THE UNIVERSITY OF ILLINOIS LIBRARY Cop NOnce: Return or renew all Library Materials! The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for discipli- nary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN 5 L161 O-1096 FURTHER STUDIES ON ZINC SULFATE IN PEACH SPRAYS WITH LIMITED TESTS IN APPLE SPRAYS By K. J. KADOW and H. W. ANDERSON UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION Bulletin 424 CONTENTS PAGE LABORATORY STUDIES 132 FIELD STUDIES WITH PEACH TREES 134 FIELD STUDIES WITH APPLE TREES 136 SUMMARY AND CONCLUSIONS 138 LITERATURE CITED 140 Urbana, Illinois July, Publications in the Bulletin series report the results of investigations made by or sponsored by the Experiment Station Further Studies on Zinc Sulfate in Peach Sprays, With Limited Tests in Apple Sprays K. J. KADOW and H. W. ANDERSON" INTRODUCTION and recommendation of zinc sulfate as an ingredient in peach sprays by Roberts and Pierce 12 * in 1929 "^ was one of the most important recent contributions to the peach- growing industry. Until this chemical was added to peach spray mix- tures, acid lead arsenate and hydrated lime, with or without sulfur, were the standard materials for peach sprays. Acid lead arsenate, however, often caused severe injury to trees and fruit, altho the seriousness of the injury had not been really appreciated until the work of Haensler and Martin 4 * was published in 1925. Zinc sulfate in peach sprays serves to reduce this injury. When zinc sulfate was first recommended as an ingredient for peach sprays, its value in reducing spray injury was not fully realized. It was considered primarily a bactericide, fungicide, and plant stimu- lant. Contributions to a better understanding of the value of zinc sulfate in spray combinations have been made by Roberts et a/, 12 ' 20 * Poole, 10 ' lx * Anderson, 2 * Anderson and Thornberry, 3 * Hurt, 3 ' 6 * Adams, 1 * Rudolph, 21 * Kadow, 7 * and Kadow and Anderson. 8 - 9 * It now appears certain that the "corrective effect" of zinc sulfate on lead arsenate - lime injury is the principal reason for including it in peach sprays. In some sections of the United States, and in certain other parts of the world, zinc has proved very satisfactory as a remedy for some physiological diseases, none of which have been identified as yet in this state. Apparently Illinois soils have sufficient available zinc to permit proper plant development. Consequently in this state the only justification for commercial applications of zinc sulfate in peach sprays is to reduce the amount of lead arsenate injury. As soon as it became apparent that zinc sulfate was of considerable value in reducing lead arsenate - lime injury to the peach, growers "K. J. KADOW, Associate Pathologist, Department of Horticulture, and H. W. ANDERSON, Chief in Pomological Pathology. The authors wish to acknowledge the advice given by W. A. Ruth, Chief in Pomological Physiology, on certain chemical aspects of this study, and the help of W. P. Flint, Chief Entomologist, M. D. Farrar, Research Entomologist, and S. C. Chandler, Field Entomologist, of the Illinois State Natural History Survey, on entomological phases of the problem. *These numbers refer to literature citations on page 140. 