r~ /.*w.- v .-^ ' 4 V *■%'' . •£*• :V£ C Tj'^: / 'v-.'^r/V* t' ; J, Jfe& yj gl* - •■ \ ftXft ,?.r • ‘-Vt *'• .*«->. , C* -*T‘-. >»£’'<* - r ■•/V> I ft •' ■''•/ \.'. • ‘.o'. > I f ' ■ "" ' ft ft.; " . . - v \hi : . ■ I ■i(>n -riXv; ; i . . .»* L 32 _ V- • f • LSZp 'Cv 7®3fe ; i-ft 'ft'-- • ''-.ftft 5*7 - :.i,- *' - j* -: - ' *! , .»• . '.-» ^vvV s > >-?*■«.> ,• iHftftv . .>» TV'i*fj A;, i Wite ■ ■/-V-j !'■ - '•••?' ' - f v jv r fVr;:£t., ,sj%« 1 ' ' U»£it«| cincL Gti 1 C AAiA* B 5vov- *'., ; r^ ^>£ cXi-iA£s> p\: | V CtC rTL w U/V'CU U O ;i *v ft/ftpr?-# 1 ' •'•>•• ft ft ...., ft-- #■> ' /ft::.-* ft ft. \ SCrVi. . .. '. . ” . 'rf • &• * '••.••'■'« j r^. ; ; .■ ■■"■>’ ■■ ' 'v-.. A,.* if n.W?i3 ■ v-i ■ «■ ■- ', -t '. ■■■;' - v-»./ :. '•ST.?jKr Jr - a . «-•• r^. * ., .. j I 1 Z&tlA'&'A. ■ < t- . .. - V- -t;. •tt;'-. ; ifl ! , - ^ • ' '^ :r c--.:-v. - - -JV .£''.. i5f ji-. f '. ^T ■ "T'y ;. . . -'^JW • ■.'■■'COi ~ w*?*# ■ - -■• v 1 : V. V '■>. *„ ! - •-‘ . V ::;vv<--..;?:- _:a^- .,y; %;V. ■ '•.. ", - -'•.> i*;.. •■; ;■' ; ' .-.; ; . •■•■-■.;. - I ' . V .• •' - :; ; T "'H' Wr- • •• ^v-.-ft ■ ftsfos^ - i ft';, ••; ft v.. ^ -'. • . i - i ■ : -•^'/: ; ‘..'. v ^''*. 'x r |*€^e»vi ''v • v.i s v..■■■•- . •: ,A • ;. A< * h / '/ • ■ ■ ' ■ •- •' • •- •' s : '/ - .-'' Aj ■ ' • ••-'-* 1 . . I , - • 1 v; w-- > ...^-•- r .’“ :-• •"’■• ■ '< ' - V- '"•• t" •'• S..--. ■ '•;* ; VW,'. -.!■» : ' A J&V ‘ \ -ft.ft -" . -ftV %• s 11 *: ■• x'-vV' 1 ’ V I \ .;-. . '- : rft : ~ ft"#- •r^:. ,ftX. /•> :’V ^ •;)• -'•>»- ••/ ft. ' •.• : *' *'■"’ V' ... "' .^-"^'ft^', '."' a.T'-.'v .. ft.. A , >■■. « tf,. ■'. ' ■ • '. t-.‘. , ■' •: ft"; - ; : - ftft.: A r-;:-. ' ft..; K '.'■^•- : -"-;ft.- ; : ft-,, ft .,.' :A ' :r ft ft, .ft 1 '-ft. r• V. *.'• ■ : •— '■•..'■ A '-} i?i'- . ^ •'.-. t ■■••' v .'• ' ^v . ;V V■ 'J:'■;•./ ■ - &.*:• ■-: ft - - ft- » • • • : :' ■-: ®!je Htfitarp of tfje 'aUntbctrjSttj* of iSortfj Carolina Collection of Jlortl) Caroliniana in book gibcn bj> Ifl.C, of" ft-^t4xCxeilhLr^ Cp L S"^p f . \y THE BULLETIN OF THE NORTH CAROLINA DEPARTMENT OF AGRICULTURE RALEIGH MARCH, 1923 The Plum Curculio on Peaches in North Carolina—Its Life 4 History and Control Published by the State Department of Agriculture for the AGRICULTURAL EXPERIMENT STATION of the NORTH CAROLINA DEPARTMENT OF AGRICULTURE and the NORTH CAROLINA STATE COLLEGE OF AGRICULTURE AND ENGINEERING The results published here have been obtained in the Co-operative Work of these Institutions PUBLISHED MONTHLY AND SENT FREE TO CITIZENS ON APPLICATION Entered at the Postoffice at Raleigh, N. C., as second-class matter February 7, 1901, under Act of June 6, 1900. Digitized by the Internet Archive in 2019 with funding from University of North Carolina at Chapel Hill https://archive.org/details/plumcurculioonpeOOIeib The Plum Curculio on Peaches in North Carolina Its Life History and Control R. W. Leiby and John B. Gill During the past few years the control of the plum curculio has be¬ come a most important factor in the growing of peaches in the Sand¬ hill section of North Carolina. This pest became so serious in 1921 that State and Federal aid was requested to study the insect, and to instruct growers in the methods of its control. Accordingly, Dr. R. W. Leiby, representing the Division of Entomology of the North Carolina Department of Agriculture and Experiment Station, and Mr. John B. Gill, representing the Bureau of Entomology of the U. S. Depart¬ ment of Agriculture, established a laboratory at Aberdeen, N. C., dur¬ ing the season of 1922. This locality was in the midst of a section which in 1922 produced 1,450 cars of peaches. The objects were to ascertain the life-history and habits of the cur¬ culio by orchard and insectary studies, to conduct experiments in the control of the insect in the orchard, and to personally assist growers in the prosecution of control measures found previously to have been effective in Georgia by Federal Avorkers of the Bureau of Entomology. The present bulletin is prepared at the request of peach growers for their future guidance in combating the curculio. It includes a sum¬ mary of the life-history of the curculio as ascertained for the season of 1922 by the senior author with the assistance of James F. Tarlton,* and the results of field experiments conducted by the authors in the control of the curculio by dusting and spraying. LIFE-HISTORY AND HABITS The plum curculio is a hard snout beetle measuring about three eighths of an inch in length. This beetle is the parent of the cream-colored legless grub or “worm” familiar to all peach growers, that is found in the small dropped fruit, or in ripening peaches next to the pit, where its feeding has caused the infested fruit to be Avorthless. In North Carolina this insect is knoA\ 7 n to also attack cultivated plums, apples, cherries, and wild plums, the latter probably being its native food plant. This insect like other beetles passes through four stages m develop¬ ing a complete generation; the egg Avhich is laid by the parent beet e under the skin of the fruit; the larva which hatches from the egg and develops in the flesh of the fruit; the pupa or resting stage which is passed in a small earthen cell in the soil; and the adult or beetle stage which develops from the pupal stage. *Temporarily employed by the Federal Bureau of Entomology as laboratory and Held helper. 