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UNIVERSITY OF ILLINOIS 
 
 Agricultural Experiment Station 
 
 URBANA, OCTOBER, 1902. 
 
 BULLETIN NO. 80. 
 
 METHODS AND RESULTS OF FIELD INSECTI- 
 CIDE WORK AGAINST THE SAN JOSE 
 SCALE, 1899-1902. 
 
 BY S. A. FORBES, STATE ENTOMOLOGIST. 
 
 On April 11, 1899, an emergency bill was approved by Gov- 
 ernor John R. Tanner of Illinois requiring 1 the State Entomologist 
 to "treat and disinfect once thoroughly," at the expense of the 
 State, all orchard property which that officer had reason to believe 
 had become infested with the San Jose scale before the year 1899, 
 a fact which marked a new departure in the struggle for the con- 
 trol of the San Jose scale in Illinois. Unfortunately, the appro- 
 priation of $6,000 made for the expenses of this work was 
 insufficient for its purpose, being 1 indeed but half the sum esti- 
 mated by me as necessary to give a single insecticide treatment to 
 all the premises then known to be infested. This fact put an 
 effectual bar upon preliminary experiments with insecticides, since 
 it was evidently my duty to apply the appropriation at once and as 
 far as it would go to the immediate purpose expressed in the law, 
 that of a thorough insecticide treatment of infested premises. 
 
 Being thus limited to action on lines fixed by the existing state 
 
 463 
 
464 BULLETIN NO. 80. [October, 
 
 of our knowledge of insecticide methods, it was my first duty to 
 make choice of the procedure which seemed most likely to enable 
 me to exterminate the scale locally by a single treatment. This 
 choice necessarily lay between liquid and gaseous insecticides, 
 applied by spraying 1 and by fumigation respectively. 
 
 The liquid insecticides well enough known at the time to make 
 them practically available for the destruction of the San Jose scale 
 were the whale-oil soap solution and the emulsions or mechanical 
 mixtures of kerosene and water. Crude petroleum was then com- 
 ing into use, it is true, but the results reported were too variable 
 to entitle it to confidence as both efficient and safe. To extermin- 
 ate the scale in orchards with a liquid insecticide required that the 
 fluid should be so distributed as to reach every scale on every tree 
 in quantity sufficient to kill the insect. This was obviously an 
 impossible task, especially if we take into account the frequency 
 with which these minute scales are secreted under bark, behind 
 buds, etc. ; and this conclusion was confirmed by two years of pre- 
 vious experience with the use of whale-oil soap, during which 
 orchards and town lots at twenty-one localities in Illinois had been 
 carefully and thoroughly treated by two of my assistants, Prof. H. 
 E. Summers, now State Entomologist of Iowa, and Mr. R. W. 
 Braucher, a graduate in horticulture from the University of Illi- 
 nois. Subsequent inspections of the premises treated disclosed the 
 fact that the extermination of the scale was accomplished in no 
 case except where every visibly infested tree and shrub was 
 destroyed, together with all adjacent vegetation to which the scale 
 might possibly have spread. 
 
 The fumigation method had this theoretical advantage over 
 that with the liquid spray, that an insecticide vapor set free under 
 a close tent enveloping the infested tree would be carried by spon- 
 taneous diffusion to all parts of the inclosed space, and would thus 
 presumably reach every particle of the infested surface and kill 
 every scale, provided the operation were intelligently and carefully 
 conducted. There seemed, in short, a reasonable possibility that 
 expert fumigation would exterminate locally where the conditions 
 were not unfavorable to thorough work, while such a result seemed 
 clearly impossible with the liquid spray. I consequently decided 
 to make a trial of orchard fumigation with hydrocyanic acid gas, 
 applied after the method which had been in use for several years 
 in the citrus orchards of the Pacific coast. 
 
 The opinion current among entomologists with respect to 
 fumigation as an orchard method was well shown by statements 
 of experimental results appearing at about this time, and especial- 
 
IQO2.] THE SAN JOSE SCALE. 465 
 
 i 
 
 ly by those published in August, 1898, in Bulletin 57 of the Mary- 
 land Experiment Station, and in the fall of that year in Bulletin 
 No. 17 of the Entomological Division of the U. S. Department of 
 Agriculture. In the first of these bulletins, entitled "A Report on 
 the San Jose Scale in Maryland and Remedies for its Suppression 
 and Control," Prof. W. G. Johnson, State Entomologist of Mary- 
 land, gives an account of various experiments with this insecticide 
 gas, made in the fall of 1897 and the spring of 1898 on bearing 
 orchard trees in Maryland. As a conclusion from experiments on 
 fifty-three dwarf Bartlett pear-trees conducted from September 27 
 to October 1 by liberating gas under inclosing tents, he says (p. 86) 
 that "the San Jose scale is entirely destroyed by the gas when 
 used on calm, dry, sunny or cloudy days"; that "the cost of 
 treatment, aside from the equipment, is less than that for whale- 
 oil soap"; that "trees treated at night with very strong doses of 
 gas do not have the foliage or dormant leaf and fruit buds affected 
 at all, even where double the amount of gas ordinarily used is 
 generated "; and that " trees treated in the morning before 9 a. m. 
 and in the afternoon after 4 p. m. have the foliage very little 
 affected by the gas." These tests were thought by him so grati- 
 fying that a meeting of those especially interested was called for a 
 demonstration of the operation, and at a dinner served by the 
 owner of 'the infested premises all the speakers "were unanimous 
 in the opinion that the experiment was complete in every respect." 
 In a later report on this same experiment, read August 19, 1898, at 
 the Tenth Annual Meeting of the Association of Economic Ento- 
 mologists, Professor Johnson says: * 
 
 "In order that I might report the definite and final results of 
 these experiments, I made a careful examination of every tree in 
 the orchard on Tuesday and Wednesday of this week. Where 
 there were hundreds and thousands of scales breeding on the trees 
 at this time last year not one can be found now, except upon trees 
 under 5 feet in height and on those fumigated when the foliage was 
 wet with dew or fog or immediately after a rain, and even on 
 these trees the young larvae are very few as compared with their 
 number at this time last year. Where the fruit was much pitted 
 and scarred by the scale last year not one has been seen upon a pear 
 thus far this season. 
 
 "In all, the experiment is thoroughly satisfactory, in that it 
 demonstrates by actual trial that this method can be used in our 
 largest bearing orchards, even under the most adverse conditions, 
 with excellent results." 
 
 * Bull. No. 17, N. S., U. S. Dept. Agr., Div. Ent., pp. 41 and 42. 
 
466 BULLETIN NO. 80. [October, 
 
 Fourteen very badly infested plum-trees were also treated 
 March 17 and 18, 1898, with hydrocyanic acid gas liberated under 
 tents, and no living- scales had been found on them three months 
 later. "The general outcome of these experiments," says Profes- 
 sor Johnson,* "up to the present time, June 15, is so far satisfac- 
 tory. We cannot hope to find a remedy for the San Jose scale that 
 is more effective than hydrocyanic acid gas." Referring to this 
 experiment againf August 19, five months after the treatment was 
 given, he says: 
 
 " The gas can also be used in the spring in peach, plum, and 
 apple orchards after the buds have begun to unfold. A block of 
 one hundred six-year old plum-trees at Annapolis Junction was 
 fumigated March 17 and 18, 1898, and up to the present time not a 
 living scale has been found upon any trees, except those sprayed 
 with 50 and 100 per cent, gasoline. The trees in this orchard 
 were very badly infested, the most of them being so literally 
 covered it was impossible to see the bark at any point on the trunk 
 and larger branches. 
 
 "Other experiments were conducted in scale-infested bearing 
 orchards in May, June, and July, the results of which cannot be 
 finally reported at this time, except that no living scales have been 
 found upon any of the fumigated trees." 
 
 The operations reported in the present paper can scarcely be 
 called experiments, since they were an attempt to make practical 
 application in the field of methods based on the experimental work 
 and practical experience of others. Those with hydrocyanic acid 
 gas may be taken, however, as a test of the fumigation method as 
 applied to common orchards and fruit plantations in southern Illi- 
 nois under conditions more favorable in some respects and less 
 favorable in others than those of ordinary orchard practice. A 
 considerable series of operations was carried on over a large terri- 
 tory by a single party under the direction of one foreman especially 
 selected and carefully instructed for this work, and his manage- 
 ment was doubtless more intelligent and exact than that of the 
 ordinary foreman or owner of an orchard would have been. On 
 the other hand, the conditions which he had to meet were of course 
 much more varied than those to which any single orchardist would 
 be subject, and the limitations of time and expense were such that 
 the work must move steadily forward whenever at all practicable 
 a fact which made it impossible to choose favorable weather and 
 
 *Md. Bull. 57, p. 90. 
 
 t Bull. No. 17, N. S., U. S. Dept. Agr., Div. Ent., p. 42. 
 
IQ02.] THE SAN JOSE SCALE. 467 
 
 to suspend operations temporarily when it was likely that the best 
 results could not be obtained. 
 
 It has seemed to me, nevertheless, that the outcome of this 
 campaign is well worthy of report, since it indicates with approxi- 
 mate fairness what can be accomplished by practical work on a 
 large scale by the intelligent fruit grower so unfortunate as to 
 have become the victim of the San Jose scale. Owing to the fact 
 that these were not regarded as experimental but practical opera- 
 tions only, the notes of the work were not as full as I could now 
 desire. They were, however, carefully made by competent men, 
 and are entirely reliable so far as they go. 
 
 EXPERIENCE WITH ORCHARD FUMIGATION. 
 
