the very great difference in appearance of the trees now. Those that were treated have made double the growth this season that the untreated hrees have. They are holding their leaves late and have twice the buds set for another year, and are fresher and healthier in every way. Experiment 7: June 23, 1894. — The result of this experiment thus far seems to show that the formula used is not strong enough to accomplish the work desired. There is at this date less difference to be noted between the treated and untreated trees than in any other experiment. October 1, 1894. — This experiment has resulted about as I thought it would, from the appearance of the trees in June. I do not think formula B is strong enough. Experiment 8: Jime 23, 1894. — I regard this as one of the most valuable experiments in the series. It has so far shown the best results. The imtreated trees look as though a blight had struck them, appearing at this date as if they were going to die, while the sprayed trees look as fresh and healthy as young trees that never had any disease. One curious thing I have noticed is in relation to a branch from one of the untreated trees which reaches across to one of the treated ones. This l)ranch, of course, got sprayed when the tree was sprayed with which it mingles, and it is as full of leaves and fruit as the treated tree, while the balance of the tree to which it belongs is bare of leaves and fruit. October 1, 1894. — The final results of this experiment have proved w^hat I expected. There is a greater difference in yield than in any other experiment, while the differ- ence in appearance between the treated and untreated trees is yet very marked. The treated trees look as fresh and healthy as young trees, while the others still look very bad. These trees have always been very heavy bearers, and consequently have not attained a very large size. They were never very badly affected by leaf curl till this year. AUXILIARY WORK. 131 In the eight experiinont.s described by Mr. Hawley the percentages of not gain in fruit of the sprayed trees over the unsprayed wore as follows: Tablk 35. — I'erccntages of net gain in fruit shown in eight spraying experiments conduded by Mr. Smith Hawley, of Ludington, Mich. Experiment No. Formula. a Net gain. Pa- cent. 191 46 174 41 Experiment No. Formula. Net gain. 1 A 5. (; Per cent. 35 ') C 6 A 49 3 B B and C . . 7 B 21 4 8 C 1,424 a See table 34. ' Owing to the fact that Mr. Hawley's experiments were conducted with different varieties of peach, an accurate comparison can not be instituted between them. From the very excellent results obtained in experiment 8, where the unsprayed trees lost 90 per cent of their leaves and the sprayed trees only 3 per cent, and where the net gain in fruit by the sprayed trees was 1,424 per cent of the yield of the unsprayed trees, the writer believes Mr. Hawley's conclusions are correct, viz, that the spray used in this experiment gave the best results. That the ^;ame spray did not give equalh^ striking contrasts in experiments 2, 4, and 5 is probably due mainly to the fact that the trees of these experiments were not of the same variety as those of experiment 8, but were much more resistant to disease, hence no spray could have produced in the former experiments the .same con- trast between sprayed and misprayed trees. That the trees of experi- ments 2, 4, and 5 were not as badly diseased as those of experiment 8 is shown to be a fact, for the unsprayed trees of the latter experiment lost 00 per cent of their leaves from curl, while those of the former experiments lost only .50 per cent. The same evidence is given by the fruit. The un.sprayed trees of experiment 8 bore only 3.7 pounds of fruit per tree, while the unsprayed trees of experiments 2, 4, and 5 averaged 45. T, 11.6, and ^2.4 pounds of fruit per tree, respectiveh'. From the preceding facts it appears that the most active and satis- factory spray used })y ]\Ir. Hawley was that containing a pounds of copper sulphate, 5 pounds of (piickliuie,' and 45 gallons of water. This is e.specially interesting from the fact that this spray also gave the best results among the 35 fornmlse tested by the writer in the Sacra- mento Valley. The relative value of the stronger sulphur spray (formula A) and the Bordeaux mixture used ))v Mr. Hawley (formula C) is well Itrought out in an experiment conducted I)}' him on a somewhat similar scale, but with a single variety of peach — Hills Chile. This experiment admits of very satisfactory comparisons being drawn, and is summarized in the foUowiuof table: 132 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Table 36. — Experiment No. 9, conducted by Mr. Smith Hawley. Row No. Formula used. Variety of trees. Age of trees. Num- ber of trees. Date of spraying. Total yield of fruit. Net gain of fruit over yield of un- sprayed trees. 1 A Hills Chile i'ears. 5 5 5 5 6 6 6 6 April 12 Pounds. 270 63 306 189 Per cent. 328 2 do Unsprayed February 8 January 19 3 c do 354 4 A do V 200 The preceding experiment shows that Mr. Hawley obtained from his Hills Chile trees a net gain in fruit of 354 per cent b}^ spraying with the Bordeaux mixture (formula (y), and a net gain of 328 per cent with the stronger sulphur spray when applied on April 12 and 200 per cent when applied on January 19. These results indicate that the early winter treatment will probably not prove as effective in Michigan as a treatment of the trees shortly before the buds swell in the spring. It is probable, however, that the copper sprays will act more quickly than the sulphur sprays, on which account the latter should be allowed somewhat more time for action than the copper sprays, by applying them a little earlier in the spring. The copper sprays may be applied until the lirst buds begin to open, if neces- sary, but such a late application of the sidphur sprays would endanger the buds and new growth. The following are Mr. Hawley's notes on this experiment : Experiment P.- June 23, 1894. — This experiment, although on a small scale, has lieen very inter- sting and instructive, and has been noted and admired by all who saw it. The rees stand on a slope, and a person standing on the opposite slope,' only a few rods away, can see every tree, and the best possible chance is had to observe the effect of the different sprays, and to compare the treated with the untreated trees. The con- trast at this time is very remarkable. The trees were quite badly affected by leaf curl last year. October 1, 1894. — The contrast between the treated and untreated trees is very great as regards yield of fruit, and the contrast in the trees themselves at this date is quite as remarkable. The treated trees look fresh and healthy and have made a fine growth, while the untreated trees look sickly and have made very little growth, looking, in fact, a year or two younger, as regards size, than the others. Late in the season of 1894 Mr. Hawley tested the sulphur and copper sprays to ascertain the comparative action of the same upon buds which were considerably swollen. He learned that the sulphur spraj^ injured the buds to such an extent as to reduce the yield, while it prevented curl. The copper spray, however, prevented curl and gave a decided increase in yield. He thus reaches the conclusion that formula A is more injurious to buds than formula C. While this is true if the spray is applied at too late a date, it ma}' be safely applied at an earlier date. It should also be mentioned that the .sulphur sprays AUXILIARY WORK. 133 have insecticidal properties much :superior to those of the copper sprays. The DepartiiuMit work condueted by Mr. Ilawley seems to haveclearly demonstrated the possibility of controlling- the most severe attacks of curl in the lake shore region of Michigan with a single spraying, when this is done thoroughly and at the proper time. In experiment 8 the untreated trees were so badly ali'ected that, as already stated, 90 per cent of the foliage and all but 3.7 pounds of the fruit fell from the trees, ])ut ])v spraying similar trees Mr. Ha wlev saved all but 3 per cent of the lea\es-^a gain of 2,1>00 per cent of foliage — besides increasing the yield of fruit 1,424 per cent. In other words, the sprayed trees held 30 times as much spring foliage and over 15 times as much fruit as the unspr^iyed trees at their side, all being of the same variet}'. In the southern portion of the Michigan frjuit belt a number of growers assisted the Department in conducting experiments. Among the reports received from that section is one by Mr. George Lannin, of South Haven. Mr. Lanuin's work is summarized in the following table : T.\HLE o7. — Experimental work conducted by Mr. George Lannin, of South Ifaven, Midi., in the spring and mmnicr of 1895. [Nature of soil, sandy.] Formulae for •lo gallons of water. Variety of trees. Age of trees. Number of trees— Date of— Percentage of leaves lost by— Date when loss of leaves was esti- mated. Fruit produced by- a V o ¥ First spray- ing. Second spray- ing. o g P. - CO i -a s & a i 0) u ci' ft 1 OS p. a t3 1 (E) 2 {F) 3 (G) 4 flO lbs. sul- I phur, 20 lbs. 1 lime, 5 lbs. { salt. 5 llxs. copper sulphate, 10 lbs. lime. (2 lbs. copper 1 sulphate, :? 1 pt.s. ammo- 1 nia. [5 oz. copper 1 carbonate, 3 I pts. ammo l nia. ^Barnard Hills Chile VHales Early >Crawfords \jite. Years. 6 6 6 10 10 10 10 10 10 10 10 Apr. 10 ...do.. ...do.. ...do.. .May 17 June 25 ...do.. June 8 20 15 20 10 40 35 40 30 July 10 ...do.. ...do.. ...do.. Lbs. 1,200 1,300 1,760 1,800 Lbs. 830 GOO 680 700 The spray formulse tested by Mr. Lannin were not included in the work of Mr. Hawlev, and are therefore characterized as Formulae D, E, F. and G. As Mr. Lannin sprayed difierent varieties of peach trees with 4 formulte, the experiments can not ])e compared with one another 134 PEACH LEAF OUKL*. ITS NATURE AND TREATMENT. to advantage. The value of all the sprays used is shown, however, by the gain in fruit obtained. The percentage of net gain in fruit was 44, 116, 158, and 157 per cent, respectively. These figures show that the eau celeste (Formula F) and the ammoniacal copper carbonate (Formula G) gave satisfactory results. The action of the disease on the foliage of the trees of experiment 3 was more severe than it was on the foliage of the trees of experiment 4. The unsprayed trees of the former experiment lost 10 per cent more of their leaves than the trees of the latter. The percentage of gain in fruit from the sprayed trees of experiment 3 was, however, fully as great as that from the sprayed trees of experiment 4. This shows that the eau celeste (Formula F) was more effective in combating the disease than the ammoniacal copper carbonate, which was applied in experiment 4. Mr. F. N. Chesebro, of South Haven, sprayed 19 Crawfords Late and 19 Oldmixon trees in the spring of 1894, leaving 19 trees of each variety for comparison. The formula used was 15 pounds of sulphur, 30 pounds of lime, and 10 pounds of salt to 60 gallons of water. Mr. Chesebro did not report the exact yield of his trees, but stated that the sprayed trees lost 20 per cent of their foliage and the unsprayed trees 80 per cent — a saving of 60 per cent of the foliage by a single spraying. His report is as follows: Table 38. — Experimental ivork conducted by Mr. F. N. Chesebro, of South' Haven, Mich., in the spring of 1894- [Variety of trees, Crawfords Late and Oldmixon Cling; nature of soil, sandy loam.] Number of Per cent of ^ trees— ^ leaves lost by— a Date . when Formula. i '6 to P. 0) i)lied March 20 to 2(5 trees, with 2 check rows of 26 trees. Curl developed on 3 per cent of the foliage of the treated trees, but the controla were almost destroyed. 138 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Formula K (5 pounds sulphur, 15 pounds lime) Mas applied March 19 to 278 trees in a block 10 rows wide, with control rows of 69 trees each on each side. Curl appeared on about 2 per cent of the foliage of the treated trees, while the check rows were, as in the previous year, a mass of curled leaves and twisted branches. Formula K was also applied to 25 Salway trees and to 15 Alexanders, which had curled very badly for many years, the Salways always being defoliated completely. These trees were 8 years old. No curl appeared on either variety. Formula L (5 pounds copper sulphate, 15 pounds lime) was applied March 13 and again March 21 to 262 trees, with 7 check rows interspersed through the l)lock. Less than one-fourth of 1 per cent of curl appeared on the treated trees of this test, while the check rows were almost destroyed by the disease. The greater portion of these imtreated trees have been dug up and replaced (February 13, 1895) . Treated trees in this block made an excellent growth, though cultivated only moderately, and a great majority were absolutely free from curl. The ammoniacal copper carbonate. Formula M (5 ounces copper carbonate, 3 jjuats 26° ammonia) ^ was applied March 22 to 210 trees, 2 check rows of 69 trees being left alongside. Less than 3 per cent of curl appeared on the block, while 65 per cent of the foliage of the control trees was curled. This formula was also applied twice, at intervals of two weeks, upon 5 acres of trees upon which no curl could be found. This experiment, though remarkably successful, was not as conclusive as desired, as no control trees were left. This was upon a block of thrifty trees, of which I did not care to sacrifice any portion to an experiment. The same treatment had pre- served them the previous year, and I feared a change. All my treated trees have grown satisfactorily this year, but the 10-acre check block of imtreated trees was so nearly destroyed by curl that all the trees will be dug up. Several hundred are dead, and of the remainder I think no tree has had a growth of 12 inches. It will be seen from Mr. Lownsdale's report of the work in 1894 that several of the sprays used gave most excellent results. On May 18 of that year he wrote: Curl has developed moderately, and everywhere the better condition of treated over untreated trees is apparent. The trees treated with 5 pounds of copper sul- phate and 15 pounds of lime may be said to be absolutely free from the curl and the experiment a success. This block was sprayed twice in March. The check rows in this block and alongside are curled as badly as any trees except seedlings. The modified eau celeste (Formula J) is also giving good results, as is the 5 pounds of sulphur and 15 pounds of lime; but I believe the copper sulphate, 5-pound for- mula, is in the lead. This may be attributed to more thorough work, as most of the other sprays were only applied once. Owing to the fact that no fruit records could be obtained from Mr. Lownsdale's experiments in 1894, as the trees were yet too small, arrangements were made for the testing of some of the more valuable sprays in the spring of 1895. The experiments of 1895 show the gain in both foliage and fruit, though the jdeld was low, resulting from the use of 5 sprays — 1 sulphur and 4 copper. The experiments were con- fined to the Crawf ords Early variety, and in each experiment the trees received two sprayings in March. All trees were 4 years old, but rather small. Mr. Lownsdale's data on this work are presented in the following table: AUXILIARY WORK. 139 Tabi>k 39. — Experimental work conducted hy Mr. M. 0. Lownsdale, of Lafaydte, Orey., in the spring and summer of 1895. [Variety of trees, Crawfords Early; nature of soil, red hill.] F o r mu 1 re for '15 gallons of water. 110 lbs. sulphur •JO lbs. lime [ft lbs. stilt 15 lbs. copper sul- l)hate llO lbs. lime [2 lbs. copper sul- phate [3 pts. ammonia 15 oz. copper car- bonate [3 pt-s. ammonia... (5 lbs. copper sul- phate 15 lbs. lime Number of trees. Date of— Leaves lost by- Fruit pro- duced by— Age of trees. Date when I0.SS of leaves was esti- mated. ■i First spray- Second spray- i i >. " a; ft2 0, ing. ing. M*^ C t3 P. ■ m el t3 a, Yrs. Per ct. Per ct. IJlK. Lbs. \ ^ 8() 91 Mar. 7 Mar. 27 10 35 June 18 340 187 f ** f ^ 110 110 CS 87 ....do... ....do... 5 35 30 ....do... ....do... 480 807 62 Mar. 9 ....do... 193 1 ' 2ti8 07 Mar. 8 Mar. 28 Tr i - fling. 30 ....do... 1,204 h 189 91 Mar. 9 ....do... None . 