4 The Bulletin, March, 1923 Hibernation and emergence. The beetles hibernate in the woods ad¬ jacent to or near the orchard presumably under leaves or in tufts of grass, and in similarly suitable places in the orchard. Most of the beetles leave their winter quarters and fly to the orchard early in the spring while others reach the orchard later. Thus in 1922 the first beetle was taken in the orchard on March 27, the number coming to the orchard gradually rising till April 10 when the number decreased up until May 19. Hence the beetles came from hibernation to the orchard over a period of about seven weeks, the heaviest emergence be¬ ing during the week of March 30, when according to the jarring records approximately 70 percent of the beetles reached the orchard. Feeding and egg laying. Upon arriving in the orchard the beetles first feed upon the unfolding leaves and green shucks of the blooms; and while the shucks are being shed they feed upon the young fruit. Dur¬ ing this period the beetles mate. In feeding upon the fruit two kinds of punctures are made, the cir¬ cular one being usually a feeding puncture only, while the crescentic puncture usually indicates that an egg has been laid in the feeding puncture under the crescentic cut. In laying an egg in a young peach, the female first cuts through the pubescence of the fruit and eats out a small cavity under the skin. She then turns about and inserts a minute colorless egg into the hole. A crescentic shaped slit is then cut in front of and underneath the egg, which leaves the egg in the fleshy flap of the fruit. However, eggs are frequently placed in simple circular punctures made directly under the pubescence of the small peach. In 1922 the first egg was found deposited in the orchard on April 11, with a very high percentage of the eggs laid within ten days after the shucks were shed. The insectary records show an average of 4.7 eggs deposited each day by individual females during April, while in May and early June an average of only 1.5 eggs was deposited daily by individual females. The length of the egg stage was found to cover a period of three to five days. A series of 128 eggs in plums and 96 eggs in peaches showed the average length of the egg stage during the spring of 1922 to be 4.0 and 4.3 days respectively. Development of spring brood of larvae* Upon emerging from the egg the minute white larvae or “worms” bore into and feed upon the flesh of the young fruit. Continued feeding causes the infested fruit to become discolored, somewhat shrunken, and finally to drop, although a very few of the small fruits may remain on the trees until after the larvae abandon the fruit. Our insectary records show that the larvae become fully grown in an average of 16 days, whereupon they emerge from the drops (fig. 1) and burrow into the soil. At a depth of three *The first brood of beetles to develop in the season from overwintering beetles is designated in this circular as the Spring brood. •M P # Plum Curculio on Peaches 5 or four inches in loose sandy soil, each larva forms with the aid of its body a small oval cel] m which it transforms to the pupal and later o the adult stage. Where the soil is infrequently or never disturbed the earthen cell is made at a depth of only one or two inches. During the season of 1922 the first larvae of the spring brood were seen to emerge from drops on April 27, and the last larvae emerged in numbers on May 26. Fifty percent of a total of 5,212 larvae, reared fiom dropped fruit during May, emerged between May 3 and 19, this interval representing the peak of larval emergence for this brood from drops. A few larvae of this same generation emerge from early varie¬ ties (Mayflower, Alexander and Arp) as they ripen, which is during the latter part of May and the first half of June. Such larvae also come from eggs laid by overwintering beetles in the fruits about two weeks before these early varieties ripen. For the most part, however, the overwintering beetles temporarily cease egg laying in the mid¬ season and late varieties of fruits, while the latter are in the stone hardening period. This habit probably accounts for the fact as ex¬ perienced by growers that the early varieties of peaches are seldom abnormally wormy at the time of harvest. It is the development of these larvae in early varieties as they ripen, that prolongs the period of larval emergence of this brood into June, although as pointed out above, the maximum emergence is between May 9 and 13 from the small dropped fruit. Development of curculio and emergence from the soil—spring brood. The insect spends approximately a total of 31 days in the ground in the larval, pupal, and adult stages. A series of 1,037 beetles reared in cages in the insectary required an average of 31.2 days before the adults emerged, while a series of 386 beetles reared outdoors in ground cages in the orchard required an average of 31.5 days for emergence. Of the 31 day period in the ground, 14 days are passed in the larval stage, 12 days in the pupal stage, and 5 days in the beetle stage. There is no evidence that the beetles remain in sandy soil until a rain softens it to facilitate emergence, for they have been observed to emerge readily in very dry sandy soil. It was ascertained that in 1922, 63 percent of the beetles of the spring brood emerged between June 9 and 12, with the first beetle emerging June 1 and the last July 7. It is of interest to note that the number of beetles caught by jarring increased perceptibly about this time. Thus the jarring records show that 6 curculios were caught on May 29, 18 on June 3, 68 on June 7, 81 on June 10, and 72 on June 14. The beetles in the orchard at this time (about June 15) therefore be¬ long to both the group that overwintered and the recently developed spring brood, although the number of surviving overwintering beetles in a well cared for orchard is very small, because of the natural mortality and the previous application of poison sprays. 6 The Bulletin, March, 1923 Summer egg laying in late varieties of peaches. 1 After the beetles of the spring brood emerge they feed upon fruit in the orchard. The in¬ sectary investigations indicate that only about 20 percent of the females of this spring brood lays eggs. It is the combined egg laying of the surviving overwintering beetles and the spring brood of beetles, in ripen¬ ing mid-season varieties and late varieties that have passed through the stone hardening period, that is responsible for the development of a summer brood 2 of larvae and adults, the larvae emerging in numbers from the fruit at the time that the Belle and Elberta varieties are ripening. The egg laying records of 73 beetles of the spring brood confined in cages with ripening mid-season and green late varieties of fruit are shown in Table 1. Of the 73 beetles (approximately half of which were females) only 7 deposited eggs during the 49 day period of June 4 to July 19 (ripening period in 1922 of Alexander to Elberta varie¬ ties). The average number of eggs laid by these seven females was -46, or a little less than one egg per day for each egg-laying female during the 49 day period. The