 Having decided on an extensive practical trial of orchard fumi- 
 gation with hydrocyanic acid gas, I found it necessary first to pro- 
 vide expert advice and supervision with respect to the practical 
 operation, with which none of my office force had any personal 
 acquaintance, and for this purpose, after considerable correspond- 
 ence, I secured the aid of Prof. Charles W. Woodworth, Assistant 
 Professor of Entomology at the University of California and Ento- 
 mologist of the California Agricultural Experiment Station. Pro- 
 fessor Woodworth being a graduate of the University of Illinois 
 was well known to me personally, and was particularly useful to 
 us because he had made a special study of fumigation operations 
 in California. He had, in fact, published an elaborate bulletin on 
 "Orchard Fumigation,"* which was the principal reliance of 
 economic entomologists interested, and remains to-day the best 
 brief practical treatise on the subject. 
 
 Arriving in May, 1899, he inspected parts of our infested dis- 
 tricts, planned our equipment and superintended its manufacture, 
 coached our first fumigating squad, and supervised its practice 
 work first on the Experiment Station farm, at Urbana, and later 
 on premises infested by the San Jose scale at Monticello, in 
 Piatt county. 
 
 Description of Equipment. Our tents to cover infested trees 
 and confine the insecticide gas liberated under them were all made 
 of eight-ounce canvas, treated in two different ways to make them 
 impermeable to the gas. The first lot were thoroughly sized with 
 flour paste and covered, when dry, with a thin black paint; and 
 the second lot were saturated with boiled linseed oil and left spread 
 out until dry. The latter method of preparation proved the more 
 satisfactory and durable. The paint was likely to wear and crack 
 
 * Bull. 122, Calif. Apr. Exper. Station. 
 
468 BULLETIN NO. 80. [October, 
 
 with use, and the sizing 1 and painting 1 were more laborious 
 and costly than filling 1 with oil. The latter operation was conve- 
 niently and rapidly performed (as shown in Plate I.) by the aid of a 
 common spray pump provided with an adjustable nozzle. Great 
 care was necessary that the oil in the tents should be thoroughly 
 dried out before they were folded, as otherwise they were liable to 
 heat, with the effect to destroy the cloth if not to set up spontane- 
 ous combustion. 
 
 The fumigation outfit consisted of forty-seven tents, three 
 pairs of lifting 1 poles, and several sets of generators for the prepa- 
 ration of the gas. All except the smallest tents were flat oblong 
 sheets of canvas, rounded at the corners and sewed with overlap- 
 ping double seams. Seven of these were SO X 60 feet in diameter, 
 ten were 40 X 48 feet, and twenty were 32 X 38 feet. There were 
 also ten conical tents eleven feet in diameter at the base, used for 
 the smallest trees. For lifting these tents into place there were 
 two 14-foot scantlings for the smaller sheet tents, two 20-foot lifts 
 made of 2 X 4 scantlings, spliced and reinforced, and two 30-foot 
 masts. Each pole when in use was fitted with a pulley, through 
 which ran a three-fourths inch rope, and was also provided with 
 from one to three guy-ropes with which to direct its motions as 
 the tents were being lifted and drawn into place. For trees twelve 
 feet in height, or less, one 14-foot pole was the most convenient 
 lift. For those between twelve and eighteen feet one 20-foot pole 
 was commonly used unless the top of the tree was unusually broad, 
 when two were necessary. For still larger trees the 30-foot masts 
 were used, one or both according to the size of the tree. 
 
 Description of the Operation. The method of handling the 
 tents and of liberating the gas was substantially the same as that 
 described and amply illustrated in Professor Woodworth's Bulletin 
 122, already referred to (pp. 20-30). Different phases and varia- 
 tions of the operation are illustrated in Plates II. VI. At- 
 tempts were made at first to fumigate very large trees, even when 
 two tents of the largest size were necessary, one being drawn over 
 the other so as to lap upon it several feet. (See Plate V.) 
 
 In ordinary work with one pole three men were required to 
 handle the tent, but when two poles were used a fourth man was 
 necessary. Two others were needed for the process of fumigation, 
 making a squad of six for the entire operation. 
 
 For peach- and apple-trees of medium size, that is, 12 to 18 
 feet in height with a spread of 8 to 15 feet, a squad of three men 
 with a single 20-foot lifting pole did the work most expeditiously. 
 The pole was leaned against the tree on the side opposite that 
 
1902.] THE SAN JOSE SCALE. 469 
 
 from which the tent was to be raised, and one end of the rope run- 
 ning- through the pulley at the top of the pole was thrown over the 
 center of the tree and made fast to the nearest edge of the tent. 
 The pole man then hauled the tent upward to the pulley, or at 
 least high enough to clear the tree, and fastened his rope, took the 
 guy-rope hanging- from the top of the pole, moved forward far 
 enough to get the necessary leverage and drew the tent over the 
 tree, the other two men of the squad, one at each side of the tent, 
 spreading it over the sides of the tree and adjusting- it to the top. 
 This operation is illustrated by Plate II., taken just as the men 
 have begun to pull the tent forward over the tree. After the tent 
 had been drawn forward far enough one tent man loosened the 
 pulley rope and let the pole fall, the pole man detached the rope 
 from the canvas and set the pole up at another tree, while the tent 
 men ran a binding rope about the tent below the tree top, drew it 
 closely, and tied the ends together. The borders of the tent were 
 then laid close to the ground, and weighted with earth if high 
 wind made this necessary, and the tent was carefully searched for 
 possible leaks. 
 
 The fumig-ator prepared the charg-e according to the formula 
 of the California Bulletin for winter treatment. He measured the 
 circumference of the tent at its largest diameter and estimated the 
 distance over the top from his knowledge of the length and width 
 of the tent in use. The "acid man" measured the required 
 amount of water and acid, poured them into the generator and held 
 up the border of the tent while the fumigator put the generator in 
 place near the trunk, charged it, and withdrew. He then quickly 
 dropped the tent, seeing that it lay close to the earth, permitting 
 no gas to escape. 
 
 The chemicals used were in the proportions indicated for a 
 .3% gas in the table on page 28 of the California Bulletin. From 
 the fact that the tent was usually drawn in below the head by a 
 rope while the measurement was made round the top of the tree at 
 its greatest diameter, the proportion of gas was in most cases con- 
 siderably stronger than .3%. After charging the tent with the 
 gas it was left to stand forty minutes, at the end of which time it 
 was taken down and moved to another tree. 
 
 Preliminary Operation at Monticello. Fumigation can be done 
 while the leaves are on the trees only at night or on dark and 
 cloudy days, and our first attempts being made in June (1899), the 
 work was done entirely at night. The infested place nearest to 
 my office and most convenient of access was Monticello, in Piatt 
 county, where the San Jose scale had been found on a few town 
 
470 BULLETIN NO. 80. [October, 
 
 lots containing 1 various species of fruit and ornamental trees and 
 shrubs. 
 
 A brief operation there demonstrated at once the impractica- 
 bility of satisfactory fumigation work on the miscellaneous stock 
 of an ordinary town lot. The trees infested were of various shapes 
 and size, some of them too large to be inclosed by a tent. Trees, 
 shrubs, and vines were often mingled in thicket-like masses which 
 could not be covered securely, and the various kinds of vegetation 
 which it was necessary to treat were variously sensitive to the 
 withering- action of the gas. 
 
 After one night's work of my field party on the grounds of a 
 prominent citizen I was summoned by telegraph both by the fore- 
 man of the fumigating squad and by the owner of the premises, 
 and experienced no small difficulty in re-establishing cordial relations 
 between the parties concerned. To do a thorough piece of work 
 some destruction of small shrubbery had been necessary, and the 
 leaves of several kinds of vines and shrubs were badly withered by 
 the g-as. 
 
 An inspection made the following year, April 14, 1900, showed 
 an unexpectedly favorable result. On one tree heavily coated with 
 scales many living specimens were found under a crust of the dead, 
 but elsewhere two hours' search disclosed but three living- scales. 
 The place had been temporarily saved from serious damage by the 
 scale, but at a cost exceeding the value of the rescued property, 
 and the failure to exterminate was evident. No attempt has since 
 been made by me to treat miscellaneous trees and shrubs on town 
 lots by the fumigation method. 
 
 The trees and shrubbery on twenty-one lots in this town all 
 on which the San Jose scale could be found were sprayed with a 
 twenty per cent, soap emulsion of kerosene April 10-19, 1900. 
 
 Orchard Fumigation at Sparta. A region of more than 
 twenty-five square miles about Sparta, in Randolph county, was 
 known by me to be generally infested with the San Jose scale in 
 the fall of 1899, this and the neighborhood of Richview, in an 
 adjoining county, being the most important infested districts 
 discovered in Illinois up to that time. After the completion 
 of the the annual nursery inspection of 1899, preparations were 
 made for a general campaign with the fumigation equipment in 
 this neighborhood, and my party took the field at Sparta Octo- 
 ber 18 under the charge of Mr. E. C- Green, with Mr. R. W. 
 Braucher as inspector. Here it continued actively at work for the 
 next two months, by which time it was evident that with the 
 appropriations available it was altogether impossible to treat the 
 
IQO2.] THE SAN JOSE SCALE. 471 
 
 infested premises of this region fully by the fumigation method, 
 and the party was transferred to Rich view, in Washing-ton county, 
 for work on another plan. 
 
 The Sparta district was mainly one of small farm orchards, of 
 which only here and there one had expanded in a way to make its 
 fruit an important part of the owner's crop. Many of the infest- 
 ed orchards were very old or contained some very old trees of a 
 size to make fumigation exceedingly difficult or to put it altogether 
 out of the question (Plate VII.). Taking- one orchard with 
 another, infested trees of every size were to be found, from those 
 recently set out to giant survivors of the plantings of the early pio- 
 neers. The owners had often neglected their trees until it seemed 
 a waste of public funds to attempt to save them when infested by 
 the San Jose scale ; but as the law gave me no power to condemn 
 a tree until its value was altogether gone, I was obliged to treat 
 such trees whether they were worth the cost of treatment or not. 
 Osage orange hedges had become extensively infested by the scale 
 in this district, in one instance at a distance of a quarter of a mile 
 from the nearest orchard. Thickets of escaped fruit trees were 
 growing beside the roads in fence corners, or by the borders of 
 woods, and these were often more or less infested, and as the 
 country still contained many remnants of its original forest cover- 
 ing there seemed a considerable probability that the scale was ob- 
 scurely distributed far and wide through this forest growth. 
 