40 ....do... 1,048 15 But few comments upon the preceding table are required. It makes the fact perfectly evident that two spring sprayings are sufficient to almost absolutely control leaf curl in the Willamette Vallej'. In a letter written June 25, 1895, Mr. Lownsdale says: Peach leaf curl has not developed a.s badly in this section as it did last year. I have estimated that about 40 per cent appeared on most of my control trees. Two sprays with lime, 10 and 15 pounds, and copper sulphate, 5 pounds, were an abso- lute success. Lime in the amount of 15 pounds gives the best results, there being 100 per cent of healthy foliage on trees sprayed with this amount and 5 pounds of cop- per sulphate. Practically the same results were obtained with two applications of the ammoniacal copper carbonate. It is impossible to find a curled leaf on acres and acres of treated trees. In the Rogue River Valley, in the southern tier of counties of Oregon, the conditions are somewhat more fayorable for peach culture than in much of the Willamette Valley. The climate is somewhat intermedi- ate in charactei" between that of northwestern Oregon and northern California. Peach culture is quite extensive about Ashland, Medford, etc. The reports of Air. E. F. Meissner, of Kerby, Josephine County, and of Mr. N. S. Bennett, of Medford, Jackson County, are fairly rep- resentative of those received from experiments conducted in southern Oregon. Mr. Aleissner's report again shows the great effectiveness of 5 pounds of copper sulphate, 10 pounds of lime, and 45 gallons of water. With this formula he sprayed 4 Salway trees 4 years old, leavingan equal number unsprayed for comparison. Two treatments were given, the first February 22, the second March 10, 1895. From the sprayed trees 10 per cent of the foliage was lost from curl, while from the 140 PEACH LEAF CURL I ITS NATURE AND TREATMENT. unsprayed trees 90 per cent was lost, leaving the trees nearh^ bare. Unfortunately, frost killed the buds, and no comparison of fruit was possible, but it is safe to say that the fall of 90 per cent of the leaves would have caused the loss of the crop, while 10 per cent loss would have occasioned little, if any, falling of fruit. Mr. Meissner writes respecting his work that the copper sulphate spray "has given far better results than the sulphur, lime, and salt," and that "the trees sprayed with the bluestone mixture look the best of any in the orchard. " Mr. Bennett used the 5-pound formula for the Bordeaux mixture as given for Mr. Meissner, He sprayed but once, on March 11, 1895. The 29 trees sprayed averaged 41 pounds of fruit per tree, while the single control tree jdelded but 9 pounds, or a net gain in fruit of 388 per cent. The fact of most interest in connection with this work is, however, that the variety treated was the Elberta, which is probably more universally susceptible to leaf curl than any other variety now grown in the United States. The control of curl on this variety was almost absolute, as will be seen from the following letter from Mr. Bennett: I send you to-day a report of the spraying for leaf curl. The experiment was an honest trial, and I feel very jubilant over the success. I have reported only the Elberta variety, as it was one of that kind which I left unsprayed. I am more than pleased with the results, and can say that a good trial is all that any man needs who has the welfare of his orchard at heart (his pocketbook as well) . The peaches from the sjirayed trees were first-class, clean, and sold at the highest market price. I notice a very marked difference in the general health of the trees in favor of those sprayed. The leaves lost by the sprayed trees were, perhajis, one-half of 1 per cent. The unsprayed tree was a little above an average tree in the spring. There were 29 sprayed trees, which yielded an average of 44 pounds of choice fruit to the tree, nearly half of which packed 56 peaches to the box. I sprayed 75 Wheatland trees with the same success as far as leaf curl is concerned. They are fine, healthy trees now, and bore a good crop this season. They have been bad about curling, but I left an Elberta because that variety is the worst to curl, and if spraying did them no good I intended to grub them out. Mr. P. W. Olwell, of Centralpoint, Oreg., applied the sulphur spray to 400 Muir trees in his orchard, leaving 25 trees unsprayed for comparison. The formula used by Mr. Olwell was 15 pounds of sulphur, 30 pounds of lime, and 10 pounds of salt to 60 gallons of water. His trees were 5 years old, growing in black, loamy soil. They were sprayed March 10. The sprayed trees did not lose any foliage from disease, while the control trees lost 25 per cent. The fruit records were not reported. NOTES ON THE AUXILL^RY EXPERIMENTS IN CALIFORNIA, Besides the experimental work conducted by the writer in the Sac- ramento Valley in the years 1894 and 1895, a considerable number of growers assisted in carrying on experiments in different portions of AUXILIARY WORK. 141 California. Reports have been riH'eivod from s(^veral of these growers, and while in some instances they are not as complete as desired, the results shown are amply sufficient to determine the practical value of the work undertaken. Among- the more complete and carefully prepared reports is one from Mr. A. D. Cutts, of Live Oak, Sutter County. The work was carried out in the Avintei" of 185*2-1>8, and was one of the experiments which led to the writer's detailed series of experiments outlined in the present bulletin. In this orchard the spray was not used in 1898 for the control of leaf curl, but was applied for the purpose of destroying- the San Jose scale, which was gaining- a foothold in the orchard. The trees infested by scale were scattered through a 40-acre block of the Crawfords Late variety. These trees had been marked, and in Febru- ar}^, 1898, were thoroughly sprayed with the sulphur spray, consist- ing of 15 pounds sulphur, 30 pounds lime, 10 pounds salt, and 60 gal- lons water. Only a few of the trees were entirely sprayed. As curl developed seriously in that region in the spring of 1893, the contrast between the scattered sprayed trees and the remainder of the block was very striking, and Mr. Cutts kindly consented to preserve the records of yield of a few of the sprayed and unsprayed trees for use in this connection. In the table which follows is shown the amount of fruit produced by each of the 9 sprayed trees included in Mr. Cutts's records, as well as the weight and number of first, second, and third quality peaches. The same facts are given for an equal num- ber of neighboring unsprayed trees for comparison. Tablk 40. — Experimental work, conducted hy Mr. A. D. Cutts, of Live Oak, Cal., in the sjmng and summer of 1893. [Cra^yfords Late, 4 years old.] Sprayed trees. Unsprayed trees. Total pounds of— Number of— Total pounds of— Number of— >. >. >. >, !>. >> >, >-, >, 03 w a tS tree. r-3 rs 7 o 30- j1 " P^J 3 0) II P 2 ^in *i a •C a "O c3 -^ t- '^.h ■C E. *- CS "O K "C « ^ CO "^ u « S - k ^ S ^ ^-^ a^ Ui^-* tf ^ c S •a o •-* t, ^ ■^ j_l o .^ >: ^ o. •^ a 1 E E ^ E-i £ £ Eh 1^ 1 156 116 32 9 276 96 29 41 23 12 6 . 102 56 56 2 . 226 180 119 180 176 279 55 126 189 146 100 146 164 225 38 106 20 28 13 25 17 34 12 15 17 7 6 9 6 20 5 5 735 615 385 605 668 815 148 367 126 110 70 138 86 151 60 65 130 45 54 60 32 139 30 27 2 1 2 1 4 3 3 4 5 2 2 5 6 7 1 3 8 ...... 1 3 3 8 8 9 18 Total. 1,497 1,218 196 83 4,514 902 646 68 31 21 6 120 79 56 The average yield of fruit of the sprayed trees given in the table was 166.22 pounds per tree, while the average yield of the unsprayed trees was but 6.4ri: pounds. This rcjorcsents a gain in fruit bv the 142 PEACH LEAF CURL! ITS NATURE AND TREATMENT. sprayed trees above the yield of the unspra>'ed trees of 24.8 times the yield of the latter. In other words, there was a gain in yield of 2,481 per cent from spraying. Much valuable information was also supplied by Mr. Cutts in relation to the preparation and application of sprays, and the writer has considered these subjects in other portions of the bulletin. Some of the more striking photographs of sprayed and unsprayed trees have also been obtained from Mr. Cutts's orchard, as well as the records of fruit buds elsewhere discussed (Pis. VII and XX). The report of a test of the Bordeaux mixture (5 pounds copper sulphate, 10 pounds lime, and 45 gallons water) was furnished b}^ Mr. H. B. Gaylord, of Auburn, Placer County. This experiment was made in the spring of 1895. Mr. Gaylord sprayed 10 Heaths Cling peach trees and 4 nectarine trees, the variety of which was not stated. The spraying was done February 15. Mr. Gaylord states that the unsprayed nectarines curled so badly that they bore no fruit at all, while the 4 sprayed trees yielded 320 pounds. He says that every alternate tree was sprayed in a row of nectarines, and that the sprayed peach trees were in the worst places in the orchard. Respecting the result of the work Mr. Gaylord writes, in part: I herewith send you a partial report on the experiment for leaf curl. I used only one formula. The result is perfectly satisfactory. I sprayed some peach and some nectarine trees, both with good results. One nectarine tree sprayed has not a curled leaf, while one of the same kind, about 15 feet from it, which was not sprayed, has lost nearly all its leaves. The contrast is so great that it would be wortli while to have them photographed. A neighbor, Mr. G. P. Dixon, used formula 3 (2 pounds copper sulphate, 3 pints ammonia, and 45 gallons water) with the same results, so that I am satisfied that the copper sulphate is what does the work. Mr. Gaylord also states that no leaves were lost from the peach trees sprayed, while all of the leaves curled on the unsprayed trees of the remainder of the orchard. In Amador County an extensive experiment was made in the spring of 1895, by Mr. George Woolsey, of lone. Mr. Woolsey sprayed some 2,500 trees of various varieties of peach and nectarine with 5 pounds of copper sulphate, 10 pounds of lime, and 45 gallons of water, and left 720 trees unspra3^cd for comparison. The spraying was done from Februarj'^ 20 to March 10. Most of the sprayed trees lost no foliage, but a few in a wet situation lost not to exceed 25 per cent, while the unsprayed trees lost not less than 50 per cent of the leaves and a large amount of fruit. Mr. Woolsey gives some notes respecting the work in the spring of 1895, as follows: A block of about 200 trees, Salways 12 to 15 years old, on well-drained soil, and 500 Salways 4 years old, adjoining, I did not spray, thinking they were curl proof. I regret I did not spray them. * * * Tlie leaves are dropping, as well as a large percentage of the fruit. I shall certainly spray them in the future. * * * The DESCRIPTION OF PLATE XX. Sprayed and unsprayed Crawfords Late trees in the orchard of Mr. A. D. Cutts, Live Oak. The tree at the right was sprayed in February, 1893, with Ume, sulphur, and salt; the trees at the left were untreated. See "Notes on auxiliary experi- ments in California," for a full account of the work at Liveoak. (Photographed in May, 1893, after most of the diseased leaves had fallen from the unsprayed trees. Compare with PI. VII.) Bull. 20, Div. Veg. Phys. & Path., U. S. Dept of Agriculture. Plate XX. ».,..■,;, , .v;,.r ..' fc-^- ^i^T** ' f/ ■. ... C^':r ?&:L--.-»>>i*r^ AUXILIARY WORK. 143 apparent result of Hprayinfj, one api)lication, is as follows: Four control trees of Early Rivers, adjoining trees si)rayed March 2, are badly curled, leaveH dropi)ing, and also the greater portion of the fruit. The adjoining sprayed trees of this tender variety are all right (no curl) and make quite a marked contrast. Besides these, 4 white nectarines and 4 Bilyeau peaclxes, left at the same time, show curl and loss of fruit, although not as badly as the Early Rivers. The surrounding sprayed trees look vigorous and healthy, with no curl. Mr. Woolsey was among the first pcacli growers to adopt the copper sprays for the control of curl. His first experiments were made in 18J>2, and tliev proved so satisfactory that he sprayed quite (extensively in 1893 and again in 1894. The work in 1893 was of special interest, as the following extract from a conmmnication received from liim will show: I sprayed nearly all my peach and apricot trees. I say nearly all; for, time jjress- ing, I found I would not get over all the peaches, so to save what I considered the most valuable portion, viz, the 3'oung lower growth, I had that sprayed and left the tops unsprayed. The season was a damp one and leaf curl was very prevalent with my neighbors. On my place all trees sprayed were exempt, all others badly affected and crops on them almost a failure. On the ones partly sprayed there was a healthy growth on the lower part of the trees, while they were denuded of foliage above. Mr. Woolsey's work in 1894 was negative, owing to the nondev^^lop- ment of the disease that season. Two peach growers of Eldorado County, Mr. John M. Da}^, of Placendlle, and Mr. A. L. Kramp, of Diamond Spring, furnished the writer with reports of their experiments conducted in the spring and summer of 1895. Mr. Day tried 4 formuhe, each showing a decided saving of foliage, but the fruit was lost from frost. The spray used by Mr. Kramp was composed of 10 pounds sulphur, 20 pounds lime, 5 pounds salt, and 45 gallons of water. He sprayed 600 trees, 3 years old, of the Hales Early, Briggs Early, and Wilcox Cling varieties, and 3,000 unsprayed trees were left for comparison. Tlie sprayed trees lost no foliage and yielded 48,000 pounds of peaches, while the unsprayed trees lost not less than 50 per cent of their leaves and yielded 00,000 pounds. The average yield of the spra3'ed trees was thus 80 pounds per tree, while tlie average yield of the unsprayed trees was but 20 pounds, a net gain of 300 per cent. Gen. N. P. Chipman, of Red Blufl", has been using for at least two years a formula for Bordeaux mixture which gave the writer exceed- ingly good results at Biggs (see row 21 of the writer's experiments, p. 117). Mr. Chipman writes that his experiments were upon several varieties of peach trees and that excellent results were obtained. He further says: "1 used equal parts, or 5 pounds bluestone, 5 pounds quicklime, and 45 gallons water. I believe you have found an infalli- ble remed3^ I have used this spray two years with good effect." Mr, Chipman first observed the effects of this spray in the experiment block at the Rio Bonito orchard, in the summer of 1895. 144 PEACH LEAF CURL: ITS NATURE AND TREATMENT. NOTES ON THE AUXILIARY EXPERIMENTS IN NEW YORK, INDIANA, AND OTHER PEACH-GROWING STATES. Much experiineiital work for the control of leaf curl has l^een under- taken at the suggestion of the Department b}^ the peach growers of New York, Indiana, Illinois, Ohio, Kentucky, Maryland, Pennsylva- nia, Georgia, Tennessee, North Carolina, Arkansas, Missouri, Kansas, and other peach-growing States not already considered in this bulletin. For instance, SO prominent peach growers of various peach-growing centers of New York were given full instructions for the control of curl in the winters of 1893-94 and 1891^95, and requested to report their work, which in a number of instances was carefuUj^ done. The same is true of 54 growers in Ohio, 136 in Pennsylvania, etc., and in each case where the work was properly conducted the results were in har- monj^ with those already discussed in this chapter. For this reason, as well as from the fact that the work already considered has been selected from those sections of the country which are fully represen- tative of the different climatic conditions, it is not thought necessary or desirable to enter much further into the details of the work. One or two experiments may be mentioned, however, before closing the consideration of this phase of the subject. Mr. Joseph M. Cravens, of Madison, Ind., reported almost absolute success in the control of curl in his orchard. The sprayed trees of the 4 experiments made in no case showed more than 3 per cent of curled leaves, while the amount of curl on the foliage of the unsprayed trees ranged from 25 to 45 per cent. Mr. Cravens states in a letter accompanying his report that he sprayed separate rows through his orchard which were sufficiently far apart not to have the spray affect the intervening rows even if the wind blew at the time of application, and further that he is satisfied that two of the sprays used would have given absolute results had they been applied to every portion of every twig. Mr. W. T. Mann, of Barkers, N. Y., sprayed 25 trees with the lime, sulphur, and salt spray April 9, 1894, and left 25 trees at their side without spraying for comparsion. On May 28 only 42 diseased leaves were found on the 25 spraj^ed trees, while as high as 40 per cent of curled foliage was present on some of the unsprayed trees. On the same date as the other spraying was done 25 trees were spmyed with Bordeaux mixture, while 21 were left for comparison. By May 28 only 59 curled leaves had developed on the entire 25 sprayed trees, while of the 21 unsprayed trees several had as high as 30 to 35 per cent of curled leaves. Mr. Mann says that from the fact that among the 50 trees treated not one showed an appreciable amount of disease, while all through the orchard trees were badly affected, was to him very satisfactory evidence of the value of the treatment, especially as AUXILIARY WOKK. 145 ho did not undortako tho work witli any oroat doo-rcc of confidence as to .succe.s.sful results. Mr. James A. Staples, of Marlboro, N. Y., states that in the sea- sons of 1894, 18J>5, and 18'JO he made the spray tests on pcnu-h trees for leaf curl which had been sugj^ested l)y the writer, and says he is well satisfied that the disease can be controlled by proper spraying. He states that the winter treatment gave him the best results. Mr. A. D. Tripp, of North RidgeAvay, N. Y., states in his report of spra}^ work for curl that he treated 208 trees and left S'20 trees unsprayed. From the sprayed trees he gathered "360 baskets of as fine fruit as ever went to market." The baskets were one-third of a bushel, and the peaches averaged 66 to the basket. From the untreated trees only 15 baskets w^ere gathered, and a portion of this fruit was imper- fect. The variety was the Elberta. 19093— No^ 20 10 CHAPTER VIII. PREPARATION, COMPOSITION, AND GENERAL CHARACTERS OF THE SPRAYS USED. PREPARATION OF THE COPPER SPRAYS. It is not the intention to consider in this place the many forms of copper sprays which have been used at one time or another in the treatment of fungous diseases, but to confine the discussion to those forms tested in the present work. Most of the formula? for those copper sprays which have been tested in the treatment of peach leaf curl have been personally prepared at one time or another and the results thev gave have been carefully studied. Several other formulae have been recommended by the writer, but these were prepared and applied by the growers themselves, so that for the results of this work their reports have been consulted. There are still a few other formula? for copper sprays which have been reported upon, but these are the suggestions of others or were chosen by the growers themselves. The difierent copper sprays which have been tested in separate form (not in union with other fungicides) are shown in the following list. This list includes 22 distinct formula?. Each formula is that used with 45 gallons of water, except the first for Bordeaux mixture, which was with 48 gallons. Table 41. — Copper sprays applied for the control of peach leaf curl. Copper sulphate solution: * 4 pounds copper sulphate, 45 gallons water. * 2 pounds copper sulphate, 45 gallons water. Bordeaux mixture: t24 pounds copper sulphate, 45 pounds lime. *6 poimds copper sulphate, lo pounds lime. i 5 pounds copper sulphate, 15 pounds lime. *.3 pounds copper sulphate, 15 pounds lime. j 6 pounds copper sulphate, 10 pounds lime. * 5 pounds copper sulphate, 10 pounds lime. * 3 pounds copper sulphate, 10 pounds lime. * 5 pounds copper sulphate, 5 pomids lime. * 4 pomids copper sulphate, 5 pounds lime. *3 pounds copper sulphate, 5 pounds lime. * Prepared and tested by the writer, and in many cases also tested ]jy growers. t Chosen and tested by grower. i Recommended by the writer, but tested by the growers. 146 PREPAKATI N OF THE COPPER SPRAYS. 