THE UNIVERSITY OF ILLINOIS LIBRARY A6RIGDLTURAL. LIBRARY UNIVERSITY OF ILLINOIS Agricultural Experiment Station BULLETIN NO. 222 FIELD EXPERIMENTS IN SPRAYING APPLE ORCHARDS FOR THE CONTROL OF APPLE BLOTCH BY A. J. GUNDEKSON CONTENTS OF BULLETIN No. 222 PAGE INTRODUCTION 551 Objects 551 Location and Description of Orchard 551 Apparatus and Preparation of Materials 552 Method of Eecording Results 552 Weather Conditions as Affecting Blotch 553 EXPERIMENTS IN 1916 553 Relative Values of Bordeaux and Lime Sulfur 553 Value of Different Applications of Bordeaux and Lime Sulfur 555 Effect of Interchanging Bordeaux and Lime Sulfur 559 Summary of Results for 1916 560 Incidental Observations 561 EXPERIMENTS IN. 1917 561 Effect of Dormant Applications of Copper Sulfate, Scalecide, Lime Sul- fur, and Lime-Sulfur Copper-Sulf ate Mixture 563 Relative Values of Bordeaux and Lime Sulfur 563 Value of Different Applications of Bordeaux and Lime Sulfur 565 Affect of the Addition of Arsenate of Lead to Lime Sulfur 568 Relative Merits of Dusting and Liquid Spraying. 568 Summary of Results for 1917 570 Incidental Observations 570 EXPERIMENTS IN 1918 571 Relative Values of Bordeaux and Lime Sulfur 571 Value of Different Applications of Bordeaux and Lime Sulfur 573 Summary of Results for 1918 573 Incidental Observations 573 RECOMMENDATIONS FOR THE CONTROL OF APPLE BLOTCH. . . .575 FIELD EXPERIMENTS IN SPRAYING APPLE ORCHARDS FOR THE CONTROL OF APPLE BLOTCH BY A. J. GUNDERSON, ASSOCIATE IN POMOLOGY INTRODUCTION Apple blotch is the most destructive fungous disease of apple orchards in southern Illinois and during the past few seasons obser- vations have disclosed its presence in certain apple orchards of central and western Illinois. There is no question but that blotch is spread- ing northward but it is doubtful if the orchards of northern Illinois will ever become seriously infected. Damage caused by apple blotch is two-fold, consisting in injury to the fruit in the form of spotting, which reduces its commercial value, and in canker infection of small limbs, twigs, and fruit spurs, which reduces the productiveness of the trees. Infection of the wood is actually killing hundreds of Duchess apple trees in southern Illi- nois and in a large measure is responsible for the weakened and un- productive condition of hundreds of Ben Davis .and Gano trees in the southern counties of the state. In view of such conditions it was considered important that meth- ods of spraying for the control of apple blotch be tested. OBJECTS Spraying experiments on the control of apple blotch were carried on during the years 1916, 1917, and 1918 at Flora. The chief objects of these investigations were to study the following points in the con- trol of blotch: (1) the relative values of Bordeaux and lime sulfur; (2) the value of different applications of Bordeaux and lime sulfur; (3) the effect of interchanging Bordeaux and lime sulfur; (4) the effect of dormant applications of copper sulfate, Scalecide, lime sulfur, and a combination of lime sulfur and copper sulfate; (5) the effect of the addition of arsenate of lead to lime sulfur; and (6) the rela- tive values of dusting and spraying. LOCATION AND DESCRIPTION OF ORCHARD Experiments were conducted in the Suggett orchard, located about one and one-half miles southeast of Flora. The orchard consisted of thirty-eight acres of eighteen-year-old Ben Davis. At the beginning 551 552 BULLETIN No. 222 [September, of the work in 1916 the trees were in very poor condition, owing to lack of nutrition, diseases, and the fact that no spraying or pruning had been done for years. The result was that every tree in the orchard was seriously infected with apple blotch, cankers appearing on twigs, water sprouts, and fruit spurs. Bitter-rot and black-rot cankers were also present to some extent. The tops of the trees were very dense and contained considerable dead wood. In laying out the experiments, the orchard was divided into plats containing four trees each, except in the case of the dusted plat, which contained twenty-six trees. A check, or unsprayed, row