 Notwithstanding the discouraging features of the situation 
 we made a serious attempt at fumigation here, which presently 
 took the form, however, of a preliminary operation to show what 
 was practicable by this method in such a place, and what must be 
 otherwise provided for. , 
 
 General Results. From our experience at this place it soon 
 became clear that local extermination of the scale was impractica- 
 ble by fumigation, or by a single operation of any kind, unless 
 power were given to destroy utterly everything infested which 
 could not be cleared of the scale at once ; that many of the trees 
 were too large to fumigate, and hence could be treated only with 
 a liquid spray ; that the fumigation process in such a region was 
 slow and extremely costly as compared with any other known ; and 
 that weather conditions often greatly diminished its efficiency by 
 making- it practically impossible to hold the gas under the tents at 
 full strength long enough to produce the desired effect. In very 
 windy weather no care in the management could prevent the rapid 
 escape of the gas, as was shown by the strong smell of it on the 
 leeward side of the tent and the absence of any such smell when 
 
472 BULLETIN NO. 80. [October, 
 
 the tree was uncovered ; and when the weather was very cold the 
 watery vapor from the generators condensed on the canvas and im- 
 mediately froze, lining- the tents with ice. In this condition they 
 were likely to break when folded in handling, and the brittle 
 branches of the tree breaking when the heavy tent was hauled 
 across the top, the tents were often torn by the jagged stubs. 
 
 Furthermore, it appeared from subsequent inspections that the 
 cases were few in which all the scales on a tree appeared to be 
 killed, and the frequency with which scales were found alive on the 
 lower part of the trunk, while all were seemingly dead on the re- 
 mainder of the tree, showed that the insecticide gas did not diffuse 
 equally under the tent, but tended to rise, leaving near the ground 
 a layer of insufficiently poisoned air. As this unequal diffusion of 
 the gas has since been demonstrated in closed rooms, a fact now 
 taken into account in the construction of fumigation houses, it is 
 evident that we have here a serious objection to the whole process 
 of orchard fumigation for the San Jose scale. We now know that 
 peculiar methods and special precautions are necessary to secure an 
 equal diffusion of the gas, even in the air-tight rooms used in nur- 
 sery fumigation, and with the varied conditions and rapid work of 
 orchard fumigation it is clearly impossible to secure a uniform 
 action even in the average case. 
 
 Details of the Work and its Results. The following items con- 
 cerning thirteen representative orchards fumigated at Sparta are 
 taken from the field reports of the foreman and inspector. 
 
 No. 1. On the place of Alvin Blair three hundred and ninety- 
 five trees, most of them peach, were fumigated from October 20 to- 
 November 4. They were of medium size except a few of the apple- 
 trees, which were very large, requiring the use of two of the 
 largest tents lapped together over one tree and tied down with 
 ropes. The peach-trees had been severely cut back the preced- 
 ing spring previous to spraying with whale-oil soap (see Plate 
 IX.), and the sharp stubs remaining punctured the tents, thus 
 making necessary constant inspection and frequent repair of leaks. 
 No doubt some gas escaped and some trees were imperfectly treat- 
 ed. A high wind was blowing when much of the work was done, 
 and great embarrassment was also caused by cold and rainy 
 weather, the tents tearing easily when wet and frozen. This 
 place was inspected September 10 of the following year (1900), 
 and badly infested peach-trees were found scattered through the 
 orchard, the wood of two years' growth sometimes almost incrusted. 
 In one row which was carefully examined the scale was found on 
 seventy-three per cent, of the trees. 
 
IQ02.] THE SAN JOSE SCALE. 473 
 
 No. 2. On J. W. Robinson's place one hundred and seventy- 
 seven trees, thirty-six grape-vines, and seven shrubs were fumi- 
 gated October 18-20. This place had also been sprayed with 
 whale-oil soap early in May of the same year to check the spread 
 of the scale. September 10, 1900, twenty-seven trees were inspect- 
 ed, and scales were found on twenty-one. Two of these were very 
 badly infested, but it was surmised that these had been left with- 
 out treatment on the promise of the owner to destroy them as 
 worthless. ^ 
 
 No. 3. The place of Mrs. J. B. Hayer was probably the one 
 first infested in this whole region, one orchard having- been com- 
 pletely destroyed by the owner because of injury by the scale. The 
 trees remaining were mainly apple and pear, most of them very 
 badly infested. One hundred and seventy trees were fumigated 
 here November 24-27, high winds causing- considerable trouble. 
 September 12 of the following year no badly infested trees were 
 seen, but living scales were found on thirty per cent, of the trees. 
 
 No. 4. On the place of Jefferson Porch both peach- and apple- 
 trees were badly infested. The fumigation squad was here from 
 November 28 to December 2, treating- eighty trees of medium size. 
 September 11 of the following- year living- scales were found on 
 fifty-three per cent, of the trees, but were numerous on none. 
 
 No. 5. On the place of J. K. Blair ninety-one peach-trees were 
 fumigated November 6 and 8, some of these badly infested and 
 others slig-htly so. Twenty-eig-ht large old apple- and peach-trees 
 were marked for removal. Those fumigated were planted so close 
 together that they could be treated only with great difficulty, and 
 the canvas was badly torn in the operation. The treatment proved, 
 however, to be unusually effective, and living- scales were found 
 September 8, 1900, on only two of the trees. A plum-tree badly 
 infested when fumigated appeared at this time to be entirely free 
 of living scales. 
 
 No. 6. In an orchard of several acres belonging to Sylvester 
 Brown most of the trees were infested, some of them badly so. 
 Many of them were large, requiring two of the largest tents to cover 
 them. Ninety-one trees were fumigated November 8-11, and 
 thirty-five were marked for removal, eight of them large old apple- 
 trees. September 10, 1900, but five infested trees could be found 
 in this orchard, and on one of the old apple-trees badly infested 
 the preceding year not a living scale could be detected. 
 
 No. 7. November 18-23, two hundred and twelve small to 
 medium trees were fumigated on Mr. James Davidson's place, a 
 few apple- and two pear-trees too large to be covered by tents be- 
 
474 BULLETIN NO. 80. [October, 
 
 ing left for the spraying- gang. September 11, 1900, living- scales 
 were found on four of these trees, but all the others were appar- 
 ently clean. 
 
 No. 8. November 23 and 24, twenty-three trees were fumi- 
 gated, together with a few grape-vines, on the place of Charles 
 Lott. Although a strong north wind made the handling of the 
 tents unusually difficult, no living- scales could be found on this 
 place September 11, 1900, except on one apple-tree left for removal 
 by the owner as worthless, but which he had failed to destroy. 
 
 No. 9. December 4, 1899, seventy small trees were fumigated 
 on William Wilson's place, thirty per cent, of which were found 
 infested by a few living- scales September 11 of the following- year. 
 
 No. 10. On Thomas H. Wilson's place a few trees were re- 
 ported infested in a six-acre orchard of apple and peach. One hun- 
 dred and twenty-six trees were fumigated here December 4 and 5, 
 and September 11 of the following year living scales were found 
 on ninety per cent, of them. The wind was troublesome at this 
 place, the canvas was stiff with ice and easily torn, and lumps of 
 frozen earth were dug up to hold the bottom of the tent in place. 
 
 No. 11. A thirty-five-acre orchard of Thomas Brown's, in 
 which a number of infested peach-trees were found along one side, 
 was treated December 7-16, 348 trees being fumigated here in all. 
 These ranged from six to twenty-five feet in height, the majority 
 requiring tents of medium size. On the 14th of December a moist 
 snow stopped the work, which was resumed the following day in 
 snow about a foot deep. September 12, 1900, a few scales were 
 found on five of the trees, but the others were seemingly clear. 
 
 No. 12. On the place of Frank Blair occupied by William 
 Blair was a badly infested young orchard and two infested hedges 
 near by. One hundred and eighty-five trees of medium size were 
 fumigated here November 11-15. September 8 of the following 
 year twenty-nine of these trees were critically examined, and six- 
 teen were found very slightly infested. The bases of the trunks of 
 some were, however, well stocked with living scales, and sprouts 
 growing up from near the base had thus become heavily infested. 
 
 No. 1?. On the place of James A. Wood sixty trees, some of 
 them badly infested, were fumigated December 6, and one was 
 cut down as worthless because of the scale. A few were very 
 large, requiring two of the largest tents to cover them. Septem- 
 ber 11, 1900, four of these trees were still badly infested, and thir- 
 ty-five per cent, of them showed more or less of the scale. 
 
 Orchard Fumigation at Richview. With the transfer from 
 Sparta to Richview the problem of local extermination was materi- 
 
1902.] THE SAN JOSE SCALE. 475 
 
 ally simplified. The latter town is in the midst of a typical fruit 
 district. The orchards are large and mainly well kept ; they are 
 comparatively young- and uniform and contain but few overgrown 
 trees ; the infested district was not hopelessly large ; and the sur- 
 roundings were not unfavorable to thorough work, the presence of 
 Osage orange hedges being the most unfavorable feature. 
 