147 Bordeaux mixture — Continued *2 pounds foi)per yulpliate, 5 pounds lime. *(> pounds copper sulphate, 4 pounds lime. *() pounds copper sulphate, 15 poun pints ammonia (26°). Modified cau celeste: *4 jKHinds copper sulphate, 5 ])ounds sal soda, ;^ pints annncjnia (26°). *2 i>ounds copper sulphate, 15 pounds sal soda, 2 pints annnonia (26°). Ammoniacal copper carhonaie: *5 ounces copper carbonate, H pints annnonia (26°). *3 ounces copper carbonate, 2 pints ammonia (26°) . * Prepared and tested by the writer, and in many cases also testf^l by growers. The preparation of the copper sprays containing different chemical constituents will be considered in the order in which they appear in the preceding list. COPPER SULPilATE SOLUTION. Copper sulphate (CuSO^.SHgO), commonly called blue vitriol or bluestone, forms, when dissolved in water, one of the most active fiuigicides known. This chemical, the composition, manufacture, and sources of supply of which will be more fully considered in a follow- ing chapter, dissolves in cold water, but somewhat more readily in hot water. As usually sold, the crystals are large, but a fine form may also be had in the market. If the large crystals are purchased and it is desired to dissolve them rapidly, they may be ground in a bone or shell mill before placing in the water. This has frequently been done by the writer when quick work was necessary. Copper sulphate may be manufactured by dissolving the black oxide of copper in sulphuric acid, or by the various modifications of this process hereinafter discussed. A watery solution of this chemical is strongly acid, and for this reason a simple solution of copper sulphate is very corrosive and injurious tu tender plant tissues, as foliage and opening ])uds. To avoid this injurious action, efforts have been made to obtain from the copper sulphate solution a spray retaining the fungicidal action of the copper, l)ut by the addition of other chemicals to neutralize or largely remove its acid reaction and consequent cor- rosive effects upon plants. As a result there are a very considerable number of copper sprays, representing various modifications of the simple solution of copper sulphate. Owing to the acidity of a solution of copper sulphate, the sulphate should not be dissolved or handled in metal dishes of any kind, espe- cially those of iron. The copper will often go to the metal, thus injuring the effectiveness of the spray, and the acid may also injure or destroy the dishes. The most suitable vessels for dissolving copper 148 PEACH LEAF CURL*. ITS NATURE AND TREATMENT. sulphate for work xuch. as here discussed are those composed wholly of wood, preferably of oak, and may be in the form of barrels, casks, vats, or tanks, of a capacity corresponding* to the respective needs of the growers. For small orchards a few good oak barrels of 45 or 60 gallons capacity are very suitable. As concentrated solutions of cop- per sulphate can be made, enough of the sulphate can be easily dis- solved in a 60-gallon barrel to serve for 300 or even 1,200 gallons of spray when properly reduced. It is well, when possible, to use 2 gallons of water to each pound of sulphate when dissolving the latter, but stock solutions may be of two to four times this strength. A solution of copper sulphate is heavier than water, so that it is an advantage in hastening the dissolving process to retain the chemical near the top of the water. If this can be done, the heavier copper solution will settle to the bottom of the Imrrel, leaving the purer water to continue the dissolving action upon the sulphate. The placing of the copper in a gunny sack and suspending the latter in the water has been recommended, but it is thought that other means more suitable may be found. The use of sacks or other cloths about the spraj^ tanks is hardly advisable, as the freer the tanks are kept from lint, strings, fibers, etc., arising from straining cloths, sacks, frayed staves, and stirring sticks, the less trouble the sprayer will have with his nozzles in the orchard, and the better, quicker, and cheaper can the spray work ])e done. Instead of a sack, a clean willow or hard-wood splint basket may be used for suspending the chemicals. A box may also be easily made for the purpose. It should have a diameter, when about 1 foot deep, sufficient to hold the copper sulphate to be dissolved, and it should be open at the top, with strong 1-inch slats across the l)ottom, the latter to be set one-fourth inch apart. If the box be fitted with a strong hoop bail it may be suspended in the barrel by placing a stick through the l)ail and across the top of the barrel. As a rule, how- ever, the writer has found it sufficient to place the copper sulphate directly in the bottom of a good oak barrel, filling the latter one-third to one-half f idl of water, and stirring and crushing the crystals with a clean hard-wood pounder. A half hour's work is sufiicient to dissolve many pounds of copper sulphate in this manner. With three or four good barrels one man can thus keep a large spraying gang supplied with material, if the water be convenient. It is always an advantage to place the copper in water in the barrels over night, when possible, as sufficient material is thus easily made ready in the morning for a half day's spraying. It is an advantage to strain all water before the copper sulphate is added, as afterwards ordinary strainers are liable to be injured by the acid, and, as before stated, the use of cloth strainers is not advisable. The eyes and hands should be protected as nuich as possible from PREPARATION OF THE COPPER SPRAYS. 149 injiny by this spra^v (p. 171). The unaltered solution of the copper sulphate is not only unpleasant to handle and apply, and injurious to tender veo^etahle tissues, but it is quite injurious to all metallic parts of pumps, hose, extension rods, and nozzles, nozzles ])eing eaten out very rapidl}' by it. For these various reasons the solution of copper sulphate is rarely used as a spray in an munoditied form. In most cases its corrosive action is more or less altered or lUHitralized through the addition of some modif3nng agent. In other words, the copper sulphate solution is used as a base or stock solution for the preparation of several more or less noninjurious and eipially effective sprays, as the Bordeaux mixture, the eau celeste, the modified eau celeste, the ammoniacal copper carbonate, etc. For this purpose it may be prepared in a concentrated solution, to be used as a stock solution for the preparation of any of the modified sprays mentioned, as already pointed out. A convenient strength for stock solutions is 1 pound of copper sul- phate to 1 or 2 gallons of water. In using stock solutions, two matters should always be considered: (1) The pails, barrels, or tanks used should be carefully gauged and marked, so that the nvimber of gallons of water or of the solution they contain may be known and not guessed at.^ (2) Before dipping from a stock solution any required number of gallons, the solution should be thoroughly stirred, otherwise the last dipped out will be very much stronger than that coming from the top, and consequently the work will be inaccurate and often very unsatisfactory; moreover, neglect of this precaution might, in many cases, lead to the injury or even to the destruction of the plants treated. It may also be said that the copper sulphate solution should be cold when used in the preparation of Bordeaux mixture, eau celeste, modified eau celeste, or ammoniacal copper car})onate. BORDEAUX MIXTUKE. Bordeaux mixture is prepared b}' uniting the milk of lime with a solution of copper sulphate. The reaction which tak(\s place when the two solutions are united as well as the other chemical phases ' The following rules for measuring square and round tanks and casks may prove of value in this connection: Circular chleiiia. — ^lultiply the square (jf the diameter in feet by tlio deptli in feet and the product by 5| for the contents in gallons. Circular ca.<ar-e with PI. XXII.) Bull. 20, Div. Veg. Phys, & Path., U. S, Dept. of Agricultun Plate XXI PKErABATlUN OF THK SULPHUK SPKAYS. 15U puinpod from the truck tank into the spraj^ tank in the orchard. The brass strainer cloth employed by tinners in making- strainer pails is used for this purpose. It is very necessary to strain well, as in the unstrained spray there are always dregs that fill the nozzle and delay work. Mr. C\itts says that in tanks of this kind it is necessar}- to stir the spray frequently while boiling to thoroughly mix the different ingredients. Three hours" boiling is better than two. He also says that one man, at $2 per day, will tend the boiler and prepare from 1,500 to 2,000 gallons of spray per day, and that it will require about one-half cord of 4-foot wood to generate the steam in such a boiler as he uses. In preparing the sulphur sprays for orchards containing 500 to 1,000 acres of trees it is desirable to have tanks of larger size than those used by Mr. Cutts and to avoid as much pumping and trans- ferring of the sprays as possible. One of the most convenient and complete spray -cooking plants for orchards of large size which has thus far been seen by the writer will here be described. This plant is at the Rio Bonito orchard. The water for preparing sprays at this orchard is obtained from a well and is forced l)y means of a rotary force pump run by steam power into a large storage tank elevated upon a heav}^ framework some 30 feet above the ground. About 10 feet above the ground and at one corner of the open framework of the tank house is placed a circular tank holding about 300 gallons. This is a storage tank to receive the spray when prepared for the orchard. The bottom of this circular tank is supplied with steam pipes, so that the contents may be kept hot and ready for use. From the outer side of this storage tank, near the bottom, is a discharge pipe with valve and hose attached, through which the spra}' may be run b}^ gravity into the tops of the 300-gallon spray tanks on wagons which are used in the orchard. These wagons are driven to the side of the stoi-age tank and filled with boiling spray in a few minutes, much as street-sprinkling tanks are driven under the elevated hydrants and filled. The boiling tank proper is built of 2-inch surfaced pine plank within a firm framework, properly bolted, and rests firmly upon the ground. It is situated within the heavy framework of the water tank house. This boiling tank is approximately 18 feet long, 3 feet wide, and 3 feet deep, and its full capacity is 1,200 gallons. In the center of the tank house is a water pipe connected with the large water tank above. Near the bottom of this standpipe are hydrants for the attachment of hose, thus allowing of water being drawn directly from the water supply above into the boiling tank by opening a h^'drant. An unlimited supply of cold water is thus alwa^^s at hand without the necessity of lifting a pailful by hand. The steam pipe for heating the sprays in the boil- ing tank extends from end to end along the bottom within the wooden tank, and every 2 or 3 feet along this pipe are cross pipes leading toward each side of the tank. The ends of the central pipe and its branches 160 PEACH LEAF CUKL: ITS NATUEE AND TREATMENT. are closed. Along both sides of this main pipe and its lateral branches are drilled small holes for the escape of steam into the tank. The flow of steam to the tank is controlled by means of a globe valve in the steam supply pipe, the valve being- conveniently placed for the workman at the tank. Broad board covers are made for covering the whole tank when the boiling is in progress. As in the case of the spray-boiling plant of Mr. Cutts, the main steam pipe leads from the tank directly to the steam dome of the boiler. The spray is prepared in the boiling tank of double strength, and when sufficiently boiled is elevated to the storage tank above by means of an appliance planned like an injector of a boiler. An iron pipe about 2 inches in diameter leads from the boiling tank upward and over the top of the storage tank described. In this pipe is placed the injector, which is supplied with two lateral connections. One of these connections is with the cold-water supply pipe, and the other is with the main steam supply pipe. In each of the pipes connected with the injector are placed globe valves for the control of the inflow of water, steam, and hot spray. When it is desired to fill the storage tank above with hot spray from the boiling tank below, the valve opening into the steam pipe leading from the injector to the steam dome is opened. The live steam at once escapes through the injector into the pipe leading to the storage tank and then out of the end of the pipe. The valves leading to the boiling tank and the cold-water supply are now opened in such a manner that about equal parts of cold water and hot spray are admitted to the injector, and the escaping steam, by means of its tendency to form a vacuum, soon causes a combined stream of hot spray and cold water to follow up the pipe and escape into the storage tank above. There is thus established a kind of steam siphon, which soon carries up 150 gallons of boiled spray and an equal amount of cold water, filling the 300-gallon storage tank with spray of the required strength, the strength of the spray in the boil- ing tank being double that required. This work is accomplished by a careful adjustment of the inflow of steam, spray, and water to the injector, the storage tank being filled without the necessity of lifting a pound of spray b}^ hand. The combining of the cold water with the hot spray in the injector is found to be necessary to the proper working of the latter as the temperature of the injector would otherwise become too high for efficient work. When the storage tank is full, steam is turned into the pipes situated at its bottom, and the spray is again heated to the boiling point and kept very hot until drawn off' into .a spray tank and taken to the orchard. The facilit}' with which a plant of this description may be operated will depend to quite an extent upon the nature and capacity of the boiler used for generating steam. The more easily steam can be generated and the greater capacity for steam which the boiler possesses the better for the work. 3ull. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate XXII. Steam Spray-cooking Appliances for Large Orchards. DKSCKirTIOX OF PLATE XXII. Fiir. I sliows sulphur, lime, a nd Halt Hpray-t-ooking appliances used on tiie Kio lionito Rancho. Tlie lieavv franiewiiik at the left supports a larj^e water tauk not nhown in the photofrraph. This tank is tilled ifroni a well by means of a steam rotary forces l>unip, and sui»plies all water required in cooking and reducing sprays. On the irmund, at the farther side of the framework of the tank, is shown a long wooden vat from which steam is issuing. This rectangular vat, :e extend from the rear of the wagou when in use in the orchard. PREPARATION OF COMBINED COPPER AND SULPHUR SPRAYS. ICl By referring to PI. XXII and the descriptions of tigures the reader may obtain a good idea of the arrangement of this extensive spray cooking plant, as well as of the boiler supplying steam. PREPARATION OF COMBINED COPPER AND SULPHUR SPRAYS AND NOTES ON OTHER SPRAYS TESTED. For many years the use of combmed copper and sulphur sprays has been practiced l)y peach growers in Oregon, and as they have reported good results the writer prepared the following four formul{\3 of this character for the control of curl. BORDEAUX MIXTURE AND SULPHUR SPRAYS COMBINED. The formulre of the combined Bordeaux mixture and sulphur sprays tested are given in the following list: List of sulphur sprays coinhined wiUi Bordeaux mixture. 3 pounds copper sulphate, 10 pounds sulphur, 20 pounds lime. 3 pounds copper sulphate, 10 pounds sulphur, 10 pounds lime. 3 pounds copper sulphate, 5 pounds sulphur, 10 pounds lime. 2 povmds copper sulphate, 5 pounds sulphur, 10 pounds lime. In preparing these combined sprays, which were found somewhat more effective in the control of peach leaf curl than the sulphur sprays alone, the Bordeaux mixture was added to the fully prepared sulphur spray. A portion of the lime given in the formula was reserved for making the Bordeaux mixture, while the remainder of the lime was comljined and boiled with the sulphur in the manner already described. When the sulphur spraj' had been placed in the spray tank, the Bor- deaux mixture, which had been freshly prepared from the copper sulphate and the remainder of the lime, was added, and after thorough mixing was at once applied to the trees. The union of the yellow sulphur spray with the blue Bordeaux mixture forms a spray of a distinct green color. The application of this spray is similar to that of the sulphur spra}^, requiring the same class of nozzles. MISCELLANEOUS SPRAYS. A large number of sprat's not included in the preceding descrip- tions have been prepared and tested for peach leaf curl, and some of them have been discussed in other portions of this bulletin. Several of them were tested for the purpose of learning the value of the separate ingredients of the leading sprays, as salt, lime, etc. Among these were lime, applied as a simple milk of lime; salt, applied in solutions of different strengths; and lime and .salt combined, applied as a whitewash. Sulphur was tested in the form of sulphide of potassium, applied in various strengths in liquid form, and the union of this sul- phide of potassium with milk of lime was also tested. Iron sidphate, 19093— No. 20 11 •162 PEACH LEAF CURL: ITS NATURE AND TREATMENT. sulphur, and lime were tested iu combination by adding to the sulphur spraj' a mixture prepared b}^ uniting the milk of lime with a solution of iron sulphate. The union of the milk of lime with the iron sulphate solution produced a lead-colored mixture resembling Bordeaux mix- ture in consistency, and when united with the sulphur solution the color was dark green or approaching black. Iron sulphate and lime were also tested separately. While some of these sprays gaye eyidence of considerable fungi- cidal action, none of them gaye results which Ayould warrant their substitution for the sprays already considered in preyious chapters, and hence it is unnecessary to enter further into details respecting their preparation. The results of their use may be learned in the chapters of this bulletin which relate to the action of the sprays on the foliage and the fruit. GENERAL CHARACTERS OF THE SPRAYS TESTED. There are certain general characters of sprays adapting them or making them unsuitable for yarious classes of work, and to these it may be well to allude. THE EXin'RIXG QrALITIES OF THE SPRAYS. In the worK here described careful notes were made on the enduring or weathering qualities of the sprays tested. During the last week in April and first week in March, 1895, 35 sprays, of different formulte, were applied in the experimental block in the Eio Bonito orchard, most of them to 10 large trees, as has heretofore been shown. On August 10, or fiye months after the spraying was completed, the trees of each experiment row were examined to' ascertain as far as possible the enduring or weathering qualities of the sprays, and according to the notes made at that time the appearance of the sprays upon the trees, after fiye months' weather- ing, maj' be grouped under the following four heads or classes; (1) Sprays showing quite distinctly upon the trees on August 10. (2) Sprays moderately eyident on August 10. (3) Sprays little eyident on August 10. (1) Sprays not obseryable on August 10. The spra3"s classed under the first head, were those applied to rows 1, 3, 7, 9, 13, 15, 18, 19, 21, 22, 25, 33, 36, 11, 11, 15, 50. 