records also show that from 8 to 23 days (average 15.6 days) intervened between the time of emergence from the soil and the laying of the first egg by each of the seven beetles. It is of interest to note that the 73 beetles made a total of 4,358 punc¬ tures (feeding and egg-laying) during the 49 day period, an average of about 60 punctures for each beetle. Egg-laying beetles make con¬ siderably more feeding punctures than those that do not lay eggs. Emergence of summer brood larvae. Field observations show that the mid-season varieties like Carman, Slappey and Hiley are each normally more wormy at harvest than the preceding variety. It is believed that this is due to the gradual increase in the number of spring brood individuals laying eggs up until the time that the Ililey variety ripens,* although during the same period the egg laying by overwintering beetles declines. The summer brood of larvae emerges from the ripening fruit over a rather long period of time, i.e. from approximately July 4 to August 10. Of the larvae emerging from Carman variety as it ripens, most are probably from eggs laid by overwintering adults, and are therefore 1 In the sandhill section of North Carolina the varieties ripening previous to Carman are known as early varieties ; Carman, Slappey, and Hiley are mid-season varieties ; while Belle, Elberta, and Hale are late season varieties. Since the details of this bulletin are intended to apply primarily to the sandhill section, the terms early, mid- and late season are here used to include the varieties mentioned in their respective categories above. 2 This second brood is termed the summer brood in this bulletin because it is developed during the period of July and August. *This opinion may appear to be unsound in the case of two adjacent peach growers where one finds one variety (like Hiley) more wormy than that of his neighbor in the same season. However, the difference here would clearly be due to ineffective control measures practiced by one of the two growers. The opinion of the writers is based upon what we believe would occur naturally in the orchard if artificial and cultural control measures were not instituted. Plum Curculio on Peaches stiictly speaking, first brood larvae although they emerge simultane¬ ously with some larvae that developed from eggs laid by the spring brood adults. The larvae from Slappey, Hiley, Belle, Elberta and Hale are believed to develop very largely from eggs laid by spring brood adults. The brood of larvae emerging during July and early August is therefore predominantly a second brood. The height of emergence of larvae of the summer brood appears to be about the time that the Belle variety ripens, which in 1922 was July 16 to 26; although the Elberta variety also ripened during the latter part of this period. Einergence and habits of summer brood adults. The larvae of this brood upon emerging from the fruit, burrow into the soil and transform into pupae and then into adult beetles. About 31 days later the beetles emerge from the soil. In 1922 most of the beetles of this summer brood emerged between August 19 and 26A TABLE 1-INSECTARY RECORDS OF FEEDING AND EGG LAYING ACTIVITIES OF SPRING BROOD BEETLES BETWEEN JUNE 4 AND JULY 19, 1922* EXPERI¬ MENT NO. CURCULIOS iif EXPERIMENT CURCULIOS LAYING EGGS TOTAL NUMBER OF EGGS LAID BY CURCULIOS DATE FIRST EGG LAID DAYS AFTER EMERGENCE FIRST EGG WAS LAID NUMBER OF PUNCTURES MADE 1 2 o 0 127 2 6 1 49 June 22 19 468 3 10 1 36 June 18 14 591 4 10 1 55 June 27 23 618 5 8 o 0 252 6 8 1 53 June 14 8 679 7 6 o 0 307 8 9 1 12 June 21 14 578 9 14 2 116 June 22 15 738 June 23 16 Total 73 7 321 4358 Average 46 June 21 15.6 60 *Discontinued insectary studies on this date in order to examine the harvested fruit of the expeii mentally sprayed and dusted plats in the orchard. At the time of maximum emergence of the summer brood of beetles, all commercial varieties of peaches have been harvested. The beetles then feed upon the foliage or upon scattered fruit left on the tiees. If peaches were available after emergence ol the beetles, it is possible that a third brood of beetles could be reared in the same season. So far as known, however, a third brood is not developed in peaches in North Carolina. About September first the beetles in the orchard, according to our life-history studies, would represent both spring brood and summer ♦Data based on limited observations. 8 The Bulletin, March, 1923 brood beetles. It is even possible that a stray overwintering beetle may be found at this time. The senior writer has kept overwintering beetles collected March 29 alive in cages until August 16 by supplying them with abundant fresh foliage and fruit. At the approach of cold weather, the beetles migrate from the orchard to the woods Jr to suitable hibernating places, there to pass the winter and emerge the following spring. INSECT ENEMIES Two kinds of insect parasites, one a small four winged fly, Triaspis curculionis Bitch, and another, a true two winged fly, Myophasia glo- bosa Twnsd, were reared from the larvae during the summer of 1922. The former species was reared in early June and the latter species in late July and early August. Neither of these parasites was bred in any numbers that would appreciably reduce the curculio infestation. Ants are believed to be somevdiat efficient in reducing the numbers of curculio larvae. They were frequently observed in the act of de¬ vouring curculio larvae when placed on the soil among or near the ants. EXPERIMENTS IN CONTROL The control experiments carried out during the season 1922 con¬ sisted of dusting or spraying three blocks of Elberta trees to compare the effectiveness of these methods of application of materials; the spray¬ ing of two blocks of the Belle variety from one of which the drops were picked up to determine the value of picking up the drops; and the burning over of a portion of the waste land on one side of an orchard, to ascertain the effectiveness of this practice for the destruction of hibernating curculios. The insectary control experiments included a study of the resistance of beetles to various strengths of poison, and a study of the effect of rains upon foliage and fruit recently treated with poison. The field dusting and spraying