 With the advantage of two months of active field experience 
 my party was prepared to do thorough and careful work at this 
 place, and the instructions were to spare no labor or pains to kill 
 every scale in every infested orchard. Hydrocyanic acid gas was 
 used for all trees to which it was adapted, but the attempt to 
 cover very large trees with tents was given up, such trees being 
 severely pruned and thoroughly sprayed with kerosene emulsion 
 diluted to contain twenty per cent, of the oil. (See Plate VIII.) 
 
 Great care was taken that the tents should be kept in perfect 
 repair, and every part of the work was carried on under the imme- 
 diate supervision of Mr. Green, foreman of the squad, or of Mr. 
 Braucher, the inspector. The treatment was applied thoroughly, 
 not only to all trees on which the scale could be found but to oth- 
 ers near enough to stand in any danger of infestation. Owners of 
 infested hedges were induced to destroy them (Plate IX.) ; trees 
 very badly infested were, as a rule, cut out and burned ; and, in 
 short, nothing was omitted which would help to make the work 
 effective and complete. 
 
 We had also at Richview the especial advantage of the coun- 
 tenance, aid, and influence of Mr. J. W. Stanton, Treasurer of the 
 State Horticultural Society, himself an owner of large fruit farms, 
 and a man whose character and experience made his judgment and 
 advice acceptable to his entire neighborhood. 
 
 The work here began December 22, 1899, and continued to 
 February 10, by which time all premises known to be infested had 
 been treated, with the exception of one large apple orchard so far 
 removed from any other fruit plantation that no danger was ap- 
 prehended of an escape of the scale from it to any other property. 
 A general inspection of this region was made after a lapse of two 
 years, in March, 1902, all the places previously infested being then 
 very carefully examined by Mr. R. W. Braucher, my most acute 
 and experienced inspector. 
 
 Details of the Richview Work. No. 1. The first place treated 
 at Richview was an orchard of apples and peaches on the James 
 Newcome Estate, owned at the time by J. W. Stanton and George 
 McCoy. 2,087 trees of small to medium size were treated by fumi- 
 gation between December 22 and January 4. On four of these 
 
476 BULLETIN NO. 80. [ October, 
 
 days December 29 and 30 and January 1 and 2 the weather was 
 extremely cold, and fires were kept burning- in the orchards to keep 
 the water from freezing-. The canvas was so stiff with ice that it 
 was easily torn, and it was difficult to bring- the skirts of the tent 
 so close to the ground as to prevent all leakag-e of g-as. When the 
 tents were removed from the trees, at the end of forty minutes, no 
 odor of the g-as was perceptible during- this coldest weather, al- 
 though at other times it was very distinct. This work was done 
 under the constant personal supervision of either Mr. Braucher or 
 Mr. Green. 
 
 March 6, 1902, many trees in this orchard were badly infest- 
 ed, and some of them were almost completely incrusted by the 
 scale. 
 
 No. 2. In the apple orchard of Levi Walker, a few trees along- 
 one side were found infested and also an adjoining Osage orange 
 hedg-e. This place was fumigated January 8 and 9, during a Jan- 
 uary thaw following upon two days of rain. January 8 mud and 
 water were ankle deep in that part of the orchard where the work 
 was done. The canvas became very heavy and five men were 
 needed to handle the tents. One hundred and thirty-five trees 
 were fumigated, ranging in height from twelve to twenty feet, 
 and the infested Osage orange hedge was cut out about a month 
 later.' Forty-seven rods of high and heavy hedge were cut away, 
 and the stumps were sprayed with strong kerosene emulsion. 
 
 March 7 to 12, 1902, this orchard and hedge were examined by 
 Mr. Braucher. An occasional tree was found slighly infested with 
 the scale in that part of the orchard fumigated two years before, 
 and the hedge, which had grown up from the roots, was again 
 badly infested. 
 
 No. 3. In a small orchard belonging to I. H. Jones forty-seven 
 trees were fumigated January 10-12. One old peach-tree was des- 
 troyed, and two plum-trees were subsequently sprayed with kero- 
 sene emulsion. March 15, 1902, three trees on this place were 
 found slightly infested with the scale. 
 
 No. 4. January 12, sixty apple- and pear-trees of medium size 
 and smaller were fumigated in a small infested orchard belonging 
 to Mr. James Ewing, many of them completely incrusted by the 
 scale. March 14, 1902, only three infested trees could be found on 
 this place, and the scale was scarce on these. 
 
 No. 5. In the orchard of George McCoy, composed of trees of 
 medium size or larger, were a few slightly infested trees. All 
 these were fumigated January 13, together with others around 
 them for several rows in all directions, one hundred and thirty- 
 
Ig02.] THE SAN JOSE SCALE. 477 
 
 eight trees in all. Owing- to the discovery of a single suspicious 
 scale on an adjoining Osage orange hedge a considerable section 
 of the hedge was destroyed February 10. March 6, 1902, the part 
 of this orchard treated two years before had again become slightly 
 infested, and the adjoining hedge was reported as in bad condition 
 from the presence of the scale. 
 
 No. 6. The orchard of Jasper Wilgus was generally and vari- 
 ously infested, many of the trees being in rather bad condition. 
 Two hundred and seventy-eight small to medium trees were fumi- 
 gated here on the 15th and 16th of January, two hundred peach- 
 and apple-trees were destroyed by the owner as worthless, and one 
 hundred and sixty-one trees too large to fumigate were sprayed 
 with twenty per cent, kerosene emulsion January 23-26. February 
 9, three rods of hedge infested by the scale were removed and des- 
 troyed. This place was inspected February 28 and March 14, 1902, 
 at which time some of the trees in that part of the orchard which 
 had been fumigated were again badly infested, as well as a consid- 
 erable length of the Osage orange hedge. On the large trees 
 which had been sprayed with kerosene, on the other hand, only a 
 few scales could be found. 
 
 No. 7. In a small orchard on a town lot belonging to William 
 Edwards forty-one trees were fumigated January 17, including sev- 
 eral reported as infested. March 1, 1902, the scale could be found 
 only on a single tree. 
 
 No. 8. In a small infested orchard belonging to Thomas Hoke 
 forty-six badly infested trees were fumigated January 10 to 20, and 
 fifteen were destroyed as worthless. March 1, 1902, thirty five of 
 the trees were re-examined, and thirty-two of them were generally 
 infested by the scale to an extent to require another treatment 
 without delay. 
 
 No. 9. January 27 one hundred and seventy-two peach- and 
 apple-trees were fumigated in an infested orchard belonging to 
 Mrs. E. A. Glenn, and eleven trees were sprayed with 20 per cent, 
 kerosene emulsion. According to a report of an inspection of 
 eighty-eight of the fumigated trees made February 28 and March 
 1, 1902, thirty-two of these were again infested to an extent to re- 
 quire speedy treatment as a protection to adjacent orchards in 
 which the scale had not been found. 
 
 No. 10. On J. Bennett's place fifteen trees were fumigated 
 January 17, and on February 2 one large apple-tree was sprayed 
 with kerosene emulsion. March 1, 1902, two small trees slightly 
 infested furnished the only remaining traces of the scale. 
 
 No. 11. One hundred and thirteen trees were fumigated Jan- 
 
478 BULLETIN NO. 80. \_October, 
 
 uary 20 and 22 in an infested orchard belonging- to W. H. Grove; 
 and February 2, sixty-seven trees additional were sprayed with a 
 twenty per cent, emulsion of kerosene. March 1, 1902, twenty-nine 
 of these orchard trees were found infested, and also a few peach 
 sprouts along- one side of the place. 
 
 No. 12. The pear and apple orchards of J. W. Stanton were 
 somewhat infested at this time, although they had been extensive- 
 ly treated with insecticide sprays since the first discovery of the 
 scale on his premises three years before. Seven hundred and sev- 
 enteen apple-trees in one corner of an infested orchard were futni- 
 g-ated January 22-25, and about thirty larg-e peach-trees were re- 
 moved. January 27-29 nine hundred dwarf pears were sprayed 
 with kerosene emulsion, a part of it containing- twenty per cent, of 
 kerosene, and the remainder, by mistake of an assistant, fifty per 
 cent. With this latter streng-th over one hundred trees were treat- 
 ed. Two years later, February 28 and March 4 and 5, 1902, all 
 these orchards were critically examined and only a few scattering- 
 scales were found. The trees treated with a fifty per cent, emul- 
 sion had not been injured in the least. It should be said that this 
 orchard was in excellent condition, its owner being- an experienced 
 and careful fruit grower, and everything- was consequently favora- 
 ble to effective work. 
 
 No. 13. January 25 and 26 thirty-five larg-e trees were fumi- 
 gated in an infested orchard of apple and peach belonging- to S. 
 Newcome. March 15, 1902, Inspector Braucher reported that 
 eighteen trees were slig-htly infested, but less so than two years 
 before. 
 
 No. 14. Nineteen trees were fumigated January 26 in an in- 
 fested apple orchard belonging to Edward Aplin, and some peach- 
 trees were destroyed at the owner's request. March 14, 1902, a few 
 slightly infested trees were found. 
 
 No. 15. January 26 nineteen trees were fumigated on Mrs. R. 
 R. S. Vasey's place, and February 6 one very large tree was spray- 
 ed with kerosene emulsion. March 14, 1902, three slightly infest- 
 ed trees were found by my inspector on these premises. 
 
 No. 16. On Dr. W. Smeaton's place, in charge of L. D. Allen, 
 sixty-seven trees, mostly peach and some of them badly infested, 
 were fumigated January 27. This place was inspected March 12, 
 1902, and a few trees found slightly infested. A hedge on the 
 place was now infested and required treatment. 
 
 No. 17. January 26 an infested tree on the place of Mrs. 
 Simeon Shinall was fumigated, but an inspection of it March 15, 
 1902, showed it to be slightly infested. 
 