was left thru the entire length of the orchard. APPARATUS AND PREPARATION OF MATERIALS Whenever Bordeaux was used in these treatments it was made ac- cording to the following formula: 6 pounds of copper sulfate and 8 pounds of lime in 100 gallons of water. For dormant spraying, copper sulfate was used at the rate of 8 pounds in 100 gallons of water; commercial lime sulfur at the rate of 11 gallons in 100 gallons of water; Scalecide at the rate of 6 gallons in 100 gallons of water ; and lime-sulfur and copper-sulf ate mixture at the rate of 11 gallons of commercial lime sulfur and 8 pounds of copper sulfate in 100 gallons of water. For summer spraying commercial sulfur was used at the rate of 2,1/2 gallons in 100 gallons of water. Powdered arsenate of lead was used at the rate of 2 pounds in 100 gallons of water. The dust mixture used was composed of 85 percent superfine sulfur and 15 percent powdered arsenate of lead. During 1916 all sprays were applied with a Hardie No. 32 hand outfit, at about 125 pounds pressure. In 1917 and 1918, a triplex Bean sprayer was used with pressure ranging from 175 to 250 pounds. During 1916 and 1917, rods and disc nozzles were used in spraying the trees, while in 1918 spraying was done from the ground with a Bean spray gun, and from the tower with rod and disc nozzles. Severe lime-sulfur injury to foliage due to drenching with the spray gun resulted in discontinuing its use after the first three summer sprays had been applied. The dust was applied by means of a dusting machine of small type driven by a 11/2 horse-power engine. METHOD OF EECORDING RESULTS Records were kept thruout the season on the appearance of the foliage with regard to fungi, insects, spray injury, and vigor. At harvest time two representative trees from each sprayed plat were picked and all the apples placed on a sorting table and counted. From these, two hundred apples were chosen at random and carefully 1919] SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH 553 examined. The fruit from three representative unsprayed trees, one at each end and one in the center of the check row, was similarly handled, and the results averaged. WEATHER CONDITIONS AS AFFECTING BLOTCH Weather conditions affect the development of most fungous dis- eases. Differences of opinion exist, however, as to what conditions are most favorable to blotch development. Scott and Rorer claim that blotch develops in cool or warm weather, but that rains or heavy dews are necessary to the germination of the spores and their spread from cankers to the fruit. Lewis states that blotch develops equally well in either dry or wet weather, but says nothing about the effect of rain upon spore dissemination. During 1916 and 1918 frequent showers occurred at Flora during the period from four to six weeks after the fall of the bloom. In these years blotch infection on unsprayed trees was 93.24 and 94.0 percent respectively. During the same period in 19l7, little rain fell and blotch infection on unsprayed trees was 75.5 percent. Certain com- mercial orchards in southern Illinois appeared to have less blotch on the fruit in 1917 than in 1916 and 1918. During the period from four to six weeks after the fall of the bloom in 1916, 1917, and 1918, the temperature at Flora averaged between 65 and 70 degrees. The amount and frequency of the rainfall, therefore, appeared to be the factor which caused greater dissemination of spores and offered excel- lent conditions for their growth. During the season of 1918 frequent rains prevented a good deal of spraying in commercial orchards in central and southern ^Illinois, with the result that there was unusual opportunity for Hotch infec- tion and the disease actually proved very serious. Then, too, such rains rendered the sprays that were applied less effective. EXPERIMENTS IN 1916 Experiments in 1916 were conducted with reference to: (1) the relative values of Bordeaux and lime sulfur as sprays for blotch; (2) the value of different applications of Bordeaux and lime sulfur as sprays for blotch; and (3) the effect on blotch control of inter- changing Bordeaux and lime sulfur. RELATIVE VALUES OF BORDEAUX AND LIME SULFUR Spraying investigations, previously conducted, both in Illinois, and in other states, had shown Bordeaux to be from slightly to consid- 554 BULLETIN No. 222 [September, S .5° O t- O CO O O i-J O 04 O 04' r-i e co 1 pq to 3 O §00 O i-l O O O in O £ •C 0 CO T-H OQ 00 as o w s g^ 01 03 03 tuo •s I co IO GO O> O4 CO b- i—l i— 1 t- b- CO iH O O4 i— 1 Tt< 04 •* 04 O4 jf-5"^ OJ w QJ ^ C* Percent M erious t-; T); 04 00 ITS i— 1 ^•g ^ 0 =H .