131 132 BULLETIN No. 424 began using zinc in their sprays in varying amounts, usually at the rate of 8-8-100, as originally recommended. In the meantime the authors of the present bulletin began experiments to determine more exactly the amount of zinc necessary to prevent spray injury. The results of these studies, together with data on limited tests of zinc sulfate as an ingredient in apple sprays, are presented in this bulletin. LABORATORY STUDIES The chemical aspects of this problem were reviewed in detail by the present investigators in a recent discussion 8 * of the relation of ZnSO 4 7H 2 O to spray injury, and therefore will not be reconsidered in this paper. Among the chemical relations there reviewed, the im- portant facts to remember in connection with the present discussion are: (1) that under conditions of high temperature and high hu- midity the Ca(OH) 2 added to PbHAsO 4 to prevent the formation of water-soluble arsenic quickly carbonates; and (2) that the Ca(OH) 2 after it has carbonated actually increases instead of reduces water- soluble arsenic. In the laboratory studies reported below CaCO 3 or Ca(OH) 2 was used along with PbHAsO 4 at a constant ratio of 6 pounds and 3 pounds respectively in 100 gallons of water. Various amounts of ZnSO 4 7H 2 O ranging from 6 pounds to }4 pound in 100 gallons of water were added. The PbHAsO 4 , ZnSO 4 7H 2 O and Ca(OH) 2 were well-known commercial brands, while the CaCO 3 was a "C.P." product. Thruout this experiment ordinary tap water was used, for it was determined at the beginning of the study that the results when tap water was used were about the same as when distilled water was used. The analyses for water-soluble arsenic were made by the Gutzeit method 22 * and are expressed as the percentage of water-soluble As 2 O 5 present in the PbHAsO 4 used. In general the technic employed was as follows: The materials were weighed, mixed with water, placed in closed con- tainers on a shaking machine, and analyzed for water-soluble arsenic after various periods of shaking. Fifty-cc. samples of some of the mixtures thus prepared were spread in thin films over glass plates. The plates were allowed to dry at room temperature. After they were completely dry they were held in a constant temperature-humidity case* in a saturated atmos- "Funds for equipping this case were provided by a grant in aid of re- search to the junior author by the American Association for the Advancement of Science. FURTHER STUDIES ON ZINC SULFATE IN SPRAYS 133 phere at 85 F. After ten days the material was carefully washed off the plates and filtered, and the filtrate was analyzed for water-soluble arsenic. In determining the amount of ZnSO 4 7H 2 O necessary to reduce water- soluble arsenic in the mixtures, CaCO 3 was used instead of Ca(OH) 2 in order to eliminate the necessity of carbonating the Ca(OH) 2 and also to insure the presence of a uniform carbonate radical as well as a uniform pH value of the mixture. The results of these studies are shown in Table 1. The data there given represent an average of two completely duplicated series. Under the conditions of the experiment, 14 pound of ZnSO 4 7H 2 O added to mixtures of PbHAsO 4 and CaCO 3 was as effective as larger amounts in reducing water-soluble arsenic. TABLE 1. WATER-SOLUBLE ARSENIC IN SPRAY MIXTURES (Laboratory studies) Chemical material in mixtures* (pounds of 100 gallons of water) Held in suspension with constant mixing Exposure to air on glass plates after mixing Water-soluble AsjOs based on PbHAsO4 PbH\sO 4 . 3 Ibs. hours 1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 1 2 1 2 1 2 days io io io io 10 perct. .320 .540 .110 .930 .070 Trace 1.340 1.680 .040 .042 .054 .048 .049 .048 .051 .048 .046 .042 .045 .042 .042 .040 PbHAsO4 . . . 3 Ibs. \ Ca(OH)j 6 Ibs./ PbHAsO* . . . 3 Ibs. 1 Ca(OH)i 6 Ibs. \ ZnSO4-7H s O. 6 Ibs. j Lead arsenate Calcium carbc PbHAsO4. 3 Ibs. \ nate 6 Ibs. J . . 3 Ibs. ) CaCO 3 6 Ibs. ! ZnSO4-7HzO. 6 Ibs. ] PbHAsO4 . . . . 3 Ibs. 1 CaCOs 6 Ibs. \ ZnSO4-7HzO. 4 Ibs. j PbHAsO 4 . . . . 3 Ibs. 1 CaCOs ... . 6 Ibs \ ZnSO4-7HjO. 2 Ibs. j PbHAsO4. . . . 3 Ibs. 1 CaCOs 6 Ibs. > ZnSO4-7H 2 O. 1 lb. J PbHAsO4. . . . 3 Ibs. 1 CaCOs 6 Ibs. \ ZnSO4-7H 8 O % lb J PbHAsO4 . . . . 