UNIVERSITY OF CALIFORNIA PUBLICATIONS. COLLEGE OF AGRICULTURE. AGRICULTURAL EXPERIMENT STATION. THE PEACH-WORM By WARREN T. CLARKE. The Peach-Worm and its Injury. BULLETIN No. 144 (Berkeley, September, 1902.) SACRAMENTO: a. j. johnston, : : : : superintendent state printing. 1902. BENJAMIN IDE WHEELER, Ph.D., LL.D., President of the University. EXPERIMENT STATION STAFF. E. W. HILGARD, Ph.D., LL.D., Director and Chemist. E. J. WICKSON, M.A., Horticulturist, and Superintendent of Central Station Grounds. W. A. SETCHELL, Ph.D., Botanist. R. H. LOUGHRIDGE, Ph.D., Agricultural Geologist and Soil Physicist. (Soils and Alkali.) C. W. WOODWORTH, M.S., Entomologist. *M. E. JAFFA, M.S., Assistant Chemist. (Foods, Fertilizers.) G. W. SHAW, M.A., Ph.D., Assistant Chemist. (Soils, Beet-Sugar.) GEORGE E. COLBY, M.S., Assistant Chemist. (Fruits, Waters, Insecticides.) LEROY ANDERSON, M.S.A., Animal Industries. San Luis Obispo. A. R. WARD, B.S.A., D.V.M., Veterinarian, Bacteriologist. E. H. TWIGHT, B.Sc, Diploma E.A.M., Viticulturist. E. W. MAJOR, B.Agr., Dairy Husbandry. A. V. STCJBENRAUCH, M.S., Assistant Horticulturist and Superintendent of Substations. *J. BURTT D AV T," Assistant Botanist. H. M. HALL, M.S., Assistant Botanist. W. T. CLARKE, Assistant Entomologist. C. A. TRIEBEL, Ph.G., Student Assistant in Agricultural Laboratory. C. A. COLMORE, B.S., Clerk to the Director. EMIL KELLNER, Foreman of Central Station Grounds. JOHN TUOHY, Patron, ) y Tulare Substation, Tulare. JULIUS FORRER, Foreman, ) R. C. RUST, Patron, ) y Foothill Substation, Jackson. JOHN H. BARBER, Foreman, ) S. D. MERK, Patron, ) y Coast Range Substation, Paso Robles. J. H. OOLEY, Workmanin charge, ) S. N. ANDROUS, Patron, ) ( Pomona. y Southern California Substation, < J. W. MILLS, Foreman, ) ( Ontario V. C. RICHARDS, Patron, T. L. BOHLENDER, in charge, ROY JONES, Patron, WM. SHUTT, Foreman, * Absent on leave. y Southern California Substation, < y Forestry Station, Chico. Forestry Station, Santa Monica. The Station publications (Reports and Bulletins) will be sent to any. citizen of the State on application, so long as available. CONTENTS. Page. INTRODUCTORY NOTE BY C. W. WOODWORTH 5 REVIEW OF CONDITIONS IN PLACER COUNTY, AND PEACH-WORM LITERATURE 5 WINTER CONDITIONS AND WORK 8 Hibernating Larvje 9 Parasitism 10 Distribution of Worms in Orchard 10 Pruning as a Control Measure 11 Winter Spraying Experiments 12 Resistance to penetration 12 Winter spraying 12 Experiments with the Active Worms 13 Artificially-induced activity 13 Experiments in penetrability 14 SPRING CONDITIONS AND WORK 15 Spraying Experiments 15 Danger to blossoms ._ 15 Spring History of the Worm .. 18 Escape from burrow 18 Attack on buds 19 Results on Bud-Worm of Earlier Work . 20 The pupa 22 Pupation 22 Campaign Against Pup^:..- 23 Band traps 23 Oil spraying 24 The Moth 25 Lantern traps 25 Egg-Laying 26 Worms of Second Generation 26 Attempt to poison these worms 27 STUDY OF THE FRUIT WORM 29 The First Fruit Worms -. 29 Pupation 30 The Moth and Egg-Laying 3L Worms of Third Generation 31 FALL HISTORY OF THE INSECT 31 Peach-Worm Calendar 32 RESULTS OF SPRAYING EXPERIMENTS 32 Tables Showing Results on Different Varieties . 33 Unsprayed Trees 36 Sprayed Trees 36 Failure of IXL compound 36 The use of oil for killing the pupae 36 Winter spraying with lime, salt and sulfur 37 Spring spraying with lime, salt and sulfur _ 37 Miscellaneous Results 38 Loss due to adjacent infested orchards 38 Loss from careless work 39 . Saving by careful work 40 Use of oil and distillate emulsion 40 GENERAL CONCLUSIONS AND RECOMMENDATIONS 42 THE PEACH-WORM. By WARREN T. CLARKE. Introductory Note. — The investigations reported in this bulletin were undertaken at the request and with the cooperation of the peach-growers of Placer County. At the Farmers' Institutes held last winter at Loomis and Newcastle this Department was urged to help in the fight against the peach- worm. The work was finally made possible through the agreement, by certain public-spirited gentlemen at Newcastle, to provide for the local expenses of the study. These expenses were finally assumed by the Supervisors to the sum of $330. The University contributed the services of the Assistant Entomologist, W. T. Clarke, who began his work on the 2d of January of the present year, having his headquarters at Newcastle. Early in February a press bulletin was issued, as a result of this study, recommend- ing a method of treatment which has proven to be remarkably efficient. The majority of growers in Placer County, and doubtless many elsewhere, availed themselves of this information and have already reaped very material benefits. The people of Placer County have left nothing undone that would aid Mr. Clarke in this study, and this bulletin represents the results of this year's spraying experience of practically the whole acreage of the largest fresh-fruit-shipping section of the State. Many points in the life history of the peach-worm have been cleared up in this study, and the facts have been found to be in many important particulars at variance with the accounts of the insect heretofore published. C. W. Woodworth. Probably the most serious peach pest in California is the peach-worm (Anarsia lineatella Zell.), a widely distributed insect, attacking also plums and apricots, but so far as now known, confining its attack to the stone fruits. Its greatest and most evident damage is the injury to the fruit of the peach, grown for Eastern shipment as fresh fruit. In some seasons this loss has aggregated as high as thirty per cent of the entire crop. Some idea of the magnitude of the damage may be gained from the following table, which presents the losses suffered by the growers of fresh fruit alone during the past four years: Table Showing Loss Due to the Work of the Peach-Worm in Fresh Fruit. Not Injured. Injured by Worm. Shipped. Not Shipped. , * ( t *• , Year. Carloads. Value. Per cent Lost. Value Lost. 1898 1,103 $661,800 25 $220,000 1899 2,625 1,575,000 20 393,000 1900 1,361 816,600 25 272,000 1901 1,901 1,140,600 30 488,000 Total in four years 6,990 $1,194,000 25 $1,373,000 These figures are, of course, only estimates, but are believed to be safely on the conservative side and understate the actual loss in fruit suffered in the seasons under consideration. b UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. To the aggregate loss shown in this table of over one and one third million dollars, must be added the loss in value of the fruit grown for canning and drying. The damage done by the insect is by no means confined to the fruit, but great injury is at times also done to the trees themselves. The insect feeds in the spring upon the new growth as soon as it appears, long before the peaches are formed, causing this new growth to die just as it is starting. It is known at this time as the " bud-worm," and its attack has frequently been so severe as actually to cause the death of the infested trees. In parts of California the loss in this way has been in some regions very heavy, but the actual money loss in cases of this kind can hardly be accurately estimated. In spite of these great losses the peach is considered a very profitable crop in many parts of California, being grown to a considerable extent in the Vaca Valley and adjacent valleys of the foothills of the Coast Range of mountains, in the Santa Clara Valley, and in some of the more favorable portions of the Sacramento and San Joaquin valleys, as well as in the Placer County region, where these investigations were mostly made. The Placer County peach section, which is probably the best, and certainly largest, green-fruit-producing section in the State, is in the Sierra foothill region, at an elevation of from 600 to 1,200 feet above sea-level. The large proportion of the peach orchards of this section are to be found in the scope of country extending from Auburn on the northeast to Rocklin on the southwest, a distance of fourteen miles along the Central Pacific Railway, and covering the country for from three to ten miles on either side of this railway. Loomis, Penryn, and particularly Newcastle are shipping points in this region. From the region above described fully ninety per cent of the fresh- peach shipments of the State are made, and the actual loss from the peach-worm here is most clearly felt. The peach-moth has been long known to entomologists, having been originally described as a European insect in 1839 by C. P. Zeller, in Isis, p. 190. In 1860, Dr. B. Clemens redescribed the moth in Proc. Acad. Nat. Sci., Phil., p. 169, as Anarsia pruinella, and in 1872 the same writer identified this insect as the A. lineatella of Zeller in "Tineina of North America," p. 36. Again in 187-2, W. Saunders, in Annual Report Entom. Soc. Ontario, p. 15, describes a worm attacking the root and crown of the strawberry, and considers it to be identical with the peach-worm. This belief is shared by other writers, until the work of A. B. Cordley, reported in Bulletin 45, Oregon Agric. Exper. Station, June, 1897, p. 123, made it very probable that the peach-worm and the strawberry crown-borer are distinct insects. In July, 1872, T. Glover, in Entom. Rec. Monthly Rep., U. S. Dept. Agric, pp. 304-305, reports the peach-worm in Maryland and Virginia. peach-worm: experimental orchards. 7 In 1879, J. H. Comstock, in Rept. U. S. Dept. Agric, p. 255, briefly notes its twig-boring habit and describes the pupation of the second generation on the peach. The next work of economic importance was that of Edw. M. Ehrhorn, reported by Alexander Craw in Bulletin 67, California State Board of Horticulture, 1893 (1894), page 9; it showed that the insect wintered in the early larval form in chambers hollowed out in the bark of the crotches of the branches of the trees. Mr. Ehrhorn's investiga- tions were continued in 1896-97 by C. L. Marlatt at Washington with material furnished by Mr. Ehrhorn from California, and the results were published in 1898 in Bulletin 10 (new series), U. S. Dept. of Agric, Div. of Entom., pp. 7-20. The insect has been reported by other writers as being present in Delaware, Illinois, Colorado, and Washington; and doubtless occurs in all peach-growing localities. The article by Marlatt gives the fullest account of the insect that has yet appeared. This work was unfortunately done under rather unnat- ural conditions, and does not agree in many instances with the actual orchard habits of the insect here in California. The other Eastern observations were very fragmentary, and required verification here before being of much value as a basis for a scheme of repression. The writer was somewhat acquainted with the insect from previous studies in the Santa Clara Valley, and from the 2d of January has kept it under continuous observation in breeding-cages, on a large covered tree, and in the orchards in Placer County, particularly about New- castle, which was headquarters for the investigation. No pains were spared to make the work as exhaustive as possible. The location of the larger part of the experiments was in an orchard one eighth of a mile southeast of Newcastle, which will be referred to as the Newcastle station. Another station was located in an orchard two miles north of Newcastle, which we designate as the Ophir station; a third, in an orchard one mile east of Newcastle, known as station A; a fourth, in an orchard one and a half miles south of Newcastle, called station B; and a fifth, in an orchard three miles northeast of Loomis, and referred to as station C. These five places include some two hun- dred acres of peach trees of many varieties. The number of trees treated in the experiments carried on in these places amount to a total of some 12,000. The experiments were not confined to these places, however, for work was done in many other orchards. The work done in these other orchards was sufficient to secure some valuable results, and some four- teen of these in which records were kept are reported in the following pages in conjunction with the work and results on the different stations. These other places will be referred to by numbers. 