-H 1=3 o 02 'H^^ 3 I CO 34 CD ' 00 •* b- r-J O CO 04 B J> fti fi aj i p > 5 oi 04' CD' co co i— 1 TjH i-l b- O5 03 P*- W < H P l| f- - « CO iH -^ . C4 OO CO CO •* CO I-l .. „ -* < J G TJH in to E •it 'e H CO CO CO CO S .2 KM ^ ^ 03 Is - 0 •^ CO CO CO CO ^r s rH f~i i~H ^H C4 03* _ CO "3 o3 * o3 o3 * o3 J S 'pj rS "Is " o «H ® «H Treatm H -4-J. ^ P -4-3 C 03 e8 03 03 03 03 £ g 2 2 g 2 03 nj 03 w ro 03 +3 ft *w CH ^ B "9 9 || | || | || ..*.. 2 Jl b- rH CO C4 03 r-l O3 CO H 1919] SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH 555 erably more effective than lime sulfur in the control of blotch.1 Such results, however, could not be considered complete. The fact that lime sulfur in some cases had given good results, altho not equal to those from Bordeaux, made further comparative tests of these materials advisable. Then, too, the injurious effect of Bordeaux upon the fruit, following applications against blotch in southern Illinois orchards, emphasized the need of an effective substitute. As a further test of the relative values of Bordeaux and lime sul- fur as sprays for blotch on Ben Davis in southern Illinois, the plats were sprayed with these materials as shown in Table 1. The data presented show that Bordeaux was decidedly superior to lime sulfur in the control of blotch. In Plat 7, where Bordeaux was applied three, five, seven and ten weeks after the fall of the petals, there was 12.73 percent blotch, as compared with 42.12 percent blotch on Plat 11, which was sprayed with lime sulfur at the same periods. A similar comparison is presented between Plat 6, which was sprayed with Bordeaux three, five, and ten weeks after the fall of the petals, resulting in 16.06 percent blotch, and Plat 12, which was sprayed with lime sulfur at these three periods, and showed 73.68 percent blotch. The unsprayed row showed 93.24 percent blotch. Very usual differences between the effect of the two sprays upon the fruit is shown in the russet column. Plats 11 and 12, which were sprayed with lime sulfur, alone, show about the same percentage of russet as the unsprayed row. It may be concluded, therefore, that something other than the spray russetted the fruit. As regards Plats 6 and 7, which were sprayed with Bordeaux three and four times, respectively, it will be noted, after subtracting the amount of russet on the unsprayed row, that the Bordeaux caused a good deal of russet. Plats 11 and 12 show a small percentage of lime-sulfur burn. This developed a few days following the application of lime sulfur arsen- ate of lead made in mid-July, when the temperature was extremely high. It occurred on the fruit which had received too much spray and was therefore confined to scattered areas of the trees. Scott and Korer found, from investigations carried on in Arkan- sas during 1907. that the principal blotch infection on apples occurred from four to six weeks after the fall of the petals, and that scattering infections continued to take place thruout the season.2 They recom- 1U. S. Dept. Agr. Bur. Plant Indus. Circ. 54, p. 13. 1910. Kans. Agr. Exp. Sta. Bui. 196. 1913. 111. Agr. Exp. Sta. Bui. 185, p. 111. 1916. 2U. S. Dept. Agr. Bur. Plant Indus. Bui. 144, p. 21. 1909. 556 BULLETIN No. 222 [September, !_| 1 w 000*00000 rH S 02 M 3 m 0 eo OOOOOOOO (M (M PH i •rH rH O 00 §M EH rQ 4) P •( rrH. PI *~3 r»> 03 ro 1 - ,?'3Hl a i ri <» 1 03 SSSS^^^S 111 H be CO OH cc o P^ H M 03 *Q r— 1 *H W § P ICOrHrHt-jCJJt-jW •— i 'S ° S E 'C Oq O I— 1 rH *H r-H pjT PM 03 OJ Ktj i^ g ^ 3 1*1 M -4 ! OJ rH t-. QO OJ O t>; cjq ri to cj P 1 P 3 §CO Oi t— rH CO CQ CO t- »O r(H W rH rH OJ III P fl ts 0 0 i . CD O _ .