51, 56, and 57; under the second head, those applied to rows 6, 10, 12, 16, 28, 12, 48, and 51; under the third head, those applied to rows 27 and 35; and under the fourth head, those applied to rows 30, 32, 38, 39, and 47. By referring to page 73 the reader will find a table giying the formulae for sprays applied to each of the rows named, and an examination of these formulae will bring out the following facts: All the sprays GENERAL CHARACTERS OF THE SPRAYS TESTED. 163 included under the first two headings contain lime, while those under headings 3 and 4 contain none; all formula' containing 15, 20, or 30 pounds of lime to 45 gallons of water fall under tiie lirst head. Of the 18 sprat's containing 4, 6, 8, and 10 pounds of lime, 10 fall under the first heading and 8 under the second: copper sulphate enters into the composition of 8 of the 10 sprays falling under the first head, while the remaining 2 contain iron sulphate; of the 8 sprays which fall under the second heading, only 1 contains copper sulphate, and that but 2 pounds, while 5 are sulphur sprays. These facts seem to show that the union of copper sulphate and lime produces a spray possessing decidedly greater weathering qualities than the union of sulphur and lime. In the following list are shown the pounds of lime contained in the various sprays tested; the numbers of the rows of trees to which each amount of lime was applied; the position of each spray as grouped according to its apparent weathering qualities into classes 1, 2. 3, or 4; and references showing the nature of all the sprays containing lime: Weather-resist h7g rjualities of sprays. 30 pounds lime in formula, class 1, rows 1 1 and 7t. 20 pounds lime in formula, class 1, rows 3t, 9t, 13t, 36t*, and 44°. 15 pound.s lime in formula, class 1, rows 15*, 33*, and 57t. 10 pounds lime in formula, class 1, rows 18t*, 19t*, 41* 45*, 50tt, 54*, and 56ttt; class 2, rows Gf, 12t, and 48t°. 8 pounds lime in formula, class 2, row lOf. 5 pounds lime in formula, class 1, rows 21*, 22*, 25*; class 2, rows 28*, 42t°, and 51t. 4 pounds lime in formula, class 2, row 16t. No lime in formula, cla-s 3, rows 27 and 35; class 4, rows 30, 32, 38, 39 and 47. t Sulphur and lime, or sulphur, lime, and salt. t* Copper sulphate, sulphur, and lime. °Lime. * Copper sulphate and lime. tt Iron sulphate and lime. ttt Iron sulphate, sulphur, and lime. t° Potassium sulphide and lime. It may be well to state in connection with the above list that while all the .sprays not containing lime are clas.sed under the third and fourth heads, this arrangement ma}' not correctly represent their respective enduring qualities. As they are without lime, the eye can not detect their presence in manj- cases where it is possible the chemi- cals may realh' be present in effective quantity, and it is therefore apparent that the value of such a list is largely of a comparative nature among those spra3's containing more or less lime in various combinations. The general facts appear to be. as already indicated, that the copper sprays are more enduring than the sulphur sprays, considering pound 164 PEACH LEAF CURL: ITS NATURE AND TREATMENT. for pound of lime iu their composition, and also that the amount of lime may be much less in the copper than in the sulphur sprays and still maintain the enduring qualities. It is likewise the opinion of the writer that where a winter spray of copper and lime has proved of poorer weathering quality than is desirable in a given climate, the cop- per should be increased as well as the lime when greater resistance to weathering is sought. In other words, while the increase of lime enhances the weathering qualities of the spray, it also has a tendency to retard or obscure the action of the copper it contains, unless the latter is increased somewhat in proportion to the increase of lime. THE CORROSIVE ACTION OF THE SPRAYS. As the present use of sprays has been limited to their winter appli- cation, the notes on their corrosive action relate largely to the action upon dormant trees or upon the vegetation immediately following the commencement of spring growth. In each case these remarks relate to the use of sprays upon peach trees, which are known to be among the most tender deciduous fruit trees commonly grown in the temperate zone. The sulphur sprays of the greater strengths used in these experi- ments caused in many cases the loss of some of the liner and weaker inner growth of the trees. This is more apt to be the case, it is believed, when the spraj" is applied shortly before growth begins in the spring. Where very strong sprays of this class are to be used, it is well to apply them comparatively early in the dormant period, say four weeks earlier than the copper sprays. Sprays having not more than 10 pounds of sulphur to 15 gallons of spray may be used with little danger up to within four weeks of the swelling of the buds. There is no danger of injuring twigs or buds with the copper sprays if properly prepared and applied before the buds have opened. Well- made Bordeaux mixture may be used even as late as the opening of the first blossom buds. The ammoniacal copper carbonate may also be safely used to a late date, and both may be again applied, if desired, after the trees have passed out of bloom. The simple solution of copper sul- phate and the eau celeste may be safely used to within a week of the opening of peach buds, but they should never be used upon the foliage of the tree. Modified eau celeste is less corrosive than the eau celeste, and may be used until the first buds begin to open, but from observa- tion in other classes of spray work it is believed to be unsafe to apply this spray to the leaves of the peach. The injurious action of the sulphur sprays when combined with Bor- deaux mixture is fairh^ to be compared with the action of the sulphur spraj^s alone when containing equal amounts of sulphur. The spray composed of iron sulphate and lime is more apt to injure tender shoots and buds than the Bordeaux mixture, and such a spray can not be recommended for use upon foliage. GENERAL CHARACTERS OF THE SPRAYS TESTED. 165 Milk of lime appears to he practically harmless when applied to dormant trees or to trees in leaf; hence any injurious action resulting from the use of sprays containing lime should he charged to the other ingredients or to the lime as altered or moditied through combination with such other constituents. ADVANTAGES OF DISCERNIBLE AND INDISCERNIBLE SPRAYS. Reference has been made in a brief way to the advantages possessed bj^ certain sprays in forming a visible deposit upon the surfaces sprayed. While sprays forming such a visible deposit are decidedly advantageous for all winter work, those leaving no such disthict deposit are most desirable for the treatment of fruit, especially when approach- ing maturity. The advantages of white sprays in the winter treat- ment of deciduous trees are obvious, it being possible with such sprays to clearly see what portions of the plant have been thoroughly and properl}'^ covered. This advantage may even make the difference between success and failure in the work. Some recent experiments in apph^ng whitewash or sprays contain- ing large amounts of lime have tended to show that the opening of the buds may be somewhat retarded by such winter treatment. The theory is that whitening the trees prevents, to some extent, their absorption of heat from the sun's rays, and that this aids in keeping the trees in a dormant condition somewhat later than would otherwise be the case. Whether this will prove of enough importance to warrant the outla}' for spraying remains to he shown. An illustrated article on this sub- ject appeared in the Canadian Horticulturist for January. 1899.^ All sprays, both copper and sulphur, which contain lime are adapted to the purposes here considered. The Bordeaux mixtures and sulphur sprays used in the work descril)ed are distinctly observable upon the trees when applied, and after drying for a very short time the treated trees become decided!}' white. The greater the amount of lime the whiter the trees. (Pl.^ XXIII.) In the summer treatment of trees and plants having fruit approach- ing maturity, the use of clear sprat's is often most to be recommended. The spray now best adapted for this purpose is the ammoniacal copper carbonate. A stronger spray, though making less showing than Bordeaux mixture, is the modified eau celeste. As this is apt to cause injury in some cases, it is desirable to use Bordeaux mixture for summer work up to a date when the fruit is approaching maturity, and then to adopt the ammoniacal copper carbonate. The time at which the summer use of Bordeaux mixture should be discarded for the ammoniacal copper carljonate will depend largely upon the amount of summer rains in the locality' where used. In New York State, for instance, where summer showers are frequent, the lime-containing * Orr, W. M., 1. c, pp. 18-20. See further remarks on this subject on p. 150. 166 PEACH LEAF CURL*. ITS NATURE AND TREATMENT. Bordeaux mixture could be used upon fruit until a later date in the summer than it could in California, where almost no summer showers occur, and where the lime would remain upon the fruit until the latter was mature. This matter leads us naturally to the consideration of sprat's adapted for wet and for dry localities. SPRAYS ADAPTED TO USE IN WET AND IN DRY LOCALITIES. Little can be said on this subject that has not been previously touched upon in this bulletin. A few general remarks, however, ma}^ be of advantage to the grower. The enduring qualities of sprat's containing lime increase w^here the ratio of the other ingredients is maintained, very largely in proportion to the increase of the lime which the formula? contain. For instance, the relative proportions of copper sulphate and lime being maintained, a Bordeaux mixture which contains 10 pounds of lime to 15 gallons of spray will obviously endure much longer upon the trees in a wet climate than a Bordeaux mixture containing but 5 pounds of lime to the same amount of spray. To avoid the loss in activity and effectiveness of a spray containing a large amount of lime, the fungicide, be it copper or sulphur, should be increased so as to maintain the same or nearly the same ratio between the copper and lime which exists in the spray containing less lime. It is advised, therefore, that sprays to be used in a wet climate, especialh^ those intended for winter application, should be made stronger, both in lime and in the essential fungicide they contain, than is found necessary in a dry climate. If two spraj-ings are neces- sary, both should be given the dormant trees. In wet climates the conditions favorable to the development of curl and other fungous diseases are increased. This supplies a further reason for using sprays containing increased amounts of fungicide and having greater enduring qualities than sprays used in dr^' localities. The soil conditions in wet situations are apt to delay spray work till the last moment compatible with effective work. In such cases the amount of copper should be sufficient, if this class of sprays be used, to act promptly. If the Bordeaux mixture be applied under such circum- stances, it will not be found desirable to reduce the copper below- the equivalent of 1 pound of copper for each pound of lime, and a higher proportion may often be used to advautange on dormant trees. CHAPTER IX. THE APPLICATION OF SPRAYS. GENERAL ACCESSORIES FOK WINTER SPRAYING. To tliose who have sprayed for 3'ears and have learned T)v experience the most suitable appliances for such work the present remarks may not prove of direct value. They are especially intended, however, for those undertaking" such work for the first time. NOZZLES SUITED TO WINTER WORK. The past few years have seen in the United States a very great increas-e in the styles and places of manufacture of nozzles and other spraying appliances. At the present time the number of stjdes and makes of nozzles often leads to confusion in the mind of the prospective sprayer. In fact, however, there are but few essential features to a good nozzle. The form of greatest importance for most classes of work is that which gives to the discharged spray a rotary or cvclone motion. This movement is given in a very simple manner by admitting the stream at an angle into a circular chamber in the nozzle, so that it first strikes the curving side of the chamber, and is thus forced to assume a circular or rotary motion. The revolving stream then passes through the small central opening of the discharge plate and widens into a cone- shaped spray, which gives to this nozzle certain advantages not enjoyed by several other types now on the market. Spray from such a nozzle covers a greater area without moving the nozzle than is covered with most other types. There are nozzles, however, capable of throwing spray to greater heights. The rotary motion assumed by the spra}' in the cyclone or Yermorel nozzles is a dissipation of force, at least in most forms of these nozzles, so far as concerns the throwing of sprays to a great distance. A type of nozzle first used near San Jose. Cal., and now bearing the name. of that town, is perhaps better adapted to long-distance spraying, and has been extensively used on the Pacific coast. The spray is formed by the tiuid passing, under high pressure, through a narrow slit in a rubber or metallic plate. Where the rubber plate is used the escape of small particles may take place through the temporary expansion of the opening in the plate. The cyclone nozzles are now made by many manufacturers in difi'erent portions of the country, and may be obtained through any first-class 167 168 PEACH LEAF CURLI ITS NATURE AND TREATMENT. Fig. 1.— Cyclone nozzle, with direct discharge and degorger, for thin sprays. hardware dealer in the United States. The San Jose nozzle is also obtainable through hardware dealers generally. There are many types and styles of cyclone nozzles. Some are planned to throw the spray away from the workman, with direct or forward discharge (fig. 1). Others are so constructed that the spray is discharged laterally or at a more or less acute angle (figs. 2 and 3). In using these nozzles for winter work on deciduous trees it has been found that most thorough and most satisfactory work can be done with less waste of spray when nozzles having a lateral discharge are emploj^ed. The reasons for this are evident. Dormant deciduous trees are but a skeleton or framework, presenting to the sprayer but a limited surface for stopping a direct spray. For this reason, where a nozzle hav- ing a direct discharge is emplo^xd, a large portion of the spra}' will of necessity' pass through the limbs of the tree and fall upon the ground, while at best it will pass through the tree but once. By using the cyclone nozzle with lateral discharge, however, the cone of spray may be directed upward through the whole top, and in falling back it passes through the tree a second time. Here is a decided gain in the limb surface which will be reached by the use of a given amount of spray. The nozzle having lateral discharge can also be handled to much greater advantage than the nozzle with direct discharge. By turning the extension pipe which bears the nozzle, the cone of spray may lie directed upward, downward, or laterally upon the limbs as desired. This has proven of great advantage in doing thorough work. The ordinary lateral discharge cyclone nozzles are suitable for use with most of the copper sprays. For use with the sulphur spraj's or Bordeaux mixture containing a large amount of lime, the common Vermorel or cyclone nozzle is rather too light and the opening too small. In California a special form of nozzle is in use for the application of such sprays (fig. 3). This nozzle is manufactured in San Francisco, and may be obtained from the leading hardware firms of that city. The nozzle is of the cyclone pattern, but is much larger, heavier, and stronger than the ordinary' type of cyclone or Vermorel. The dis- charge opening is of sufficient size to allow of the use of thick sprays, and the discharge plate is heavj^ enough to withstand much wear from corrosive fluids. A fact of prime importance, however, for the work Fig. 2.— Cyclone nozzle, with lateral dis- charge, for thin sprays. Fig. 3.— Heavy cyclone noz- zle, with oblique discharge, for thick sprays. GENERAL ACCESSORIES FOR WINTER SPRAYING. 169 being considered, is that the nozzle discharges the spray at an angle of al»out 45'^ with a lino leading directly from the sprayer. This gives the nozzle the advantages of both the lateral and direct dis- charge. The work of either of these types (figs. 1, 2, and 3) may l)e accomplished with this angular discharge. Makers of cyclone nozzles of all kinds are usually able to suppl}'' the discharge plates of the nozzles separate!