1902.] THE SAN JOSE SCALE. 479 
 
 Comment on the above Results. The foregoing statements of 
 conditions found at Sparta and at Richview are not strictly com- 
 parable with each other because the inspection at Sparta was 
 made in September, 1900, eight or nine months after the insecticide 
 treatment, and that at Richview was made in February and 
 March, 1902. The Sparta region was inspected in the midst of the 
 first growing season after the trees were treated and before the 
 time of most rapid multiplication of the scale, which is usually 
 the month of October in southern Illinois, while the Richview 
 inspection was made after a lapse of two complete seasons of 
 growth and multiplication. 
 
 The best results of orchard fumigation obtained by my parties 
 are shown by the inspection reports on places 5, 6, 7, and 8 in the 
 Sparta district, and 3, 4, 7, and 12 at Richview. In the four 
 Sparta orchards, where 317 trees were sprayed in the fall of 1899, 
 the scale could be found on only 11 of them in September, 1900; 
 ami in the first three Richview orchards, where 148 trees were 
 treated, only seven proved to be infested two years later. At Sparta 
 Nc. 8 a close approximation seems to have been made to a complete 
 extermination of the scale and the same may be said of Richview 
 No. 7, and perhaps, also, of No. 12. 
 
 The most serious obstacle to work was that offered by cold 
 and freezing weather, as is shown especially by No. 10 at Sparta 
 and No. 1 at Richview, High winds were less disadvantageous 
 (see Nos. 3 and 8 of the Sparta district), and excellent results may 
 be obtained in spite of them, as shown especially by No. 8. Nei- 
 ther snow nor wet weather diminished noticeably the effectiveness 
 of the operation, as shown by No. 11 at Sparta and No. 2 at Rich- 
 view. It would appear from Sparta No. 6 that large trees can be 
 fumigated effectively by the use of two tents at once, overlapping 
 by their edges. 
 
 In none of the cases here described was even a single orchard 
 completely cleared of the scale, unless possibly at Sparta No. 7, 
 a fact which taken in connection with the costliness of fumigation 
 as compared with other equally if not more effective methods puts 
 it completely out of the field for ordinary orchard work in Illinois. 
 
 COST OF ORCHARD FUMIGATION. 
 
 The expenses of our work are divisible roughly into those for 
 exploration and inspection of the infested territory, for equipment, 
 for transportation of the outfit and party from place to place, for 
 supervision and general management, and for the operation of 
 fumigation itself. All except the last of these were so largely 
 
480 BULLETIN NO. 80. [October, 
 
 special to our undertaking- and so little like those of the ordinary 
 owner of an orchard that they would be of little or no practical in- 
 terest. For the great variety of trees on which we had to work in 
 fumigating- everything in an extensive district, we needed a 
 greater variety and a larg-er number of tents than would usually 
 be necessary in private work, and the cost of extensive inspection 
 and that of transportation would be avoided by the orchardist 
 working- only on his own premises. The expenses of actual futni- 
 g-ation, however, would be about the same ordinarily as in our 
 work, provided that the private owner had to hire all his labor but 
 made no charg-e for his own services, and this item of our account 
 will consequently be useful for comparison. It must be remem- 
 bered, as explained elsewhere, that the necessity we were under 
 to keep the party at work in g-ood weather and bad, whenever work 
 was at all possible, increased the averag-e cost of fumigation per 
 tree above what it would have been if our men could have been 
 laid by in bad weather without expense, or could have been other- 
 wise profitably employed. 
 
 At Sparta 2,297 trees were fumigated on seventeen different 
 premises an average of 135 trees at each place. 1,160 Ibs. of 
 cyanide of potassium and 290 gallons of common sulphuric acid 
 were used in this work, at a cost of $412; and 1,700 hours of labor 
 were required, at 10 cents an hour. The total expense was $582 
 an average of 25 cents a tree. 
 
 At Richview, where the trees were smaller and conditions were 
 more favorable generally, 3,879 trees were fumigated on seventeen 
 different places, an average of 228 trees on each. 994 Ibs. of cya- 
 nide of potassium and 248 gallons of sulphuric acid were used, at a 
 cost of $353; and the bill for labor was $113 for 1,130 hours an 
 average, all told, of 12 cents a tree. 
 
 Taking both places together, the cost of the mere fumigation of 
 6,176 trees was $1,048, or approximately 17 cents a tree. Compari- 
 sons of effectiveness and cost by this and other methods will be made 
 later in this article, after a detail and discussion of the results of 
 the use of the fluid insecticides. 
 
 TREATMENT WITH WHALE-OIL SOAP. 
 
 Our experience in the treatment of many thousand trees with 
 this well-known insecticide, prepared in the usual strength of two 
 pounds to the gallon of water, has merely served to confirm the 
 common conclusions with respect to it. It has proved to be very 
 efficient for the destruction of the scale, killing practically all 
 reached by it ; has done no injury to trees or shrubs ; but has 
 
1902.] THE SAN JOSE SCALE. 481 
 
 proven dangerous to the fruit buds of the peach unless applied in 
 spring 1 after the buds begin to swell. It is much the most expen- 
 sive of the sprays of which we have made use, costing at the rate 
 of $6.50 per hundred gallons, and has also been the most inconve- 
 nient of application in cold weather. This solution is only fluid 
 while warm, becoming of a semi-gelatinous consistency when 
 entirely cool, and if, owing to the clogging of the nozzle, 'it was 
 necessary to stop its flow for a little time, the delivery hose was 
 sure to clog and fill if the weather was much below freezing. Our 
 work was all done with potash soaps, but I have made no compar- 
 ative tests of these and soda soaps, and have failed to find any pub- 
 lished evidence in support of the very common preference of the 
 former as an insecticide. 
 
 EXPERIENCE WITH KEROSENE EMULSION. 
 
 The heavy cost of the whale-oil soap solution, the annoyance 
 and delay caused by its clogging in the delivery hose in very cold 
 weather, and the practical certainty that a large proportion, if not 
 all, of the fruit buds of peach-trees sprayed with it would be killed 
 except in the comparatively small number of cases where our treat- 
 ment could be applied in spring, led to the substitution for it dur- 
 ing the winter of 1899 and 1900 of an emulsion of kerosene diluted 
 with water and varying in actual practice to contain from 20 to 25 
 per cent, of kerosene. 
 
 Beginning at Sparta and Richview in January, 1900, its use 
 was continued through February and March at Carterville and 
 Albion, and at Monticello until April 19, by which time the season 
 was too far advanced to permit further use of this winter spray 
 without injury to the unfolding leaves. 5,315 trees were sprayed 
 with it in these places and at this time. November 8 of this same 
 year insecticide work was begun at Quincy, where a 25 per cent, 
 kerosene emulsion was used on one large and three small orchards 
 November 14 to December 19, and a 20 per cent, emulsion on an- 
 other at New Boston, in Mercer county, December 29-31. At 
 Barry, in Pike county, an apple orchard of 500 trees was sprayed 
 with it, partly as an experiment, January 7-14, 1901. The mix- 
 ture used there was in three different strengths, containing 20 per 
 cent., 25 per cent., and 40 per cent, of kerosene respectively. 
 
 The orchard insecticide work of the fall of 1901 began Novem- 
 ber 25, and at first a 25 per cent, emulsion of kerosene was used for 
 everything. December 9, however, instructions were issued to spray 
 all peach- and plum-trees with the so-called California wash of 
 lime, sulphur, and salt, and to use the kerosene emulsion for 
 
482 BULLETIN NO. 80. [October, 
 
 other trees only on sunny days, substituting whale-oil soap for it 
 whenever the weather was dark. Finally, on February 5, 1902, 
 my chief inspector, Mr. Green, was directed to stop the use of ker- 
 osene altogether, and to dispose of his stock on hand. This order 
 was made in consequence of a report by Mr. Braucher, then en- 
 gaged in inspecting orchards which had been treated by us in the 
 fall and winter of the preceding year, to the effect that apple-trees 
 had apparently been injured in November of that year in the New 
 Boston orchard mentioned above by a 20 per cent, emulsion applied 
 by Mr. Green. 
 
 Kerosene Emulsion at Richvieiu. The operations at Rich view 
 in 1900 fairly represent the cost and the results. One thousand 
 five hundred and thirty-five trees were treated at this place at an 
 expense of $17.65 for oil, $37.65 for labor at ten cents an hour, and 
 $16.73 for the hire of a horse a total of $72.03, or an average of 
 somewhat less than five cents a tree.* The results reported can- 
 not be readily summarized and are consequently given in detail for 
 several typical lots of trees. 
 
 No. 1. One hundred and fifteen apple-, pear-, and peach-trees, 
 most of them large and old, treated with 20 per cent, emulsion 
 January 26-29 and February 1, 1900, on the premises of Mr. G. T. 
 Hoke two town lots and an old orchard near by. October 8, 1900, 
 a few living scales were found on some of the peach-trees that had 
 been sprayed. March 11, 1902, the trees on the town lots were 
 slightly infested, and a few scales were found on some of the 
 orchard trees. 
 
 No. 2. Nine trees on a town lot belonging to Mr. K. Mark 
 were treated February 1, 1900. March 11, 1902, 5 of the 9 trees 
 were slightly infested. 
 
 No. 3. Twenty infested trees varying from medium to large 
 belonging to Mr. Charles Miller were sprayed February 1 and 2, 
 1900, and March 11, 1902, scales were found on only one of these 
 trees. 
 
 No. 4. Twelve badly infested peach-trees, small to medium 
 in size, sprayed February 3, 1900, were found generally infested, 
 but not heavily so, on March 22, 1902. 
 
 No. 5. Of 36 infested peach-trees belonging to Mr. John Gay r 
 treated February 23, 1900, 20 were found infested March 3, 1902. 
 