5 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. WINTER CONDITIONS, AND WORK OF THE WORM. The investigation of the peach-worm began by a study of the insect in its winter burrow within the bark, at the crotches of the tree. The position on the tree generally chosen for the purpose is the crotch formed where the new wood joins that of the previous year, though older crotches are occasionally selected. There appears to be something in the physical make-up of the crotch bark that is preferred by the worm for its winter quarters. When the same sort of new bark is formed in other situations, such as that growing over a wound in the older part of the tree, then the worm may also be commonly found in this situation. The position taken in the crotches is that which brings the hibernating chamber invariably on the upper exposure of the limbs. We have never found the burrows on the lower side. Fig. 1. Twig showing winter burrow, natural size. Fig. 2. The same burrow shown in Fig. 1, enlarged. The location of these burrows may be discovered by the presence of a small mound, which is in reality a silken tube covered with a complete, closely-arranged covering of minute pellets of masticated bark. The color of these pellets on a recently constructed tube is a reddish-brown, of the same shade shown by the bark some hours after it has been cut, and changes to a darker brown after continued exposure to the weather. These mounds are completed in the fall preliminary to the worm's going into winter quarters. They are not added to, nor increased in length, during the winter, even where we have carefully clipped away the tube. Several such uncovered burrows were kept under observation from January 3d to March 5th without any additions being made. The worms on this latter date were removed and found to be alive and apparently healthy. The pellet-covered tubes, shown in natural size in Fig. 1, are rather minute and will usually escape notice. They are peach-worm: winter conditions. y quite characteristic in form and are easily recognized in any of their modifications by the aid of a glass, when the bead-like arrangement of the pellets on the tubes, as shown in Figs. 2 and 3, will be noted. The hibernation burrows are cut out well beneath the bark, and extend into the cambium layer. In the majority of cases they are found just beneath a thin layer of the greener cells below the brown bark, while the greater part of the burrow is in the yellowish portion of the cambium. The burrow is generally about three times as large as the worm occupy- ing it, and is lined with silk. The silken tube previously referred to, which projects from the mouth of the burrow, is an extension of this lining. This silk-lined chamber is very efficient as a protection from all inclemencies of the weather, and likewise protects the worm from sprays in a remarkable manner, as will be seen from the experiments detailed later on. mfM Fig. 3. The same burrow laid open, showing how the worm begins its spring work. Hibernating Larvx. — The hibernating larvae occupying the silk-lined burrows are commonly found at the deep end of the chambers with their heads toward the silken tubes, though they may be found in almost any position. Their age, as they were found in January, is not known, though there was some variation in size and two stages of growth were present, judging by the sizes of the heads. These hibernating worms ranged from 1 to \\ millimeters* in length. The abdomen and thorax varied in color in different specimens from light brown to white, the head and cervical and anal plates being a shining black, in sharp con- trast to the rest of the body. The space between the second and third thoracic segments is noticeably and characteristically lighter in color and more evident than that between any of the other segments. The creature is ornamented with hairs, which spring singly from minute *A millimeter is equal to -^ of an inch. 10 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. tubercles and which are rather sparsely scattered over it. The general appearance of the larva and the position of the thoracic and abdominal legs are shown, very much enlarged, in Fig. 4. No perceptible change in the size or color of the insect occurred from January 2d until about March 1st. Parasitism. — The insect was to a slight extent attacked by parasites during the hibernation period, but the amount of benefit derived from this source was extremely small in the Placer County region during the season of 1902. The larvae of a Proctotrupid fly was found destroying the worms in three different cases, while a predaceous mite, which was probably the same as that mentioned by C. L. Marlatt (Bui. 10, n. s., U. S. Dept. of Agric, Div. of Entom., p. 17) was occasionally noted. The total number of hibernating worms destroyed by these natural Wintering larva; much magnified. enemies was less than one per cent. We were unable, during the season of 1902, to confirm the statement made by Mr. Marlatt in the above- cited publication, that this mite "causes the death of from 75 to 95 per cent of the young larvre." DISTRIBUTION OF WORMS IN ORCHARDS. The distribution of the hibernating worms was very general and uni- form over infested orchards, and, except where modified by evident local conditions, the worms were about equally numerous on all the trees. Indeed, as far as hibernation is concerned the variety of the peach seemed of no significance, the worms being found at this season evenly distributed among the early, midsummer, and late trees. There are some modifying conditions, however, that do result in certain trees being more heavily infested than their neighbors. It is a custom in many orchards to throw out the wormy fruit in piles near the packing-sheds. These sheds are generally placed among the trees, and the piles of rejected wormy fruit are thus usually in close proximity to these trees. It was found that where this custom prevailed these neighboring trees were much more heavily infested than were the rest peach-worm: winter control measures. 11 *mk3o 30 20 of the trees in the orchard. This condition is illustrated by the accom- panying diagram (Fig. 5), which is of a packing-shed and orchard in the district under investigation. The trees in this orchard are five years old, strong and healthy, but the fruit the previous season was very wormy. The trees generally in this orchard had from five to eight hibernat- ing larvae in them when investigated. The distribution here had been very plainly affected by the local conditions. A similar state of affairs was found to be present wherever similar conditions exist. In certain orchards it has been the habit to distribute the wormy, unmarketable fruit about the less vigorous trees as a fertilizer. It was found that these trees were infested from five to ten times as heavily as the rest of the orchard. The practice of allowing the wormy fruit to remain in such a condition that the woms may fully develop and carry on the infection could be easily avoided by covering the piles with earth, when the heat developed by fermentation would be sufficient to destroy the worms. 75- 'kc h- c u. 116. •'-':■}'- • 6C Packing, 5hed Fig. 5. Diagram of a portion of an orchard showing abundance of worms on trees near cull pile. PRUNING AS A CONTROL MEASURE. Some have supposed that in the process of pruning, many of the worms in their winter quarters were destroyed. The percentage of the worms so destroyed, however, is usually very small, as we have deter- mined in many cases by actual count. This counting of the hibernating chambers in trees before and after the pruning showed, on an average, that generally one worm in ten was cut away. As the prunings are removed from the orchard and destroyed the hibernating worms in them are effectually disposed of, but the destruction of only ten per cent is not a very good degree of efficiency. 12 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. No great dependence can therefore be placed in the ordinary pruning as a control for the peach-worm. WINTER SPRAYING EXPERIMENTS. The practice usually advised for fighting the peach-worm is to spray the trees in the same way as for scale insects. The field work, therefore, began by an attempt to find the best spraying material for this purpose. A series of experiments was undertaken, with the idea of determining the practicability of killing the insect at this time. These experiments began January 9th, and were continued until past the middle of the month. Kerosene emulsion was the first material tried. The emulsions were made up according to the following formulae: 1st. 150° kerosene, 1-J pints; sour milk, 1 pint; water, 2 gallons. 2d. \ pound hard soap dissolved in 2 quarts of water and 1 pint of kerosene. Each of these emulsions was diluted with two gallons of water, and infested trees were thoroughly sprayed with these mixtures; but to our surprise, when the worms were examined, to ascertain the results of the treatments, no effect whatever was observable. Resistance to Penetration. — Upon the failure of the above experiments we began a study in the laboratory. In order to test the penetration of these substances under the most severe conditions, we submerged in the emulsion twigs containing the worms and kept them there two days. When the twigs were taken out after this soaking for forty-eight hours, the worms were found none the worse for the experience. That there might be no doubt as to the killing power of the emulsions used, the material was sprayed on several worms with an atomizer, and these worms were dead dn from forty-five minutes to one hour and fifteen minutes. The lime, salt and sulfur spray was experimented with, with exactly the same results; showing the same lack of power to penetrate to the worm in its winter home, but killing readily when it was applied to its unprotected body. The same results were also obtained with the distillate oil (28°) and a number of other sprays used. This whole series of experiments indicated the futility of attacking the worm while the winter conditions prevailed, at least under the conditions found in Placer County. Winter Spraying. — Notwithstanding the fact that our experiments had indicated the comparative, futility of winter spraying as a control for the peach-worm, we made careful observations on the few orchards that were sprayed at this time with the lime, salt and sulfur. The conditions found on these places were similar in character. They were all strongly infested with the hibernating larvae. The spray material was, in each case, carefully prepared and applied to the trees; the effort peach-worm: winter control measures. 