}', and this is convenient for the grower, where the original discharge plates have been worn out. The separate discharge plates usually sell at 25 cents each. HOSE AND EXTENSION" PIPES. Fig. 4. — Wire-extended suction hose. Rublier hose of good quality is most satisfactory for aA kinds of spray work. The strongest and, best hose will usually prove cheapest if properly cared for. All hose should be thoroughly washed, both inside and outside, at the close of each day's work, and it should be well scrubbed, washed, and dried when the sprav work is com- pleted, and stored in a uniformly cool. dark, and medium dry place. Practice varies somewhat as to the internal diameter of hose used. One-half inch is perhaps the most common size. The external diameter of the hose should not be so small nor its flexibility so great that it will easily kink and twist upon itself. Hose which does this is a constant source of annoyance, causing loss of time and often endangering itself. Where possible, it is best to have all lines of discharge hose leading from the pump pass from the back end of the wagon, between two short stakes, one at each corner. With such an arrangement there is little danger of its being caught in the wheels or run over by them. Many lines of hose are injured or destroyed in this Avay. The stakes at the back corners of the wagon also serve as a means of winding up the hose preparatory to going to or from the orchard. Couplings for connecting 1, 2, 3. or 4 lines of hose with the pump may usually be obtained from responsible hard- ware firms, or through them from the manufacturers of the pumps used. The more common hose couplings are nearl}' always in stock at such hardware houses. For most pumps it is well to supply wire-extended suc- tion hose (fig. 4). Some stjdes have the spiral wire coil within the interior; others have it embedded in the rubber. When the metallic spiral is exposed to the spray in the interior of the hose it should be of brass, if possible, to enable it to withstand the corrosive action of the sprays. 170 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Brass suction pipe strainers for attachment to the end of the pipe may be had of different forms. They are necessar}' when the end of the suction pipe is simply lowered into the spray tank or when it rests upon the bottom of the tank. The extension pipes used by different growers vary. Some adopt common three-eighths or one-fourth inch iron tubing, while others obtain the bamboo-covered extensions, which latter contain one-fourth inch pipe. The essentials of an extension pipe are a brass coupling for connecting the hose, a good brass stopcock for controlling the flow of spra}^, a metallic pipe of sufficient length (which should be determined by the height of the trees to be sprayed), and upon the end of the pipe a thread and shoulder for the attachment of the nozzle and the recep- tion of a washer. The ordinary length of extension pipes is 8 or 10 feet, but where trees are large a 12-foot pipe may be needed. Either of these lengths are now obtainable from dealers in spraying supplies in the forni of bamboo extensions (fig. 5). There are advantages in the bamboo extension pipes over uncovered iron tubing. Where hot sulphur sprays are used the bamboo cover prevents the hands from feeling the heat, and where cold sprays are applied in very cold weather the bare, wet pipe is liable to chill or even freeze to the hand. The greater size of the extension pipe which is covered b}' bamboo also adds to the ease with which the pipe may be held and turned in the hands. PROTECTION OF THE SPRAYER. The nature of spray work makes it unpleasant for the workman, but much of this inconvenience arises from an incomplete or improper preparation for the work. Men who would not care to work in a rain storm without suitable covering are often improperl}^ protected against the similar or worse conditions prevailing when they are spray- ing. In the spraying of large orchards it has been learned that one of the most suitable coverings for men who are applying sprays is a sail- or's oilskin suit and sou'wester. This covering is light, impervious to wind and water, and is not as liable to crack as rubber clothing. What- ever form of head covering may be chosen it should be soft, so as not to be interfered with by limbs, and it should extend in front to pro- tect the eyes and behind to protect the neck. It is always desirable to protect the hands with long rubber gloves, and these can usually be obtained from or through druggists. In selecting such goods, how- ever, it is well to learn how long they have been held in stock by the dealer, and if they have been kept for more than a year it is best to order new ones from the manufacturer, as such goods soon rot when held in stock. Besides, new stock is no more expensive than old, and it will frequently endure twice as much use. Numbers 11 or 12 are usually about the right sizes for ordinary hands. Most wear can be SPRAY PUMPS. 171 obtained from gloves which are large for the hands, and in such the hands are not as apt to perspire. Where ruT)ber gloves are not obtain- able the hands may be greatly protected and kept soft b}- rubbing them thoroughly, as often as necessaiy, with a piece of beef suet. If corrosive sprays are to be applied, such as the simple solution of copper sulphate, eau celeste, etc., it may be found necessary to protect the eyes. For this purpose ordinary clear glass goggles may be used, or the sprayer may provide himself with mica goggles of large size, such as are worn in some portions of the country by men employed about thrashing machines. Both the glass and the mica goggles may be usually purchased through druggists. PUMPS FOR VARIOUS SIZED ORCHARDS. The selection of a good spray pump is advisable. The difference between the lirst cost of a poor pump and that of a good one is little, while the difference in the ex- pense of spraying an orchard with a poor and a good pump is apt to be considerable. There are some features which every spray pump should possess. It should be furnished with an air chamber for the regulation of the tiow. and the wearing parts should be of brass or brass lined. It should be strong and work easily, be supplied with means for iirm attachment, and have capacity sufficient to maintain the recjuired pressure without undue rapidity of stroke. Pumps for small orchards should be capable of throwing two good sprat's. Such pumps, suited for attachment to the top or side of barrels, or to other raised tanks or foundations, are shown in tigs. 6 and 7. These pumps are supplied with air chambers and are of sulEcient capacity for ordinary orchard spraying. Each has a con- nection for a small pipe leading down from the discharge pipe to the bottom of the barrel or tank. By opening a stopcock in the pipe a stream may be forced back into the tank close to the end of the suction pipe, thus serving to free the suction from deposit and to agitate the spray. These pumps can be obtained with brass-lined cylinders. The stroke is upward and downward. (See also PI. XXVI.) Fig. (). — Spniy piimp fur iitJu on barrt-l ur tank. 172 PEACH LEAF CURL: ITS NATURE AND TREATMENT. For orchards of medium to large size it is l)etter to obtain more powerful pumps — those capable of throwing four strong sprays. The pimips shown in figs. 8, 9, and 10 are admirably suited for this class of work. Pumps of the type shown in fig. 8 are used in the 1,600- acre Rio Bonito orchard. In this orchard one man pumps for four men spraying (Pis. XXVII and XXVIII). In many portions of California the pneumatic pump, shown in fig. 10, is a favorite. It has been used extensively in the spraying of orange groves where the trees are large and where high pressure is necessary to throw the spray to their tops. The pumps shown in figs, 8 and 9 have perpen- FiG. 7. — Spray pump for use on barrel or tank. dicular levers, thus avoiding the bending or stooping motion of the operator. The levers of each of the three styles shown are long, and both the strength and capacity of the pump is sufficient. The style of pumps, both for small and large orchards, to which attention is here called, will be found figured and listed in catalogues usually to be found in the hands of leading hardware dealers. Within the past few vears leading orchardists and others have tested, with varying success, the application of difi'erent motive powers to the operation of spra}" pumps. Steam and gasoline engines have received most attention for thi-< ]i-u-poso. Many of the power SPRAY PUMPS. 173 sprayers as now constructed are heavy, cumbersome affairs, which could never l)e of practical value in everyday orchard work. Of the machines or descriptions of the same which have come to the writer's attention, none have thus far appeared better adapted to practical and continuous orchard work than one in use at San Diego. This machine was planned and constructed for Mr. H. R. Gunnis, of San Diego, and has seen practical service for several years. It has been more or less changed and perfected from time to time, such improvements being made as have seemed best from experience gained in actual and extensive orchard work. This machine, as first called to the attention of the writer l)v Mr. Gunnis in the earlv part of July. 1805, is illus- trated in PI. XXIX. The photograph from which this plate was made was taken while the machine was being- used in spraving a young orchard near Santa Barbara. In reference to the changes made since this photograph was taken, Mr. Gunnis writes: •'The changes made in the machine since I corresponded with you regarding it in 1895 consist in the addition of a rotary supply pump and the use of a tender cart for haul- ing the material to the machine instead of having to shut down and go to the material every time the tank is emptied."' ^Ir. Gunnis further says, under date of March 10, 1890: ''The machine is still in constant use, and I can still say. as 1 wrote you over three years ago, that it has developed no defects whatever. Some of the parts wore out from actual service and have been replaced, but no changes have been made in its construction. * * * The use of the supply pump and tender increases the capacity of the outfit 25 or 30 per cent, especially in large orchards. In very small places it can also be used economically by two men, both spraying, as a good, steady team can soon be taught to move and stop at the word. In this case it is not necessary to use the tender." While it is believed that the machine which Mr. Gunnis has built and operated is superior to any other of its class, I am informed that the gentleman contemplates still further improvements. In regard ^pray pnmi) for general orehnrd work, upright 174 PEACH LEAF CURL: ITS NATURE AND TREATMENT. to these changes Mr. Gunuis says that he is now building from nis own designs, and has almost completed, a small gasoline engine of 3 to 4 horsepower, weighing less than 200 pounds. This engine is intended for use with a spraying machine embodying' all the features of his old apparatus, but lighter and more compact. He also has plans under way for a self-propelling machine, in ^vhich the extra power required will not cost half of what it does to feed a team, and which can be much more easily controlled. Fig. 9. — Spray pump for geufral orchard -work, upright lever. PI. XXX shows the right and left sides of Mr. Gunnis s sprayer as it appeared after the addition of the rotary- pump for tilling the spray tank. A detailed description of this machine was prepared by Gunnis and published in the Yearbook of the Department for Mr, 1896 (pages 73 and 74), in an article by L. O. Howard, on the use of steam apparatus for spraying. Those wishing more complete details may refer to ]\Ir. Gunnis direct, to whom the writer is indebted for the illustrations and facts here giyen. THE APPLICATION' OF SPRAYS. 175 SPK.VYINC; TANKS. A great variet\^ of forms and sizes of spray tanks are in use. For small orchards, scarcely' anything better could be desired than large oak barrels holding GO to 80 gallons. These may be swung upon wheels separately if desired, but the most convenient way is to place them tirmly in a one or two horse wagon. Large tanks, well hooped, are also very suitable for large orchards. Casks of this kind, holding 300 gallons, may easily be placed in the bottom of a two-horse wagon, leaving abundant room for placing and operating the heavy hand pump. Such casks are shown in Pis. XXVII and XXVIII. The manner of securing the tank by placing side timbers inside of the wagon bolsters is shown in PI. XXII, as is also the stirring stick which projects from a square hole in the top of the cask. Rectang-ular plank tanks are used by some, but it is generally found more difficult to keep them from leaking than in the case of casks, where the hoops may be tightened at will. Numerous spray carts, bar- rel attachments, etc.. are illustrated in E. G. Lodeman's Avork on The Spraying of Plants. The use of iron tanks is rare, and is hardly to be advised for general spray work, owing to the corrosive action of many sprays. For special sprays, as the kerosene emulsion, such tanks may, however, be safely employed. All spray tanks should be arranged in such a manner as to be easily cleaned, especialh' where Bordeaux mixture or the sulphur sprays are to be used, and the}' should be provided with some means for stirring or agitating the spray. The entrance to all suction pipes should be guarded with tine brass wire screen. It is well to wash the tanks out thorouohlv at least once a dav. Fig 10. — Pneumatic pump for general spraying. APPLYING WINTKR SPRAYS FOR CURL. A stud}' of the many experiments conducted ])y the growers and described in this bulletin will give much infonuation relative to the proper time for applying sprays for the control of curl. A presenta tion of a few general principles involved may, however, be properly made in this place. 176 PEACH LEAF CURL: ITS MATURE AXD TREATMENT. THE TIME FOR WINTER SPRAYING. The proper time for the application of winter sprays for the control of peach leaf curl depends very largely upon the conditions of climate, season, and situation of the orchard. The object to be attained is to prevent the fungus from infecting the lirst growth of spring. It has become apparent from the man}' and wideh" separated experiments which are here described that nearly if not all this infection result, from the spores of the fungus, which are present upon the tree and not. as formerly supposed, from a perennial mycelium, and it natui ally follows that these spores are to be destroj^ed or their germination prevented if the new growth is to be kept exempt from curl. When a spore is about to germinate or has just begun to germinate, its mem- branes are most tender and susceptible to fungicides. That most of the spores of JExoascus deformans enter upon the stage of germina- tion at or about the time of the pushing of the first leaf buds in the spring admits of little doubt. That is the time when the tissues of the peach leaf are most tender, imd when their infection by curl is actually known to take place. The preceding facts indicate that the time when the fungicide is apt to do the greatest good is just before or at the time of the earliest push- ing of the peach leaf buds. The spray should be everywhere present upon the trees just prior to the beginning of growth. To obtain this object it should be applied from one to three weeks before growth begins. This time may usuall}' be determined l\y carefully watch- ing the fruit buds, which show signs of swelling some time before thev open. "When thev first begin to swell, the sprav mav be at once applied (Pis. XXIII, XX lY, and XXV). This plan relates to regions of moderate rainfall, where a single thorough spraying, with sprays sutficiently strong and active, will prove sufficient. In regions of heavy precipitation more spray should be applied to the trees. It should be stronger and have greater adher- ing qualities, or else more than one spraying during the winter will be required to give the best results. If two sprayings are given, it is better to apply both to the dormant tree than to delay the second treatment till the leaf buds have opened The first spraying may be given in the fall or a few weeks before the second. THE MAXXER OF APPLYING WINTER SPRAYS. The source of infection of the spring foliag of the peach by the fungus of leaf curl is local — i. e., it is to be found upon every portion of the tree. This fact is sufficient to shov that any portions of the tree not reached by the spra}' will be as subjec to the disease as if no spraying had been done. It thus becomes apparent that ver}- thorough work is essential to the general control of the disease upon the tree. DESCRIPTION OF PLAT?: XXIII. This plate shows tlie condition of the trees in the experiment block of the liio Bonito orchard at the close of the spray work in the spring of 1895. The row of trees at the left has been sprayed; that at the right has been left unsprayed for com- parison. The first 10 trees on the left have been treated with a spray containing a moderate amount of lime; the second 10 in the same row were treated with a spray containing more lime, and they are much whiter than those in the foreground. Each row of 10 sprayed trees on the left and the corresponding row of 10 unsprayed trees on the right constituted an experiment. The uniformity in tlie size of the trees in these experiments is here shown to advantage. It should be noted that the buds are still closed, while tiie spraying is completed. Bull. 20, Div. Veg. Phys. & Patn., U, S. Dept. of Agriculture. Plate XXIII. *%r V^'l <-'/ DESCRIPTION OF PLATi: XXIV. A portion of the Lovell trees in the Rio Bonito orchard left unpruned until too late to spray, many of the flowers being already open. This plate should be com- pared with PI. XXV, which shows how the orchard should be pruned before spray- ing, and also with PI. XXIII, which shows how far l)ud development may ordinarilj- be allowed to advance in the spring up to the time the s})ray work is completed. Bull. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate XXIV. 5 H ~ o T o DESCRIPTION OF PLATE XXV. A properly pruned portion of the Rio Bonito orchard, which has developed too far for the best results of spraying. Spraying should be completed by the time the buds have developed as far as those shown in PI. XXIII. Bull. 20. Div. Veg. Phys. & Path., U. S. Dept. of Agriculture. Plate XXV. SPRAYING WHERE SEVERAL DISEASES ARE PRESENT. 