experiments were conducted in the orchards of the Hoffman Barms,* Hoffman, N. C. The jarring records secured in connection with the burning of an area adjacent to an orch¬ ard were ascertained in one of the Halbert Blue* orchards at Aberdeen. The experiments were primarily designed to secure comprehensive evidence of the value of the control recommendations given to com¬ mercial peach growers throughout the season in circulars and by per¬ sonal visitation, and to ascertain the adaptability of the recommenda¬ tions to the sandhill section of North Carolina. The control recom¬ mendations advocated to growers originated in part from the work of the Bederal Bureau of Entomology in Georgia, and were a modification of those previously advocated by the Division of Entomology of this State. *The thanks of the writers are due Messrs. W. R. Land, Reid Page and U. R. Simp¬ kins, owners of Hoffman Farms, and to Halbert Blue, for their kindness in placing these orchards at our disposal for experimental purposes. 9 Plum Curculio on Peac hes Field Dusting and Spraying Experiments—Elberta Variety i/orr:r/.vrr;r b £S t ‘r r*-'» t™" k« well «t witt fruit. This oreh.ri had , „ re »*i„Tfit«L !fm“ o approximately 60 percent, m spite of the fact that it had been fre¬ quently, but irregularly sprayed. All waste lands about the orchard had been burned over in the early spring of 1922. Description and treatment of plats. Plat I consisted of 35 trees re- ceived no treatment and was used as a check against the other plats. Plat II consisted of S4 trees and was sprayed three times. Plat III con¬ sisted of 90 trees and was sprayed four times.* Plat IV consisted of 18 trees and was dusted four times.* The dates of application, material and formulas used, are shown m table 2. It should be noted that all Fig. 1. Curculio larvae are commonly developed in drops. These should be picked up before the larvae emerge and none should he overlooked. (From U. S. D. A. Circular 216 by Snapp, Turner and Roberts). drops were regularly picked up from all trees except those in the check-plat 1. The first application was made on plats III and IV immediately after the petals had fallen, this application being omitted on plat II. The second application was made on all treated plats just after the *The regular schedule growers were advised to use. 10 The Bulletin, March, 1923 WASTE LAND PLAT I CHECK 35 TREES PLAT H 3 SPRAYS 84- TREES PLAT m 4 SPRAYS 90 TREES PLAT ET 4 DUSTS 18 TREES Q —3 Uj U O CJ h~ < > Z3 o PLAT sn 4 SPRAYS PICK UP DROPS 89 TREES PLATE 4 SPRAYS LEAVE DROPS 81 TREES PLAT ¥ CHECK Z0 TREES 31 ROWS ELBERTA AND GEORGIA BELLE o 0 o o o o o o o 0 o o o o o o 0 • • o o o o o X o o X 0 o • • • o o o o o o 0 0 o o • • • • o o o o o • o o o o o o o o o o o X o • • o X o o o o o 0 0 o o o o • o o o o o o o o o o o o • o o o o • • o 0 • © o • X X o o X o o o o o o o o o o o o o o o o o o o o X o o o o o o o o o o o o o o X o X o o o o X o • o o • • • o • 0 o o o G • X o • • o o • • X o o o o 0 o 0 o X o o o o o o o 0 0 o o o 0 o o o o o o o o o 0 0 0 o X o o o o o o o o o o X X X X o o o X o o o o o X X X o o o o o o o o o o o o X o • o • o • o X o • o o X X o o X o o • o o • o o o X X X o o • o • o • • o o o X X o o o o o o o o o o o o X X o o o o o o o o o o o o Oe O Ui o HIGHWAY LIGHT WOODS Fig. 2. Diagram of orchard experimental plats. The circles represent the location of trees; the solid circles the count or record trees selected in each plat; while the crosses represent missing or replanted trees. Hoffman Farms, Hoffman, N. C., 1922. Plum Curculio on Peaches 11 shucks were shed. The third application, made on all treated plats was given two weeks after the second; and the fourth was made on all treated plats about. a month before the variety ripened. The dates upon which all applications were made are given in table 2. In all spraying either a Bean Triplex 200-gallon sprayer or a Friend 100-gallon sprayer was used at a pressure of 175 to 200 pounds. The sprayers were fitted up with two leads of hose and two nozzles to each lead. The dusting machine used was a Niagara model Dl-2. A total of 427 gallons of spray was used in three applications to plat II (84 trees) ; 533 gallons in four applications to plat III (90 trees) ; and a total of 152 pounds of dusting mixture was used in four applications on plat IV (78 trees). All of the liquid and dry applications were made thoroughly. After the fruit had set, ten trees known as record or count trees (designated by solid circles in the plats in figure 2) were selected in or near the center of each plat, and these were marked by muslin bands. From each of the ten record trees in each of the four plats, a record of each drop and harvested fruit was secured. It is from these record trees that the percentage of infestation by curculio in the drops and harvested fruit was ascertained, the assumption being that each ten trees represented the curculio infestation in its respective plat. A total of 16 examinations of different pickings of drops from the record trees was made on plat I, and 14 examinations on each of plats II, III and IV. These examinations were made between April 25 and July 24 with most of the examinations made during the latter part of April and in May. A total of 5,319 drops was examined from the ten record trees of plat I, 3,198 from plat II, 4,211 from plat III and 2,829 from plat IV, making a grand total of 15,557 drops examined on the four plats. The fruit was harvested in four different pickings made between July 24 and 28. The ten record trees of plat I yielded 4,645 fruits at harvest, those of plat II yielded 4,646 fruits, those of plat III yielded 6,359 fruits and those of plat IV yielded 4,414 fruits or a total of 20,064 fruits harvested on the four plats. A grand total of 35,621 drops and harvested fruit was examined from the 40 record trees of the four plats. Discussion of results, The percentage of curculio wormy drops and harvested fruit of the ten record trees in each of the four plats is shown in table 2. The drops in the check were 63.62 percent wormy; those of plat II sprayed three times were 16.57 percent wormy; those of plat III sprayed four times were 8.34 percent wormy indicating that the drops in the check were nearly eight times as wormy as those ol the plat sprayed four times. The dropped fruit of plat IV dusted four times showed 8.55 percent worminess or about the same as that ot plat III sprayed four times. 