•• irch 12, 1910. 
 
 U.S. DEPARTMENT OF AGRICULTURE, 
 
 BUREAU OF ENTOMOLOGY-CIRCULAR No. 120. 
 
 L. O. HOWARD. Entomologist and Chief of Bureau. 
 
 CONTROL OF THE BROWN-ROT AND PLUM 
 CURCULIO ON PEACHES. 
 
 \Y. M. Scott, of tin Bureau of Plant Industry, 
 
 A. L. (,h uvi \\i i:. ofth. Bureau of Entomology. 
 
 
 WASHINGTON : GOVERNMENT PTINTINC OFFICE : 1910 
 
BUREAU OF ENTOMOLOGY. 
 
 L. O. Howard, Entomologist and Chief of Bureau. 
 
 C. L. Marlatt, Assistant Entomologist and Acting Chief in Absence of Chief. 
 
 R. S. Clifton, Executive Assistant. 
 Chas. J. Gilliss, Chief Clerk. 
 
 F. H. Chittenden, in charge of truck crop and stored product insect investigations. 
 
 A. D. Hopkins, in charge of forest insect investigations. 
 
 W. D. Hunter, in charge of southern field crop insect investigations. 
 
 F. M. Webster, in charge of cereal and forage insect investigations. 
 
 A. L. Quaintance, in charge of deciduous fruit insect investigations. 
 
 E. F. Phillips, in charge of bee culture. 
 
 D. M. Rogers, in charge of preventing spread of moths, field work. 
 Rolla P. Currie, in charge of editorial work. 
 
 Mabel Colcord, librarian. 
 
 [Cir. 120] (2) 
 
Circular No. 120. Issued March i 
 
 United States Department of Agriculture, 
 
 BUREAU OF ENTOMOLOGY. 
 L. O. HOWARD, Entomologist and Chief of Bureau. 
 
 CONTROL OF THK BROWN-ROT AND PLUM CURCULIO 
 
 ON PEACHES. 
 
 By 
 
 \Y. M. Scott, of tin Bureau of Plant Industry, 
 
 and 
 .'v. L. Qi iintance, oft) Entomology. 
 
 The two most important troubles of the fruitofthe peach and other 
 stone fruits are the so called "brown-rot" (Sclerotinia fructigenia (P.) 
 Schrot.) and the plum curculio ( I bnotracht lus m nuphar I lerbst i. The 
 brown-rot is a fungous disease of the flowers, twigs, and fruit, but is 
 especially destructive to the latter as it approaches maturity. Dnder 
 weather conditions favorable to the fungus from one half to three 
 fourths of the crop, or even the entire crop, maj be destroyed within 
 a few days. The marketed fruit, moreover, rarely reaches its desti 
 nation in good condition and is often a disappointment to the grower 
 as well as to the consumer. This destructive disease is well known to 
 peach growers, especially in the Southern States, and requires but 
 little in the way of description. Although young green fruit may 
 become infected, it is the ripening fruit which suffers most. The 
 disease first appears as a ■-mall brown spot, which rapidly enlarges 
 involving in a few days the entire fruit. On the surface of the 
 diseased -pot-, minute tufts of spore bearing threads appear, giving 
 to the fruit a grayish, moldy appearance. 
 
 The plum curculio. in the course of it- feeding and egg laying, 
 punctures the fruit, and is often so abundant that not a. single fruit 
 escapes injury. The puncture- form a nidus for brown-rot spores, 
 greatly favoring infection. Larva' of the curculio. hatching from the 
 
 j- placed beneath the skin of the peach, make their way to the pit. 
 and by their injury cause much of the young fruit to drop. Fruit 
 iufe-ted later in the season may ripen prematurely and fall or lie badly 
 misshapen. Wornainess of peaches in the East is entirely due to the 
 plum curculio, and the injuries of this insect cause, in i he aggregate, 
 a loss each year to fruit growers of many thousands of dollar-. As 
 
 [Cir. 120| (3) 
 
4 
 
 the cuvculio, by its punctures, opens the way for brown-rot infection 
 of peaches, plums, etc., its control becomes doubly important. 
 
 While the curculio is not of itself the cause of brown-rot, its work 
 very great ly favors the disease. Furthermore, it is practically certain 
 that the curculio distributes the spores of the fungus, and in the course 
 of its feeding and egg laying actually infects the fruit with the fungus. 
 
 As is well known, the foliage of the peach and other stone fruits is 
 especially sensitive to sprays, such as Paris green and Bordeaux mix- 
 ture. This has largely prevented the use of Bordeaux mixture and 
 other copper compounds for the control of peach diseases. While it 
 has been known for several years that arsenate of lead could be used 
 in the treatment for curculio, some injury has resulted, and on account 
 of the well-known sensitiveness of peach foliage entomologists have 
 been cautious about recommending it. The combination treatment for 
 fungous diseases and insect enemies so successful in the treatment of 
 the apple, grape, etc., has, therefore, not been possible on the peach. 
 