3 Ibs. 1 CaCOs 6 Ibs \ ZnSO4-7H 2 O. J^ lb. J PbHAsO 4 . . 3 Ibs. 1 CaCOs 6 Ibs. > ZnSO4-7HjO. X lb. J "The CaCOa used in this series was a chemically pure product of the Grasselli Chemical Company, other materials were ordinary commercial products. Tap water was used thruout. The experi- t was Hur>liratvl anrt th results listed above are averages of the two series. ment was duplicated, an 134 BULLETIN No. 424 FIELD STUDIES WITH PEACH TREES Unfortunately the field studies concerning the use of zinc sulfate in peach sprays were practically complete before the laboratory experi- ment described above was conducted ; consequently they were not planned in the light of the foregoing data. One pound in 100 gallons of spray was the smallest amount of ZnSO 4 7H 2 O used under field conditions, and therefore no information can be given as to whether one- fourth pound would be as effective in the field as it was in the laboratory. Except for the 1935 studies, the field experiments with the peach were planned for reasons other than to determine the minimum amount of zinc sulfate necessary to eliminate spray injury. Fortun- ately, however, much of the data secured since 1932 has a direct bear- ing upon this point. The studies were conducted in four different localities within the state. The spray schedules applied are given on pages 141 to 143. Hale and Elberta trees, all of bearing age, were used. In examining the data from these experiments (Table 2) it must be borne in mind that comparisons should not be made between separate experiments (that is, experiments in different orchards) nor between results in different years. The orchards varied considerably in soil type and tree vigor, and these variations of course had some effect upon the results. Likewise, the weather, which has a very important bearing upon spray injury, varied widely from orchard to orchard and from year to year. The importance of weather in relation to spray injury is clearly reflected in the data from the Urbana tests for 1934 and 1935. The 1935 season was the most favorable one for spray-injury studies of this nature that has occurred in Illinois for several years. The 1934 season was about average. The varying amounts of lead arsenate used constituted another important source of variation between tests. Thus, in order to gain an idea of the effects of zinc sulfate in re- ducing spray injury, comparisons must be made within a given test. Six such comparisons may be made from Table 2. The plots which are comparable are grouped together. No significant difference in the amount of spray injury on compa- rable plots in which varying amounts of zinc sulfate were used is ap- parent from these data (Table 2). One plot in the 1932 Carbondale experiment gave results that were entirely out of line with all other results. This particular plot was on very poor hilly soil where the trees were less vigorous than on other plots, and these conditions may explain the high percentage of injury which occurred. FURTHER STUDIES ON ZINC SULFATE IN SPRAYS 135 Location and year of experiment, with comments C. J. Thomas orchard, Carbondale, 1932. Trees in excellent vigor. Good, well-drained soil. C. J. Thomas orchard, Carbondale, 1932. Trees in moderate vigor. Fair soil, well drained. Land quite hilly. (fThis plot was on extra-poor hilly ground.) E. C. Riechman orchard, Irvinglon, 1933. Trees in poor vigor. Soil well drained and low in fertility. (*Number of drops under 10 trees selected at random; not figured in percent of fruit in- jured. ttAverage of two records taken at different times.) U. of I. orchard, Urbana, 1934. Trees moderate vigor. Good soil well drained. U. of I. orchard, Urbana, 1935. Trees moderate vigor. Good soil, well drained. Peach scab in the check plot of Hale was 28 percent; Elberta 5 percent; all other plots free. (**A11 fruit examined drops included in percent of injured fruit.) U. of I. orchard, Olney, 1935. Trees in excellent vigor. Soil poor, good surface drainage. (The zinc sulfate used in this test was of the formula ZnSO< 1 HzO, and in addition to the materials listed 6 pounds of Kolofog were added to each plot.) j ,; * 3 "c" c fe :::::: 222 ' 1 '?