Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. Washington, D. C. September 13, 1923 FURTHER STUDIES WITH PARADICHLOROBENZENE FOR PEACH BORER CONTROL WITH SPECIAL REFERENCE TO ITS USE ON YOUNG PEACH TREES. By Outver I. Snapp, Entomologist, and CuarLtes H. ALDEN, Scientific Assistant, Fruit Insect Investigations, Bureau of Entomology. CONTENTS. Page. Page. Introduction. ......--)------2--+0----2+-022-- 1 | Laboratory experiments—Continued. | Experimental results in the field...........-.- 2 Mortality of peach-borer larvee exposed | Efiect of paradichlorobenzene on the trees... 6 to paradichlorobenzene....... Bats}. 14 | Results from winter and spring treatments. . 10 Effect of temperature and moisture on Correct method of applying paradichloro- the effectiveness of paradichloroben- OTRO Ce spt dope < crerera' aya) <1 Aa aint Bim ae o's 4 12 DONC Y Feces ho a ctoptd ee ps pane ete aoe 15 Laboratory experimenits....................- FS | UML on onc alon aa canlnae sets oem Acae eee 18 Rate of evaporation of paradichloro- DEHZERDCLYSUQIS: «0225 oc no. sai weet asese INTRODUCTION. The use of paradichlorobenzene for the control of the peach borer (Aegeria exitiosa Say) on trees 6 years of age and older has rapidly increased in popularity among peach growers since the appearance of the report by E. B. Blakeslee ‘ on his experiments on this new method of control of this most destructive enemy of the peach. Peach growers throughout the area of distribution of the peach » borer east of the Rocky Mountains have already adopted the treat- ment to a large extent, and in certain important peach-growing areas where the borer is excessively troublesome the employment of para- dichlorobenzene has become rather, general. Thus in Georgia dene, during 1921, 250,000 pounds of the chemical were used, and possibly more was required during the season of 1922. The experimental results obtained by Blakeslee showed that this chemical is safe when properly employed for the control of the peach borer on trees 6 years of age and older. In certain cases, however, injury to trees younger than about 6 years occurred. Since the peach borer is often very destructive in young orchards, it is highly desir- » able, if possible, to use the chemical on trees of all ages. Further experimentation by the Bureau of Entomology and several of the agricultural experiment stations, notably those of New Jersey, Mary- 1U.S8. Dept. of Agriculture Bulletin 796, Use of Toxic Gases as a Possible Means of Control of the Peach-Tree Borer. 1919. 46631 °—23——1 2 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. land, Indiana, and Illinois, indicates that this can be done, provided the directions for use are carefully followed. Beginning with the fall of 1921 and extending through the spring of 1922, extensive experiments with paradichlorobenzene were conducted by the Bureau of Entomology in the peach belt of Georgia on trees ranging from | to 6 years of age. At the same time studies were made in the laboratory on the effect of temperature and moisture on the rate of evaporation of the chemical, in order to obtain results for compar- ison with those obtained under orchard conditions. This bulletin gives a report of progress rather than specific recom- mendations as to the use of paradichlorobenzene on peach trees younger than 6 years of age. The results obtained are very favorable to the employment of the chemical on young trees. Injury resulted only to a few trees in the way of brown lesions in the outer bark layers. Nevertheless, final recommendations can not be made until additional experimental work is completed. In the meantime peach erowers should decide for themselves whether, in view of their indi- vidual conditions, they are warranted in adopting the treatment on young trees, or whether they should continue the well-known practice of worming. EXPERIMENTAL RESULTS IN THE FIELD. The chief objects of the field experiments were (1) to ascertain | what dosages can be used effectively and with safety on young peach trees; (2) to note effects from not opening up soil mounds six weeks after applying the chemical and to note the effects from allowing the crystals to remain around the trees all winter; (3) to determine the effectiveness of late fall, winter, and spring applications to peach trees. The object of the laboratory work was to determine the effect of temperature and moisture on the rate of evaporation of paradichloro- benzene, and to ascertain what influence these factors have on the mortality of the peach borer from the toxic gas. FIVE-YEAR-OLD ORCHARD TREES. One hundred and twenty-two trees were used in an experiment on 5-year-old trees. Both long exposures of small doses and short ex- osures of large doses were tested. For the long-exposure tests one- alf, three-fourths, and 1-ounce doses were applied October 12, 1921. The soil was removed and examinations made on groups of five trees in each test three, four, and six weeks after the material was applied, and on five trees the examination was not made or the soil disturbed until the spring of 1922. Some of the trees in the check or untreated plat of this experiment were examined for borers six weeks after the application was made to the treated trees, and the others the follow- ing spring. or the short-exposure tests, 14, 2, and 24 ounce doses were applied October 20, 1921. The soil was removed and examinations made on groups of 5 trees in each test 4, 8, and 12 days later. The trees in the check or untreated plat of this experiment were examined for borers during the latter part of November. Table 1 gives the results on the effectiveness of the various doses of paradichiorobenzene at different exposures as used on the 5-year-old orchard trees. PARADICHLOROBENZENE ON YOUNG PEACH TREES. a. TaBLeE 1.—Results of different treatments of paradichlorobenzene on peach-borer larve in 5-year-old Redbird peach trees, Fort Valley, Ga., 1921-22. Per cent of larve. Number of larve found. Num- ltol c= of ae Date = ose. | appli amined. é trees. id j -| Dead. | ee | Active. " ae ‘Ounces.| 1921. | 1921-29. | | | 5 4 | Oct. 12| Nov. 3! 22 | 8 2 1 | 72.7 \. 18,2} 9.1 5 2 a ees 9 | 28 i 0 0| 100.0] 0 0 5 | hep ada. - <-| 23 42 3 0 0} 100.0 0 | 0 5 | 4 |...do....| Apr. 13 | Over win- 4 0 0 | 100.0 ! 0 | 0 ter. 5 ae) 5.00. ..-|.Nov.. 3 22 6 1 0 85.7 14.3 | 0 5 af 2 Goel. 9 28 17 i) 0 100.0 0 0 5 742. :00-. = 5 23 42 5 0 0 190.0 | 0 0 5 2 }...do....| Apr. 13 | Over win- 1 0 0 100.0 | 0 0 ter. 5 femss-d0...:|INov. 3 22 8 0 0 100.0 | 0 0 5 is OO... _ 9 28 19 0 0 100. 0 | 0 0 5 1 S°do. | - 23 42 5 0 0 100.0 | 0 | 0 5 1* |..-do...-| Apr. 13 | Over win- 2 0 0 100.0 | 0 | 0 ter. } } 5 13 | Oct. 20 | Oct. 24 + 2 2 04 50.0 | 50.0 | 0 5 de paris 6 (pai 28 8 3 0 1 83.3 0 16.7 5 Pie do. Nev. 1 12 16 1 0 94.1 5.9 0 5 2712 00-- 1) Oct... .24 4 it 7 0 36. 4 63.6 0 5 ie de... 28 8 4 | 0 0} 100.0 0 0 5 Zt G0.-.. | iNove — 1 12 6 0 0 100.0 0 0 5 23 1...do..-.| Oct. 24 4 12 7 0 63.2 36.8 0 5 7 ty ea 6s ae 28 8 8 0 0 100.0 0 0 5 Pas d6s2 ONO. 12 4 0 0 100.0 0 0 4 | Check. |..20.20... oN) Me deme etrang &. 0 0 5 0 0 100.0 40 }.(hock: |.) _...... Tip Sees | OR 0 0 61 0 0 100.0 Si ite coe Apr. 13 0 0 8 0 0 100.0 FOUR-YEAR-OLD ORCHARD TREES. In the experiment on 4-year-old trees also, 122 trees were used, and all tests conducted on the 5-year-old trees were duplicated on 4-year-old trees. Table 2 gives the larvicidal action of the various doses at different exposures on 4-year-old trees. TaBLE 2.—Resulis of different treatments of paradichlorobenzene on peach-borer larvx in 4-year-old Redbird peach trees, Marshailville, Ga., 1921-22. | Number of larve found. | Per cent of larve. ——" ize of eye Date = poset ose. | app amined. O gas. : __ trees. Dead. Gana Active. | Dead. pee Active E> | Ounces.| 1921 1921-22 Days 5 3 | Oct. 10] Nov. 1 22 17 0 0} 100.0 0 0 5 4 f- 807: 7 28 6 0 0 100.0 0 0 5 + ee do.7.. 