13 being made to cover them completely, so that the treatments should be as effective as possible. The poor results of these sprayings will be seen in the tables on pages 33 to 35, orchards Nos. A, C, 1, 7, 8, 9, and 10- Smaller experiments at the Newcastle station, made so as to keep the trees under closer observation, gave exactly similar results. Besides this work with the lime, salt and sulfur, we sprayed, early in February, six trees (three Hales and three Salways) at the Newcastle station with kerosene oil emulsified with soap in the proportion of 1 part of the emulsion to 8 parts of water on one tree of each of these two varieties; the same emulsion in the proportion of 1 to 10 on two of the other trees, and a mechanical mixture of kerosene oil 1 part to water 3 parts on two more trees. And also at the Ophir station we sprayed, in the middle of February, forty-eight Salway peach trees with the so-called Hercules emulsion of 28° distillate oil, using the proportions 1 part of emulsion to 8 parts and to 12 parts of water. In all of these experiments no differences between the sprayed and the checked trees could be distinguished. The account of the ultimate condition is given on page 35. experiments with the active worm. Artificially-Induced Activity. — The fact having become thus evident that any work done toward killing the hibernating worm must be delayed, at least until the beginning of the period of its activity, we endeavored to ascertain when this activity could be expected to occur. Branches containing hibernating larvae were placed with their cut ends in moist sand in a room in which the day temperature was kept at 70° Fahr. and the night temperature fell to about 40° Fahr. They were examined from time to time, and by the end of the fourth day an appre- ciable activity was noted on the part of the worms. Upon opening their burrows at this time they were found to be quite lively in their motions. At the end of the sixth day the worms had begun to tear away the cov- ering portion of the silk lining to their winter homes. On the four- teenth day worms began to come to the surface, and continued to do so for three days, when they had apparently all come out. To arrive at the effect of continued warm conditions, a number of the chips containing winter larvae were cut from the trees. The chips were kept steadily at about the body temperature of the experimenter. The effect of this treatment was rapid, as in one case worms had worked their way out of their burrows at the end of the fourth day, and the longest time taken to emerge was six days. Considering that it was possible that the worms might be brought forth from the winter quarters by exceptional warm temperature condi- tions occasionally occurring during the winter, some of the worms were 14 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. kept under observation after they had come to the surface, to deter- mine if they would, in the absence of green food, re-imbed themselves. A number of these worms, and also a number that had been cut from their burrows, were placed upon fresh uninfested twigs, and their actions noted. During the first twenty-four hours the worms were all more or less active and restless, moving about a great deal, but with no apparent definite object. They became less active during the second twenty-four hours, but made no effort that could be recognized as an attempt to make new burrows. A progressively diminished activity continued during the third twenty-four hours and during the remainder of the time of the experiment, the worms finally dying without re-entering the bark. This experiment was carried on in duplicate, one set being under natural temperature conditions, and the Other in a room where the temperature varied between day and night from about 70° Fahr. to about 40° Fahr. The results were the same in both sets. These experiments would seem to indicate that if continued warm weather prevailed during the winter, numbers of the worms might come to the surface, and in the lack of the necessary food would perish. Experiments in Penetrability. — A series of experiments as to the penetrability of the winter quarters of the worms, after the worms had become active under the influence of an elevated temperature, was now undertaken. The sprays were the same as those previously described, and the work and the results are shown in the following tables: Table Showing Effects of Sprays on Winter Quarters of the Worm. After 6 Days of High Temperature. Spray Used. Kerosene and milk emulsion. Kerosene and soap emulsion Distillate emulsion Lime, salt and sulfur Effects at End of— 1 hour. 2 hours. 3 hours. 4 hours. Alive Alive, feeble Feeble Dead Alive Alive, feeble Dead Alive Alive, feeble Dead Alive Alive, feeble Dead After 8 Bays of High Temperature. Kerosene and milk emulsion ... Alive Alive, feeble Dead Kerosene and soap emulsion Alive Alive, feeble Dead Distillate emulsion. ._ .. Alive, feeble Dead Lime, salt and sulfur Alive, feeble Dead The results obtained in these experiments seemed definite enough to prove that spraying operations against the peach-worm, to be successful, should be delayed until such time as the worm became active. Growers were therefore advised to delay their spraying operations until the worm had eaten out of its winter nest upon the coming of the warm-weather conditions of spring. peach-worm: spring conditions. 15 SPRING CONDITIONS AND WORK. The next stage in the investigation was the planning and carrying-out of extensive field tests, based on the observations and experiments just described. SPRAYING EXPERIMENTS. The experiments undertaken at this time were of two classes — those with lime, salt and sulfur mixture, and those with oils and emulsion. Of the former there was a large series under the direct supervision and control of the writer, and a much larger amount of spraying was done by farmers in accordance with our advice. Fully eighty per cent of the spraying done in Placer County this year was timed according to these directions. In the orchards of the five stations established for this study some 12,000 bearing peach trees were sprayed with the lime, salt and sulfur compound. As full records as possible were kept of the spraying in the whole region where the investigation was made, which amounted to over two million trees which received this same treatment. Spraying was done at this time on five different places with the I X L compound, a proprietary preparation quite widely advertised. These places, which will be referred to as Nos. 2, 3, 4, 5, and 6, were treated with the compound named, following the exact directions given for the work by the manufacturers. The material was first applied just as the buds were bursting, and this was followed by another application about one month later. Altogether some 8,300 peach trees were sprayed on these five places with this compound. A close watch was kept on these orchards, for it was felt that if the material, which contains lime, salt and sulfur, would control the worm, the fact that it can be purchased ready-made and comparatively cheap would be much in its favor. The results, however, were very unsatisfactory, as will be seen below. We experimented also with distillate oils, both in mechanical mixture with water and in emulsions. A number of these oils and emulsions were furnished us by the Densmore-Stabler Refining Company of Los Angeles for the purpose of experimentation. These were the 28° dis- tillate treated and untreated, and the 33°-35° distillate and emulsions made up from these oils. Danger to Blossoms. — All this spraying in the orchards was timed as far as possible by the condition of the trees; that is, it was done gener- ally just before they burst into blossom. In very many instances the spraying could not be done until the trees were in full bloom. It has not usually been thought possible to spray when the blossoms were out without seriously injuring or killing them, especially with a spray of this strength. 16 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. Spring spraying must be done nearly at blossoming time, and may easily be delayed by various causes until the trees are in blossom; much attention was therefore given to the danger of injury by spraying while the trees were in bloom. The blossoming dates for 1902 of the various varieties of peaches grown in large quantities in the Placer County district are given in the following table. The varieties are arranged in approximately their ripening order: Blossoming Periods of Peaches. Variety. First Blossoms. Full Blossoms. Alexander March 15 March 20 Hale... .- March 15 March 20 Triumph March 16 March 2L Imperial Feb. 25 March 2 St. John Feb. 24 March 1 Early Crawford March 10 March 15 Foster March 5 March 12 Susquehanna March 5 March 12 McDevitt _. March 2 March 8 Levi .- ... .. March 13 March 18 Salvvay ...... March 15 March 20 The large experiment was with one lot of some two hundred Hale trees at the Newcastle station, which were sprayed with the lime, salt and sulfur compound on March 17th and 18th, just as the trees were nearing the period of full bloom. This is a variety that exhibits a strong tendency to drop the buds in the spring, yet the trees that were sprayed when in blossom set fruit quite as freely as the unsprayed check trees in the neighborhood, and also as did the trees that were sprayed earlier in the season. Of course, some blossoms were injured by this treatment, but abso- lutely no commercial damage was done, and the fruit on these trees was evenly distributed and had to be thinned. The injury to blossoms apparently occurred only when a fully open blossom stood in such a position as to be filled by the spray and to retain this material in the cup. This combination of conditions, however, existed in so few cases that the number of blossoms that were killed by the spray was exceed- ingly small. A tree will have blossoms in all conditions from the swelling bud to the fully open flower, and if the latter had been all killed it is possible that there might be no real loss. The effect of the atmospheric conditions was seen very clearly in a portion of this experiment. During a few hours of the time when this work was being done the atmosphere became extremely dry, because of a north wind. The trees sprayed during this time lost a much larger number of blossoms, and tender twigs were also killed. No damage, however, occurred when the usual moist atmospheric conditions of this season of the year prevailed. Our experience this season has indicated that the blossom of this variety of peach is more susceptible to injury by peach-worm: spring control measures. 