 *The average cost of spraying 5,710 trees, from January, 1000, to January, 
 1001, at five different localities was 4^ cents a tree. The premises treated were 
 mainly town lots, requiring frequent interruption of operations and consequently 
 increased expense. In three orchards near Barry 1,486 trees were sprayed,, 
 and at a cost of 3.2 cents per tree. 
 
IQ02.] THE SAN JOSE SCALE. 483 
 
 No. 6. February 3-6, 1900, 4 infested trees on a town lot be- 
 longing- to Mr. N. F. Tate, and a large pear-tree also infested on 
 another lot, were sprayed with 20 per cent, emulsion. A large apple- 
 tree was destroyed at this time as practically worthless from the 
 abundance of the scale. Two years later, March 13, 1 902, all 5 
 of the trees sprayed were slightly infested, as were also sprouts 
 from the root of the apple-tree destroyed. 
 
 No. 7. February 6, 1900, 12 orchard trees belonging- to Mr. 
 C. P. Cooper were sprayed, and March 12, 1902, two years later, the 
 scale was found on 2 of these trees. 
 
 No. 8. Three large peach-trees in an orchard of Mrs. M. A. 
 Robins were sprayed February 6, 1900, and March 17, 1902, two 
 years later, 2 of the 3 were slightly infested. 
 
 Similar data are given for seven other premises, all pointing to 
 the conclusion that trees were rarely cleared of the scale completely 
 by this insecticide spray, but that a single treatment would serve as 
 an efficient protection for at least two years. In several of these 
 cases another insecticide treatment would be necessary by the end 
 of another year at the farthest. No injury to trees of any kind 
 was done by this twenty per cent, emulsion distributed at Rich- 
 view in January and February of this year. 
 
 Experience at Carterville, Albion, and Monticello, Spring of 
 /poo. Beginning with March 5 and continuing to March 17, 2,272 
 trees, belonging to six owners, at Carterville were sprayed with a 
 twenty percent, emulsion with Mr. Green in charge. These trees 
 were of mixed kinds, mainly apple, but including also plum, pear, 
 and peach. Subsequent visits made in 1901 and 1902 showed that 
 no injury whatever was done to any of these trees. 
 
 At Albion 674 trees were treated, mostly peach but with some 
 apple, plum, and pear, all receiving a twenty per cent, emulsion 
 between March 23 and 29. These trees were scattered in small 
 lots upon twenty-four town premises. This place was repeatedly 
 visited by inspectors and spraying parties up to the winter of 1902, 
 and no trace of injury by the kerosene treatment was discovered. 
 
 Kssentially the same statement may be made with respect to 
 Monticello, where 843 fruit trees of various kinds, including apple, 
 peach, and plum, were sprayed on twenty-two premises from April 
 10 to 19, no appreciable injury following. 
 
 Experiment -with Kerosene Emulsion at Barry. The only 
 strict experiment with this spray made by us in the winter of 1901 
 was the last operation of the season that in the apple orchard of 
 Belah Wright, at Barry, Pike county. Five hundred trees were 
 treated here January 7-14, 150 of them with 20 per cent, emulsion, 
 
484 BULLETIN NO. 80. [October, 
 
 223 with a 25 per cent., and 127 at a strength of 40 per cent. Jan- 
 uary 7 and 8, when the 20 and 25 per cent, mixtures were applied, 
 the weather was cloudy and rather warm. January 9 a sleety rain 
 fell, covering- the trees with ice which continued until January 14, 
 when the 40 per cent, mixture was applied. This was a clear day 
 with no wind. 
 
 Regarding this as an experimental test of the effects of the 
 soap emulsion of kerosene, both on the scale and on the tree, I sent 
 Mr. Braucher for an inspection of this orchard October 2, 1901, be- 
 fore beginning the fall work of the season. A general view of the 
 orchard showed that the treatment as a whole had been very ef- 
 fective, but that more scales had survived in that section of the or- 
 chard treated with the 20 per cent, emulsion than in either of the 
 other two. Two trees were found, in fact, in this part which 
 were regarded as badly infested, and on several others scattering 
 scales were seen. None of the trees had been noticeably injured 
 even by the strongest spray, if exception be made of a small spot of 
 deadened bark on a single tree which might possibly have been 
 due to it. In the section treated with 40 per cent, of kerosene 
 scarcely a scale escaped, and even where 25 per cent, was used the 
 treatment was very effective. 
 
 At New Boston. December 22, 1900, in an orchard belonging 
 to W. Esley, near New Boston, in Mercer county, both apple- and 
 peach-trees were found generally infested, some of the former be- 
 ing practically incrusted. December 24-28 this orchard was 
 pruned and prepared for spraying by Mr. Green. December 29 
 and 31, 239 trees were treated with a 20 per cent, emulsion of kero- 
 sene, the 29th being very cold, clear, and bright, and the 31st cold 
 and dull. Part of the peach-trees were pruned as a preparation for 
 treatment and were then thoroughly sprayed, but another lot of 
 peaches, not known to be infested, were pruned slightly or not at 
 all previous to the insecticide spray. January 17, 1902, an inspec- 
 tion by Mr. Braucher showed that ten of the thirteen small peach- 
 trees which had been pruned were dead and another badly injured, 
 while the adjacent lot, not pruned, were not reported as injured at 
 all. Of the 75 young apple-trees generally and badly infested 
 which had been treated December 29, 20 were dead and 10 were 
 badly injured, and on 26 there were still small numbers of living 
 scales. Ten-year-old apple-trees sprayed December 31 were not in- 
 jured, neither were cherry, pear, and plum sprayed at the same time. 
 
 No explanation of this extraordinary occurrence can be sug- 
 gested. The oil, although bought locally, was said to be of the 
 same brand and grade as that used elsewhere without injury, and 
 
1002.] THE SAN JOSE SCALE. 485 
 
 the treatment was not peculiar in any discernible particular. On 
 this account, even more than if a satisfactory explanation were 
 forthcoming-, the occurrence suggested caution in the use of the 
 kerosene emulsion, and Mr. Braucher's report was followed at once, 
 as already stated, by orders to substitute whale-oil soap for the 
 emulsion in all our field work. 
 
 Kerosene Emulsion at Qumcy.Two other cases of apparent 
 injury to trees by kerosene emulsion occurred in the fall of 1900 at 
 Quincy. 
 
 No. 1. In an orchard mainly of peach-trees, belonging- to Mr. 
 Gustav Klarner, 7 trees were found October 3, 1900, infested with 
 the San Jose scale, and were destroyed with the owner's consent 
 November 8. Mr. Klarner wished to be sure that no scale re- 
 mained on his place, and in view of the probability that other trees 
 in the orchard were obscurely infested Mr. Green proceeded to 
 spray all the trees, 997 in number, near enough those infested to 
 endanger them in the least. After pruning them carefully as a 
 means of securing a thorough distribution of the spray, he began 
 the treatment November 14 with an emulsion containing- 23 per 
 cent, of kerosene. 
 
 The weather was unusually variable, but not cold at any time. 
 The first day of the operation was cloudy and dull, and the second, 
 November 15, was sunny and bright. Nothing was done on the 
 16th, 17th, 18th, or 20th because of rains, and only a little on the 
 19th, which was a damp and misty day. Spraying was resumed 
 on the 21st and continued until the 23d, the first two of these 
 days being bright and the last one dull. 
 
 There was nothing uncommon in this operation except that 
 the brand of oil, purchased in the local market, was different from 
 that ordinarily used by us elsewhere, and the emulsion was also a 
 little stronger than the usual 20 per cent. 
 
 This orchard was inspected by Mr. Braucher between January 
 20 and February 17, 1902, that is fifteen months after treatment, 
 but by this time extensive changes had been made in it by the 
 owner, who had replaced many trees said to have been injured or 
 killed, and had dug out a part of a large block, planting the ground 
 to raspberries. In the part still standing 324 trees were either 
 wanting or had been replaced by others the preceding spring. Mr. 
 Klarner himself estimated his loss at 700 peach-trees. 
 
 No. 2. On the premises of Wm. C. Burgdorf, near Quincy, 
 were scattered plots of mixed fruit-trees, pear, peach, cherry, and 
 apple, among which Mr. Green found November 10, 1900, trees 
 infested with the San Jose scale. Two small blocks of eighteen- 
 
486 BULLETIN NO. 80. [October, 
 
 year old peach-trees, 196 in all, were grubbed out by the owner of 
 his own accord between November 12 and 21, and 248 fruit trees re- 
 maining- were sprayed by Mr. Green with twenty-five per cent, kero- 
 sene emulsion November 30 and December 3. The weather was 
 bright, with little or no wind. February 18 and 19, 1902, Mr. 
 Braucher found that the trees treated in this orchard were either 
 killed or injured, the peach having- suffered worst. Injury to the 
 cherry is also especially mentioned. Four or five of these trees 
 had been grubbed out, and some others were nearly dead. The 
 San Jose scale was detected at this time on ten peach-trees, all 
 in one lot which had been sprayed by Mr. Green. 
 
 No. 3. On the place of August Burgdorf, at Quincy, was an 
 orchard of fifteen-year-old apple-trees which, because of its close 
 proximity to a badly infested tree belonging to a neighbor, Mr. 
 Green regarded as probably infested. Thirty-six of these trees 
 nearest the infested tree were sprayed by him with a 25 per cent, 
 emulsion December 4 a fair day with a light breeze together 
 with four other trees near by. February 18, 1902, this apple orchard 
 was found by Mr. Braucher uninjured and apparently free from 
 the scale, but two trees in an adjacent lot which had not been 
 sprayed were at this time slightly infested. 
 