21 42 2 0 0! 100.0 0 0 5 q 133540) 52.2 Apr. 10 | Over win- 2 0 0 100. 0 0 0 ter. 5 2 |...do.....]| Nov. 1 22 i 0 0 100.0 0 0 5 3 |...do.... 7 28 2 0 0 100. 0 0 0 5 yr: (es ae 21 42 0 0 J eee Sees ee 5 ; do. 0_/ApeU10 eg 3 0 0 100.0 0 0 er. i 5 Be J7.80-c- 5 Noy. 1 22 10 5 0 66.7 33.3 0 5 4 43--dp. 2-4 7 28 0 0 OP -Oi2 i. 4. 1S. TSh SABLE ’ 5 1 a ae 21 42 3 0 0 100.0 0 0 5 b Aietdo 0 | 9009-5 tS, She 5 | OWe seas 28 days 1} 87.5 | 20} 19} Oj; O {100 1519} OO} O} 100 42 days 0 |100 20! 5] 01} 07100 15} 8}| O} O| 100 Over winter... 0 |100 15} 6; 0} O /}100 15|} 6| O| Of 100 Chiecle-estti eae: ts sync Ne 559 heh eee [ee ale le aol ota oa eee scm ab at. Sep eecteie sales. c eae |e et eS. 13-ounce dose. 2-ounce dose. 24-ounce dose. Check, Days larvae were Larve. 3 Larve. 3 Larve. 3 Larve. exposed to = a = gas (1921). td i od oS AP © Powahe ve Oo} 2/8 ao} .] & = -18 °o rs) amt Wass ° o | o ° . <>) e| Sis he o| 8 = = | al eshte mn S\a\x Che) St oe oper hs 1S yrs li sas worl SB hyo 1s) [ts pS Alaliat& IH JAslal/sa]/ a [Hh ljAlajai & |aelali4a Adnyset fh ck 5 P4 Py Of 5526 1/20 W221 13 | FOV 6219 1S PS 145 FO 56.3 Eel. yaa Sidavse seek sa 1D 1 Ou ake Qh. 7} 20st. | abel O000. OC LALS) |. Sites Ole ON TOO || 2 ah lete alee A shysi 222282 A822 25 6 8057 |) 208,719 fe 42") OFF 90-5 715 15 | OAT O00" ale 9. | eee Stee POON cers eoas a aie tae ee => fecgcinty o> -|aer57a sited eee Ee - - lor etas SS. Hey Sock cere! esas. seen ee 2 ci systems SARS: acid A PEAS Soe Bieta |e apes a ERS eee gee hea Peak) bea lool paaleose gee cee ADU S ee Seta seals wes) eek eek | feta | Stee A= ee eeal eae ioe Weise oll arte €) PARADICHLOROBENZENE ON YOUNG PEACH TREES. rf ONE-YEAR-OLD TREES. Eight 1-year-old Hiley peach trees exposed 12 days with one-half and three-fourths ounce doses showed no injury to either the trees or trunks. Of four 1-year-old Hiley trees exposed 18 days to l-ounce doses two of the trunks showed some injury which might be attributed to the paradichlorobenzene. The trunk of one of these trees showed severe popper with small brown lesions in the outer bark layers at about the place where the crystal ring had been placed. The cambium was uninjured. The other injured tree showed only slight peppering of the outer bark layers with small brown lesions. Both of these trees appeared very healthy from the top, and had appar- ently not been affected by the paradichlorobenzene dose. TWO-YEAR-OLD TREES. Of thirty 2-year Hiley peach trees exposed to one-half and three- fourths ounce doses from three to six weeks, all appeared very healthy and vigorous from the top when the final examinations for tree in- jury were made. (PI.I.) The trunks also showed no injury what- ever, with the exception of four. These four showed a slightly pep- pered appearance in the outer bark layers, but the cambium was uninjured. Of sixty 2-year-old trees treated with doses varying from three-fourths to 2 ounces exposed to the gas from 4 to 12 days, all were very healthy and growing vigorously. The trunks of 58 were uninjured, while 2 showed the outer bark layers slightly pep- pered with brown lesions. The 15 check or untreated trees were all healthy and vigorous when each examination was made. The trunks showed no abnormal condition of the outer bark layers or cambium. THREE-YEAR-OLD TREES. Sixty 3-year-old Hale peach trees treated with doses varying from one-half to 1 ounce showed no injury from the paradichlorobenzene to either the trunk or the tree at any of the three examinations. The mounds around 15 of these trees were not disturbed after the paradichlorobenzene was applied until the spring of 1922. The other 45 trees were exposed to the gas for periods varying from three to six weeks. Forty-five other 3-year-old trees treated with 14 to 24 ounce doses and exposed from 4 to 12 days showed no injury to the trunk or tree at any of the examinations. The 17 trees used as checks in this experiment appeared the same as the treated