12 The Bulletin, March, 1923 TABLE 2— CURCULIO INFESTATION OF FRUIT OF TEN TREES IN EACH OF FOUR ELBERTA PLATS—DROPS AND HARVESTED FRUIT. PLATS II AND III WERE SPRAYED; PLAT IV DUSTED. ALL DROPS PICKED UP REGULARLY FROM PLATS II. Ill AND IV. HOFFMAN, N. C., 1922 * Percentage of fruit wormy Plat No. Dates TREATED Material USED Formula Drops Harvested fruit Drops and HARVESTED FRUIT I Check No Treatment None None 63.62 37.71 52.46 II 3 Sprays Apr. 12 Apr. 26 June 21 AL-L SBLS-AL SBLS-AL 1-3-50 8-8-1-50 8-8-1-50 16.57 8.91 12.03 III 4 Sprays Apr. 4 Apr. 12 Apr. 26 June 21 AL-L AL-L SBLS-AL SBLS-AL 1-3-50 1-3-50 8-8-1-50 8-8-1-50 8.34 6.13 7.01 IV 4 Dusts Apr. 4 Apr. 13 May 1 June 22 S-AL-L S-AL-L S-AL-L S-AL-L 80-5-15 80-5-15 80-5-15 80-5-15 • 8.55 5.69 6.81 Key to table. AL-L—Arsenate of lead and lime; SBLS-AL—Self-boiled lime-sulphur and arsen¬ ate of lead; S-AL-L—Sulphur, arsenate of lead and lime. 1-3-50—one pound powdered lead arsenate, 3 pounds stone lime and 50 gallons of water; 8-8-1-50—8 pounds sulphur, 8 pounds stone lime, 1 pound lead arsenate and 50 gallons of water; 80—5—15—dusting formula of 80 pounds sulphur, 5 pounds arsen¬ ate of lead, and 15 pounds hydrated lime. It should be stated that the drops included not only the small fruits that fell when they were small (fig. 1), but those which were nearly full grown or entirely grown, and fell normally, up until the time of picking. There were relatively more of the drops of the latter class in the check plat than in any of the other plats, and some of these full grown drops nearly all of which were wormy, might have well been in¬ cluded as harvested fruit. This would decrease the percentage of wormi¬ ness of drops but increase percentage of worminess of harvested fruit. As table 2 indicates 37.71 percent of the harvested fruit of the check was wormy. This percentage was reduced in the adjacent plat II to 8.91 percent, the plat having been sprayed three times and having the first application, made on plats III and IV, omitted. The control on plat II is unusually good in view of its location, one end of it having been adjacent to unwooded waste land. Plats III and IV which were sprayed and dusted four times each respectively showed their harvested fruit to be 6.13 aud 5.69 percent wormy. The difference of .44 percent worminess in favor of plat IV might safely be charged to the location of this plat, which was seven rows farther from the unwooded waste land than the location of plat III. The writers feel that the percentages of worminess are representative of the various plats. It is true that the check (plat I) was located at one end of the orchard, and it was on this account subject to greater Plum Curculio on Peaches 13 curculio attack by reason of its location next to unwooded waste land; but on tlie other hand the trees in this plat were more vigorous, larger, and bore more fruit (drops and harvested fruit) by 27 percent than those of plat II, and 37 percent more than plat IY, although 6 percent less than those of plat III. If the diseases—scab and brown rot—were in¬ cluded in the check, the percentage of unmarketable fruit would be, of course, somewhat greater. Experiment to Ascertain Value of Picking up Dropped Fruit—Belle Variety This experiment was conducted in the opposite end of the orchard from that in which the spraying and dusting experiments were con¬ ducted. The variety selected was Belle. The trees were six years old. Description and treatment of plats. Three plats of trees were used in this experiment (see diagram on page 10). Plat Y consisting of 20 trees served as a check and received no treatment. Plats YI and YII consisting of 81 and 89 trees respectively were sprayed exactly as de¬ scribed for plat III (except for the dates of application which are given in table 3) ; but the drops were picked up regularly between April 25 and May 21 on plat YII and left on the ground in plat YI. Else¬ where in the general orchard, which was sprayed four times, the drops were picked up. As in plats I to IY, ten record trees were selected in approximately the center of each plat early in the season. Each drop and harvested fruit from these record trees was examined for curculio, brown rot, and scab. The record of each ten trees was taken as representative of the infesta¬ tion in its respective plat. A total of 4,343 drops and 14,6/5 harvested fruits was examined from the 30 record trees of the three plats. Discussion of results. As is shown in table 3, the check (plat Y) was found to have 31.5 percent of its harvested fruit wormy. In plat YII where the drops were picked up, only 0.61 percent of the harvested fruit was wormy. In plat YI where the drops were left on the giound, ^.0o percent of the harvested fruit was found wormy. These results indi¬ cate that the plat where the trees were sprayed and the drops picked up was only one fiftieth as wormy at harvest as the check plat; and that the plat where the trees were sprayed but the drops left on the ground was one fifteenth as wormy as the check plat. The figures further indicate that the plat where the drops were left on the ground, was more than three times as wormy as the plat where the drops were picked up. If the spring bred brood of beetles is an important factor in causing the fruit as it ripens to become wormy to an appreciable extent, we should expect the plat in which the drops were not picked up to be more wormv at harvest than it proved to be. We should expect it to have shown perhaps as much as ten to twenty percent worminess. Ihe toi- lowing statement of conditions as observed during the season on these 14 The Bulletin, March, 1923 plats may explain why the harvested fruit in the plat where the drops were left on the ground did not show greater worminess. A study of the activity of the curculio during the season, indicated that the migration of adult beetles into this end of the orchard was late. The early drops were comparatively free of worms while the later drops were suprisingly heavily infested. It appeared that the later infestation was due largely to egg