> > g a • o i HH 02 fcH * j 5 £ « ii 3 - iS A SB .£i £ 8 S .. •• •• ^ H ° »OCNieOCOrHOS5OOD IO ^O t^> g 13 T ^ c i TH CO CO 10 CO rH s E H ^ i i LJ "j t, OQ M m r-H hH S to «T fe O 10 io" 10* »o" 0 .rH -M •> -. ^ •> r> 05 03 ri 0 fc •t-H Q IO ft (M (M O9 CQ C4 Oq 09 M 0 13 7.1 PL, ^•f EH : j i j ! J ! J i J : J i : 73 P< 1 j ^ * ri * ri * ri * ri * 'Q «H ft o «H rj ft 1 ^jO ^jO .JjO ^jO 4J® HJ 5 '^9 O H a 2 0-2 S-2 o-2 S-2 o-2 s-2 'C S *H -2 03 ri g2 gS gfl gfl go gS ma -5* •* ^* *rf EH O EH H§ t3§ bS bS bS faS fa§ WQQ rigQ rigQ riQQ "QQ ™CQ ^*CD -*^ rH ^ rH L,j3 rHM rHrS rHB? " rrT-t^ ri r^J 3 <» Q> f '•-'b.i "HM "HVI "t-ivi ''-'M ''-'M **-<*> S 33 rgg "38 3s 33 33 '"S ** rH *H ri | oori cnri cori ccri mri cori oori c-1 QJ O fr^ ^ O) (D0* flj" ffl® OJ** O)W (D*1 *" "™ r-l -H W i gb S*-1 S^ S'-1 SM S^ S^1 .So .So .So .So .So .So .So o JPQ r^PQ JW rHPQ rHPQ ^PQ rnPQ r?H sg^S •< _l_3 TJ rH G> 09 oo b- eo >o o o b- eo OS > OJ u h £ s CO t- 3 oq ca oTrS *^ 03 5 nT "® &3 "o ea oi co* eo *i_i **^ CL s iH 5| eo os 0 °«H ,_, S 0 ^i a> ^ o •*-> u -*3 «H S *H 03 -*^ < 5 — - o3 *w Si H Jg CD os oo oo CM rH oo o3 oo M •H 10 00 QJ O M s H ( |l> eo . "* <• T-H CD >• O 1 g & H O 0 P 'ft CO O) _. > > 0 •rt o a> •<* IO CO la PI CO CO co .2 irT 10" wT 0 0 •*f •^ •^ O ^3 e»T eo eo" fc 4 " c 73 £ " CS •-1 cS 1-1 03 "3 "a O "" O I~* O ~ V B £ =« 2- o 3 £ — — 0 03 £ a « s s "S £ a « £ •+J CO — 00 13 ca ^^2 ^ C8 ^ * rt 3 ra i! « gS a « 3* S M = o B «| 3 3 00 Cj ^ 3 ic n 3 3 oo o3 "S a> -3 " §3 .§ o B W T3 .§s 0^ I] E -4J o |5f JCQ UW a ca *Z ^ ° o ta o 03 •_ GQ t— ] ^ I— 1 I rH cq eo 1919} SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH SS9 41.27 percent control was exerted by the three weeks spray, Bordeaux applied five weeks after the fall of the petals actually gave 35.91 per- cent control. On Plat 7, where Bordeaux was applied three, five, and seven weeks after the fall of the petals, there was 12.73 percent blotch, or 80.51 percent control. Since the three- and five-weeks sprays of Bordeaux gave a combined control of 77.18 percent, the actual blotch control exerted by the seven weeks spray was 3.33 percent. In percentages of russet present important differences appear be- tween the effects of lime sulfur and of Bordeaux. It will be noted that the percentages present in Plats 1, 2, 3, and 4, sprayed with lime sulfur, were very nearly the same as the percentage present on the unsprayed row ; hence the conclusion is that something other than the sprays caused this injury. Reference to Plats 5, 6, and 7 will show that considerable russet appeared on the fruit. Since it was observed in the orchard that russeting of the fruit occurred prior to July 1, and since Plat 5, sprayed with Bordeaux three weeks after the fall of the petals, showed more russet than was present on Plat 6 and almost as much as was present on Plat 7, it may be concluded that the application of Bordeaux three weeks after the fall of the petals caused the russet on all of the plats minus the percentage which ap- peared on the unsprayed row. It will be noted that no burn appeared on Plats 1, 2, or 3, but that a small amount appeared on Plat 4, due to lime sulfur arsenate of lead applied seven weeks after the fall of the petals during very hot, dry weather. EFFECT OF INTERCHANGING BORDEAUX AND LIME SULFUR During the wet season of 1915 certain growers in southern Illinois reported serious russeting of fruit even tho Bordeaux had been used three weeks after the fall of the petals, and even later. Such an occurrence is rare, altho experiments conducted by this station in 1912 showed that Bordeaux applied three weeks after the fall of the petals caused 33.1 percent slight russet.1 Investigations on the con- trol of blotch have shown that the first and most important spray is the one applied three or four weeks after the fall of petals.2 Since russetting of the fruit may follow such an application and applications made still later, it was thought that lime sulfur, which usually does not cause russet, might be substituted for Bordeaux at these times. Accordingly sprays were applied as shown in Table 3. The first, sec- ond, and sixth applications were the same in all plats. 