trees when each examination was made. The 83-year-old trees used for this experiment were exceedingly healthy and vigorous, and the bark layers were thick for trees of that age. FOUR-YEAR-OLD TREES. The trees used for the four-year experiment were of the Redbird variety, and the orchard as a whole was in very poor condition and the trees neglected. Sixty of these trees were treated with doses varying from one-half to 1 ounce and 45 were exposed to the gas for periods ranging from three to six weeks. The mounds around the remaining 15 were not disturbed until the spring of 1922. At the final examination 16 of the 60 trees showed peppering with brown lesions on the trunk at about the place where the paradichlorobenzene 8 BULLETIN 1169, U. S. DEPARTMENT OF. AGRICULTURE. ring had come in close proximity to the bark. The trunks of the other trees did not show any injurious effects from the use of the chemical. A detailed study of the bark of some of the injured trees showed brown flecks in the 1920 and 1921 layers, and two flecks had merged into the 1922 layer. The layers inside and outside of the 1920 and 1921 layers were practically free from flecks. The injury occurred over a distance of about 1 inch at the point where the crys- tals had been placed around the tree. There was no injury above or below this point. The gas passed through from 2 to 4 millimeters of outer bark layers without causing any visible injury. In the next 2 millimeters of bark, which includes the 1920 and 1921 bark layers, brown flecks from 4 to 1 millimeter in diameter, somewhat ellipsoidal, the long axis parallel with the bark rays, extended to within 1 milli- meter of the cambium at the time of treatment. The largest flecks were about 3 millimeters long and 1 millimeter wide and about 10 flecks may occur per centimeter of circumference of the tree. Of forty-five 4-year-old trees treated with doses varying from 14 to 24 ounces and exposed to the gas from 4 to 12 days, 44 were healthy and showed no injury to the trunk. One showed some peppering. The 17 untreated trees were all healthy. On account of improper handling and neglect in the 4-year-old orchard, the trees had made very poor growth. Measurements of the trees used for paradichlorobenzene experiments in this orchard averaged 1 foot 1 inch in circumference, and 9 feet 2 inches in height. The measurements of the trees used in the 3-year-old orchard aver- aged 1 foot 24 inches in circumference and 10 feet 5 inches in height. The difference in size and vitality perhaps influenced injury on the 4-year-old trees, where the bark layers were perhaps even thinner than the layers on the vigorous 3-year-old trees, which showed no indications whatever of injury from the use of paradichlorobenzene. FIVE-YEAR-OLD TREES. Sixty 5-year-old Redbird peach trees were treated with doses vary- ing from one-half to 1 ounce, 45 of which were exposed to the gas for periods ranging from 3 to 6 weeks, while the mounds around the remain- ing 15 were allowed to remain around the trees throughout the winter. At each examination made for tree injury no injurious effects from the use of the paradichlorobenzene to the trunk or tree in the case of these trees were observed. Forty-five trees were exposed to 14 to 24 ounce doses for from 4 to 12 days with no injury to either the trunk or the tree. The check or untreated trees were in the same condition as the treated ones, and in no case among all the 5-year-old trees used for the experiment could any injury to the tree or trunk be attributed to paradichlorobenzene. SIX-YEAR-OLD TREES. Forty 6-year-old Redbird peach trees were treated with 1-ounce doses late in the fall of 1921, and the mounds left up around the trees over winter. Examinations made in the spring and again in July of 1922 showed no tree or trunk injury from the late use of the chemical on trees of this age and from allowing the mounds to remain around the trees over winter. Twenty-four trees treated in the spring of 1922 with 1-ounce doses showed no injury from paradichlorobenzene ‘ Bul. 1169, U. S. Dept. of Agriculture. PLATE I. CONDITION OF 2-YEAR-OLD HILEY PEACH ORCHARD IN THE SPRING AFTER BEING PARTIALLY TREATED WITH PARADICHLOROBENZENE THE PRECEDING FALL. 1. First four rows treated, others untreated. 