 No. 4. On Mr. Henry Hoffmeister's place, near Quincy, H. O. 
 Woodworth found November 30, 1899, two apple-trees infested by 
 the San Jose scale, and in November, 1 900, Mr. Green reported 
 three apple-trees badly infested and several peach-trees slightly so. 
 These apple-trees and a few of the peach-trees were taken out by 
 the owner and all the remainder were pruned by him preparatory 
 to the application of the spray. In Mr. Green's judgment, as ex- 
 pressed at the time, this pruning was too severe and not according 
 to his instructions, which he had illustrated by the sample pruning 
 of a single tree. An emulsion containing twenty-six per cent, of 
 kerosene was used on this place by Mr. Green December 17 to 19, 
 the weather of the first day being dull and that of the other two 
 days bright and fair. February 15, 1902, the trees on this place 
 were in good condition according to Mr. Braucher's report, except 
 for some apparent injury by the spray. It was said, however, by 
 the tenant in charge that some of the trees sprayed had died and 
 had been taken out. 
 
 All the orchards on the two places just described were sprayed 
 with the same oil as that used on Mr. Klarner's place (No. 1), and 
 the general remarks made concerning that place apply also to these. 
 
Ig02.] THE SAN JOSE SCALE. 4&7 
 
 KEROSENE EMULSION. SEASON OF 1901-02. 
 
 The fact has already been mentioned that from November 25, 
 1901, to December 9 of the same year a soap emulsion containing 
 25 per cent, of kerosene was used by our spraying- parties on every- 
 thing treated by them, and that from December 9 to February 5 it 
 was applied to all trees but peach and plum, these being treated 
 with the California wash. At the latter date its use was wholly 
 abandoned and whale-oil soap was substituted for it, this and the 
 California wash being- the only insecticides applied during the re- 
 mainder of the season. 
 
 The emulsion was used within this period on 6,536 trees at 14 
 different places in central and southern Illinois. The larg-est use 
 of it was made at Makanda and Carterville, where it was applied 
 to 1,975 and 1,770 trees respectively. August 15 and 16, 1902, Mr. 
 Titus visited these two localities under instructions to look care- 
 fully into the condition of the trees which had been treated with 
 this kerosene spray, and according- to his report no damage had 
 been done at either place to trees of any description, while the 
 effect on the scale was very satisfactory. 
 
 January 6-9, 1902, about 700 trees belonging- to Dr. H. V. 
 Ferrell, of Carterville, mainly apple but some of them cherry and 
 pear, were treated with a 25 per cent, emulsion, and 130 trees, all 
 apple but one which was a pear tree were sprayed at the same 
 time on the place of Mr. J. W. Ghent. August 15, no injury from 
 spraying could be detected in these orchards, which bore a crop of 
 apples equal to the average crop of uninfested orchards in the 
 neighborhood. 
 
 At Makanda 450 trees belonging- to S. Y. Dickinson, mainly 
 apple with a few cherry and plum, received the same kerosene 
 treatment December 11-28, 1901. The apple orchard was on a 
 steep clay slope and appeared to have suffered considerably from 
 the drought of the preceding year, but there was no tangible evi- 
 dence Aug. 16 of any injury due to the insecticide treatment applied. 
 
 On the place of Lammer Brothers, about 225 apple- and pear- 
 trees were treated December 31 with a 25 per cent, emulsion, and 
 owing to some apprehension of injury on the part of the owners 
 this place was very thoroughly examined by Mr. Titus August 16. 
 The trees were absolutely uninjured, as were also 530 apple-trees 
 belonging to Mr. S. A. Carr, treated in the same way and exam- 
 ined at the same time. 
 
 Indeed the only injury done to trees by kerosene during the 
 winter of 1901-02 of which I have been able to learn, was that to 
 peaches on the place of Mr. Henry Archer, near Beamington, 
 
488 BULLETIN NO. 80. [October, 
 
 Sangamon county. A mixed orchard of 513 trees was sprayed 
 here November 29 to December 4 with a 23 per cent, emulsion of 
 kerosene. The orchard was variously composed of young- and old 
 trees, and included apple, pear, plum, peach, cherry and quince. 
 The young- trees sprayed peach, cherry, and pear were wholly 
 uninjured, but certain old peach-trees were, with few exceptions, 
 dead by July 12, when the place was inspected at -my direction by 
 one of my nursery inspectors, Dr. W. C. Bag-ley. From his report 
 it appears that the young- orchard above mentioned had been cul- 
 tivated the preceding- year, but that the old orchard in which the 
 dead peach-trees stood had received but little care, not having 
 been cultivated for several years, and that the trees of various 
 kinds remaining- in it, both those which had not been sprayed and 
 those which had survived the treatment, were in poor and un- 
 thrifty condition. The weather of the days during- which the old- 
 er peach-trees were sprayed was somewhat unfavorable, with fogs, 
 mists, and cloudy sky. No harm was done to apple or quince. A few 
 of the pear-trees had died after being- sprayed, but as the blig-ht was 
 prevalent on the place, their death was probably due to that disease. 
 An apple orchard belonging- to Mr. I. N. Lowe, near Auburn, in 
 Sang-amon county, sprayed with a 25 per cent, emulsion showed 
 no sign of injury on the 12th of the following- July, and a few 
 peach-trees on these premises treated in the same way and at the 
 same time were also unharmed. 
 
 FIELD USE OF THE LIME, SALT, AND SULPHUR WASH. 
 
 From December 9, 1901, to April 15, 1902, all peach-trees receiv- 
 ing- insecticide treatment by my field parties were sprayed with few 
 exceptions with a mixture of lime, sulphur, and salt, known as 
 the " California wash, " and as a matter of convenience in spray- 
 ing- mixed orchards, some trees of other kinds received the same 
 treatment. This wash was used on 433 different premises in 13 
 infested districts, but owing- to occasional deficiencies in detail in 
 operators' reports the total number of trees to which it was ap- 
 plied cannot be precisely given. Separate mention is made of its 
 use, however, on 4,976 peach-trees, 463 plum, 586 apple, 111 pear, 
 31 quince, and various other kinds sufficient to bring- the distin- 
 guishable total up to 9,000 trees. 
 
 During- this period of four months of southern Illinois winter, 
 the weather was, of course, widely various. The season was, as a 
 whole, rather unusually favorable to insecticide work, but rains, 
 sleets, snows, and freezing weather came frequently enough to test 
 
1902.] THE SAN JOSE SCALE. 4&> 
 
 quite fully the general effect of the weather on the efficiency of the 
 insecticide. Although no exact account of the results over all the 
 great area treated can now be given, a general statement may be 
 made that the effect has been excellent and entirely satisfactory so 
 far as I now can judge. 
 
 To secure an exact basis for a general judgment of the out- 
 come I sent Mr. Titus in August, 1902, to examine orchards 
 treated with this wash the previous winter and spring, and I have 
 his report of the results of an inspection of 25 orchards in four dif- 
 ferent localities, Summerfield, Makanda, Albion, and Browns, 
 and of many town lots at the first and last of these places. Al- 
 though these localities inspected formed but a small part of the 
 number treated, they constitute a larger and more varied experi- 
 ment with this wash than has hitherto been attempted anywhere 
 east of the Pacific region, and a report of results will no doubt be 
 appreciated at this time. 
 
 Formulas for the California wash have varied considerably in 
 the literature of the subject, and as it is possible that conflicting 
 statements concerning its value may be due in part to these varia- 
 tions in composition, the following description of the wash used 
 during the winter in Illinois will have its value in this connection. 
 The mixture was made as follows : Fifteen pounds of stone lime 
 were slaked in a kettle over a fire ; fifteen pounds of sulphur were 
 sifted or stirred in as the lime was slaking, these materials being 
 boiled vigorously until the lime and sulphur were entirely dissolved 
 usually something over an hour ; and fifteen pounds of salt were 
 then put in and the whole was boiled a quarter of an hour longer. 
 Enough hot water was added to make fifty gallons, and the mix- 
 ture was sprayed while warm through a nozzle with a large cap 
 for a coarse spray. When the material first dried on the tree it 
 gave the bark a saffron-yellow color, which changed in twenty- 
 four hours to a dull green and then gradually faded to a greenish 
 gray. 
 
 The California Wash at Summerjield. No. 1. One hundred 
 and forty-five peach-, plum-, and pear-trees sprayed on the place of 
 Wm. Hagemann between March 29 and April 2. Practically all of 
 these trees were badly infested with the scale. On the 29th of 
 March the weather was clear at first, with the temperature rang- 
 ing from 48 to 66 degrees, but a hard rain fell in the afternoon 
 with a light northwest wind. From March 31 to April 2 the 
 weather was continuously cloudy but there was no rain; the wind, 
 northwest and west, from brisk to high; and the temperature ranged 
 from 36 to 62 degrees. 
 
4QO BULLETIN NO. 8o. [October, 
 
 August 16 several peach- and pear-trees were examined on this 
 place and one thousand scales were carefully examined, pains be- 
 ing- taken, as in all other cases on this trip, to select the scales 
 from all parts of the tree. Not a living scale was found on this 
 place. 
 
 No. 2. Twenty-three slightly infested peach-trees sprayed 
 March 22 and 24 in the orchard of Messrs. B. and A. Baer. The 
 weather was clear on the first of these days but cloudy the second, 
 the temperature ranging from 42 to 72 degrees. August 16 no 
 living scales could be found. 
 
 No. 3. Twenty-four badly infested peach-trees belonging to 
 Mrs. Mary Reibold treated the 15th and 18th of March, the first 
 day cloudy throughout with a temperature ranging from 54 to 62 
 degrees, the wind at first south, changing to northwest at four 
 o'clock, rain from noon onward. March 18, clear all day and cool, 
 temperature from 20 to 34 degrees, with light wind. August 20, no 
 living scale to be found. 
 