'HI. Agr. Exp. Sta. Bui. 185, p. 179. 1916. 2U. S. Dept. Agr. Bur. Plant. Bui. 144, p. 22. 1909. Kans. Agr. Exp. Sta. Bui. 196, p. 572. 1913. 560 BULLETIN No. 222 [September, The results show that in Plat 7, where Bordeaux was applied three, five, and seven weeks after the fall of the petals, there was 12.73 percent blotch. In Plat 10, where lime sulfur was substituted for Bordeaux in the spray three weeks after the fall of the petals, there was 49.49 percent blotch. In Plat 9, where lime sulfur was sub- stituted for Bordeaux in the sprays three and five weeks after the fall of the petals, there was 36.86 percent blotch. These results show that lime sulfur did not control blotch as well as Bordeaux when substituted for the latter spray either three or five weeks after the fall of the petals. It will be noted that in Plat 10 the substitution of lime sulfur for Bordeaux in the spray three weeks after the fall of the petals eliminated the russet factor but did not satisfactorily control blotch. The same is true for Plat 9, where lime sulfur was substituted for Bordeaux in the sprays applied three and five weeks after the fall of the petals. The russet present on the fruit of Plats 9 and 10 was caused by something other than the sprays, since the unsprayed row shows 2.57 percent serious and 21.76 slight russet. By sub- tracting these amounts from the percent of russet for Plat 7, it will be found that Bordeaux applied three weeks after the fall of the petals actually caused 13.21 percent serious and 21.99 percent slight russet. SUMMARY OF RESULTS FOB 1916 1. Bordeaux proved superior to lime sulfur as a spray for blotch. 2. The most important sprays in the control of blotch were those applied three and five weeks after the fall of the petals ; when applied seven weeks after the fall of the petals these sprays were of less value. Lime sulfur applied ten days after the fall of the petals failed to exert any control over blotch. 3. Individual sprays of Bordeaux applied three, five, or seven weeks after the fall of the petals proved superior to similar indi- vidual applications of lime sulfur. This superiority may have been due to the greater adhesiveness of Bordeaux. 4. Bordeaux applied three weeks after the fall of the petals russetted the fruit. 5. The substitution of lime sulfur for .Bordeaux three or five weeks after the fall of the petals eliminated russet but failed to control blotch. The russet caused by Bordeaux applied three weeks after the fall of the petals was less injurious to the quality and the appearance of the fruit than was the increase in amount of blotch caused by substituting lime sulfur for Bordeaux at this application. SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH 561 INCIDENTAL OBSERVATIONS 1. Blotch appeared on the fruit of the unsprayed row about June 15, six weeks after the fall of the petals. Later in the season it was detected on the foliage both of unsprayed and of sprayed trees, particularly in the interiors of the trees. 2. At picking time it was seen that the greatest blotch infection on the sprayed trees appeared on the fruit located on the interior parts of the trees, where the foliage was very dense. The sprays would doubtless have been more effective if the trees had been thoroly pruned. On blotch-infected trees water sprouts are usually more seriously effected by the disease because the fungus seems to thrive better on such new, tender wood. Thoroness of application to the interior of the tree is therefore essential; the spray should cover not only the fruit and foliage but also the new growth in order to prevent the formation of cankers thereon. When spraying trees for blotch, pressures of 200 to 225 pounds should be used and the man on the ground should direct the spray to the interior parts of the trees and to the undersides of fruit and branches. 3. Some spray injury to foliage resulted from the use of both Bordeaux and lime sulfur. 