177 Thorough .spray work requires that the sprays be applied in as cahn weather as possible. Wind greatly retards and lowers the class of work done. Sprays should likewise not l)e applied when the twigs or limbs of the trees are covered by frost, snow, or sleet, or by the water of rains, dew, or heavy fogs. To avoid the presence of hanging drops of dew upon the limbs, it is frecjuently necessary to delay spraying until late in the morning. Such delay is preferable to the application of spray to the dripping trees. When the twigs are dry the sprav dries where it strikes, and succeeding dews or showers, if the latter are not too heavy, will not wash oil' the spray to a very injurious extent. If the sprayer is provided with suital)le extension pipe and nozzle with lateral discharge, the work of spraying peach trees of ordinary size may be rapidly and easily done. The cone of spray is first turned upward under the l)ase of one of the main limbs of the tree and the pipe moved so that the spray passes outward toward the end of the limb, spraying the entire under surface of the limb from base to tip. The sides and top of the liml) are now sprayed, together with all of its terminal branches and twigs. Each main limb of the tree is treated in like manner, the sprayer passing about the tree as the work is com- pleted. The habit of actively moving the nozzle back and forth while at work will soon be acquired b}^ the workman desirous of doing good work, and hy this means the most uniform spraying is accomplished. SPRAYING WHERE OTHER DISEASES ARE PRESENT WITH CURL. There are many peach diseases which may coexist upon the tree with curl. Many of these are amenable, in whole or in part, to treat- ment adapted to the control of curl, but in some cases where two or more are present it ma}' be advisable to make slight alterations in the treatment. The following notes on some of the more common dis- eases may prove of value. PRUNE RUST OX THE PEACH {Puccinia jminl Fers.) . - It is a fact which does not appear to be generally known that prune rust infests the tender branches of the peach as well as its leaves. This has been found especially true in young trees. S\)oyq- clusters are found upon the young shoots before growth begins in the spring, showing that the disease winters over by means of spores produced upon and remaining attached to the branches, as well as by the spores produced upon the leaves and scattered o\er the tree. Where the trees are suffering from rust it is therefore apparent that a thorough winter treatment is required to clean the tree and prevent the spring infection, hence such spraying is reconunended for the control of both curl and rust, though the full control of th(^ latter disease is very 19093— No. 20 12 178 PEACH LEAF CURL: ITS NATURE AND TREATMENT. difficult and will, at best, be necessarily followed by several summer treatments. There can be little doubt, however, that a thorough winter spraying will prevent a greater portion of the injurj^ from rust than an}^ single spraying applied at a later date, as it gives a practi- cally clean tree at the opening of the season of growth. Winter sprays for the control of rust must be strong; but summer sprays if strong should be positively neutral and noncorrosive, as peach foliage is exceedingly tender. MILDEW OF THE PEACH {Poclosplixra oxyacantlix De B.) . Peach mildew is widely distributed in the United States and in Europe. The fungus causing it attacks the leaves, fruit, and tender branches in the early part of the summer. The branches serve for the wintering over of the spores, thus aiding in supplying the source of spring infection. Winter treatment of the trees, with either the copper or sulphur sprays, will largely limit this spring infection, but later treatment with weak spraj^s will often be necessary for full control. BROWN ROT OF THE PEACH {MonUia fructigena FeTS.) . Brown rot of the peach has become one of the worst fungous dis- eases of the peach over large portions of the United States. It is quite general throughout most peach-growing sections of the East, and has become well established in the Pacific Northwest. It has been shown by Erwin F. Smith that the fungus winters over in the diseased branches and in the dried fruit adhering to the tree. These facts point to a thorough winter spraying with active fungicides as one of the first steps required in its treatment. Summer sprayings will also be required, and even when thoroughly followed up, the disease will prove hard to control. Too much stress can not be laid, however, upon the necessity of disinfecting the dormant tree as perfectly as possible by thorough winter treatment. BLACK SPOT OF THE PEACH {Cladosj^orium carpophihuu Thiim.y . This disease, which produces black spots upon the peach, is well known in many portions of the United States and in Europe, and in the East and South, especially in Texas, it has become quite trouble- some. In some parts of Europe it has been known as a true epiphy- totic. Whether this Cladosporium infes^the_ branches the writer can not say, but it appears not improbj jjle that such is true, or in any case that the spores probably find winter lodgment upon_the_tree itself. Black spot has been controlled in Texas by the use of the copper sprays, and there seems no reason- to doubt that the winter treatment of the infected trees would largely tend to disinfect them and materi- ally reduce tl^e summer dev elopment of thejdisease. SPRAYING WHERP: SEVERAL DISEASES ARE PRESENT. 179 •\VINTKK ULIGIIT OF THE I'EACH AND OTUEK SPOT AND SIIOT-IIOLE DISEASES, SUCH AS Pln/Husticia clrcuiiD^cixxd kerk., Ccrvospora circumscissa axcc. , etc. In the Northwest, on the riieitic c-oast, there are several diseases of the peach not generally known throughout the East, and also several other diseases connnon to both sections of the country. These troubles are genoriilly known as leaf spot or shot-hole diseases. One very widely distrilmted disease is that pi'oduced by Cercosjx/ra ciroum^, 7, 10, 12, 13, 15, 16, 18, 19, 21, 22, 25, 27^ 28, 33, 35, 30, 38, 39, 41, 45, 47, 48, 50, 51, 54, h'6^ and 57 — total, 30 rows. 180 PEACH LEAF CURL! ITS NATURE AND TREATMENT. Sprayed rows showino- a trace of sooty mold: Nos. 42 and -44: (sul- phide of potassiuiii was applied to row 42 and simple milk of lime to row 44) — total, 2 rows. Unsprayed rows showing' the presence of sooty mold upon the trees August 10: Nos. 2, 5, 8, 11, 14, IT, 20, 23, 26, 21), 34, 87, 40, 43, 46, 49, 52, 55, and 58 — total, 19 rows. Unsprayed trees showing no sooty mold, none. Rows sprayed in 1894, but not spra^'ed in 1895: No. 4. no mold apparent; No. 24, some mold present; No. 53, a little mold present — total, 3 rows. Rows for which no notes on sooty mold were obtained: Nos. 9, 30, 31, and 32 — total, 4 rows. The above notes show that records of the soot}' mold were obtained from 32 rows of sprayed trees 5 months after treatment. Of these, 80 rows showed no sooty mold, while 2 showed a very little. Neither of- these exceptional rows was sprayed with a generally recognized fungicide. On the other hand, of the 19 unsprayed rows examined, all showed sooty mold. The record for rows sprayed in 1894 but left unsprayed in 1895, shows that the trees had but little mold upon them 17 months after spraying. The preceding facts show the disinfecting value of a single winter spraying, even where the whole tree surface is covered with fungous mycelium and spores. ANIMAL PARASITES OF THE PEACH TREE. Among the insect pests of the peach tree now prevalent in many parts of the United States, the San Jose scale (Asjjuliotu-s per/u'cio-sm Com.) is probably the most injurious. This pest, as is already- well known on the Pacific coast, can be controlled by winter spraying with the sulphur sprays considered in this bulletin. Where the insect is known to be present, the strongest of these sprays described should be used, and it would be well to apply it somewhat earlier in the spring than where weaker sprays are used. All leaf -eating insects depositing winter eggs upon the tree ma}" be largely controlled by the winter use of sulphur sprays. There is also a mite {Phytoptus sp. ?) infesting the peach leaves in Califor- nia, which (the writer believes may be destroyed in this manner, from the fait that experiments conducted in 1895 in the Sacramento Valley showed that the same line of treatment is efl'ective in the destruction of a related mite {PJtytoj^tus j>yi'l Sor.) upon the pear. Mr. William N. Runyon, of Courtland, Cal., makes the following statement respecting the peach moth, which may also prove of value to growers suffering from this pest: "'" Incidentall}' I would state that experience shows that peach trees sprayed with lime, sulphur, and salt are not diibject to the attacks of the larva of the peach moth. Some growers Vlaim a saving of 90 per cent of affected fruit." CHAPTER X. NATURE AND SOURCE OF THE SPRAYING MATERIALS USED. Tlu' following notes on the chemicals for sprays are presented for the general information of the fruit grower. The facts given are those which every sprayer should understand. Spraying is frequently retarded or prevented owing to a want of information relative to the nature, sources of suppl}^, or true value of the chemicals required. A grower uninformed upon the last-named point is often at the mercy of local druggists or other dealers. For example, copper carbonate can be made by the grower himself at from 13 to 14 cents per pound, and ammonia of 26° strength may be pur- chased at al)out (>() cents per gallon, w^hile local prices have been known to range as high as $1 per pound for copper carbonate and ^1.50 per gallon for ammonia, which makes it impossible to undertake sprav work. The writer has found the same conditions prevailing in respect to prices for sulphur, which is used very largelj in the sulphur sprays and for the treatment of mildew. In some cases the prices asked by dealers in the East have been 100 or 500 per cent higher than growers have for years been paving in California. It can not be expected that the sulphur sprays will be generally used in the East under such conditions. copi'p^R SULPHATE (fomuda CuS0^5H.,0). Of all fungicides thus far known, copper sulphate is the most important. It is conmioid}' known as blue vitriol or ])luestone in the United States. Its foreign names are largely equivalents of these terms, although the Germans also apply th(> name of copper vitriol {Kupfei'rlft'iol). When pure, copper sulphate crystallizes in large. Hue, triclinic prisms. It contains about 25.3 per cent of copper, and dissolves in four i)arts of cold water and two parts of boiling water. The presence of iron is indicated by a greenish color of the crystals or at the surface of a watery solution when exposed ro the air. A solution of pure copper sulphate should be blue. The presence of a small amount of iron, which commonly occurs when copper sulphate is manufactured ns a by-product in modern smelting works, does not necessarily detract from its value as a fungicide, while this by-product 181 182 PEACH LEAF CUKL: ITS NATURE AND TREATMENT. may often be purchased at a somewhat lower figure than a purer article. Spra^ying tests have been made b}' the writer for the com- paiison of pure commercial bluestone with that obtained as a by-prod- uct of smelting works, and which contained a considerable amount of iron, and the results showed that the latter article contained fully as great fungicidal value as the former. The manufacture of copper sulphate is carried on at a considerable number of estal^lishments in the United States, and various processes are followed. A large amount of this chemical is also imported, chiefly from England. Bluestone is prepared l:)y dissolving cupric oxide in sulphuric acid, or by oxidizing the sulphide of copper, the latter being the cheaper process. Mr. Alfred Rapp, a gentleman who has enjoyed a wide experience, has kindly supplied the following facts respecting the manufacture of copper sulphate by a leading smelting firm of the Pacific coast. He states that the copper is mainly derived from mattes produced in the blast furnaces, and, secondlj^, from an acid solution of sulphate of copper resulting from the precipitation of silver by metallic copper out of a sulphate solution. To bring the copper in the difl^erent mattes in solution they are first crushed and pulverized to about one-thirty-second of an inch or finer, and subjected to a roasting process by which the sulphur is nearly all oxidized. The roasted matte contains the copper as oxide and partly as sulphate, with a small amount still as sulphide. This material is pulverized once more and fed into lead-lined leaching tanks, where the acid copper sulphate solution is added, and, if necessary, sulphuric acid. The whole mass is heated by steam running through lead pipes. The copper oxide and the copper sulphate in the roast is thus brought in solution as a sulphate. About 80 per cent of the copper contained in the m.attes is thus leached out. The resulting solution, of course, is not a neutral one, but still contains an excess of free sulphuric acid. This solution is transferred to other lead-lined tanks, containing, suspended from wooden sticks, strips of lead about 3 inches wide, the central portion of which is bent downward l>etween the sticks so as to form a loop, which is held b}- the ends of the lead strips being bent over the sticks. The copper sulphate when run down to these crystallizing tanks is about 36^ to 44'^ B. During the cooling process, which takes about four to seven days, the copper sulphate, or rather part of it, separates out of the solution as blue crystals, which are deposited upon the strips of lead. ' These crystals are dried and packed in barrels ready for the market). This, Mr. Rapp adds, is the general way in which bluestone is maae the world over, except that they have at the works considered, in audition to the copper in the mattes, the acid copper sulphate soiutiori from a silver refinery. NATURE AND SOURCE OF SPRAYING MATERIALS. 183 Water drain ino^ from copper iiiinos sometimes carries copper sulphate in solution, in which case the crystals are procured hy evaporatino- the excess of water. Barrels of coppej- sulphate weigh from 300 to 000 pounds. The mamifa('turer''s price of copper sidphate will depend largel}'^ upon the price of copper and sulphuric acid — two leading constituents, as they are sold in the market — and upon supply and demand. The cost to the manufacturer will not, however, necessarily depend upon the market value of copper and acid, for one or both may be ol)tained by him as by-products in other regular and profitable lines of manu- facture, such as the smelting of gold and silver ores, etc.^ COPPER CARBONATE. Chopper carbonate as usually prepared shows the following formula: CuCOg. CuHjO^. It is widel}' used in the preparation of ammoni- acal copper carbonate sprays, and is especially well adapted to the treatment of maturing fn^it where sul)ject to fungous diseases. As commonl}" sold on the market, the carbonate of copper is green and finely granular or powdery. It contains about 57.4: per cent of cop- per. Native minerals of similar composition occur, such as malachite and azurite. Copper carbonate is manufactured by a number of firms in the United States, but much less extensively than the sulphate. In most cases it is prepared b}^ adding to a solution of copper sulphate an excess of sodium carbonate (sal soda) in solution. This gives a floc- culent mixture of pale blue color, afterwards changing to green. Heating makes the precipitate more granular. Owing to the difficulty of obtaining carbonate of copper in smaller towns, as well as the high price usually charged for it, the Depart- ment has usuall}' recommended that the fruit growers prepare it. The following instructions for this work were published by the writer in a circular sent to the peach g-rowers of the country in 18!'-1— 95: In a barrel dissolve B pounds of copper sulphate in 4 gallons of hot ' Owing to the somewhat enhanced value of copper at this time (March, 1899) , the wholesalepriceof coi)per8ulphatehasadvanced. San Francisco producers quote copper sulphate in barrels, f. o. b., at 5\ cents, and carload lots at 5 cents per ]iound; Omaha ((notations are, by the ton or carload, 5^ cents; one New York firm (juotes 5| cents l)y the l)arrel or ton and .5^ cents by the carload, and a second firm quotes 6 cents by tbe barrel, 5^% cents by the ton, and 5| cents by the carload; Denver quotations are 6 cents by the barrel, 5| cents by the ton, and .5.1 cents by the carload; Cleveland quotes 6 cents per pound in any (|uantity; one Philadelphia firm quotes 6 cents by the barrel, 5| cents l)y the ton, and 5f cents by the carload, and a second firm quotes .5| cents by the barrel, 5^ cents by the ton, and 5} cents by the carload; Baltimore quotes 5| cents by the barrel, 5^ cents by the ton, and b^ cents by the carload; Great Falls, Mont., quotes 4| cents per pound in carload lots and 5 cents per pound for less than carload lots, etc. 184 PEACH LEAF CUKL: ITS NATURE A"ND TREATMENT. water. In another wooden vessel dissolve 7 pounds of washing or sal soda, in 2 gallons of hot water. The soda should be clear (translucent), and not white and powdery, as it appears when air slaked. When cool, pour the soda solution slowly into the copper solution. As soon as bubbles cease to rise fill the l)arrel with water, stir thor- oughly, and allow the mixture to stand over night to settle. The next day siphon off all the clear liquid from the top with a piece of hose, fill the barrel with water, stir thoroughh^, and allow it to stand a second night. Siphon off the clear liquid the second day, fill the bar- rel with water, stir, and siphon off' the clear liquid once more the third day. Now pour the wet sediment from the barrel into a crock or other earthen dish, strain out the excess of water through a cloth, and dry slowly in an open oven, stirring occasionallv, if necessar}^ to prevent overheating. Prepared in this manner there should be obtained, if none of the sediment in the barrel be lost, about 2.65 pounds of carbonate of copper. Owing most probably to the comparatively limited sale of carbonate of copper, the market price has been and still remains too high. It can rarely be obtained for less than 30 to 40 cents per pound, which is from two to three times the cost to the grower when it is prepared at home. This condition reacts upon the manufacturer by causing the grower to make his own carbonate, the market never feeling his demand. With fungicides which the grower is unable to prepare the conditions are different. His needs increase the demand in the market, and increased demand tends ultimately to lower prices. The cost of copper carl)onate when prepared b}- the grower will depend upon the cost of copper sulphate and sal soda. Quotations of March and April, 1899, placed copper sulphate at 5 cents per pound by the barrel and sal soda at 3*0 of a cent per pound in like quan- tity. At these rates the. grower should be able to prepare the car- bonate of copper at about 12.3 cents per pound. Quotations on larger lots of sal soda and copper sulphate placed the price at -jV of a cent and 41 cenfe per pound, respectively. At these prices the raw mate- rials for a pound of copper carbonate would cost about 11.8 cents. These facts bhow that wholesale druggists and manufacturing chemists could place the carbonate upon the market at 15 or 20 cents per pound and still make a good profit, even when Iniying their sodium carbonate and copper sulphate in the o^^en market. If we go a step farther back, howeveb", we may see that the first cost of copper carbonate can be greatlv reduced below any figures here given. Ten-elevenths of the cost is seen to depend upon the price of copper sulphate, and the first cost of tl^is latter depends upon the cost to the manufacturer of sulphuric acid\and copper. Both of these articles may be produced as l)y -products lof modern smelting processes. A firm at Blacksburg, S. C, informs the writer that they employ gold-bearing pyrites for the manufacture of sulphuric acid, the sulphur fumes being driven NATURE ANT) SOiniCE OF Sl'RAYTXO MATERIALS. 