17 spraying than is the case with any other; and only during the time drying winds are blowing need there be any hesitancy in spraying, even though the tree is in bloom. The latest spraying in the experimental orchards on Early Crawfords was March 5th and 7th, a few days before the first blossoms appeared, but after the buds were beginning to burst. No trace of injury was observed. Some Fosters were sprayed on March 1st, and others on March 5th and 7th. On the latter date, one of the trees that was nearly in full bloom, -having a large number of fully opened flowers on it, was sprayed with especial pains and thoroughness, completely drench- ing it with the spraying material, in order to produce injury, if possible. A careful watch was kept of this tree, and the actual loss to it, so far as could be made out, was eleven blossoms. The tree in question is four- teen years old, and had many hundreds of blossoms out when the Fig. 6. Fruit from thinning of Foster tree sprayed when in full bloom. spraying was done. So much fruit set on this tree that heavy thinning- out had to be done late in April, when 1,635 peaches were taken from it, leaving still a good crop on the tree. (See Fig. 6.) A number of Susquehanna trees were sprayed on March 12th, 13th, and 14th, just when they were in full bloom; no apparent damage was done to the flowers, and the fruit required very heavy thinning. Spraying was done on a number of the McDevitts on the 11th of March, after some of the blossoms had fallen, and again no damage was done. These experiments were practically duplicated in many different orchards, and the same results were obtained in each case. It can thus be safely said that late spraying with lime, salt and sulfur, under the conditions obtaining in Placer County, does not in any appreciable way 2— Bul. 144 18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. affect the crop, provided the spraying is not done when the atmosphere is extremely dry. Our work with oils and emulsions began on March 31st, when the trees had begun to set fruit and most of the blossoms had fallen. Enough of these remained, however, for us to see the effect of the materials used on the flowers, and some slight loss of fruit through burning of the blos- soms was shown. This burning was quite as evident when the emul- sions were used as weak as one part of the emulsion to fourteen of water as when the distillate oil was used in the proportion of one of the oil to three of water. Altogether one hundred and sixty-eight Salway peach trees were sprayed with these materials. We also experimented with the so-called Hercules emulsion of 28° distillate oil, spraying fourteen Salwa)' peach trees on March 22d with this preparation, used in the proportion of one to ten of water. At this time the trees were just past full bloom, and the spraying resulted in considerable loss, on account of the blossoms being scorched. Fully one fifth of the blossoms on these trees were destroyed by the spray. SPRING HISTORY OF THE WORM. As the spring opened it became possible to follow the beginning of the spring activity as it occurred in the orchard under normal conditions. The worms remained inactive in their burrows until early in March, when they began to work their way out. Escape from Burrow. — The process of leaving the burrow was observed very continuously during this time in the breeding-cages, where twigs containing hibernating larvao were placed with their ends in moist sand; on the net-covered tree, where one hundred and thirty-five worms were under observation; and also in the orchard trees, where perfectly natural conditions were found. These three sets of observations gave results that tallied in all particulars. It was found that when the warm- weather conditions had prevailed to a sufficient extent to make the sap begin to flow appreciably in the tree, then the worms also became active and began to work their way out of their winter burrows. Their first efforts to obtain this end consisted in a tearing away of the silk lining of the burrows. This tearing-away process began with the removal of the floor portion of the lining, and continued until about two thirds of the covering portion had been removed. While doing this the worms first fed on the tender tissues of the bark beneath the original burrow, but after a few days they began to eat their way toward the surface, filling the burrows behind them with excrement. They usually reached the surface in from ten days to two weeks. During this time a considerable increase in size could be seen, and also a marked change in color, the worms becoming of a much darker shade. peach-worm: spring history. 19 Attack on Buds. — The worms when they appeared on the surface were from 3 to 4 millimeters in length. These worms spent the first two or three days after leaving their burrows wandering about on the bark of the tree. They then attacked the young growth and bored their way into the pith of the starting bud, either from the side or at the tip, the latter being the point most generally chosen. Frequently the worms contented themselves with merely boring into the pith from the side and then withdrawing and attacking some other shoot. The twig so attacked was so weakened at the point where entry was made that the portion above the wound soon died away. One worm might attack many buds in this way and the injury to the tree be multiplied. The worm, again, frequently bored its way into the pith of the chosen shoot and then took a downward course, eating away all of Fig. 7. Wilting following attack of bud- worm. Fig. 8. Section of twig, show- ing burrow made by bud-worm. the twig save a mere shell of bark and fibrous material on the outside of its burrow. This burrow was partly filled with excrement, but at no time did we find a burrow sufficiently filled with voided material to interfere with the ready passage of the worm up or down. The worms might attack a number of twigs in this way, and here also the injury that a single worm might do was multiplied. The twig that is attacked very quickly wilts and dies, and this wilted appearance of the twigs is a good indication of the presence of the worm at work in the tree. Indeed, the work done by the worm at this time and the after-appear- ance of the twig are quite characteristic and easily recognized. In Fig. 7 is given a good illustration of this work of the " bud-worm," as the creature is known in this stage of its life, and the wilted appearance of three or four leaves above the point where the worm is at work can be seen. Fig. 8 shows a section of a newly-started twig, down which a worm had burrowed its way until it had reached the old and hard wood. 20 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. Again, in Fig. 9 can be seen a photograph of, first, a twig which had not been attacked at any time by the "bud-worm," and then of several on which the attack was very severe. It will be seen from these illus- trations that the work of the "bud-worm" may result in very serious consequences to the tree as well as to the crop, if not actually threat- ening the very existence of the tree itself. In many instances of the bud-worm work that came under observation this season, the tree appeared as though burned by fire. The attack of the bud-worm is generally more to be noticed and feared on young trees than on older ones. We have found that three or four worms could completely destroy a three-year-old tree, and while this attack on an older tree would be serious, yet it would not be fatal. \ K i I |v/Pf IB? ft 'U: < ^ Jm f WJ^'i, *\0'* wi f it 1*$ } t'tfa k T Fig. 9. Results of bud-worm attack, shown in the six twigs on right. Left-hand twig has not been attacked. The most serious work of this kind is in newly-placed grafts and dormant buds, which are very frequently attacked and destroyed. The work of the worms in the buds and new twigs continued until pupation was first observed in the latter part of April. The full-grown larvse at this time were about 10 millimeters in length and the general color quite dark, the characteristics as shown by the young larvae remaining almost unchanged. RESULTS ON BUD-WORM OF EARLIER WORK. Our first comparisons of the effect of the spraying experiments were made possible when the bud-worm work began to be evident, which was in the latter part of March and early in April. At this time it was found that the worms were very plentiful all over the district on such trees as had not been sprayed at all. From one of our check-trees at peach- worm: spring control measures. 21 the Newcastle station we cut out eighteen bud-worms, and the average number on some forty un sprayed trees on this place was eleven worms. The same heavy infestation was shown at the Ophir station also, while from one unsprayed tree at station A we removed twenty-three bud- worms. Check-trees at stations B and C were also badly infested ; while the unsprayed orchards generally were infested at the rate of from two to ten worms to the tree. The number of bud-worms found on the check-trees through the whole district indicated that the season was a favorable one for the peach-worm. On sprayed trees, using the same bud-worm basis of computation, we found that where the IX L compound had been used no control of the worm whatever had been obtained. The trees on places 2, 3, 4, 5, and 6 were as badly infested with the bud-worm as though no spray at all had been used, and from five to twelve worms were cut from many of the trees on these places. Some of the trees, and this especially on place No. 6, appeared as though burned, as the result of the work of the bud-worm. No " curl-leaf" was noted among these trees, and their general condition, other than the effect of the bud-worms, was fair. The trees which had been sprayed with the distillate oils and emul- sions showed a very much lighter attack of the bud-worms, for among these trees it was found that the average number of bud-worms was from one to two to the tree; while from the check-trees, unsprayed, on the same orchard, we cut from eight to twelve bud-worms. These oil- sprayed trees were affected with "curl-leaf" quite severely. The lime-salt-and-sulfur-sprayed trees, when the spraying had been done in the early spring, showed the most satisfactory results of any at this time. On the various station orchards, comprising over 12,000 peach trees, the average number of bud-worms was about one to every ten trees, and this average was maintained on many other orchards in the district. Indeed, it was a difficult matter to find the worms in these orchards, and it was only by the closest scrutiny of the trees that they could be located in them. The general condition of these trees was excellent and a marked absence of " curl-leaf" was noted. An examination of the trees in orchard No. 1, that had been sprayed with the lime, salt and sulfur early in February, showed that the attack by bud-worms was severe. On many of the trees from which we cut the worms we found from five to nine to the tree. The general condi- tion of the trees was good and a very small amount of " curl-leaf" was present. Winter spraying with the Hercules distillate emulsion in February at the Ophir station also resulted in leaving the bud-worms in dangerous numbers. The trees of the kerosene emulsion and the kerosene oil and water experiments at the Newcastle station, which had been winter- sprayed, showed also heavy infestation. Indeed, the condition of these 22 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. trees was so bad that, fearing the moths might spread from them to the balance of the orchard, all the bud-worms were cut from the twigs. The following table gives this work and its result in detail : Table Showing Bud-Worms on Winter-Sprayed and Unsprayed Trees. Variety. Hale Hale Hale Salway Salway Salway Spray Used in Winter. Kerosene emulsion 1 part, water 8 parts.. Kerosene emulsion 1 part, water 10 parts. Kerosene 1 part, water 3 parts Kerosene emulsion 1 part, water 8 parts .. Kerosene emulsion 1 part, water 10 parts. Kerosene 1 part, water 3 parts Bud-Worms Removed from Sprayed Trees. Bud-Worms on Unsprayed Check-Trees. 