4. Lime sulfur arsenate of lead applied during the hot weather of mid-July caused a negligible amount of burn on the fruit; that the injury was not greater was probably due to the fact that the trees were not drenched. EXPERIMENTS IN 1917 The results obtained at Flora in 1916 had thoroly demonstrated that before the most thoro and effective spraying can be done against blotch, the trees must be pruned so as to open up the tops. The results had also demonstrated that cankered water sprouts, which are usually a serious source of infection, should be removed. Accord- ingly this work was thoroly done during the winter of 1916-17 pre- paratory to the experiments of 1917. The experiments of 1916 had also shown that 125 pounds pres- sure is insufficient if a fine penetrating spray is desired, and in order to obtain high pressures, a power sprayer was secured for the sea- son of 1917. Spraying investigations at Flora during 1917 were conducted to determine the following points in the control of blotch: (1) the effect of dormant applications of copper sulfate, Scalecide, lime sulfur, and lime-sulfur copper-sulfate mixture; (2) the relative value of Bor- deaux and lime sulfur; (3) the value of different applications of Bordeaux and lime sulfur; (4) the effect of the addition of arsenate of lead to lime sulfur; and (5) the relative merits of dusting and liquid spraying. 562 BULLETIN No. 222 [September, TABLE 4. — EFFECTS OF DORMANT APPLICATIONS OF COPPER SULFATE, SCALECIDE, LIME SULFUR, AND LIME SULFUR COPPER SULFATE IN THE EXPERI- MENTS AT FLORA, 1917 Plat Treatment Applications1 Total No. picked apples Percentage affected by blotch 1 2 3 4 5 6 7 8 Copper sulf ate 1 2, 3, 4, 5, 6, 7 1580 2010 1468 2500 2471 1891 2960 1986 7.0 14.0 10.0 16.0 6.5 9.0 11.5 9.5 Lime sulfur arsenate of lead. Sealecide 1 2, 3, 4, 5, 6, 7 1 2, 3, 4, 5, 6, 7 Lime sulfur arsenate of lead. Lime sulfur Lime sulfur arsenate of lead. Lime sulfur copper sulf ate... Lime sulfur arsenate of lead. Lime sulfur arsenate of lead Copper sulfate 1 2, 3, 4, 5, 6, 7 2,3,4,5,6,7 1 2,3 4,5,6,7 1 2,3 4,5,6,7 1 2,3 4,5,6,7 Lime sulfur arsenate of lead. Bordeaux arsenate of lead . . . Sealecide Lime sulfur arsenate of lead Bordeaux arsenate of lead . . . Lime sulfur Lime sulfur arsenate of lead. Bordeaux arsenate of lead . . . 9 Lime sulfur copper sulfate . . . Lime sulfur arsenate of lead Bordeaux arsenate of lead . . . 1 2,3 4,5,6,7 1504 13.0 10 Check Lime sulfur arsenate of lead Bordeaux arsenate of lead . . . No treatment 2,3 4, 5, 6, 7 None 1897 1101 8.5 75.5 "I: Dormant, March 31 4: Three weeks after fall of petals, May 28 2: Cluster-bud, April 20 5: Five weeks after fall of petals, June 12 3: Fall of petals, May 7 6: Seven weeks after fall of petals, June 26 7: Ten weeks after fall of petals, July 17 1919] SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH 563 EFFECT OF DORMANT APPLICATIONS OF COPPER SULFATE, SCALECIDE, LIME SULFUR, AND LIME-SULFUR COPPER-SULFATE MIXTURE Certain apple growers in this state had expressed the belief that a dormant application of lime-sulfur or copper-sulfate solution will reduce blotch infection, presumably by destroying the cankers. No experimental evidence, however, was available on this point. In 1907 this station reported on tests involving the spraying of bitter-rot cankers with copper-sulfate solution both in the laboratory and in the field. The results of such experiments demonstrated that bitter- rot cankers could not be destroyed by an external application of copper sulfate.1 It was thought, however, that since the mycelium of blotch fungus works just beneath the bark or the epidermis, a dormant spray of certain soluble materials might penetrate the dis- eased tissues and destroy the mycelium. In conjunction with the plat tests, the results of which are pre- sented in Table 4, ten one-year-old blotch cankers on water sprouts were sprayed with copper sulfate, Scalecide, lime sulfur, and lime- sulfur copper-sulfate mixture. The sprays were applied on March 30 by means of an atomizer. Ten cankers were left unsprayed to be used as checks. The data presented show that a dormant application of copper