*H 1 :::: gggg f 88888888888 ::::: : B 5 --'" - - ->- "rt^- ^ XS "5 <5 - - >0 10 i5 -i- *0 0^0 ** 2^22" oowocoo a^-./> e*::'' ESS 2 5 ?$-"" -~~-3 1 1 - T3 ; cu d; ^g^sssss; SSSSS 3.^0 sssss ssssssssssss aa-s-s ^1 (NCS(NfNtStSr)fS ^ M ^ ^^ _OJ rtrtrtcs rtrt 5rt 5 rt ; 2 ;j : IIIIIIII Illll S35S Si3Si3w SEWEWESESESE (3SS33S 1 u s.. 1 D|| % f 5 rt .s '3 00^00^^*00^*0 SliiS Hit tiiii i i i S i i iiiiii 136 BULLETIN No. 424 The serious injury in the Urbana plots in 1935 (Table 2) brought out the fact that altho zinc sulfate is very effective in preventing lead arsenate injury to the peach in a normal season, considerable spray injury is likely to result, even tho zinc sulfate is used in the spray mixture, if weather conditions are especially conducive to injury. Frequent light showers, heavy night dews, and high humidity acceler- ate spray injury. FIELD STUDIES WITH APPLE TREES Fruit growers who have observed the beneficial results of zinc sulfate in peach sprays have requested investigations of the possible usefulness of this material in the apple spray program. When in con- sequence this experiment was undertaken, it was recognized that in- formation on the fungicidal value of zinc sulfate in relation to apple scab (Venturia inaequalis (Cke.) Wint.) might be secured while ob- taining data on spray injury. And, inasmuch as no information on whether or not the addition of zinc sulfate to lead-lime sprays affects the insecticidal value of the sprays had been secured from the peach spray experiments, it was hoped that such information could be obtained from observations on control of codling moths in this experiment. The experiment was conducted on Ben Davis apples in the com- mercial orchard at the University farm, Urbana. There were two trees in each plot except the check, which had one tree only. The studies were planned on a small scale with the intention of enlarging the plots another season if the results the first year justified such action. The spray schedule followed is given on page 144. Apple scab was first observed in the check plot on May 14. This was the correct time for the calyx spray, which was applied on May 15. Sprays were applied at intervals of ten days to two weeks there- after. Codling moth injury was first observed in the plots July 4. Both apple scab and codling moth were thus unusually late in appearing. Soon after their appearance, however, heavy infestations were evident in the entire orchard. Furthermore, cold, wet weather prevailed during the spring, a condition that was ideal for the study of injury from those spray ma- terials which require water to liberate the injurious chemicals. Con- sidering the small size of the plots in this study, therefore, the results were much better and much more conclusive than was expected. The results on the control of apple scab and codling moth, along with comments on spray injury, are given in Table 3. Zinc sulfate and lime (Plots 3 and 4) was decidedly inferior to FURTHER STUDIES ON ZINC SULFATE IN SPRAYS 137 - I SB W pq i ~C. i I ^ S \-a E 3 & 2 \^ i ^, 1 ^j * "5 ^^ c 11 Q rt 1 v o W a o V C & 5 E >J c c .- 03 W >J O > TL o u f cd i-' *o V ^ ,2 t> a V C It 5 M &> C9 c ^* -i C 00 OJ > o **" _- "*" "irt V m 1 1 U^ P >? X S 1 < I 1 r^ 3 2 v c 3 >> a \ 1 ( 1 1 heck plot 5/14/, leaves and fruit z = 3 J3 9 ae | "5 condition. Fru o. u a o u 8 tS ondition. Fruit u c'o = 2 J a 1 c 3 | o'c 4> 0> U rt a " a n n c C V c Scab first appe About 95 pe Heavy defoliati Light defoliatii severe. Tree condition 1 i i H o '> 11 u 3 O Z X *2 V M H 1 fc X M rs ^ o -o fN 10 3 H . 