19 20 21 20 18 20 17 16 19 16 22 16 The Pupa. — The pupa or chrysalis of the peach-moth, shown in Fig. 10, varies from light to dark yellow in color. It is from 5 to 7 millimeters long, and is rather broad in comparison with its length. The segments of the abdomen are well defined, but only the last three are movable, allow- ing a certain small amount of movement of a twitching nature. The eye spots are of a darker color than the rest of the pupa, and are quite prominent. Pupation. — The worms having attained their full growth, withdrew from the green material in which they had been working and crawled down the limbs to the main branches and to the trunk. Here the rough bark offered many places of scanty concealment sufficient for pupation. The worm, in at least the greatest number of cases, chose for this purpose the hollow formed by the curling-up of small portions of the outer bark. These "curls" of the bark are quite characteristic of the peach tree and are constantly present on the trunk and larger branches. The worms, after crawling into these curls, w r eave an extremely loose cocoon — a few threads of whitish silk drawn irregularly across the open portion of the curl, and a slight silken carpet, to which the hooks at the end of the abdomen of the pupa are attached, constituting the whole structure. As far as our observations go this is always the method of cocoon- making. This cocoon merely serves to hold the pupa in place, and does Fig. 10. The pupa. Dorsal and ventral views. peach-worm: spring control measures. 23 not in any other way serve to protect it. In ninety-two per cent of the cases noted the position was well down on the trunk of the tree. In a very few cases the worms pupated in the " curls" of the bark quite well up in the tree, and in only three per cent of the cases noted did pupation take place under broken places in the bark where there is no evident curl. After choosing their pupation places and spinning their slight, web- like cocoons, the worms pro- ceeded to pass into the pupa form, attaining it in from two to two and a half days. Fig. 11 shows the pupation place and the cocoon. CAMPAIGN AGAINST THE PUPA. Two points in this matter of pupation seem of economic importance, and were made the basis of some of our ex- periments for the Control of FlG ' U - Potion place and cocoon. the worm. Unlike the codling- moth larva, peach-worms crawl down the tree to the trunk, and do not drop to the ground and then crawl to the tree. Secondly, the large majority of the worms pupate on the main trunk of the tree. These experiments consisted of the use of band traps, and of oil spray on the trunk. Band Traps. — Since the use of bands as an adjunct to spraying opera- tions in certain cases against the codling-moth is generally recognized as effective, it was thought by ourselves and by some growers that these devices might be of more or less value in the case of this insect, and that it was important to test what value they might have. To deter- mine this point, the following experiments were made: On April 15th, pieces of "sticky fly paper" were placed on the ground close about the trunk of a peach tree, in such a way that a worm coming to the tree would have to cross the paper to get on the trunk. Eleven days later there were seven pupae taken from the trunk of this tree and not a worm had been taken on the paper. On April 16th paper was placed in the same way about another tree, and fourteen days later twelve pupse were taken from the trunk of this tree, but not one worm was on 24 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. the paper. On the 4th of April bands of burlap were put about the trunks and larger limbs of five trees. These trees and the bands were carefully examined from time to time, and four of these trees yielded seven pupae apiece, yet not one of these was found beneath a band. They were all placed within the "curls" of the bark, as described above, and on the main trunk of the tree. Some were above and some below the band on the trunk. On the fifth tree one pupa out of eight was beneath the trunk band, but in a "curl" of the bark. Paper bands were used, with the same result as when the burlap was used. "Sticky paper" was used as a band in one case in this generation. This paper was placed about the trunk just where the branches began, and on this paper two worms were taken. Seven pupae were taken in a space of six inches above this band and none below it. Furthermore, we have observed in four different instances the full process of pupation in this generation, and in every instance the worm crawled down the tree from the green twigs (where it had been eating) to the main trunk, entered one of the "curls" of the bark, and there went through the process. In no case observed did the worm drop to the ground and then make its way to and up the trunk of the tree, and from our observations and from the results obtained from our "sticky paper" and band experiments, we should consider that such a proceed- ing seldom or never occurs. We could find no warrant for the use of band traps in the campaign against the peach-worm. Oil Spraying. — Early in May the conditions existing on place No. 2, which is noted as having been sprayed with the I X L compound, were very bad. The attack of the bud-worm was severe on this orchard, and at the time noted these worms had begun to pupate. The pupae seemed to be quite accessible to sprays in their slight cocoons on the trunk and larger branches, and we determined, with the assistance of the owner, to see what effect spraying with kerosene-oil and distillate-oil emulsions would have on these pupae. On May 15th and 16th, after a few moths had emerged, but while most were still in the pupa form, we sprayed these trees. The emulsions were made up of the 28° and 33° distillate and with 150° kerosene oil. These emulsions were diluted with water in the proportion of one to eight, and this material was thoroughly sprayed over the trunks and larger branches of the trees. Care was taken not to spray the material on the leaves and new growth, yet some of it did lodge in such positions. Where this occurred the leaves and twigs were badly discolored (yellowed), but in a few weeks they regained their normal color and health. This discoloration occurred quite as much in the case of the kerosene emulsion as in that of the distillate- oil emulsion. Two days after this spraying was done we removed a number of the pupae from the trees and kept them under observation peach-worm: spring control measures. 25 for four weeks. Moths emerged from two of the twenty pupae so kept, the rest having been killed by the spray. The ultimate results of this treatment, as shown by the percentage of wormy fruit, will be seen in the discussion of that subject below. THE MOTH. The adult moths began to emerge from the pupae in from ten to twelve days. They are of small size, very delicate, with narrow, well- fringed wings. The color is quite subdued, being a beautiful dark steel-gray in general effect. On closer examination it will be noticed that this general color is relieved by certain darker spots on the fore wings, which are folded over the abdomen when the insect is at rest. The palpi are quite prominent and are usually bent back over the insect's head, having the appearance of horns. The antennae are very delicate, of a grayish color, ringed with brown, and are laid on the wings when the moth is at rest. The hind wings are much lighter in color and more heavily fringed than the fore wings, and both pairs of wings seem under the magnifying glass to be dusted over with a grayish powder. The length of the moth when at rest is about 7 m.m., and with wings expanded the insect measures 14 m.m. from tip to tip. It differs from other members of the group in certain minute particulars not easy to specify. These other moths are not likely to be found in the same situations, so that the above description will enable one to be fairly cer- tain of their identity. The moths are very quick in their movements and are easily dis- turbed, flying rapidly from one place of concealment to another in the orchard. Lantern Traps. — The value of lantern traps in the war against the related potato-worm, reported in Bulletin No. 135 of this Station, sug- gested their use in this case also. The traps were therefore thoroughly tested during May, when the moths were on the wing. A number of lantern traps made after the Colorado type* were used. These traps consist of a piece of bright tin made into a funnel shape and opening into a wooden bottle. In this bottle is placed a piece of cyanide of potassium wrapped in paper. Over this a little excelsior (wood shavings packing) is placed. When in use the trap is hung to some tree in the orchard, a lantern is hung just above it, and the poison bottle is slipped over the bottom opening of the funnel. Insects attracted by the light readily find their way into the funnel and then into the poison bottle. Beetles taken thus crawl into the loose packing in the bottle and do not injure the more delicate insects which may be taken and which remain on top. Many specimens of various Bulletin 43, Colorado Experiment Station. 26 UNIVERSITY OF CALIFORNIA —EXPERIMENT STATION. genera of beetles were taken, and some moths, a few parasitic hymenop- tera, and many mosquitoes (Culex and Anopheles sp.) were victims of these traps, but we looked in vain for the peach-moth. Not a single peach-moth was taken by these traps during the experiment, in spite of the fact that they were present in numbers in the orchards. EGG-LAYING. The moths began egg laying on May 9th. The newly-placed egg is pearly white, and shows under the microscope a rather coarse reticula- tion. Before hatching the color changes to a deep yellow, almost orange color, and at this stage the egg is quite conspicuous. It is about two fifths of a millimeter in length by one fifth in breadth, being a rather long oval in shape, about twice as long as broad. These eggs were generally placed in the new twigs near the bases of the leaves, and from one half to two thirds of the distance out from the point of beginning of the twigs. The eggs were placed lengthwise of the twigs, and in a few cases were concealed beneath the bracts at the bases of the leaves. We could, how- ever, note no general attempt at con- cealment of the eggs under these bracts or spurs, as is recorded by Marlatt (Bulletin 10, n. s., U. S. Dept. of Agric, Div. of Entomology, p. 13), and they were as a rule plainly to be seen. The illustration (Fig. 12) shows the general distribution of the eggs in the neighborhood of leaf bases, some eggs being laid singly and some in loose clusters. They are rather insecurely glued to the surface of the twig. Fig 12. Eggs of Peach-moth in position on twig. WORMS OF THE SECOND GENERATION. Young worms began to come from these eggs on as early as May 19th, the period of incubation being about ten days. The newly-hatched larvae were about three fourths of a millimeter in length, and did not differ in general appearance from the hibernating worms asfiescribed on a previous page. These worms were restless for the first two or three days of their lives, wandering about on the twigs and apparently doing scarcely any eating. peach-worm: second generation. 