2. Rows to left treated, those to right untreated. 4 PARADICHLOROBENZENE ON YOUNG PEACH TREES. 9 when examinations for tree injury were made in July of the same ear. Innocase among all the 6-year-old trees treated in late fall or in the spring could any injury to the cambium layer be attributed to the paradichlorobenzene treatment. DISCUSSION. The characteristic severe tree injury from the use of paradichloro- benzene on young peach trees reported as a result of experimental work conducted in more northern latitudes did not occur on any of the young trees used for the experimental work in Georgia during 1921-22. Different climatic conditions which usually cause rapid evaporation of the crystals may be responsible, and these are such that perhaps it may be possible to use this new treatment on young peach trees in Georgia and other Southern States without injury to the tree. During a normal fall in central Georgia a 1-ounce dose placed around a peach tree will entirely evaporate and leave no traces of odor within six weeks. In no case among the 558 young peach trees used in the paradi- chlorobenzene experimental work in Georgia during 1921-22 could it be determined that the cambium layer was injured as a result of the toxic action of the gas; but in some instances, previously noted, brown lesions were observed in the outer bark layers that could be attributed to the gas, since most of the lesions were at a point on the trunk near which the crystal rmg had been placed. No special injury from leaving the mounds around the trees all winter after making the application could be discerned. Notes were kept on the quantity of crystals left and the odor present when each tree base was opened for examination. These notes re- vealed the fact that in the majority of cases 1-ounce doses will entirely evaporate and the odor disappear within six weeks during a normal October and November in the latitude of Georgia, provided too much earth is not placed over the crystals in mounding after applying the chemical. ence during a normal fall it is not necessary to uncover the base of the trees, especially the old ones, in Georgia and the Gulf States six weeks after applying the chemical in order to allow the gas to escape, or to remove any remaining crystals. If the fall is cool or if the material has been applied very late, this additional precaution against injury might be considered and the tree bases uncovered six weeks after applying the material. This precaution might also be taken if the material is used on young trees. Since the three-fourths and 1-ounce doses exposed for four weeks or longer resulted in a better control of the peach borer than the large doses with short exposures, and since the effect on the trees from these long exposures was no greater than from the large doses with short exposures, it is suggested that in using paradichlorobenzene on peach trees 4 years old or younger in Georgia the three-fourths ounce dose be used and allowed to remain around the trees for four weeks. As an added precaution against injury on young trees, uncover the base of the tree four weeks after applying the chemical. On peach trees 5 years old and older in Georgia, use the full 1-ounce dose, and if the chemical is applied at the time recommended and if the fall is not abnormally cold it will not be necessary to uncover the base of the old trees after applying the paradichlorobenzene. 