'c .c bo 1 c W t ^ Q. 2 2 ^ 00 2 ^ M n 1 >, U a ! S (N 1 ! S 3 S 10 o - - 2 3 '? g j! * u-. | CN X) j S *0 O CM 1 V W 3 ^1 i" 5.S o s gj * * z^ cd : x V i d 1 Z (M <^ ^ ./> VO t. 138 BULLETIN No. 424 copper sulfate and lime (Plot 5) or flotation sulfur (Plot 6) in the control of apple scab. Judging from this limited experiment zinc sulfate cannot be relied upon as a fungicide in an apple schedule. The effect of zinc sulfate upon arsenical injury to the apple foliage could not be determined in this experiment because of the leaf injury which occurred in Plots 2, 3, and 4 from apple scab. Undoubtedly both zinc sulfate and copper sulfate are efficient in reducing arsenical injury, but zinc sulfate is of no practical value as a fungicide. At harvest some very good data were secured on spray injury to the fruit. In all plots which received either copper sulfate or zinc sulfate sprays, the fruit was severely russeted. No russet was evident in Plot 6 until the fungicide was changed from flotation sulfur to copper sulfate in anticipation of hot, dry weather. But the weather remained cool and wet, and moderate russet resulted. Generally speaking, it is quite safe to use bordeaux after the application of the second cover spray, but in wet seasons considerable russet may result from later application, as was the case in 1935. This tendency is especially noticeable when russet-susceptible varieties are involved. Apparently zinc sulfate causes as severe russet to susceptible varieties as does copper sulfate. The effect of zinc sulfate upon the insecticidal value of lead arsenate should not be considered conclusively measured in the limited data presented here ; but, such as they are, these results indicate that the addition of zinc sulfate to lead arsenate - lime oil sprays has little effect upon the control of codling moth. Additional data are needed before this point can be definitely settled. The results obtained in this connection from the bordeaux plots were inconsistent. SUMMARY AND CONCLUSIONS The data presented in this paper terminate the Illinois study of zinc sulfate as an ingredient in peach and apple sprays. The following conclusions, drawn from seven years of experimental work on this problem, include also the salient points brought out in the former reports of this study. 1. Zinc sulfate has been found especially valuable in reducing peach spray injury resulting from applications of acid lead arsenate and lime. Applications of acid lead arsenate and lime should never be made to the peach as a spray under Illinois field conditions without adding zinc sulfate (Bui. 414 8 *). Hydrated lime added to acid lead arsenate to prevent the formation of water-soluble arsenic quickly carbonates under conditions of high temperature and humidity, and after carbonating actually increases water-soluble arsenic. The carbon FURTHER STUDIES ON ZINC SULFATE IN SPRAYS 139 dioxid of the air is the chief source for the carbonation of the lime (Bui. 414 8 *). 2. Small amounts of zinc sulfate appear to be equally as efficient as larger amounts in reducing water-soluble arsenic in peach sprays that consist of acid lead arsenate and hydrated lime or of mixtures of acid lead arsenate and calcium carbonate. One pound in 100 gallons of water, with 3 pounds of acid lead arsenate and 3 pounds of hydrated lime, is apparently sufficient to reduce spray injury effectively under average field conditions. 