27 Finally they would select a place a short distance from the tip of the twig and eat into it at the base of a leaf, bore into the pith, and then follow down the pith in the same manner as the first generation of worms did. This boring process was not observed in any case to extend down the twig more than an inch, and the same worm would attack many twigs. Frequently, also, as in the first generation, the worm would merely bite into the twig a short distance and then withdraw, not having reached the pith. In either case, however, the apparent damage was the same, as the twig died above the point of attack, and some bud below the injury would have to be forced out to take the place of the terminal bud, in order to continue the growth of the twig. This dying-back being entirely at the ends of the twigs, and the leaves soon drying to a pale yellow, rendered this injury quite evident. (See Fig. 7.) The worms act thus as "twig-borers" for a period covering about twenty days, and then seek the fruit, if any is on the tree. If there is no fruit on the tree, then the whole life of the worm will be spent as a " twig-borer," and the damage of this kind becomes all the more evident. Attempt to Poison these Worms. — Reports of success by the use of Paris green against the bud-worm indicated a possible means of control. The experimental work was done when the worms of the second generation had begun to appear, which was about May 19th, and the poison used was from samples furnished by the Station laboratory at Berkeley. These samples are designated as Nos. 610 and 611, and the following tables give the method of work and results obtained from their use. The mixtures in all cases were. made up with lime in the proportion of 5 pounds to 100 gallons of water. The lime was first slaked and a milk of lime made, and this mixture was strained to remove lumps and grit. The desired amount of Paris green was then made into a paste with water, and added to the lime water in the proportion being experimented with. The atmospheric moisture was determined by a device consisting of a string six feet long, hung in such a way that, while the air had full play upon it, it was in the shade at all times and no wind blew upon it. A light weight was hung to the end of this string. The string would shrink up when the atmosphere was humid, and regain its normal length under dry conditions. This method gave us the comparative humidity only, but this was enough for the purpose. 28 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. Table of Expekiments with Paris Green, Sample No. 610. Pr0 Used.° nS When A PP lied - 1-800 May 20, 7 a. m. May 20, 11 a. m. " May 20, 2 p.m. " May 20, 6 p. m. " May 27, 7 a. m. May 27, 11 a.m. May 27, 2 p. m. May 27, 6 p.m. 1-1600 May 22, 7 a. m. " May 22, 11 a. m. May 22, 2 p. m. " May 22, 6 p.m. May 29, 7 a.m. May 29, 11 a.m. " May 29, 2 p. m. May 29, 6 p.m. Atmospheric Humidity. High Medium Low Low Mod't'ly high Below medium Low Very low High Medium Low Very low Mod't'ly high Below medium Low Very low Condition of Leaves. Turgid Turgid Wilted Wilted Turgid Sl'tly wilted Wilted Much wilted Turgid Turgid Wilted Much wilted Turgid Sl'tly wilted Wilted Much wilted Injury to Leaves. Slight Some Much Much Some Some Much Much Some Some Much Much Slight Some Some Much Injury to Fruit. No fruit No fruit No fruit No fruit In spots In spots In spots In spots Some Some Some Some In spots In spots In spots In spots Table of Experiments with Paris Green, Sample No. 611. 1-800 1-1600 May 21, May 21, May 21, May 21, May 28, May 28, May 28, May 28, May 21, May 21, May 21, May 21, May 28, May 28, May 28, May 28, 7 A. M. 11 A. M. 2 P. M. 6 P. M. 7 A. M. 11 A. M. 2 P. M. 6 P. M. 7 A. M. 11 A. M. 2 P. M. 6 P. M. 7 A. M. 11 A. M. 2 P. M. 6 P. M. Very high Medium Low Low High Medium Low Low Very high Medium Low Low High Medium Low Low Turgid Turgid Wilted Wilted Turgid Turgid Wilted Wilted Turgid Turgid Wilted Wilted Turgid Turgid Wilted Wilted None Some Much Much Some Some Much . Much Some Some Much Much Very little Some Much Much Slight Slight Much Much Some Some Much Much In spots In spots Much Much Some Some Much Much It will be seen that, so far as the apparent injury goes, there was no material difference between the samples used, which were both greens that had passed the California test and were good. In every instance, save one, the material burned the foliage. It will be seen from the table that in the 7 a. m. experiment of May 21st, with sample No. 611, no damage was apparent, so far as the foliage is concerned, and only a slight burning of the fruit. Whatever the reason for this exception, the fact remains that, under the conditions most commonly obtained, there was more or less damage done to both leaves and fruit in all the other experiments. The damage consisted in the entire destruction of the leaves in some cases, in the destruction of the pendent portion of the leaves where a drop of the material gathered in other cases, and in spots being burned in the leaves in still others. The fruit injury consisted generally in the burning-out of spots upon it; and these spots did not develop, but either gave the fruit an unsightly appearance, or decay started in the injured place and the fruit rotted. peach- worm: second generation, history. 29 The experiments as tabulated were paralleled by another series, in which a spray of water was used before the Paris green mixture was applied, and the tree well moistened. The results in nowise differed from those reported above in detail, which were sprayed in the usual manner. These results were furthermore confirmed on another place near the Newcastle station, where spraying was being done on some pear trees with Bordeaux mixture to which Paris green had been added in the proportion of one pound of the Paris green to 180 gallons of the latter. Two peach trees, four years old and in full foliage, were, by error of the workmen, sprayed with this material. The result was that the leaves and many of the young branches were killed outright. The experiments with the Paris green were carried no further, as the damage done to the trees and fruit was so great as to render it certain that its use would be wholly inadvisable under the conditions existing in Placer County. STUDY OF THE FRUIT-WORM. Early in June the second generation of worms begins operation as fruit-worms. They had been working some time as twig-borers as already described, but for some unknown reason now began to leave the twigs and attack the fruit. It is in this work in the fruit that the insect does its greatest damage and has attracted most attention. The attack on the fruit is very characteristic, nothing else being mistakable for it. The worms of the second generation on leaving the twigs bore into the peaches at the stem end in a majority of cases. Not only is the stem end thus generally chosen for the beginning of the attack, but a certain portion of the stem end — the line that is called the suture. After boring through the skin the worm begins to feed upon the tissue of the fruit beneath, often excavating a large chamber, which is more or less filled with gummy matter and excrement. The mouth of the burrow is also generally filled with these materials mixed together. The skin above the hollowed-out portion of the fruit first turns dark and shrivels up to a certain extent, and finally decay usually sets in. When riper fruit is attacked the worm frequently burrows to and around the pit; and if the latter is split it often attacks the seed. The worm may, under certain circumstances, make its attack at other points than in the stem end of the fruit. Quite frequently when two peaches are in contact on the tree, the worm bores its way into one of the fruits at this point of contact; or if a leaf or twig touches the fruit, here also the worm may enter. The character of the injury is the same in any of these cases, and the fruit is ruined. 30 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. PUPATION. Early in July the most precocious worms of this generation begin to withdraw from the fruit and to pupate, and this coming-out for pupation continues as late as the last of August before the last of them have completed their work. The position chosen for pupation is in the stem end of the fruit, and usually not the one in which the worm has been working, but often a sound, uninjured one. The worm lays itself along the suture-hollow in the stem end of the peach, and fastens itself here by two strands of silk, making less Fig. 13. Pupse of the second generation of peach-worms in position upon the fruit. attempt at a cocoon than in the first generation. In from twenty-four to forty-eight hours it passes into the pupa form. Though this is the usual place and method of pupation in this generation, there are a number of other modes. In some instances the worms choose a space between two peaches that lie close together, finding here a satisfactory place of concealment. In a few cases this change took place in rough places on the bark, or under leaves lying against small branches or twigs. In Fig. 13 will be seen pupae in the positions chosen by the large majority of the worms as described above. These pupae do not differ in any way from those produced by the first or winter generation of worms. peach-worm: third generation. 