185 ori' witli heat and coiKlciiscd in lead cliaiiilxTs in the usual way. The acid, the linn states. i)ays tlic cxjicmscs, licncc the uold colU'cted is a l)y-])r()duct witli tlicm. For tlic same purpose sulphur may )je obtained by heat from several kinds of jiyrites — that is, from the sulphides of copper aiul iron. As already shown in tin* notes on copper sulphate, copper for the pnxhiction of this chemical may l)e d(M-ived largely from the mattes of silver sineltino- works. In view of the fact that both the cop))er and sulphur of eo})per suli)hate may be olttained as ))V-products in the exttMisive g'old and silver smeltinji' works, the tirst cost of this cluMuii-al can certainly ])e placed at a figure admitting of the manufacture of copper carbonate at a very low cost. It could prol)ably )»e placed on the mark(>t to-day by the leading smelting companies at 15 cents per pound and still leave a liberal profit on first cost. It is to be hoped that this matter will ])e looked into by some of the larger smelting firms, and that the carl)onate of copper may soon be had on the market at prices which are not prohibitive to its purchase by the horticulturists of the country.' AMMONIA {forrmda NH 3). 1 Ammonia is of gaseous nature and strongly alkaline in reaction. It is readily taken up or dissolved in water, in which form it is used in preparing the ammoniacal copper carl)onate, eau celeste, and modified eau celeste — three of the more important copper spraj's. A strong solution of ammonia may ))e commonly had on the market or from the mamifacturers. Such a solution contains, by weight, about 28 per cent of ammonia gas, and is sold as 26° ammonia, as shown by Baume's hydrometer test. A weaker solution is often prepared by druggists and is sold as anmionia Avater, or aqua ammonia. This often contains no more than 10 per cent of ammonia gas, and is obtained by reducing the stronger article wnth water. It is scarcely necessary to add that there is no economy in buying this dilute liquid. The price is apt to be out of proportion to the strength, and if quantities are to be shipped long distances there is a needless increase of freight, owing to the 'The following quotations on copper carljonate were received March, 1899: St. Ijfiuis quoten lO-pound lots at 272 cents per pound, 100-pound lots at 2-5 cents per pound, and 1,000-pound lots at 2,3 cents per pound, f. o. b. ; one Philadelphia tinn quotes 10-pound lots at 2.3 cents per pound, 100-pound lots at 22 cents per pound, 1,000-pound lots at 21 cents per pound, f. o. b., and a second house quotes 28 cents per pound for ordinary quantities and 21 cents per pound by the barrel; New York quotes 10-pound lots at .3-5 cents per pound, 100-pound lots at 28 cents per pound, and 1,000-pound lots at 22 cents per pf)und f. o. b. ; Boston quotes 10-j)oiuid lots at 20 cents per poimd, 100-pound lots at 18 cents per pound, and 1,000-pound lots at 16 cents per poiuid. The writer invites attention to the great variation in quotations from different centers of trade. It is satisfactory to note that (juotations just received from Boston indorse the view already expressed, that carhonate of copper can be placed \\\)on the market at about 15 cents perpoimd and leave a sufficient profit 10 the manufacturer. 186 PEACH LEAF CURL: ITS NATURE AND TREATMENT. added percentage of water. It is always desirable to specif}^ the strength of the ammonia solution when obtaining quotations. Plants and animals furnish the main sources of commercial ammonia. In each case the ammonia is obtained through the decomposition or destructive distillation of the organic matter. Mr. Mallinckrodt, of the Mallinckrodt Chemical Works, of St. Louis, and president of the Pacific Ammonia and Chemical Company, states that there are, as already indicated, but two prime sources from which aqua ammonia is obtained, viz, "bone liquor,-' obtained as a by-product in the manu- facture of bone coal, and "gas liquor," obtained from the scrubbing of gas in works for the manufacture of coal gas. A similar source is also found in the making of coke. It is further stated that ammonia is obtained from bone liquor almost exclusively in the form of sulphate of ammonia, often of crude quality, which is used in the manufacture of fertilizers. Gas liquor is partly worked into a sulphate of superior quality, but mostly into aqua ammonia, by what is called the direct process. It is redistilled and aqua ammonia made therefrom. Aqua ammonia ol)tained from this source is largely used in the manufacture of ice and for other technical purposes. Obtained in this wa}'^, it is said to be the cheapest article of good quality that can be supplied. A crude concentrated ammoniacal liquor is also largely made by concentrating gas liquor without purification. This concentration is carried on mainly at smaller works for the purpose of transporting the liquors in a more concentrated form, to save the expense of freight, to works where crude liquor is redistilled and manufactured into pure aqua ammonia. The concentrated liquor is, however, also largely used in the preparation of nitrate of ammonia, which is used in the manu- facture of powder, but most largely in the manufacture of soda ash. This crude liquor contains, besides a small amount of free ammonia (NH3), a considerable amount of carbonate, sulphide, cyanides, and other ammonia salts, together with tarry and empyreumatic matter resulting from the destructive distillation of coal. The strength of this liquor can not be made greater than 15 to 20 per cent, and it is doubtful if it could be advantageously used as a suljstitute for aqua ammonia in the preparation of sprays. The ammoniacal liquors obtained in the manufacture of coal gas are entirely a by-product. As the gas works of the United States have been largely supplanting coal gas with water gas, in the manufacture of which ammonia is not obtained, the quantity of ammonia produced in the country has been steadily decreasing, and the demand is being supplied principally from England. Both aqua ammonia and anh3'drous ammonia are made largely from imported sulphate of ammonia, and very large quantities of the imported article are also consiuned in the manufacture of fertilizers.^ ^San Francisco's quotation on ammonia water of 26° hydrometer test, in drums of about 750 pounds, f. 0. b., is 7^ cents per pound. NATURE AND SOURCE OF SI'KAYINd MATERIALS. 187 SODIUM CARBONATE {formula NajCOj-lOHgO). Sodium carbonate, sal .soda, or washing soda is used in making car- bonate of coppiM- from the sul})hate of copper and in preparing the modified eau celeste. As obtained in the market it is in colorless, monoclinic crystals, showing a strong}}^ alkali n(> reaction to litmus j)aper. When exposed to the air nuicli of the water of crystallization is lost from the ciystals, Avhich rapidly effloresce or slake to a white powder. A^'llen perfect, nearly two-thirds of the crystals, b}^ weight, is water. Carbonate of soda dissolves in 1.(3 parts of water at 59'^ F. and in 0.2 part of boiling water. When a solution of sal soda is added to the solution of copper sulphate in making copper carl)onate, or to any other acid solution, a decided efl'ervescence takes place, so that in making the copper carbonate the two solutions used should be united slowly or they may overflow the containing A'essels. The more com- mon impurities found in sodium carl)onate are sodium chloride (common salt) and sodium sulphate (Glauber's salt). These impurities are due to the source and manner of manufacture of the sal soda, but are not usualh' present in the latter in sufficient amount to require attention in the spray work being considered. The sources of sodium carbonate are somewhat luuuerous, Imt the commercial supply of to-day is derived mainly from common salt or from natural deposits of the carbonate. In nearly all arid countries carbonate of soda is frequently found in the soil in such quantities as to be injurious to vegetation. W^est of the Missouri River large accumu- lations of the different soluble salts of the soil are frequenth^ met with. In the East such accumulations are prevented by the greater rainfall, the salts being eventually washed from the soil and carried to the sea, but in the West they often coat the ground, appearing white or black, and are known as '" alkali beds,'' owing to the frequent pres- ence of strongly alkaline salts, such as sal soda. The most abundant constituents of these deposits are sodium sulphate, sodium chloride, and sodium carl)onate. The sodium chloride and sodium carbonate are, when in excess, so injurious to vegetation as to constitute a leading bane of the horticulturist of the western half of the I'nited States. In the great plateau region between the Rocky Mountains and the Sierra Nevada and Cascade ranges are vast stretches of alkaline soils, the soluble salts of which accunudate in lakes and along water courses through the drainage oi the winter rains. During the long, dry sum- mer these waters evaporate to a considerable extent, leaving the salts deposited along the margins of the lakes and rivers.' In some cases these deposits of alkali are conq)<)sed lai'gely of sodium car])onate, and in several instances, after passing through a simple purifying process, 'These deposits are very well sliown in the illustiatiuns of I'>ull. No. 14, Division of Soils, U. S. Dept. of Agr. 188 PEACH LEAF CUKL: ITS NATURE AND TREATMENT. this salt is obtained in a quite pure state, the original deposits contain- ing- as high as 90 per cent of sal soda. This latter is obtained from the soda lakes of South America, Egypt, etc. , as well as from those of the United States. There are several such soda lakes in Wyoming, Nevada, and California. Large amounts of sal soda are crystallized from crude carbonate of soda obtained from Soda Lake, nearRagtown, Nev. This lake is known as Big Soda Lake, to distinguish it from a smaller soda lake near by. The lake is a beautiful sheet of water, lying in a depression of the desert, the water being about 150 feet in depth at the deepest point. It is very close to the old emigrant road running from the sink of the Humboldt River to Carson River. The separa- tion of carbonate of soda from the waters of this lake is largel}'^ by solar evaporation. In the fall the salts deposited are taken up, Avashed, passed through a furnace, and shipped in sacks to San Francisco, where the soda is refined and bleached for various uses. The principal uses on the Pacific coast are in glass-making and borax-making. It is stated that sal soda obtained as here descri})ed is practically a pure article, though the natural color is somewhat yellow or brownish. It is generally useful, except as a fancy article for the retail trade. For such purposes it nuist be bleached with chloride of lime, after which it presents beautiful crj^stals. There is also a large plant in operation at Owens Lake. Cal., get- ting out carbonate of soda from the waters for the Pacific market. This product, with that alcove described, is nearl}^ equal in strength and purity to the eastern and the imported product, so much so that consumers are safe in using the western product, if desired. All or most sodas (carbonates) found on the Pacific coast proper are in the form of sesquicarbonates, and are often so much contaminated with sulphates and chlorides that much expense is entailed in their separa- tion, and they are therefore of little value as sources of supply. The second great commercial source of sal soda is common salt. The salt deposits of the country are vast and inexhaustible in quantity. The Onondaga Salt Group of the Upper Silurian alone underlies much of the large extent of country', as well as the Great Lakes, situ- ated between Salina, N. Y., and Green Bay, Wis. At certain points the salt depqsits of this group are known to exceed 100 feet in thick- ness. The deposit is tapped by wells at Warsaw, N. Y., in western Ontario, in eastern and in western Michigan, and elsewhere. The rock salt of wester^ Michigan is 20 to 80 feet in thickness, and is reached at a depth of 1,800 to 2,200 feet. Other large salt deposits are found in Kansas and in numerous other portions of the country. Sal soda is riSianufactured from salt on a commercial scale according to two leading ^Drocesses. The older of these is known as the Leblanc process, and hat? been extensively employed in England and through- out Europe. It involves two steps in the manufacture, (1) the conver- NATURE AND SOURCE OF SPRAYING MATERIALS. 189 sion of salt into sodium sulphate, and (2) the decomposition of sodium sulphate and its conversion into sodium carbonate. The tirst opera- tion is known as the "salt-cake"" process, and the second as the ''soda- ash " process. The tirst step is carried out by the application of sul- phuric acid to the salt and the decomposition of both in a fui-nace, the doul)h' (U^composition resultin»i' in the formation of hydrocidoric acid and sodium sulphate. The h3'drochloric acid is condensed and pre- served, while the salt is converted ])v heat into a hard cake of acid sodium sulphate. There is usually in this cake, however, more or less unaltered sodium chloride. In the second step the salt cake is pul- verized and mixed with an e([ual Aveio-ht of pulverized limestone or chalk and half its weit)lit of tine coal. This mixture is heated to fusion in a furnace, being constantl}' stirred or revolved. The com- bustion of the coal under the heat which is maintained seems to con- vert the sodium sulphate into sodium sulphide, and the decomposition of the sodium sulphide and limestone, with the interchange of ele- ments, produces calcium sulphide and sodium carbonate. The resulting mass is cooled in iron receivers, broken up tinely, and digested in tepid water. The alkali dissolves and leaves the insoluble impurities. The sodium solution is evaporated, and when dry the mass is calcined with one-fourth its weight of sawdust, to more fully convert the alkali into carbonate. This product— the soda ash of commerce — is again dis- solved in hot water, and the solution filtered and allowed to cool. As the solution cools the carbonate of soda is deposited in large, trans- parent crystals, such as are supplied to the trade. Soda ash was formerly largely imported from England, but in the last few years has been made in the I'^nited States to a very large extent. The dissolv- ing of the soda ash and the crystallizing of the sal soda is carried on extensively by tirms not manufacturers of the ash. A St. Louis firm states that they crystallize the solution of soda ash in tanks holding about 8,000 pounds each. After the crystallization has progressed sufficiently, which takes from ten to fourteen days, according to the temperature of the weather, the mother lye, which contains all the impurities, is drawn off and the sal soda is then broken, dried, and packed in barrels. It is stated that a newer process is to crystallize the solution in small tanks, holding perhaps 200 pounds. In this small (piantily the liquid crystallizes in a very short time, say over night, but does not give any mother lye, and consequently no impurities are removed. A system entirely diti'erent from the Leblanc process is in use in the United States in some of the leading salt regions and has come very largely into use in Europe. It is known as the ammonia soda process, or the. Solvay process. It consists in decomposing a solution of com- mon salt with ammonium bicarbonate, whereby the greater part of the sodium is precipitated as bicarbonate, while the ammonia remains in solution as auunonium chloride. This latter salt is heated with 190 PEACH LEAF CURL: ITS KATURE AND TREATMENT. lime to liberate ammonia, which is then reconverted into bicarbonate by the carbonic acid evolved in the conversion of the sodium bicar- bonate into monocarbonate by heat. The ammonium bicarbonate thus reproduced is employed to decompose fresh portions of sodium chlo- ride, so that the process is made continuous.^ SULPHUR {symbol S). The value of sulphur as a fungicide, insecticide, and germicide nas been known for many years. Its use in a powdered state has been long followed in hothouses and vineyards, and its application in the treatment of parasitic skin diseases of man and the lower animals, and in the control of fermentation in fruits and wines is equally well known. In connection with potash and soda it has been applied to the treatment of fungous diseases in the form of sulphides of these bases. The recent marked use of sulphur in preparing sulphide of lime for the spraying of trees is believed to have been lirst suggested in Cali- fornia, the idea coming, it is thought, from the use of sulphur in a similar form as a dip to Idll scab mites on sheep. The spraying of trees infested by scale insects was a natural application of its known insecticidal qualities to the needs of the orchard. In combination with lime and salt it is now very widely used on the Pacific coast. These chemicals are boiled together for a considerable time, and result in the formation of one or more of the sulphides of calcium in liquid form. While the value of this spray is well established in regions west of the Rocky Mountains, its introduction in the East has been slow, though it is almost certain to have a wide application in that section in coming years, when the full importance of winter spraying for the control of insect pests and fungous diseases is more fully appreciated. This is more especially true where both of these classes of diseases occur at one time on the same host plant. Sulphur is obtainable in the market in several forms and degrees of purity. The forms most common are known as brimstone, the flour of sulphur, and flowers of sulphur. Brimstone is sulphur in the solid form, flour of sulphur is ground brimstone, and flowers of sulphur is sulphur which has been sublimed. Common brimstone is the cheapest form on the market, flour of sulphur stands next in price, while flowers of sulphur comes still higher. The purity of any of these ^Quotations on sal soda were received as follows during March and April, 1899: San Francisco qiuotes 50-sack lots at 60 cents per 100 poimds, 10-barrel lots at 70 cents per 100 pounds, and smaller quantities at 75 cents per 100 pounds; Los Angeles quotes %y the barrel $1.25 per- 100 pounds, and by the car in sacks $1 per 100 pounds; St. l^ouis quotes by the car load in barrels 55 cents per 100 pounds; New York quotes\ f. o. b. Syracuse, in jobbing lots, barrels of 375 pounds, 40 cents per 100 pounds; ^'^^irport, N. Y., quotes 50 cents per 100 pounds, f. o. b. NATURE AND SOURCE OF SPRAYINO MATERIALS. 