laying by spring brood curculios which were reared in a wild plum thicket nearby. Because of this late migration into the orchard, the drops and harvested fruit of the check plat were quite wormy, while those of the sprayed plats VI and VII were com- TABLE 3—CURCULIO I NFESTATION 0F FRUIT 0 F TEN TREES I N EACH OF THREE PLATS, BELLE VARIETY—DROPS AND HARVESTED FRUIT. PLATS VI AND VII SPRAYED ALIKE. DROPS PICKED UP ON PLAT VII BETWEEN APRIL 25 AND MAY 1, AND LEFT ON THE GROUND IN PLAT VI. HOFFMAN, N. C., 1922. Percentage of fruit wormy Plat No. Dates TREATED Material USED Formula Drops Harvested fruit Drops and HARVESTED FRUIT V No Treatment None None 41.67 • 31.50 34.27 VI Apr. 4 Apr. 14 May 1 June 14 AL-L AL-L SBLS-AL SBLS-AL 1-3-50 1-3-50 8-8-1-50 8-8-1-50 2.71 2.03 2.17 VII Apr. 4 Apr. 14 May 1 June 14 AL-L AL-L SBLS-AL SBLS-AL 1-3-50 1-3-50 8-8-1-50 8-8-1-50 1.19 0.61 0.73 Note. —For key to mixtures and formulas see bottom of table 2. paratively free of worms. If both sprayed plats had been infested early in the season so that an appreciable spring brood could have been reared in the drops of these plats, the difference in the percentage of worminess of the two plats at harvest would doubtless have been con¬ siderably greater. The results of this experiment appear therefore somewhat inconclusive. However, if the increased percentage of worm free fruit, secured in the block where the drops were picked up, is ex¬ pressed in terms of commercial crates the value of the increase will be found greater than the cost of this control operation. Worminess of drops during the season. In connection with the value of picking up the drops, it may be stated here, that the drops which had been picked up in various orchards were brought to the insectary throughout the growing season, and the percentage of worminess as¬ certained by rearing the larvae from them. The percentage of wormi¬ ness was found to vary greatly. The higher percentages of worminess were nearly always secured from drops picked up beneath trees that Plum Curculio on Peaches 15 were growing near wooded or waste land. In one instance a bushel of drops composed of 5,338 fruits yielded 3,012 larvae—an infestation of 56.43 percent. These drops which were comparatively small were picked up on May 5, at the time when the third picking was advocated to growers. Fig. 3. Dusting in a peach orchard. It is best to proceed down each tree row and dust only on one row at a time. (From U. S. D. A. Circular 216 by Snapp, Turner and Roberts). Experiment in Burning over Waste Lands to Destroy Hibernating Beetles On March 9, one half of the lightly wooded land adjacent to one side of an orchard of twelve-year-old Elberta trees was burned over, while the other half was not burned. A better than average burn was secured. A series of 44 trees known as block A was then selected in that part of the orchard opposite the burned-over area, and a similar series of 42 trees known as block B was selected opposite the unburned area. A third series of 39 trees was selected on another side of the orchard adjacent to a cultivated field. The trees selected in each block extended six and seven rows deep into the orchard. The tiees veic then jarred for curculios over a canvas frame, an average of about twice a week from March 14 to August 9. The records of the beetles taken are of interest in connection with this experiment up until May 19 when new spring reared beetles were found in the orchard. 16 The Bulletin, March, 1923 Results and discussion of experiment. According to the totals shown in table 4, 730 beetles were jarred from the block of 44 trees located opposite that part of the woods which was not burned over, while 265 beetles were secured from a similar block of 42 trees located opposite that part of the woods which was burned over. The block of 39 trees located adjacent to a cultivated field, yielded a total of 111 beetles. The figures indicate that the burning over of the wooded land was of value Fig. 4. Spraying in a peach orchard, using two leads of hose and applying the spray to two rows at a time. (From U. S. D. A. Circular 216 by Snapp, Turner and Roberts.) in that the burning reduced the number of beetles by 62 percent. They also indicate that only 17 percent of the number that entered the orch¬ ard from block opposite the unburned area, entered the cultivated field side. Laboratory Poisoning Experiments Following each application of the recommended schedule, attention was given to ascertaining the effect of various strengths of poison upon the beetles. Many twigs were pulled from trees, that had either been sprayed or dusted under orchard conditions, and brought to the in¬ sectary. From 15 to 30 healthy curculios were then introduced in each cage containing one or two twigs, and the length of time ascertained until all the curculios died as a result of feeding upon the poisoned Plum Curculio on Peaches 17 TABLE 4 COMPARISON OF NUMBER OF BEETLES JARRED FROM THREE BLOCKS OF 12- YEAR-OLD ELBERTA PEACH TREES BETWEEN MARCH 14 AND MAY 19,1922 WOODED LAND OPPOSITE HALF OF ONE SIDE OF ORCHARD WAS BURNED OVER MARCH 9 ABERDEEN. N. C. Date jarred Number OF BEETLES SECURED FROM 44 TREES OPPOSITE UNBURNED WOODS 42 TREES OPPOSITE BURNED-OVER WOODS 39 TREES NEXT TO FIELD March 14, 16, 21, 24 0 0 o i 4 27 7 0 0 29 64 14 1 31 247 110 17 April 3 66 31 6 5 124 46 36 8 37 20 5 10 92 16 18 13 37 6 10 4 4 15 9 6 2 4 4 18 14 1 4 4 4 21 9 2 2 4 « 24 2 0 0 May 5 7 5 1 4 4 9 8 2 4 4 4 13 4 5 4 4 i 19 3 1 1 Total beetles 730 265 111 Total beetles on basis of 44 trees to each block 730 278 125 foliage. Similar curculios were, of course, placed in similar cages con¬ taining unpoisoned foliage. In general it was found that the beetles lived five to eight days before death ensued, after they had fed upon foliage and fruit which had been sprayed at the rate of one pound of powdered lead arsenate to 50 gallons of water. It was noted, however, that the beetles were usually quite inactive after the third day of ex¬ posure to sprayed fruit, and that after this time they fed very little and deposited no eggs. It is quite obvious that the beetles are strongly resistant to arsenical poisons. In connection with the poisoning experiments we have observed that moderately heavy