31 THE MOTH AND EGG-LAYING. The moths issue from these pupse in seven days, and do not differ appreciably from those of the spring generation. Egg-laying began on the second or third day after emer- gence, and usually continued for three days. These eggs, which are shown much magnified in Fig. 14, are placed on the edge of the de- pression where the stem is attached to the fruit; and were not, in any instance noted, placed on the. twigs, as are the eggs from the moths of the other generations. The eggs are usually placed singly, and no real grouping of them was seen, though in some cases two or three were found quite close together. The Fig. 14. Eggs of the second generation peach- fuzzineSS SO Characteristic of the moth in position on fruit; much magnified. peach seems to render a secure fastening of these eggs impossible, and they could be easily removed from their position. WORMS OF THE THIRD GENERATION. The young worms began to appear on the sixth day. They first wandered about on the surface of the peaches for a few hours, and then ate their way into them in much the same manner as the worms of the second generation. The worms of this brood are the only ones that enter the fruit immediately on hatching. They make, therefore, at first very minute burrows, contrasting strongly with freshly-made burrows of the preceding generation. FALL HISTORY OF THE INSECT. The worms of this generation continue their work in the fruit for about a month, when, their full growth having been reached, they come to the surface to pupate. The method of pupation and position chosen for this purpose differ in nowise from those of the second generation, as described above. About six days were spent in the pupa form, and the moths began to appear about the middle of August. Egg-laying began in the latter part of August and continued well into September. These eggs were placed sometimes in small cracks and crannies of the bark, and sometimes quite exposed on the bark of the older wood just above the crotches formed by the new wood. The eggs hatch in about five days, and the young worms, which are from one half to three fourths of a millimeter in length, immediately 32 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. proceed to bore into the bark of the crotches formed by the new wood with the growth of the previous year, and to prepare their winter quarters. In the region under investigation hibernation was well begun this season on September 1st, and the fully-made chambers, as previously described, could be found readily and in numbers. If the conditions as noted this season are normal, then the worms live in their winter quarters during all of the fall and winter months, remaining quiescent for fully half of the year. The life history as worked out in this investigation is graphically shown in the accompanying calendar. RESULTS FROM SPRAYING EXPERIMENTS. As the summer advanced the work of the worms in the fruit became more and more apparent, until, as the various kinds were picked, we were able to determine the final results obtained through the use of various spray materials. The following table is compiled from the detailed record of the experiments on the five station orchards, and from work done on twelve other selected places on which we took com- plete records. Only two not-sprayed places are directly referred to, but the heavy loss found on these places is practically the same as found on other places where there was the same neglect of spraying. The per- centages of loss were obtained in nearly all cases from actual weights of wormy fruit, though in a few instances the figures represent an actual count of the peaches. peach-worm: spraying experiments. 33 ALEXANDER. Time of first blossoms, March 15. Designation of Orchard. Spray Material. Ophir Lime, salt and sulfur Ophir Check trees . . A Lime, salt and sulfur ._ A Check tree.. B Lime, salt and sulfur C Lime, salt and sulfur ... .. 7 Lime, salt and sulfur. . . ... .. 8 Lime, salt and sulfur 9 Lime, salt and sulfur.. .. 10 Lime, salt and sulfur.. 1 Lime, salt and sulfur.. 2 I X L compound 2, resprayed 28° dist. emul., 1 to 8 parts water.. 2, resprayed 33° dist. emul., 1 to 8 parts water.. 2, resprayed 150° kero. emul., 1 to 8 parts water. 3 I X L compound 3 Check trees 4 I X L compound .. 5 I X L compound 6 I X L compound 11 No spray 12 No spray No Trees. 50 4 150 1 50 275 50* 100* 220* 300* 110* 300* 100* 100* 100* 300* 5 350* 450* 500* 400* 350* Time of Spraying. Aprill Not sprayed. .. March 12 Not sprayed... March 10 March 10 March 8 March 8 March 6 March 10 Feb. 1 to 6 March 8 May 15 May 15 May 15 Mar. 7, Apr. 6.. Not sprayed... Mar. 8, Apr. 9.. Mar. 10, Apr. 10 Mar. 8, Apr. 7._ Per Cent of Loss. 1 50 1 35 1 3 1 1 2 15 20 6 6 8 40 40 50 65 60 60 55 HALE. Time of first blossoms, March 15. Newcastle Newcastle Ophir Ophir A B C 7 8 9 10 1 2 2, resprayed 2, resprayed 2, resprayed 3 3 4 5 6 11 12 Lime, salt and sulfur ... Check trees , Lime, salt and sulfur Check tree Lime, salt and sulfur ._ Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur _. Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur I X L compound 28° dist. emul., 1 to 8 parts water... 33° dist. emul., 1 to 8 parts water ... 150° kero. emul., 1 to 8 parts water. I X L compound Check trees ._ _ .... I X L compound . I X L compound I X L compound TJnsprayed TJnsprayed 500 5 200 1 900 300 550 125* 150* 600* 550* 220 250* 85* 85* 80* 150* 5 5O0* 900* 600* 650* 800* March 17, 18.. Not sprayed .. March 31 Not sprayed . . March 13, 14.. March 10 March 8, 10 ... March 8 March 12 March 4, 5 March 12, 13.. Feb. 1 to 6.... March 8 May 15 May 15 May 15 Mar. 6, Apr. 3. Not sprayed .. Mar. 7, Apr. 5. Mar. 7, Apr. 2. Mar. 3, Apr. 4. 55 40 1 1 20 1 2 14 15 25 20 20 25 45 40 65 70 60 65 55 * Approximate. 3— Bul. 144 34 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. EARLY CRAWFORD. Time of first blossoms, March 10. Designation of Orchard. Newcastle Ophir A 7 8 9 10 1 5 11 12 2 2, resprayed 2, resprayed Newcastle Ophir A 8 9 10 1 5 B Spray Material. No. Trees. Lime, salt and sulfur 1,000 Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur... Lime, salt and sulfur Lime, salt and sulfur I X L compound No spray No spray _ I X L compound ._ 28° dist. emul., 1 to 8 parts water. 33° dist. emul., 1 to 8 parts water. 200 200 110* 300* 125* 350* 300* 400* 450 400* 130* 65* 65* Time of Spraying. March 5, 7 .. April 1 March 8 March 7 March 6, 7 . . March 3 . ... March 3 Feb. lto6 .. March 3 March 8 May 15 . May 15 . SUSQUEHANNA. Time of first blossoms, March 5. Lime, salt and sulfur.. Lime, salt and sulfur.. Lime, salt and sulfur. Lime, salt and sulfur.. Lime, salt and sulfur.. Lime, salt and sulfur.. Lime, salt and sulfur.. I X L compound Check trees 400 200 150 200* 250* 125* 200* 250* 2 March 12 ... April 1 March 3 March 3 March 1, 3 .. March 1,3... Feb. lto 6 .. Mar. 4, Apr. I Not sprayed. ST. JOHN. Time of first blossoms, February 24. IMPERIAL. Time of first blossoms, February 25. Per Cent of Loss. 2 1 1 2 12 15 18 45 45 40 25 25 1 1 3 1 5 15 25 30 50 Lime, salt and sulfur. Lime, salt and sulfur. 900 500 Feb. 21. Feb. 20. FOSTER. Time of first blossoms, March 5. Newcastle A Lime, salt and sulfur.. Lime, salt and sulfur.. 8 Lime, salt and sulfur.. 9 Lime, salt and sulfur.. 10 Lime, salt and sulfur.. resprayed I X L compound resprayed 28° distillate emulsion resprayed 28° distillate emulsion 450 350 400* 350* 400* 200 100 100 March 1 March 3 March 3 Feb. 28.. March 2 March 8 May 16. . May 16. . McDEVITT. Time of first blossoms, March 2. Newcastle Lime, salt and sulfur. Ophir A C 7 8 9 ' 10 1 11 Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur.. Lime, salt and sulfur.. Lime, salt and sulfur 300* Lime, salt and sulfur 300* Lime, salt and sulfur 150* Not sprayed 400* 330 250 400 250* 150* 250* March 4 . . April 2.... Feb. 24 ... Feb. 27.... Feb. 24 Feb. 24.... Feb. 23.... Feb. 25 Feb. 1 to 6 1 3 2 6 9 20 20 1 2 18 4 5 8 7 25 50 Approximate. peach-worm: spraying experiments. 35 LEVI. Time of first blossoms, March 13. Designation of Orchard. Spray Material. Newcastle Lime, salt and sulfur _. Ophir Lime, salt and sulfur Ophir Check trees A Lime, salt and sulfur B Lime, salt and sulfur C Lime, salt and sulfur 8 Lime, salt and sulfur 9 Lime, salt and sulfur .. 10 Lime, salt and sulfur 1 Lime, salt and sulfur 2 I X L compound 2, resprayed 28° dist. emul., 1 to 8 parts water. . 2, resprayed 33° dist. emul., 1 to 8 parts water.. 2, resprayed 150° kero. emul., 1 to 8 parts water 3 I X L compound 4 I X L compound 5 I X L compound ... _ 6 I X L compound 11 No spray 12 Lime, salt and sulfur No. Trees. 650 800 3 200 500 600 300* 350* 400 330 350* 125* 115* 110* 250* 200* 350 450 600* 450 Time of Spraying. March 13, 14 — April 2, 3. Not sprayed... March 8 March 8, 10 March 6, 7 March 9 March 8 March 12 Feb. lto6 March 7 Mayl5 May 15 May 15 Mar. 8, Apr. 2.. Mar. 6, Apr. 4.. Mar. 6, Apr. 5__ Mar. 7, Apr. 6.. Mar. 10, 11 Per Cent of Loss. 2t 25 2t It 4t 3 4 12 25 10 10 12 40 20 35 40 45 4 SALWAY. Time of first blossoms, March 15. Newcastle Newcastle Ophir Ophir A B C 7 8 9 10 1 Ophir Ophir 2 2, resprayed 2, resprayed 2, resprayed 3 4 5 6 11 12 Lime, salt and sulfur Check trees Lime, salt and sulfur Check trees Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur... Lime, salt and sulfur _. . Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur Lime, salt and sulfur Distillate emulsion^ Distillate emulsion§ I X L compound 28° dist. emul., 1 to 8 parts water... 33° dist. emul., 1 to 8 parts water... 150° kero. emul., 1 to 8 parts water. I X L compound ._ I X L compound I X L compound _ I X L compound No spray Lime, salt and sulfur 500 4 500 3 400 500 700 300* 550* 450* 450 350 48 168 560* 190* 185* 185* 150* 350* 500* 450* 300* 500 10.... March 12 Not sprayed. April 4.. Not sprayed. March 7 March 7 March 5 March 8 March 8 March 4 March 7 . .. Feb. 1 to 6 . Feb. 12 .... March 31 .. March 7, 8 . May 15, 16 . May 15, 16 . May 15, 16 . Mar. 6, Apr Mar. 6, Apr Mar. 7, Apr Mar. 7, Apr. 9. 1 50 25 2 1 5 1 2 2 5 25 50 45 18 18 18 30 25 25 40 45 4 * Approximate. t Estimate. I Hercules distillate emulsion 1 to 8, 1 to 10, and 1 to 12 parts of water, sixteen trees each. $ Densmore-Stabler untreated 28° emulsion, treated 28° emulsion, and 33° emulsion, 1 to 10 and 1 to 14 parts of water, also treated distillate oil 28°, untreated 28° oil, and 33° distillate, 1 to 3 and 1 to 4 parts of water— fourteen trees each. 36 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. UNSPRAYED TREES. The results obtained in the control of the peach-worm are well shown in these tables. It will be most evident that the season of 1902 was one in which the worms were very plentiful. The check-trees in every case were heavily infested, while the average loss among unsprayed trees indicates the presence of the worms in disastrously large numbers. Bringing together the unsprayed trees into one table, we see this fact very evident. Percentage of Loss on Unsprayed Trees. . No. of Maximum Minimum Average variety. Trees. per cent. per cent. per cent. Alexander 760 60 35 48 Hale 1,461 65 40 49 Early Crawford 850 45 40 42 Susquehanna. 2 50 50 50 McDevitt... 400 50 45 47 Levi .- 603 50 25 45 Salway.. 307 50 25 45 Total ._„ 4,884 65 25 48 SPRAYED TREES. The Failure of the I X L Compound. — The same fact is further emphasized in the case of the use of the I X L compound, which proved to be an utter failure as a means of controlling the peach-worm. Percentage of Loss on Trees Sprayed with I X L Compound. Varietv ^° - °* Maximum Minimum Average Trees. per cent. per cent. per cent. Alexander 1,600 65 40 53 Hale 2,150 70 45 60 Early Crawford 400 45 45 45 Susquehanna _. 250 30 30 30 Levi • 1,250 40 20 35 Salway 1,450 40 25 37 Total.... 7,100 70 20 50 These results are very conclusive, both because of the large number of trees concerned, and because the timing of the application was the same as that which gave the best results with the lime, salt and sulfur. The Use of Oil for Killing the Pupae. — The results obtained from the use of the distillate emulsions and kerosene-oil emulsions, following the spring use of the I X L compound, indicate a considerable saving over the loss that would have resulted from depending upon that compound. That this result would have been quite as good had the I X L compound spraying been omitted, seems more than probable, when we remember that the bud-worm attack was so severe on the place that it appeared at the time that this material had in nowise controlled the pests in this stage. The results of this work with the distillate and kerosene emul- peach-worm: effects of sprays. 