3. When zinc sulfate was used in apple sprays at concentrations of 8 pounds to 100 gallons of water with acid lead arsenate and lime, severe russet resulted to Ben Davis apples. Russet also resulted from 4- to 5-pound applications of copper sulfate in bordeaux. The influence on apples of small amounts of zinc sulfate was not determined. 4. Studies of the effect of zinc sulfate on the insecticidal value of lead arsenate and lime, conducted over a period of seven years, have not been conclusive. The limited data secured on codling moth control indicate that zinc sulfate has no marked influence in so far as this insect is concerned. The fact that oil was added to the sprays in this test may have had a bearing upon the results obtained. 5. On the basis of these studies zinc sulfate is not recommended as a fungicide in peach or apple sprays. In laboratory studies it proved much more toxic to apple scab (Venturia inaequalis (Cke.) Wint.) than to brown rot (Sclerotinia fructicola (Wint.) Rehm.). Under field conditions, however, it proved only 65 percent effective in the control of apple scab. No significant data have been secured from field studies on zinc sulfate in the control of brown rot, but laboratory tests indicate very little value for zinc sulfate in this capacity. Data presented in Bui. 414 8 * indicate that zinc sulfate does not improve the fungicidal value of lead arsenate and lime in the control of peach scab (Cladosporium carpophilum Thum). Two or three lead arsenate - lime sprays for the control of curculio with or without zinc sulfate are usually sufficient to control peach scab in Illinois. 6. According to the results of the Illinois study, zinc sulfate is not an effective bactericide for the control of bacterial spot (Phytomonas pruni (E.F.S.) Bergey et al) on peach and therefore is not recom- mended for use in this connection (Bui. 414 8 *). 7. Zinc sulfate has not been observed to impart any "stimulating effect" to the peach under Illinois field conditions, altho certain physi- ological diseases have been corrected by it in other parts of the country. Physiological studies indicate that soluble zinc is necessary 140 BULLETIN No. 424 for the proper development of many plants, including the peach (Bui. 414 8 *). LITERATURE CITED 1. ADAMS, J. F. Peach defoliation in relation to the zinc-lime spray in combi- nation with certain sulphur sprays. Del. State Bd. Agr. Bui. 22, 113-120. 1932. 2. ANDERSON, H. W. Problems on spray injury to the peach. 111. State Hort. Soc. Trans. 65, 454-468. 1931. 3. and THORNBERRY, H. H. Peach spraying experiments for brown rot and bacterial spot control. 111. State Hort. Soc. Trans. 63, 129-137. 1929. 4. HAENSLER, C. M., and MARTIN, W. H. Arsenical injury of the peach. Phytopathology 15, 321-331. 1925. 5. HURT, R. H. Zinc lime spray and its importance as a peach spray and tar oil distillates as dormant spray materials for fruit trees. Va. State Hort. Soc. Rpt. 20, 94-104. 1932. 6. Zinc and copper spray materials for peaches and apples. Va. State Hort. Soc. Rpt. 21, 55-64. 1933. 7. KADOW, K. J. Zinc sulfate as a fungicide and bactericide, together with its effect on peach growth and on peach spray injury. 111. State Hort. Soc. Trans. 68, 240-257. 1934. 8. and ANDERSON, H. W. The role of zinc sulfate in peach sprays. 111. Agr. Exp. Sta. Bui. 414. 1935. 9. . Zinc sulfate in peach and apple sprays. 111. State Hort. Soc. Trans. 69, 246-253. 1935. 10. POOLE, R. F. A study of the control of the bacterial spot of peaches and the nearly similar canker and spot caused by arsenate injury and their control. N.C. Agr. Exp. Sta. Ann. Rpt. 54, 76-79, 1931. 11. - - Arsenical injury of the peach and some results of studies on its control. Amer. Soc. Hort. Sci. Proc. 29, 42-44. 1932. 12. ROBERTS, J. W., and PIERCE, LESLIE. A promising spray for the control of peach bacterial spot. Phytopathology 19, 106-107. 