showers following a spray or dust application within twelve to twenty-four hours, decrease very decidedly the effectiveness of the poison in the spray or dust. The insectary studies on this phase indicate very conclusively that the greater the amount of rainfall fol¬ lowing an orchard spray or dust treatment, the longer the interval be¬ tween the feeding of the curculio on this foliage and its resultant death by arsenical poisoning. CURCULIO CONTROL RECOMMENDATIONS Experience has shown that in order to grow peaches commercially and reasonably free of curculio injury, it is necessary to practice sever a control measures systematically which extend throughout the growing season. These control operations may be listed under four heads: ( ) 18 The Bulletin, March, 1923 orchard sanitation, (2) applications of spray or dust mixtures, (3) picking up of dropped fruit, and (4) cultivation. It is a matter of common observation that during the season 1922, the cleanest fruit in the sandhill section was grown in the orchards where owners carried out each of these measures assiduously; and that such growers who neglected one or more of these operations, or were careless in executing the recommendations, suffered curculio injury proportionately. We know of growers who were disappointed with their results when their harvested fruit showed a small amount of worminess. Careful inquiry in some cases indicated that such growers failed to re¬ duce the worminess to the degree hoped for because of various reasons. Among these were, the failure to make a spray or dust application at the proper time, the alteration of formulas of spray mixtures which were recommended, and the carelessness in picking up all drops. Suc¬ cessful control of the curculio (and so far as our experience shows the brown-rot and scab as well) can only he obtained by adhering rigidly to the schedule and details of the following recommendations. Orchard Sanitation Since the curculio is known to spend the winter in sheltered places in woodlands, waste lands, or in piles of rubbish in or adjacent to peach orchards, it is obvious that it will he of advantage to reduce the num¬ bers of beetles by cleaning up such places. When the edge of the or¬ chards do not furnish suitable hibernating places, the beetles will of necessity search further away from the orchard for suitable quarters. This increases the hazards for their successful return the following spring. Our experiment in burning over wooded land adjacent to the orchard indicates the advisability of this practice at least as far as a control measure for the curculio is concerned. It seems advisable that the burning should extend 200 to 300 yards from the orchard. The burn¬ ing must he done thoroughly however; and this means that the vegeta¬ tion and rubbish must he entirely dry at the time of burning; otherwise the fire will not burn close to the ground, and some beetles will in con¬ sequence escape the burn. Precautions in burning are, of course, neces¬ sary and essential. Burning should never be done without competent supervision and sufficient labor to cope with any emergency that may arise. . Spraying and Dusting Applications The spraying schedule previously recommended by the bforth Caro¬ lina Department of Agriculture and Experiment Station but modified by workers of the Federal Bureau of Entomology at Fort Valley, Ga., and recommended to peach growers in this State during 1922, has been found satisfactory for the curculio both by the growers and in our own orchard tests. The brown-rot and scab diseases are seldom a serious Plum Curculio on Peaches 19 Fig. 5. View of ground rearing cages and insectary. Aberdeen, N. C., 1922. Fig. 6. . Trays for rearing curculio larvae from drops, and insectary. Aber¬ deen, N. C., 1922. 20 The Bulletin, March, 1923 factor in the sandhill section, but the schedule has also proved satisfac¬ tory for the control of these diseases in the peach sections of Georgia. It is reasonable to expect that this schedule will control brown-rot and scab in the sandhill section of this State; though it may be found ad¬ visable at times to make an extra application of self-boiled lime-sulphur as a spray, or dry sulphur as a dust, a week or ten days before the late varieties ripen. According to our present knowledge all varieties ripen¬ ing later than Carman should receive all four applications of either schedule, although in some seasons it may be advisable to also make four applications on Carman. Varieties ripening previous to the Car¬ man should receive three applications of dust or spray which are to be made at the times recommended in the schedules for the first, second, and fourth treatments. Spraying Schedule First application. Immediately after the petals fall, use one pound of powdered arsenate of lead, plus lime water in which 3 pounds of good stone lime has been slaked, to each 50 gallons of water. Second application. When the calyces or shucks are shedding, which is about ten days after the falling of the petals, use the same spray as for the first application. Third application. Two weeks after the second application or about four weeks after the petals have fallen, use 1 pound of powdered arsen¬ ate of lead with each 50 gallons of 8-8-50 self-boiled lime-sulphur. Fourth application. About four weeks before each variety is due to ripen, use the same spray as recommended for the third application. Dusting Schedule The 80-5-15 mixture composed of 80 percent sulphur, 5 percent arsen¬ ate of lead, and 15 percent hydrated lime is recommended for dusting. The applications should be made at the same times that the spray appli¬ cations are recommended, the same dusting formula being used for all dust applications. The times for dusting applications are, first, im¬ mediately after the petals have fallen; second, when the calyces or shucks are shedding; third, two weeks after the second application; fourth, about four weeks before each variety is due to ripen. Directions for Preparing Spray Mixtures Lead-lime-water mixture. Slake three pounds of stone lime in a small quantity of water and dilute to 50 gallons. Mix one pound of powdered arsenate of lead in a small quantity of water and add to the lime mix¬ ture. Agitate thoroughly before