46631°—23——2 10 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. RESULTS FROM WINTER AND SPRING TREATMENTS. To obtain information on the results that may be expected to follow the application of paradichlorobenzine to peach trees in the late fall or spring for the control of the peach borer, an experiment was conducted on 6-year-old trees during the fall of 1921 and the spring of 1922. This experiment also furnished additional data on the results from not uncovering the tree base after applying the chemical. Kighty trees were used in this experiment and 1l-ounce doses were applied in all tests. Ten of the trees were treated October 24, which was about two weeks after the usual time. These trees were not examined or the soil disturbed until May 5, 1922. Ten other trees were treated on November 9, which was about four weeks later than the time for best results. Ten others were treated on November 23, which was about six weeks late, and 10 others on December 6, which was eight weeks later than the date recommended for best results. None of these trees was examined nor was the soil around them dis- turbed until May 5, 1922. Ten untreated trees were examined on May 6, as a check on this experiment. For the spring test l-ounce doses were applied April 3, 1922, to twenty-five 6-year-old trees which had not been treated the previous fall. By this date the daily soil temperature in Georgia was averaging over 60° F. at a depth of 3 inches. These trees were all examined on May 13, 1922, or about six weeks after the material was applied. Five untreated trees used as a check on this experiment were also examined on May 13. Table 7 gives the summary of results on the effect of late fall and spring treatments of 1-ounce doses of paradichlorobenzene on peach- borer larve. TaBLe 7.—Summary of results of late fall and spring 1-ounce dose treatments of para- dichlorobenzene on peach-borer larve in 6-year-old Redbird peach trees, Fort Valley, Ga., 1921-22. Number and condition of larve. Per cent larvee. Dead. Stupefied Active. d |Z d |Z d | Num- - fe) we) w=) Date | Dateex-|p.... Ele Bie B = Aah applied. | amined. Exposed to gas. 3 | & & 3 5 & F Eb & elalts|/Elal's|}Blalta Sd eens (ed ae Ol od eons 8 jag) | 5 gel &| 5 IgE : aa © sroup es © |s> oo) oS |} oO ® : £1 S be 21S J we eda OlH lO 1oJ{e lo |6oO [BIO J A a < 1921-22. 1922. | 10.);Oct: -24.| May 5.| Over’ riwinter-| | 2222 0)-22.|_ 3 aot ag ie 2) flo 0 25.0 (193 days). LOW NONe. Sale -sdOs--< 3 Over), Winter jo: -}ec D Neer she cia. | foe IROSSTEEE - 100. 0 0 0 (177 days) 1ORVINOF. 23 |... 3002-22 Over winter] 1 D ist & eee ae as ie ees 100. 0 0 0 (163 days). LOUD ees 64). 2.d0l.2 2. Ower ) “winter-He : ofp tah Ae AS Ae oe L*gr) 0 0 100.0 (150 days). PURI MeCK.>. |) May MOMlne case amemee ace cepa? [aoe ot eee ae ae IZ B3t Lib. | 0 0 100. 0 25 | Apr. 3] May 13 | 40 days......... 7110 t 2 1 0 0 4 1 | 72.4 10.4 T7622 5 | Check... |... GO Sele ov tcn hos se eh oe ae SS eee <= 1 8} 0 0 100.0 It is difficult to locate dead borers 150 to 200 days after applying the chemical, on account of decomposi- tion; hence the few borers recorded on long exposures above. The checks show the number probably dresent when the experiment began. . be t 2 PARADICHLOROBENZENE ON YOUNG PEACH TREES. Tt Table 7 shows that the spring treatment of paradichlorobenzene in Georgia is not as effective for the control of the peach borer as the early fall treatment. ‘This is perhaps largely due to the size of the larve in the spring and the fact that many individuals are in deep galleries by that time. The larger the borers and the deeper they are in the gallery the more difficult it is to kill them with paradichloro- benzene gas. The 1922 Bees treatment gave a borer mortality of 72.4 per cent. The early fall treatment gave from 95 to 100 per cent \ A N : \) BEADS) Cee ¢ GEE! S30 SHE 4 TEMPERATURE, F Lt |s|oer TT] ee te Pan aie heer aa a 1 7) see a Fie. 1—Monthly mean soil temperature 3 inches below the surface, at Fort Valley, Ga. (The heavy horizontal line indicates the lowest temperature for best results with paradichlorobenzene.) mortality; 17.2 per cent of the borers were