1929. 13. - - Controlling peach bacterial spot. Hoosier Hort. 11, 6-12. 1929. 14. Control of peach bacterial spot. Md. Agr. Soc. Rpt. 13 (1928), 153-159. 1929. 15. - Control of peach bacterial spot. Peninsula Hort. Soc. (Del.) Trans. 42, 102-106. 1929. 16. Zinc-lime: A fungicide for the peach. Phytopath- ology 22, 415-427. 1932. 17. and DUNEGAN, J. C. Control of peach bacterial spot. 111. State Hort. Soc. Trans. 63, 423-426. 1929. 18. - Control of peach bacterial spot. Ga. State Hort. Soc. Proc. 53, 32-35. 1929. 19. - Control of peach bacterial spot. Md. Agr. Soc. Rpt. 14 (1929), 221-226. 1930. 20. - - Control of peach bacterial spot. Amer. Fruit Grower Mag. 50, 10-11. 1930. 21. RUDOLPH, B. A. Bacteriosis (blight) of the English walnut in California and its control. Cal. Agr. Exp. Sta. Bui. 564. 1933. 22. SKINNER, W. W. et al. Official and tentative methods of analysis of the association of official agriculture chemists, pp. 306-309 3d ed. Assoc. Off. Agr. Chem. Washington, D.C. 1930. FURTHER STUDIES ON ZINC SULFATE IN SPRAYS 141 o X X X X OO oo ts O *r> O O ^> O 00 CNl/i c t 3 NN NN NN NN NN J J J J < N < N Jfc s fe I 3 2 2 2 2 ei 00 t>r oo ^ ^ S IS 2* u u - 3 142 BULLETIN No. 424 SPRAY SCHEDULE No. 2. PEACH EXPERIMENTS AT E. C. RIECHMAN ORCHARD, IRVINGTON, ILLINOIS, 1933 a Early-season sprays applied PW S t ' 1 pd Shuck 2d 3d 4th 5th 1 Absolute check no sprays or dusts 2 Lead-lime 3-6-100 X X X X X 3 Lead-lime-zinc 3-8-8-100 X X X X X 4 Lead-lime-zinc 3-8-4-100 X X X X Sprays were applied at intervals of about two weeks. Orchard rather low in vigor, with general infections of peach scab and bacterial spot. All trees in the experiment were Elbertas. SPRAY SCHEDULE No. 3. PEACH EXPERIMENTS AT UNIVERSITY ORCHARD, URBANA, ILLINOIS, 1934* Plot Spray materials used Early-season sprays applied Shuck 2d 3d 4th 5th 1 Absolute check no sprays or dusts Lead-lime 3-6-100 Lead-lime-zinc 3-4-4-100 Lead-lime-zinc 3-6-6-100 X X X X X X X X X X X X X X X X 2 3 4 5 Lead-lime-zinc 3-8-8-100 Sprays were applied at intervals of two weeks. Orchard in moderate vigor. All trees in the experiment were Elbertas. FURTHER STUDIES ON ZINC SULFATE IN SPRAYS 143 SPRAY SCHEDULE No. 4. PEACH EXPERIMENTS AT UNIVERSITY ORCHARD, URBANA, ILLINOIS, 1935 a Early-season sprays applied Plrtt S r mat ri Is nspd Shuck 2d 3d 4th 5th 1 Absolute check no sprays or dusts 2 Lead-lime 3-6-100 X X X 3 Lead-lime-zinc 3-6-2-100 X X X 4 Lead-lime-zinc 3-6-4-100 X X X 5 Lead-lime-zinc 3-6-6-100 X x 6 Lead-lime-zinc 3-8-8-100 X X X 'Sprays were applied at intervals of about two weeks. Orchard in moderate vigor. Trees in the experiment were Elberta and Hale varieties. SPRAY SCHEDULE No. 5. PEACH EXPERIMENTS AT UNIVERSITY ORCHARD, OLNEY, ILLINOIS, 1935 s Plot Spray materials used Early-season sprays applied Shuck 2d 3d 4th 5th 1 Absolute check no sprays or dusts Lead-lime 2-4-1001 X X X X X X X X X X X X X X X 2 3 Kolofog 6-100/ " Lead-lime-zinc 2-4-1-1001 Kolofog 6-100/'" Lead-lime-zinc 2-4-2-1001 Kolofog 6-100/'" Lead-lime-zinc 2-4-3-1001 Kolofog 6-lOOf" Lead-lime-zinc 2-4-4-1001 Kolofog 6-1 OO/'" 4 5 6 'Sprays were applied at intervals of about two weeks. Trees in excellent vigor. All trees in this experiment were Elberta. The zinc sulfate used in this study was of the formula ZnSOi-lHjO instead of the ZnSO4-7HjO used in all the other spray tests. 80507-369928 144 BULLETIN No. 424 z > " o 3 * 58 a SS S - * ..' ..- ..!) . . 4) o rt ' -o ,; -of.:' c' Q ' is S B 1 " a^, WTf I ' ! ' ' I u !li-' I '. - ;. ;. ;. . . v . . v . . v no TJ^.I -a* 1 ,; a*' 01 ti s 9 1 o 4)a 1 ||| 1|| || IE gEg- JJ JJN JJN JJU JJU JJO ^00 tS 00 00 >C OC X <*! X 1/3 f:oC>C rOXlO JN JJN .-2-Jcfl JJU JN o a S& n 4) 3 JN E? a) ft S9 . JJU .& JU