 No. 4. Eighty peach- and plum-trees on the premises of 
 Daniel Krehbiel sprayed March 6-8 and 14-15. The weather was 
 cloudy on all these days, and rain began on the afternoon of the 
 last. Three thousand specimens of the scale examined August 20 
 and but two found alive, both partly grown. They had evidently 
 come from an infested hedge in close proximity. 
 
 No. 5. On several town lots belonging to Mr. John Eicher 17 
 trees were sprayed with lime, sulphur, and salt March 10, and 
 August 20 no living scales could be found. 
 
 No. 6. Forty trees were sprayed, a part of them with lime, 
 sulphur, and salt, on the town property of Thomas Keith March 
 10. August 20 no living scale could be found. 
 
 The California Wash at Makanda. No. 1. On the place of 
 
 Mr. S. A. Carr, near Makanda, 457 peach-trees were sprayed with 
 
 lime, sulphur, and salt late in December, beginning with the 24th. 
 
 The weather was very bad cold, with much sleet. August 16 
 
 living scale could be found on these trees. 
 
 No. 2. On the place of Mr. S. Y. Dickerson, 1,743 trees treated 
 with lime, sulphur, and salt at intervals throughout the season 
 from January 2 to March 10 appeared wholly free from living scale 
 August 16. In addition to a general inspection of these trees 2, 000 
 scales were critically examined and none found alive. 
 
 No. 3. Thirty-three peach-trees were treated December 31 
 with the California wash in the orchard of Lammer Brothers, near 
 Makanda, the weather being clear and the temperature about 40 
 
IQ02.] THE SAN JOSE SCALE. 49! 
 
 degrees. August 16 no scales were found alive in this orchard 
 where, besides a general inspection, 2,000 were examined critically. 
 
 No. 4. On the place of J. W. and J. E. Herrn 140 peach- and 
 plum-trees sprayed with the California wash March 19 and 20, 
 weather partly cloudy but without rain, thermometer 40 to 50 de- 
 grees. August 16 no living scale could be found. 
 
 No. 5. In the orchard of J. S. Springer about 190 peach- and 
 plum-trees sprayed with lime, sulphur, and salt at various dates 
 in January, February, and March. Four thousand scales critically 
 examined by Mr. Titus August 16, but none found alive. 
 
 No. 6. One hundred and sixty-two peach-trees and seven 
 plums treated March 24 to April 4 on the premises of W. H. Lipe. 
 Sky cloudy throughout but no rain. No living scales found August 
 16 by general inspection or on a critical examination of 500 speci- 
 mens. 
 
 All the orchards treated by my parties in this section were 
 found in fine condition, although some of the worst infested trees 
 had been lately attacked by the bark-borer, Scolytus rugulosusa.n 
 occurrence to be attributed to the diminished vitality of the trees 
 due to the San Jose scale. 
 
 The California Wash at Albion. No. 1. One hundred and 
 fifty-seven peach-trees treated with lime, sulphur, and salt in the 
 orchard of Hodgson Brothers, near Albion, April 5-15, the weather 
 clear throughout. The buds were unfolding at this time, and the 
 work was suspended at the latest date on account of the appear- 
 ance of the leaves. August 21 the peach-trees sprayed were in- 
 spected, but no living scale could be found. Of a thousand scales 
 examined none were alive. 
 
 No. 2. In the orchard of Mr. F. A. Kenyon 225 medium-sized 
 peach-trees were sprayed March 18 to April 2. Two thousand 
 specimens examined August 21 and two of them alive. No other 
 living scales seen in this orchard. 
 
 No. 3. On the town lots of Anna C. Ferriman 23 peach-trees 
 and 4 plums were sprayed April 7 and 8, the weather being fair. 
 August 21 no living scale was found. 
 
 No. 4. On the town lots of Samuel Churchill (administrator) 
 37 peach-trees and 12 plums were sprayed April 5 and 7, the 
 weather clear except for rain beginning at 3 o'clock p. m. on the 
 5th. Five hundred scales critically examined August 21 and no 
 living ones found. 
 
 The California Wash at Browns. No. 1. Three hundred and 
 five peach-trees sprayed February 10-14 on the place of Atkinson 
 Taylor, the weather being variable, with snow all day on the 10th 
 
492 BULLETIN NO. 80. [October, 
 
 and on the evening- of the llth. Four thousand scales examined 
 August 21 and 22 on the peach-trees sprayed and none found alive. 
 
 No. 2. In the orchard of George Briggs 22 peach-trees treat- 
 d with lime, sulphur, and salt February 1-5, the weather cloudy 
 throughout. One thousand scales examined August 21 and none 
 found alive. 
 
 No. 3. Eighty-nine peach-, apple-, pear-, and plum-trees, but 
 -mainly the first, sprayed with lime, sulphur, and salt February 25 
 to March 4. These trees were very large and badly infested. The 
 weather was clear throughout except on the 4th, which was cloudy 
 without rain. Aug. 22 no living scales could be found on the peach. 
 
 No. 4. Thirteen peach-trees sprayed with lime, sulphur, and 
 salt on the town lot of Mary E. Marriott February 6, the weather 
 being- clear. Five hundred scales examined and three found alive. 
 These were armored specimens, the only ones found alive at this 
 place, although several town premises besides those mentioned 
 above were carefully inspected. 
 
 3,931 trees in all had been sprayed with the California wash by 
 my field parties on the premises inspected by Mr. Titus in August. 
 Besides making- a careful general examination of these trees and 
 finding- no living- scales he critically scrutinized, one by one, 21,500 
 individuals and found but seven of them alive. There were no 
 crawling- young-, and none of these living- scales had reached the 
 age of reproduction. 
 
 GENERAL SUMMARY. 
 
 Four insecticides have been, extensively used as winter ap- 
 plications for the San Jose scale in our general orchard work of the 
 past three years in Illinois; hydrocyanic acid gas, whale-oil soap, 
 kerosene emulsion, and the California wash of lime, sulphur, and 
 salt, the first being applied by fumigation and the others as liquid 
 sprays. 
 
 All are efficient destroyers of the scale under favorable con- 
 ditions, but the operation of fumigation is practically restricted 
 to comparatively small trees and to comparatively mild and quiet 
 weather. The California wash has an evident advantage in per- 
 sistence of effect, which amounts to an appreciable protection of 
 the tree against immediate reinfestation. 
 
 These four insecticides differ materially in safety, in cost, and 
 in convenience of application. Fumigation with hydrocyanic acid 
 gas and spraying with the California wash are perfectly safe to 
 all trees and shrubs if applied after the old leaves have fallen and 
 before the young leaves have put forth ; whale-oil soap is likely 
 
I9O2.] THE SAN JOSE SCALE. 493 
 
 to destroy the fruit buds of the peach if used before these have be- 
 gun to swell in spring; and the kerosene emulsion in strength suf- 
 ficient to insure the destruction of the scale is uncertain in its ac- 
 tion on the more delicate kinds of trees, the peach especially, 
 and on those of any kind which are in poor condition. Serious in- 
 jury has occasionally been done to the peach, and in one case to 
 apple, by an emulsion containing only 20 per cent, of kerosene, 
 which is rather below the minimum strength at which this mix- 
 ture should be used for the destruction of the scale. A twenty- 
 five per cent, emulsion, on the other hand, is usually harmless to 
 the apple and pear, but has proved in our work to be highly 
 dangerous to the peach. 
 
 The cost of insecticide treatment includes the expense of the 
 original equipment, that of the materials consumed, and that of the 
 preparation and application of the insecticide. In respect to cost 
 of equipment fumigation is by far the most expensive, especially 
 if the trees to be treated are large, but the three insecticide sprays 
 are prepared and applied by the aid of practically the same appa- 
 ratus. 
 
 The cost of preparation and application is not materially dif- 
 ferent for the four insecticides under discussion, and will at any 
 rate vary greatly in practice according to individual circumstances. 
 With respect to cost of materials, the fumigation process is 
 much the most expensive. At Rich view, where the trees treated 
 were usually of medium size or less, the cost was nine cents a tree 
 for fumigation materials, while at Sparta, where the trees averaged 
 much larger, this cost was eighteen cents a tree. At the latter place 
 whale-oil soap, although applied only to the largest trees as a rule, 
 was used at a cost of seven cents a tree for the soap itself. At 
 Carterville and Browns the average cost of lime, salt, and sulphur 
 for the California wash was two to three cents, according to the 
 size of the trees, while the general average per tree for kerosene 
 emulsion as applied to over 5,000 trees was two cents each. 
 
 In convenience of application the preference belongs clearly to 
 the kerosene emulsion and the California wash, the use of whale- 
 oil soap being frequently embarrassed in very cold weather by the 
 solidifying 1 of the solution in the hose if the flow is stopped, and 
 the operation of fumigation being a laborious and complicated one 
 for trees above medium size. 
 
 It follows from the foregoing that of these various insecticide 
 methods and materials the best for common use against the San 
 Jose scale is spraying in winter with the California wash. 
 
494 
 
 BULLETIN NO. 80. 
 
 [ October, 
 
IQ02.J 
 
 THE SAN JOSE SCALE. 
 
 495 
 
496 
 
 BULLETIN NO. 80. 
 
 [October, 
 
1903.] 
 
 THE SAN JOSE SCALE. 
 
 497 
 
498 
 
 BULLETIN NO. 80. 
 
 [ October, 
 
1902.] 
 
 THE SAN JOSE SCALE. 
 
 499 
 
BULLETIN NO. 80. 
 
 PLATE VII. 
 
 L October, 
 
 PEAR-TREE THIRTY-FIVE FEET HIGH INFESTED BY SAN JOSE SCALE, NEAR SPARTA, ILL. 
 
IQ02.] 
 
 THE SAN JOSE SCALE. 
 
 501 
 
502 
 
 BULLETIN NO. 80. 
 
 [October, 
 
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