sulfate, Scalecide, lime sulfur, or lime-sulfur copper-sulfate mixture had no effect on the blotch. Plats 1, 2, 3, and 4, which received dormant applications of the various sprays followed by summer sprays of lime sulfur arsenate of lead showed more blotch than Plat 5, which received no dormant spray, but the same summer applications. A similar difference will be noted between Plats 6, 7, 8, and 9, which received dormant applications of the various spray materials followed by summer sprays of lime sulfur arsenate of lead and Bordeaux arsenate of lead, and Plat 10, which received no dormant spray but the same summer applications. The check plat showed 75.5 percent blotch. These results were further substantiated by the data secured from the blotch cankers on water sprouts sprayed with an atomizer. Ex- amination of these cankers early in September showed that in no case had the sprays checked the growth of the cankers. The cankers had continued their growth and had formed new pycnidia, or spore- bearing cases, and altho no examinations were made for spores, it is reasonable to conclude that these were produced. RELATIVE VALUES OF BORDEAUX AND LIME SULFUR In the experiments at Flora in 1916 Bordeaux had proved superior to lime sulfur in the control of blotch. However, as the orchard had not been pruned in many years, it had been impossible to make '111. Agr. Exp. Sta. Buls. 117 and 118. 1907. 564 BULLETIN No. 222 [September, S m 90 r-i S i 1 « « to o o o eg* >*-> •>-* ,0 f-, 0 co eg t- ,— i ^d CO eg 05 j _ P t- rH j 03 -u § in in o r-i eo r-i eo eg Or?1"1 0 CD O> CO oTla ^ rv. be CO ro "cj ^j oT rH < 3 -4-> p !>"•"* H 3 M 0) 3 .2 10 m m ^f W EH 3 PH o CO eg O •— < «H 'cd ® t-< M -1 3 .n in 10 *n m °* V Cf^ FH H H 1 «o od in ij c3 -S E 5 b» c3 *W X H p 1 9 *9 a 'S Q^ j-M a w ^ S n 0 1 •* B 1 1 S ^ » < S !1 i* k O rH rH > t> p M _ r 1 in rH O rH 02 EH T r; r eg rH rH P -t o c i i rH eg rH Th IO «0 9 E nl \ p 1 L CQ W !» +j PH ..^ rH V rH eg eo 6 SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH 565 thoro applications and it was thought that with good pruning the results might be different. As previously stated, the trees were well pruned during the winter of 1916-17 and in 1917 tests were again made with Bordeaux and lime sulfur. Sprays were applied at 225 pounds pressure. The results in Table 5 show that lime sulfur was slightly superior to Bordeaux in the control of blotch, but the difference is so slight that both sprays may be considered equally effective. The presence of russet on the fruit of both Plat 5 and Plat 10 is a rather interesting point. Bordeaux russet is a common form of fruit injury; lime-sulfur russet, however, is unusual. It will be seen by deducting the percentages of russet present on the unsprayed row from those on the sprayed plats that lime sulfur caused 30.5 percent slight russet and Bordeaux 14 percent serious and 22.5 per- cent of slight russet. Lime sulfur caused 2.5 percent serious and 1.5 percent slight burn. This injury followed the application made ten weeks after the fall of the petals, during very warm, dry weather. VALUE OF DIFFERENT APPLICATIONS OF BORDEAUX AND LIME SULFUR Experiments conducted at Flora in 1916 had shown that the most important Bordeaux and lime-sulfur sprays for blotch were those applied three and five weeks after the fall of the petals; that when applied seven weeks after the fall of the petals, these sprays were of less value. It had also been found that lime sulfur applied ten days after the fall of the petals exerted no control over blotch. As a further test of the value of different applications of lime sulfur and Bor- deaux as sprays for blotch, plats were sprayed in 1917 as shown in Table 6. The results presented for Plats 11 and 12 and Plats 16 and 17 show that the most important lime-sulfur and Bordeaux sprays against blotch were those applied three and five weeks after the fall of the petals. Such information confirms results obtained at Flora in 1916. These facts emphasize the importance of timeliness of appli- cation. It will be noted further that lime sulfur applied seven, ten, and twelve weeks after the fall of the petals caused some reduction in the amount of blotch. It is to be remembered that the greatest blotch infection occurs from four to six weeks after the fall of the petals, but that scattering infections may take place thruout the rest of the season, or young apples infected early may become a source of later infection to fruit and wood. Such conditions may explain the control exerted by spray applied seven, ten, and twelve weeks after the fall of the petals. Similar results were obtained from Bordeaux applied seven and ten weeks after the fall of the petals. 