191 forms is usually sutiiciently hioh for the use of tho horticulturist. Brimstone and flour of sulphur are usually about 98 per cent pure, while flowers of sulphur is almost entirely pure. Brimstone weighs most, flour of sulphur less, and flowers of sulphur least for a like bulk. The horticulturist uses sulphur in all the above-named forms, brim- stone being- empkwed for bleaching fruit, nuts, etc., while flour and flowers of sulphur are used in field work for the control of insect and fungous pests. A simple mode by which one may test the purity of sulphur is to weigh out any desired amoiuit and then drj'^ and burn it; the weight of the remaining incombustible portion, added to the amount of weight lost in drying, determines the amount of impurities. The sources of the sulphur supply of the United States are numer- ous and varied. A large amount of crude sulphur is imported, although much of the sulphur now used in the production of copper sulphate, sulphuric acid, and various other chemicals is obtained in the United States through the decomposition of several native metallic sulphides, such as the sulphides of iron and copper, which are known as iron and copper pyrites. It has been estimated that the amount of sulphur consumed in the United States in 1892 was 218,154 tons. The sources of this sulphur were as follows: From 100,721 tons of imported brimstone (98 per cent) 98,707 tons. From 1,825 tons of domestic brimstone (98 per cent) 1,787 tons. From 210,000 tons of imported pyrites (43 per cent) 90,300 tons. From 119,000 tons of domestic pyrites (44 per cent) 52,360 tons. At the present time the amount used is probably nuich greater than in 18:i2. Great deposits of native sulphur are found in many foreign coun- tries and in various portions of the United States. Most of the natural deposits occur in past or present mountain regions, and are of volcanic origin. '"The exhalations of volcanoes include, as a rule, sulphurous acid (SO.,) and sulphureted hydrogen (HjS), which two gases, if moist, readily decompose each other into water and sulphur, a circumstance which accounts for the constant occurrence of sulphur in all volcanic districts.'' It is estimated that 5,000,000 tons of sulphur exist in one deposit in Japan. The deposits of Sicily are famed the world over, and 100 distinct workings are said to exist in that island. In central Sicily, at Assoro, Imera, Villarosa, and elsewhere, large amounts of brimstone, in the form of short truncated pyramids, are commonl}^ seen piled near the railroad stations, as wood is piled in the United States. These large blocks, probably weighing 1< lO pounds each, are brought to the railroad on the backs of donkeys dri\'en down from the mines in the mountains in long trains. Large refineries, devoted to the refining of such l)rimstone, are located at Catania. The annual outputof sulphur in Sicily is said to exceed 300,000 tons, and the present 192 PEACH LEAF CURL: ITS NATURE AND TREATMENT, importation of the United States from Sicily is about 120,000 tons. The richer sulphur ores of Sicily run from 30 to 40 per cent of sul- phur. A considerable quantity is also imported from Japan. The leading native sulphur deposits of the United States are located in Nevada, Utah, California, \\^yoming, and Louisiana. While the amount of sulphur ore in the country is inexhaustible, the writer is informed by a New York dealer that not to exceed 3,000 tons are mined here annually, which, of course, does not include the amount extracted from pyrites. Respecting the Utah sulphur mines, which are located in the foothills of the Wasatch Mountains and in Beaver Count}^ al>out 200 miles from Salt Lake City, the writer has received the following interesting data from Mr. C. F. G. Meyer, of St. Louis: The sulphur supply at these Utah mines is practically unlimited, and the price of the product is governed entirely l)y foreign markets. The sulphur is found in an immense bed, the ore beginning at the sur- face of the earth and extending down to unknown depths. This ore is of a very soft character, containing sand, gypsum, and gravel, and has from 15 to 95 per cent sulphur. The profitable ore is mined through open cuts and hauled on a tramway to smelters. The smelters are cast-iron retorts and hold a ton of ore. Each charge is her- metically sealed and the retort is subjected to 40 atmospheres of steam pressure. Under this heat the sulphur percolates, in the shape of liquid sulphur, through the foreign matter into a pot below, from which it is drawn off and passes into a distilling vat for the purpose of per- mitting all foreign substance to settle to the bottom of the tank; thence it is drawn off' into wooden molds, holding about 200 pounds, and allowed to cool, after which it is passed through a grinding process in an attrition mill. The product obtained by the above process is about 99 per cent pure, and forms the flour of sulphur, which is extensively used, as already indicated. For obtaining what is commonly known as flowers of sulphur, which is chemically pure, the ground sulphur is passed through a resubliming vapor process. Respecting any possible advantage to the horticulturist by purchas- ing sulphur reflned in Europe in preference to that refined in the United States, a prominent sulphur refiner of San Francisco has kindly supplied the following facts: The sulphur refined is mostly from imported Sicilian and Japanese products. While there exists the remnant of a former prejudice against California sulphur, it should be of interest and value to know that there is absolutely no difference between that manufactured here and that manufactured in France, Italy, Denmark, and other European countries. Both start with the same raw material coming from Sicily, the same apparatus is employed, and even experienced foreigners are hired to refine the brimstone in the identical manner in which it is treated in the \ above places. There comes to the horticulturist no NATURE AND SUUKCE OF SPRAYING MATERIALS. 193 advantaofc, therefore, to offset tlic present duty of $8 per ton levied on the refined imported sulphur, and our agricultural population, it is claimed, is duped when demaiidino- French, Italian, or other European refined sulphur. The same manufacturer further states that Sicily sulphur of 98 per cent purity is at present admitted, to the United Stat(>s duty free, and that it can be ground or sul)limed in this country and sold at a price below the cost of the imported foreign-refined sul- phur. It is also said, as to the comparative value to the horticulturist of ground (floui-) and of sul)iinied sulphur (fiowers), that for ordinary purposes domestic ground or powdered sulphur, which averages less than 1 per cent of impurities, will answer all requirements in a wash, being finer tlian the imported, the onh' impurity being a neutral, inert volctmic ash. The sublimed sulphur, as before stated, is identical with the imported and contains little, if any, trace of anything but elementary sulphur. It is lighter in bulk and more stringy than ground sulphur (if examined under the microscope), but is not usually enough better for agricultural purposes to offset the difference in price. In other words, the difference in purity percentage between ground sulphur and sublimed sulphur is not in anj^ way commensu- rate with the difference in price, and a great saving could be effected l)y substituting the former for the latter in ninety-nine cases out of a hundred. To these views the writer would add that the flour of sulphur is cer- tainly what should be used in the preparation of sprays. As to the rela- tive value of flour of sulphur and flowers of sulphur for powdering vines for mildew, there is a difference of opinion among vine growers, the ease with which the fumes are given ofl' being considered of prime importance in the treatment of this disease.^ ^ Quotations on sulphur in March, 1899, were as follows: New York quotes flour of sulphur in 250 pound barrel lots at $2.20 per 100 pounds, 100 pound sacks at $2.15 per 100 pounds, and car loads in barrels at $1.80 per 100 pounds, and in sacks at $1.75 per 100 pounds, all f. o. b. A sec-ond New York firm quotes roll brimstone at $2 per 100 pounds; flour of suljihur, heavy, at $2.20, and light at $2.25 per 100 i)ounds by the Ijarrel; sublimed flowers of sulphur at $2.37^ per 100 pounds, in carload lots, f. o. b. ; roll brimstone, $1.70 per 100 pounds; flour of sulphur, heavy, 100 pound l)ags, $1.75; 250 pound barrels, $1.80 i)er 100 pounds; light, 175 pound barrels, $1.85 per 100 pounds; flowers of sulphur, sublimed, $2 j)er 100 pounds. San Francisco quote.s powdered sulphur, sacks or barrels, by the car load at $1.50 per 100 jjounds, less quantity at $1.60 per 100 pounds; sublimed (flowers of sulphur), sacks or barrels, car load lots, $1.75 per 100 pounds, less quantity, $1.85 per 100 pounds; roll, barrels only, $1.85 per 100 pounds; refined, l)arrels only (quality same as roll), $1.75 per 100 pounds; crude, sacks, $1.40 per 100 pomids. 19093— No. 20 13 CHAPTER XI. PEACH VARIETIES AND NURSERY STOCK IN RELATION TO CURL. COMPARISON OF PEACH VARIETIES. It is a well-known fact that certain peach varieties are less suscep tible to curl than others. When planting, many growers strive to select varieties which are known to be comparatively resistant. This has led nurserj-men to select and grow as hardy varieties as possible, and such selection has resulted in cultivated varieties becoming to some extent more hardy than the majority of seedlings. Of 97 peach growers who have stated whether, in their opinion, seedling or budded trees are most affected by curl, 60 say that seedlings are most affected, 19 think budded trees are affected most, and 28 growers have observed no difference between budded and seedling trees in this respect. In spite of the fact that some varieties of budded peaches are quite hardy, many of the finest peaches grown are much subject to curl. There are also varieties which are hardy in one locality and become very subject to the disease when grown under different conditions. There are, in fact, so many influences, such as season, soil, situation, etc., that it has been difficult to decide, except in a few cases, whether a variety ma}^ be fairly classed as hardy or susceptible. It is found by wide inquiry that a peach which is considered hardy in one portion of the country is not resistant to curl in another. The views of peach growers vary so widely respecting the hardiness of varieties that it has been thought best to give the results as obtained, rather than strive to draw from them an}^ final conclusions. Of a large number of growers who have been asked whether earlj'^ or late-blooming varieties are most affected, 70 have expressed their views. A majority, or 42 of these growers, think there is no difference between early and late blooming varieties, 23 believe early blooming varieties most subject to the disease, and only 5 believe the late bloomers most affected. It would seem that the late blooming varieties maj^ be less liable to injury, owing to the increased warmth when the}' push in the spring, Initthe difference is certainly not well marked. Respecting the hardi- ness of early or late maturing varieties, there appears to be little dif- ference from the replies to the circular letter. Among 79 peach growers who have expressed their views, 22 think early varieties most subject to the disease, 16 believe the late varieties most subject to it, and 41 think there is no difference, 194 PEACH VARIETIES IN KELATION TO CURL. 195 Besides the facts respecting the hardiness of varieties gathered by a circular letter addressed to the peach growers of the country in 1893, the following list contains such information on this subject as it has been possible to glean from the publications accessible to the writer. In this list arc tal)ulatod 101 peach varieties and a few nectarines in relation to their resistance to curl. So far as possible the form of the glands, the season of ripening, and the adhesion of pit is shown. ^ The susceptibility to curl is shown in three columns — little susceptible, mediiun susceptible, and very susceptible. Every record for or against a variety has been obtained from a distinct source from all other records for that variety, and the list includes over 1,000 records. As a record luidcr medium susceptible or very susceptible is against the variety, showing that it is subject to the disease, these two columns are added and the siun carried to a final column. This final column may thus be fairly contrasted with the iirst column, which gives the records of varieties little susceptible to curl. The entire list goes far to show that few varieties are practically free from curl in all locali- ties, and that some of the finest varieties are A^ery susceptible to it. (See for example the records under Crawfords Late, Crawf ords Early, Elberta, Heath Cling, Lovell, etc.) Table 43. — lielatlons of 2>each varieties to peach leaf curl, with records of glands, time of ripenirifj, and adhesion of pit. No. Peach varieties. Aigle de mer, Sea Eagle. Albright Alexander Alpha. Amelia Amsden Austin Beatrice Beers (smock) Bilyeaus Late Bishops Early Bonanza Boston Brandvwino Brett (Mrs.) Brices Early Briggs May Bronson (seedling) California (cling) Canada Cape Clingstone Cape Freestone Cape Pavie. Chairs (choice) r '4' ^In some instances it is known that the form of the glands of a variety is reported differently by different writers, and on this accomit a few errors may have crept into the table here given, but where it has been possible to determine such questions by referring to several authors it has bet^i done. Unfortunately the writer has not l)een able to study this matter in the orcliard except for a portion of the varieties given. 196 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Taulk 43. — Ik'lalians of peach varieties to peach leaf curl, 7i-ith records of gJandx,thm of ripening, and adhesion of pit — Continued. Peach varieties. 5 =S O Charlotte Chinese (cling) Clemence Columbia Com et Cooledge (favorite) Cots (cling) Cranes Early Yellow Crawfords Early Crawfords Late Crimson Beauty Crocketts \Yhite Crosby Doctor Hogg DowTiing Dumont Early Albert Early June Early May Early (red) Rareripe Early Rivers Early Rose - Early Slocumb Elberta Ellison Florin Fords Late White Foster Fox (seedling) General Bid well George the Fourth Georges Late Globe Gold Dust Golden Cling Golden Drop Governor Briggs Governor Garland Governor Wood Grave Cling Grosse Mignonne Grover Cleveland Hales Early Hales Late Hardy White Tuscany Hardy Yellow Tuscany Heath Cling Heath Free Henrietta, Levys Late Hills Chile Honest Abe Honey Cling Hood Cling Imperial (early) Indian Blood (cling) Ingles (seedling) Ironclad Jacques Rareripe | r Japan Blood Jenny Worrell Jenny Worthen Jones (seedling) Kalamazoo Kennedy ( cling) Keyport White Kites Honey Lady Palmerston La Fleur La Grange Large Early York, Honest John .-. . Large White Cling Large Yellow Late Admirable Late Barnard Late October PEACH VARIETIES IN RELATION TO CURL. 197 Table 43. — Relations of peach varieties to peach leaf curl, with records of glands, time of ripening, and adhesion of pit — Continued. N'o. Peaoh varieties. o 4) „• O is s ■1) 1' 6 1 3 m 3 « . p. O 3 O >, > 3 Lo . ^ (3 Q? * « U)0 r r r 1 1 1 e f c f f 1 1 1 1(11 5 1 2 2 3 102 lOi Lewis Scodling ...... 1 '""i 1 13 2 ...... 1 104 1 105 Lola (Miss) Lord Falmerston r g S V e 1 1 1 f f f f 1 lOli 1 1 1 2 2 107 Lovell 15 108 Lovetts White 2 109 1 1 nn 1 c I 111 4 1 2 112 McClish. 1 113 McCollister 1 114 e c c 1 1 1 1 1 115 McDevitts (oling) 1 1 2 2 IIG 3 117 1 ns Moore r e e 1 e 1 e f f c f f f c f c f f c '""i' 1 10 9 4 3 6 1 2 7 2 - 1 1 119 Morris AVhite 7 120 T'1 Mountain Rose g r 5 11 4 4 9 122 15 TM 125 yoblesse . s S r r(V) e 1 1 e 1 1 3 4 '"'i' 10 1 1 120 4 T'7 14 T'8 Onderdonk 2 T>c) Orange Cling 2 ISO 1S1 Pallas . r e f f 1 2 2 1 1 IS'' 2 13S Perkins 1 3 1 134 F'icquets Late r 1 1 i 3 5 1S5 1 ISfi Prtitt r g e 1 f f 1 1 1S7 President 1SH Red Ceylon 1 1 1 139 Red Cheek g 1 f i 1 1 140 141 Reeds Crawford g e f 1 1 1 142 Reeds Early Golden. . . 1 143 Reeves Favorite g 1 f i 4 4 144 145 Reine de vergers, Orchard Queen r r g s g s r 1 c 1 e 1 e 1 f f c f c f f 1 1 146 Richmond 1 147 1 ...... 1 1 13 1 1 148 Roval George 1 149 Rlinvons Orange 3 150 Sallie Worrell 1 151 Sal way 11 12 25 15' 1 153 Sellers Cling . . c f f 5 1 1 1 1 1 1 154 Sellers Free 3 155 Sener r e 156 Shinns Rareripe .. 157 g 1 f 1 2 1.58 Silver Twig . . 1 159 Smocks Free, HI. George r r r r g r r 1 1 1 u e 1 1 1 f f f f f f f f c f f c f 7 3 5 1 ,8 1 100 11 161 Snow . . 1 162 4 4 2 4 163 St. John 7 164 Steadly 2 165 ■■■■j- ...... 106 1 2 10 1 6 1 167 Strawberry Cling 4 168 g g g r 1 1 1 16 169 1 170 171 6 1 1 6 172 5 4 5 17S g g 1 e f f 1 174 Tillotsou (early ) 3 2 2 198 PEACH LEAF CURL: ITS NATURE AND TREATMENT. Table 4o. — ReUdions of peach varieties to peach leaf curl, with records of glands, time of ripening, and adhesion ofjjit — Continued. Peach varieties. 3 raying is better, the chemicals in such cases doing less harm to the tree and having a longer time to reach all spores that endanger the new growth. rSutsS. Bull. 20, Div. Veg. Phys. & Path., U. S. Dept of Agriculture. Plate XXVIII. Z r 'i. O \ \-, ^\, ^^;^-^^^^3:, s^. ... ,V^i^..: ■/ V DESCRIPTION OF PLATE XXIX. A power sprayer in use in a young orchard at Santa Barbara, C!al. This sjirayer was l)uilt by the Union Gas Engine Company, San Francisco.