 The development of the self -boiled lime-sulphur mixture, however, 
 as a fungicide has made possible the control of the brown-rot and some 
 other peach diseases. The experiments made by the Bureau of Plant 
 Industry, with the self-boiled lime-sulphur mixture on the peach, cov- 
 ering three }'ears — from 1907 to 1909 — have shown conclusively that 
 when properly made it is perfectly harmless to the foliage, fruit, and 
 tender growth of the peach, and that it will satisfactorily control brown- 
 rot, peach scab, and other fungous diseases. 
 
 In experiments conducted during the past season it was found that 
 the arsenate of lead could be combined with the self-boiled lime-sulphur 
 mixture for spraying peaches, and that this insecticide was apparently 
 less injurious in the combination than when used alone, and that the 
 combination was entirely successful in controlling the seal), brown- 
 rot, and curculio. The addition of arsenate of lead, as shown by these 
 and other experiments, has been practically without injurious effects 
 where not more than two applications have been made. Three appli- 
 cations, however, of an arsenate-of-lead spray are likely to cause 
 shot-holing of the leaves and an excessive reddening of the fruit, and 
 under certain weather conditions such symptoms may appear as the 
 result of only two applications of the poison, though ordinarily not to 
 an injurious extent. The great benefits to be derived from spraying, 
 it is believed, will much more than offsel any possible slight injury. 
 
 SOME BES1 Lis OF SPRAYING." 
 
 In experiments conducted in the Hale orchard, at Fort Valley. Ga., 
 dining 1909, by the Department of Agriculture, the practicability 
 of the control of peach scab, brown-rot, and the curculio was 
 
 o For a detailed account of these experiments, see Bulletin 174 of the Bureau of 
 Plant Industry, U. S. Department of Agriculture. 
 [Cir. 120] 
 
thoroughly demonstrated. Thus a block of 1,100 Elberta trees was 
 sprayed, first, with arsenate of lead al the rate of 2 pounds to 50 gallons 
 of water at the time the calyces, or shucks, were shedding; second, 
 with '2 pounds of arsenate of lead in self-boiled lime-sulphur mixture 
 (8 8 50) three weeks later; third, with self -boiled lime sulphur mixture 
 alone a month later; and, fourth, with self-boiled lime-sulphur mix- 
 ture a month In 'fort' the ripening period of the fruit. At picking time 
 95.5 per cenl of t he fruit from i he sprayed block was free from brown- 
 rot, 93.5 per cenl free from scab, and 72.5 per cent, free from the cur- 
 culio. On the unsprayed block only :'.T percent of the fruit was free 
 from brown-rot, 1 per cent free from scab, and 2$ per cent free from 
 curculio injury. Inpackingthe fruit for market it was found thai the 
 amount of merchantable fruit on the sprayed block was ten times as 
 great as from the unsprayed block containing the same number of 
 
 tier-. 
 
 ( )n a block of Waddell t rees spraj ed with the self-boiled lime-sulphur 
 mixture alone, one month after the falling of the petals and again one 
 month before the fruit ripened, the results were not quite so good, 
 owing to curculio infestation; but the yield of merchantable fruit 
 was, nevertheless, LOO per cenl more than thai on a similar block of 
 unsprayed trees of the same variety. 
 
 From these results and those of previous experiments we may con- 
 clude that the peach grower now has at his command a reasonably 
 safe and thoroughly effective remedy for the peach seal), brown-rot, 
 and curculio. By carefully following the instructions given below he 
 should lie able effectively to prevent these troubles at a small cost. 
 
 PREPARATION OF THE SPRAY MIXTURES. 
 
 The sprays to be employed are the self-boiled lime-sulphur mixture 
 and arsenate of lead. The arsenical is added to the lime-sulphur mix- 
 ture, permitting the treal ment of both brown-rot and. the plum curculio 
 at one and the same time. 
 
 'led lime-sulphur mixture. — This mixture is composed of 8 
 pounds of fresh stone lime and 8 pounds of sulphur (either flowers or 
 Hour may be used) to 50 gallons of water. This appears to be about 
 the correel strength, although in mild cases of scab and brown-rol a 
 weaker mixture, containing 6 pounds of each ingredienl to 50 gallons 
 of water, may be used with satisfactory resul s. The mixture can best 
 be prepared in rather large quantities — say, enough for 200 gallons al 
 i time, making the formula 32 pounds of lime and 32 pounds of 
 sulphur to be cooked with a small quantity of water (8 or L0 gallons) 
 and then diluted to 200 gallons. 
 
 The lime should be placed in a barrel and enough water poured on to 
 almost cover it. As soon as the lime begins to slake the sulphur 
 should be added after first running it through a sieve t<> break up the 
 
 120] 
 
6 
 
 lumps. The mixture should be constantly stirred and more water 
 added as needed to form a thick paste at first and then gradually a 
 thin paste. The lime will supply enough heat to boil the mixture 
 several minutes. As soon as it is well slaked water should be added 
 to cool the mixture and prevent further cooking. It is then ready to 
 be strained into the spray tank, diluted, and applied. 
 