applying. Self-boiled lime-sulphur mixture. The 8-8-50 self-boiled lime-sulphur mixture is composed of 8 pounds of good stone lime, 8 pounds of sulphur Plum Cukculio on Peaches 21 and 50 gallons of water. Any finely powdered sulphur (flowers, flour, 01 commercial ground sulphur) may be used in the mixture. The formula may be raised to 16-16-100, or 32-32-200 to meet the capacity requirement of the spray tank. The amounts used in the following directions are for a 200 gallon tank. Place 32 pounds of lime m a 50 gallon barrel and pour on enough water to start slaking. As soon as the lime begins to slake, 32 pounds of sulphur should be added, the lumps of sulphur if present having been previously broken up. Add water from time to time to keep the mixture from becoming dry, but be careful not to drown the lime, as this will cause the mixture to cease boiling. The mixture should be stirred constantly. After the mixture has boiled about five minutes, cool with water to prevent further cooking. The mixture is then ready to be strained into the spray tank and diluted to 200 gallons. Precau¬ tions should be taken to cool the mixture with water before the red streaks appear to any extent in the mixture; on the other hand the mixture must not be cooled before the boiling has progressed sufficiently. The required amount of arsenate of lead should be mixed separately in a small quantity of water, and this mixture then added to the self- boiled lime-sulphur mixture in the spray tank, when a poison is called for in connection with the self-boiled solution. Thoroughness and Timeliness in Application The fully desired results from dusting or spraying will not be ob¬ tained unless the applications are made in a thorough manner and at the proper time. This is true in the control of most insects and di¬ seases, and especially is it true of curculio control. In spraying a tree, the operator should start on the side of the tree away from the spray machine and work around the tree, being careful to cover the tree and particularly the fruit entirely. The hauling of water to the spray outfits in the orchard will very often facilitate spray¬ ing. Competent supervision of spraying is essential to see that the mixtures are properly prepared and thoroughly applied. In dusting, the machine should be driven down each tree row so that the operator can dust the near side of each tree. Unsatisfactory results are usually obtained when an effort is made to dust two or three rows at the same time. Many local conditions at th§ time of dusting will govern the exact methods to be employed, but one should aim to coat the tree lightly and envelop it in a cloud of dust. Picking Up Dropped Fruit We have previously shown that many larvae develop in the small drops in spring, and that these larvae transform to beetles in the ground which lay eggs in the late varieties of peaches. This biological habit suggests the importance of picking up all dropped fruit, and particularly 22 The Bulletin, March, 1923 the small drops found under the trees during the latter part of April and the entire month of May. It is especially important to pick up the very small drops during late April and early May. Moreover, the drops should be picked up at least three times every two weeks, and preferably twice each week. The necessity for picking up the drops frequently and regularly is readily understood when it is realized that many of the larvae do not remain in the drops more than a week after these fruits have fallen. Some of the infested fruits do not fall until after the larvae are half grown; in fact in a few instances we have seen small fruits, from which the larvae had emerged, still hanging on the tree. Cultivation of the orchard in connection with the picking up of drops is important. Picking up of drops should always immediately precede cultivation, so that none of the drops will be covered with soil. Results will certainly be unsatisfactory if the orchardist does not give due at¬ tention to the relation of the picking up of drops and cultivation. This phase of curculio control together with the timeliness and thorough¬ ness of picking up all dropped fruit, both large and small, at the times indicated, again suggests the need of good supervision in curculio con¬ trol operations. It is, of course, necessary to dispose of all dropps immediately after they have been gathered. The best way to dispose of the drops is to bury them with 'quicklime in a pit so that the top layer will be two feet below the surface of the soil. Boiling the drops may be satisfac¬ tory hut caution is urged not to allow the drops to stand around in containers so that the larvae can escape to the ground before the drops can be poured into the boiling water. The cost of picking up of drops is comparatively small when the benefits to be derived are considered. This control operation not only reduces the number of curculios but in certain seasons the amount of drown rot as well. Orchard Cultivation and the Destruction of the Curculio It is the present practice of fruit growers in the sandhill section to cultivate frequently throughout the season. This orchard operation not only benefits the trees hut is believed by the growers to destroy the larvae and pupae of the curculio while in their cells in the ground. Our observations indicate that comparatively few larvae and pupae of the curculio are destroyed by cultivation in the sandy type of soil char¬ acteristic of this sandhill section; at least the number killed by cultiva¬ tion is considerably smaller than is generally supposed by fruit growers. The senior writer has frequently disturbed larvae and pupae of the curculio in cages in the insectary and observed that a higher percentage matured than would ordinarily be expected in the case of a soft bodied insect like the immature stages of the curculio. Plum Curculio on Peaches 23 During the months of May, July and the first half of August, when the larvae and pupae of the curculio are found in the soil in numbers, cultivation of the soil will probably be of some assistance in controll¬ ing the curculio. It would seem, however, that we could not recommend a cultivation of the orchard solely for the purpose of destroying larvae and pupae of the curculio. Print Stop 18527