37 sions were certainly good enough to warrant their use, and will be useful to fruit-growers in the future, if by any chance they fail to spray at the proper time, and find that the worms are pupating in too great numbers on the trunks and larger limbs of the trees, as is their habit in the spring generation. Loss When Sprayed in March with I X L Compound, and in May with Emulsions of Distillate and of Kerosene. Varietv No - of Maximum Minimum Average y " Trees. per cent. per cent. per cent. Alexander _ . _ 300 8 6 7 Hale.... 250 25 20 21 Foster ... 200 20 20 20 Levi 350 12 10 11 Salway 560 18 18 18 Total 1,460 25 6 15 Winter Spraying with Lime, Salt and Sulfur. — When compared with the loss where no spraying has been the practice, the winter use of the lime, salt and sulfur, as shown on orchard No. 1, results in a certain amount of control of the worm. The results are by no means satis- factory, for while a great deal better than either of the treatments given above, still the work does not result in the reduction of the loss to a low enough minimum. Loss When Sprayed in Winter with Lime, Salt and Sulfur. Variptv No - of Maximum Minimum Average vaneiy. Trees. per cent. per cent. per cent. Alexander 110 20 20 20 Hale 220 25 25 25 Early Crawford 300 18 18 18 Susquehanna 200 25 25 25 McDevitt T 150 25 25 25 Levi.... 330 25 25 25 Salway 350 25 25 25 Total 1,660 25 18 24 Spring Spraying with Lime, Salt and Sulfur. — The best results were obtained by the use of lime, salt and sulfur compound, as shown by the following table: Loss when Sprayed in Spring with Lime, Salt and Sulfur. Variptv ^° - °* Maximum Minimum Average y " Trees. per cent. per cent. per ceut. Alexander 1,195 15 4 Hale 4,175 15 5 Early Crawford 2,285 15 5 St. John and Imperial 1,400 2 1 Susquehanna..-. 1,325 15 1 3 Foster 1,950 9 14 McDevitt 2,230 18 1 6 Levi 3,800 12 3 Salway 4,300 5 12 Total 22,660 18 3 38 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. In some respects the above table fails to give a correct idea of the results from the use of this mixture at the right time, since it includes two orchards, station C and orchard No. 10, in which the conditions were very unfavorable for producing good results. With these two orchards eliminated, the average amount of injury shown by the tables would not be over, one per cent. Even when they are included the efficiency of this treatment as compared with the others is very strikingly shown in the fullowing table: Comparative Statement of Loss by Different Treatments. Spraying Material. £°- of Maximum Minimum Average J Trees. per cent. per cent. per cent. Not sprayed 4,884 65 25 48 I X L compound 7,100 70 20 50 I X L compound and distillate . . 1,460 25 6 15 Winter lime, salt and sulfur 1,660 25 18 24 Spring lime, salt and sulphur 22,660 18 3 MISCELLANEOUS RESULTS. l/n sprayed peach orchard No 13 Loss 40 to 50 f -r-^To Loomis "S Un sprayed peach orchard NO. 1 1 Loss 60 to 65/. younj) peach. orchard urn prayed AU fruit wormy //*§ no.ia Sprayed peach orchard Loss Loss Due to Adjacent Infested Orchards. — The results obtained at station C show plainly the danger from careless neighbors. The location of this station is in a district where spraying is not the rule, and where the loss from wormy fruit is / usually very heavy. When the place was selected for these experiments it was found to be well stocked with hibernating larvae. The orchard had been sprayed the previous year with the lime, salt and sul- fur compound. The loss of fruit last year was reported to us as being " very heavy." Spraying operations were begun in this orchard when the buds had swollen and were nearly ready to burst out. The lime, salt and sulfur compound was pre- pared by the owner with great care and the trees thoroughly treated- While the material used and the method and time of application were in accordance with the best practice, yet when the crop was picked it was found that there was a heavy loss from wormy fruit. The location of this orchard and the relative losses here and in neigh- boring orchards are shown in Fig. 15. The loss in the sprayed place is Fig. 15. Loss caused by adjacent unsprayed orchard. peach-worm: spraying methods. 39 very much less, as will be noted, than in the unsprayed orchards, though it is much greater than in the orchards more favorably located as to neighbors. Loss from Careless Work. — Orchard No. 10 was selected and the records kept because it was a good illustration of the results of carelessly spray- ing the trees. This orchard was worked by Chinese renters under a lease requiring them to spray the place each year. The work was done, 40 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. however, in the most perfunctory manner. We visited the place a number of times while spraying was under way, and gave the matter careful attention. The lime, salt and sulfur mixture was used, but was made up in a way that rendered it practically useless. All of the materials, except the water, were being used in reduced quantities, and the mixture was scarcely, or not all, boiled. The loss found here can be directly traced to this carelessness. This orchard No. 10 lies next to the station A, on which the loss was very small. The tables will show the loss sustained in orchard No. 10 to be con- siderable, but it would not have been strange, when the method of spraying is taken into account, if it had been still greater. Saving by Careful Work. — As a contrast to these last two places, we may cite the orchard we have called station A. The owners of this orchard had suffered a heavy loss the previous year from wormy fruit. The trees were found much infested with the hibernating larvae when inspected in January. We were able to have the work of spraying done in the most careful manner on this place. Fig. 16 shows one of the spraying outfits used at this place. The contrast between this orchard and orchard No. 10 was very striking. As previously noted, these two orchards lie adjacent to each other. On three rows of Hales next to the poorly-sprayed place the loss was from five to ten times greater than the loss in the orchard as a whole. Without doubt this was due to the flight of the moths from orchard No. 10. Similar instances were noted in several cases. The Use of Oil and Distillate Emulsion. — A small number of experi- ments not noted in the above tables indicate that the emulsions of kerosene and the distillate oils, when used in the early spring, produced a good degree of control, though hardly as good as when the lime, salt and sulfur were used under identical conditions. Experiments with these materials are to be conducted, however, on a commercial scale, in order to demonstrate their real value for spring-spraying purposes. The value of these substances, as used against the pupa? of the first generation, is clearly shown. It should not be made the sole depend- ence, but rather to enable the grower to have another chance at killing the insect, when for any cause the first, or spring, spraying has been omitted or found ineffective. This treatment should be so timed in the late spring that pupation will be well under way, as determined by careful inspection of the trees at that time. The distillate oils are prepared in emulsions by certain manufacturers, and are quite cheap and effective. The oils themselves are quite readily emulsified. We have found the following formula useful: Distillate oil (28° or 33°-35°) 5 gallons. Common kitchen soap 4 to 6 pounds. peach-worm: spraying methods. 41 Dissolve the soap in about four gallons of hot water. Pour the oil into the hot suds, and thoroughly churn the two together by pumping the material back into itself through a spray pump. In from ten to fifteen minutes the material will be thoroughly emulsified, and will be of a creamy color and consistency. In this condition it readily mixes Fig. 17. Boiling the lime, salt and sulfur spray. >??. '- ,TV : H| ' HAk ^l^dft BK&M w^ww^ . /,^ - - Fig. 18. Wheeled sled and tank spraying outfit. with water. To use, dilute in the proportion of one of emulsion to eight of water, using hot water preferably. Apply to the trees warm. The kerosene-oil emulsion may be prepared in the same way, but using no more than four pounds of soap. It is to be used in the same way as the distillate emulsion, but is not quite as effective as the latter. 4— Bul. 144 42 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. GENERAL CONCLUSIONS AND RECOMMENDATIONS. The experiments reported in this bulletin prove that the peach-worm can be controlled by the use of the lime, salt and sulfur compound, if this material is prepared in the proper manner and thoroughly applied at the right time. These three factors are all essential to successful treatment. The formula for the preparation of the lime, salt and sulfur spray, as used successfully in the Placer County region this season, is as follows: Lime — — 40 pounds. Sulfur 20 pounds. Salt . - 15 pounds. Water, to make 60 gallons. Boil 10 pounds of lime and 20 pounds of sulfur in 20 gallons of water for from one and one half to two hours, or until the mixture is a deep amber color, which will indicate that the sulfur is dissolved. The balance of the lime, 30 pounds, should then be slaked in another vessel and the salt added to this latter mixture. This should be stirred until the salt is dissolved and then added to the original mixture of lime and sulfur, and the whole boiled for from thirty to forty-five minutes longer, enough water being added to bring the total amount of material up to 60 gallons. Next strain the material into the spray tank and apply to the trees hot. Do not let the material get cold, for a portion of the ingredients will then crystallize and precipitate out of the liquid, and its effectiveness is much reduced. Many different arrangements for boiling the spray are used, and each orchardist will devise the method most convenient to him. We found the device shown in Fig. 17 a con- venient arrangement. In this case a large iron cauldron was set up on an iron frame, so made that the bottom of the cauldron was about one foot above the ground, when the device was ready for use. A fire could then be easily built beneath the cauldron and the boiling thoroughly done. When it is not necessary to move the cauldron, it is well to build up a stone or brick fireplace beneath it, so arranged that a good draft can be maintained. As to the apparatus for spraying, one may employ any of the outfits of pumps, etc., commonly sold for use in orchards. Two such outfits are shown in Figs. 16 and 18, from photographs taken in the orchards this spring. The important thing in spraying work is to completely cover every tree with the material used. This thorough work must be insisted on as a requisite for successful control of the worm. The hibernating burrows in which the worms are hiding at this season may be found in any part of the tree — from the tips of the topmost branches to the ground. peach-worm: general conclusions. 43 o 44 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. The time to make the application varies with the variety. It should be done when the buds have begun to swell perceptibly, and it may be delayed, without serious injury to the tree, until after the blossoms have begun to appear, at least .under the conditions found in Placer County during the past season. The effectiveness of such treatment can now be considered to be an established fact.