566 BULLETIN No. 222 [September, i 1 * 1 to to to to to to to oo oo oi oo oo I-H IH CM CM CM CM CM CO CM o W 1 1 B O to to to O to

^ CM to CO CO nO3 *^(O3 *^O3 *tnflc3 "f_t^Cd 33o tS^O eS^3® ^^o 3PQ 33raQ 33o 335 335 335 335 335 33§5 33§5 cooajj DQcQcj '•'•>- r. """Ooj CQtOjj °°coo3c3 cocooSoS ill n§ ill ill ni nil ml J J ~'o3' o ~* • "=« <» • « "d TJ 59 fl cS • 0*0 ' * ^"0 ' •VoS'C 'SoSTJ • S a cs • s? « as O> *u 02 r— I I^S^ s^ Ss « <» cS S §§?§ .§ .§ o £ j j pa ^ i-i ** •— 5 < '^ rH rH CO ^ CO « ». "tn O2 ~ . i QJ S 0 S 'w ^ ft PH H 3j 8> a M OQ 3 .2 O IA O O O •<$ rA d eo P< SJ 5|_| O «H rH 02 cp W Ig w tH or a • " P) * g i ' C 1 -i 0 >0 t- 10 t- jcnS g ^ ^ O rH OO OO 00 •^ O "^ CO C3 1C «O t- * 5 a iJ P e H-t 02 H H g r— t~ t- b> t> rH Tn 0 O 0 «o «o o ^ 55 •< "S CJ 10s lo" © •* ** ** "* fl M •» \, \«. \, iS P "E, co eo co co J^ < H ^ of of « oa ci cJ rt o CM H 1 H —1 i— c QJ r-1 Q3 O O O ^ O «,_, ^ o o O) 1 5 ^ ^ ° ^ ° CS 1H W | CQ ^^ Co C3 O CJ O "C ^5 .S ^ 3 « « M S03 rort roflrt Sflrt ^•H »^ ;lj •*"* •« H ^! ,^H rt &H & ci *- /• cd GO -.2 ^ M ^J rH ^^ rH rt ^^ rH C3 T^ po po p o p °M 1 ftS-i "95 35 ^P^ ^P-2 rl A "g ^ 1 oocS <«ca wa3c4 ooojcd rt S, • S o s IH 'W 5 o- 5 ° CS (V e c3 eg cdai coctfcS «^§g -S .S § 2 o 1919] SPRAYING APPLE ORCHARDS FOR CONTROL OF BLOTCH 575 5. Apple blotch was first observed on the unsprayed fruit on June 19, seven weeks after the fall of the petals. 6. Unhealthy apple trees suffered more serious spray injury to foliage than vigorous trees. RECOMMENDATIONS FOR THE CONTROL OF APPLE BLOTCH The first step to take in the control of apple blotch is to remove water sprouts as they are very susceptible to blotch infection. Fol- lowing this the tops of the trees should be well pruned so as to permit thoro spraying. High pressures, from 225 to 250 pounds, should be used, driving the spray thru disc nozzles with small openings. Discs should be replaced whenever the openings wear too large to give the finest mist spray. Trees should be sprayed thoroly but not drenched and care should be taken to apply the spray to the new wood as well as to the fruit. The interior and under parts of the trees should be well sprayed. Sprays should be applied on time, not on certain dates, but with reference to the time of the fall of the petals. The following schedule is recommended for blotch-infected orchards : First Application. — The first and most important spray for apple blotch is that applied as near to three weeks after the fall of the petals as possible. Lime sulfur arsenate of lead should be used at the rate of 2,y2 gallons of lime sulfur and 2 pounds of powdered or 4 pounds of paste arsenate of lead in 100 gallons of water. Second Application. — A second and important application of lime sulfur arsenate of lead should be applied two weeks later, or five weeks after the fall of the petals. If apple blotch is to be controlled by spraying, the fruit must be protected during the period from four to six weeks after the fall of the petals, because this is the time of greatest infection. Ap- plications made three and five weeks after the fall of the petals will accomplish this protection, provided heavy rains do not occur. In the event of heavy rains following such applications, it will be neces- sary to apply extra sprays of lime sulfur. Bordeaux is more adhesive than lime sulfur but the danger from russet on Ben Davis at these periods, especially during wet weather, makes the use of lime sulfur more desirable. UNIVERSITY OF ILLINOIS-URBAN*