 The stage at which cold water should be poured on to stop the cook- 
 ing varies with different limes. Some limes are so sluggish in slaking 
 that it is difficult to obtain enough heat from them to cook the mix- 
 ture at all, while other limes become intensely hot on slaking and care 
 must be taken not to allow the boiling to proceed too far.. If the 
 mixture is allowed to remain hot fifteen or twenty minutes after the 
 slaking is completed, the sulphur gradually goes into solution, com- 
 bining with the lime to form sulphids, which are injurious to peach 
 foliage. It is therefore very important, especially with hot lime, to 
 cool the mixture quickly by adding a few buckets of water as soon as 
 the lumps of lime have slaked down. The intense heat, violent boiling, 
 and constant stirring result in a uniform mixture of finely divided 
 sulphur and lime, with only a very small percentage of the sulphur in 
 solution. It should be strained to take out the coarse particles of 
 lime, but the sulphur should be carefully worked through the strainer. 
 
 Arsenate of lead. Arsenate of lead comes on the market in a thick, 
 putty-like paste, and must be worked free in water before addition to 
 the lime-sulphur mixture. There are several brands upon the market 
 and the grower should be careful to purchase from reliable firms. 
 The addil ion of arsenate of lead to the self-boiled lime-sulphur mixture 
 will bring about a decided change in color, but without injuriously 
 affecting the value of the spray. Arsenate of lead is used at the rate 
 of '1 pounds to each 50 gallons of water or lime-sulphur mixture. 
 
 The amount of poison required for each spray tank of mixture may 
 be weighed out into a bucket, thinned with water, and poured through 
 a strainer into the spra}^ tank. In extensive operations, however, it 
 is much more convenient to prepare a stock mixture in advance. 
 Place 100 pounds of the material in a barn 1 with a bucket of water 
 and work it into a thin paste with a spade or a large paddle, then 
 dilute with water to *make exactly 25 gallons. When thoroughly 
 stirred, each gallon will contain 4 pounds of arsenate of lead, and the 
 amount of poison for each spray tank of mixture may be measured, 
 thus avoiding the trouble of weighing small lot-. 
 
 SCHEDULE OF APPLICATIONS. 
 
 For the Elberta, Bell, Reeves, and other varieties of peaches of 
 about the same ripening season, the following is advised: 
 
 First application'. — About the time the calyces, or shucks, are shed- 
 ding from the young fruit, spray with arsenide of lead at the rate of 
 
 [Cir. 120] 
 
2 pounds ti> 50 gallons of self boiled lime-sulphur mixture. Since this 
 application is rather early for scab, and since serious outbreaks of 
 brow 11 rot do nol usually occur a< this time, the self-boiled mixture 
 may be omitted in many cases with reasonable safety. But during 
 warm, rainy springs, especially in the South, the lime-sulphur mixture 
 will doubtless be necessary in this application. In case the self-boiled 
 lime-sulphur mixture is nol used there should be added to each 50 
 gallons of water the milk of lime made from slaking 2 or •". pounds of 
 good -tone lime, in order to counteract any can-tie action of the arse- 
 nate of lead. 
 
 S 'ication. — Two or three u eeks later, <>r about one monl h 
 
 after the falling of the petals, spray with the 8 v --"''» self-boiled lime- 
 sulphur mixture and 2 pounds of arsenate of lead. 
 
 d application. About one month before the fruit ripens spray 
 with the 8 s 50 self -boiled liraeisulphur mixture, omitting the poison. 
 
 For earlier maturing varieties of peaches, such as Waddell, Car- 
 man, and llilev. the firsl two treatment- outlined above will usually 
 be sufficient, but in ven wet seasons badly rotting varieties would 
 probably require three t reatments. Late variet ies, such as Smock and 
 Salway. having a longer season, would not he thoroughly protected by 
 three applications, hut on account of the expense there i- hesitation 
 in recommending a fourth spraying. In view of the results obtained 
 on midseason varieties, ii se< ms likely that three treatments will ordi- 
 narily lie sufficient for the late varieties. 
 
 APPLICATION OF rill. SPRAT MIXTURE. 
 
 During the operation of spraying, the mixture should he kept well 
 agitated. < >wing to the tendency of t he -elf- hoi led lime-sulphur mix- 
 ture and the arsenate Of lead to settle readily, this point c;m not he 
 too strongly emphasized. If the spraying outfit is not equipped with 
 a good agitator, the spray will not he evenly distributed, with the 
 result that some of the tree- will he oversprayed while others will 
 receive an insufficient application. The early applications of spray 
 should he made rather hea\ \ and very thoroughly to insure the de- 
 struction of the curculio and protection against scab. The last spray- 
 ing, a month before ripening time of the fruit, should he made with 
 tine nozzles, the object being t.> give the fruit a uniform coating of a 
 mistlike spray. Heavy drenching of the tree- al this time should 
 be avoided, to guard as much a- possible against the staining of the 
 fruit at picking time. 
 
 Approved: 
 
 .1 wil - WlL8< >\. 
 
 s /■. fury of AgricultuPi . 
 Washington. I>. C, February .'■'. /!>/>>. 
 
 [Clr. l 
 
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UNIVERSITY OF FLORIDA 
 
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