active six weeks after the spring applications were made, and 10.4 per cent of them were stupefied. Spring applications of paradichlorobenzene will not give as satis- factory control of the peach borer as the early fall applications, and they can not take the place of the fall treatments. They should only be used where for an unavoidable reason the grower was not able to apply the material in the fall. Where conditions warrant these spring applieations, they should be applied by April 1 in Georgia and the Gulf States. For best results with paradichlorobenzene, it 12 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. must be placed around the trees when the soil temperature is 60° F. orhigher. Figure 1 shows that the soil does not warm up sufficiently for applications before April 1. On the other hand it is important to prevent tree damage from the borers as soon as possible and to kill them before they have gone deep in their galleries or have attained large size. Consequently, do not wait later than April 1 for spring applications. The results from the application made on December 6 were very poor. When the examinations on these trees were made on May 5 every borer that could be located was active. Of course, some may have been killed and decomposed before the examinations were made. The poor results can be attributed to the fact that the soil is too cold during December in Georgia for the generation of gas from paradichlo- robenzene crystals. As shown in Figure 1, the average soil tem- perature during December, 1921, was 56° F. Some of the applica- tions made at two-week intervals after October 15 gave very good results, yet 25 per cent of the borers were active in the spring in trees that had been treated with paradichlorobenzene October 24, or two weeks later than the usual time. For best results, paradichlorobenzene must be applied in the early fall, at the close of the oviposition period of the adult. At this time the borers are small and the galleries are shallow. Furthermore, 1-ounce doses applied immediately after the oviposition season will pene entirely in six weeks, or before the soil temperature becomes too low for the gas to generate. ‘The work reported here shows that the best results with paradichlorobenzene for peach-borer control in central Georgia will be obtained by placing the erystals around the trees October 10. CORRECT METHOD OF APPLYING PARADICHLOROBENZENE. In practically every case where a peach grower failed to get satis- factory control of the peach borer with paradichlorobenzene it was found that the directions for applying the chemical were not closely followed. It is absolutely essential to follow the directions very closely if best results are to be obtamed with paradichlorobenzene. It must be remembered that the gas given off from paradichloro- benzene crystals is much heavier than air, and borers in a tree above the point where the crystals are placed will not be affected by the gas. Consequently, the first thing to do in treating a tree is to deter- mine the topmost borer gallery. Usually this will not be above the soil level, and, in such case, the soil should not be mounded or dis- turbed before applying the paradichlorobenzene, except to remove weeds, stones, etc., and to make the soil surface level, using the back of a shovel. If gum, sawdust, or frass is thrown out from the tree trunk above the soil level, one can be reasonably sure that some borers are working in the tree above the soil. In these cases mound up the tree with earth, so that the ring of crystals can be placed above the topmost borer gallery. This is necessary in order that the gas may reach the borers above the soil level. Do not mound trees before applying the chemical, however, unless there are distinct indi- cations of borer work above ground. The dose of paradichlorobenzene is then applied in a continuous band about 2 inches wide and about 1 inch from the tree trunk. Care ' id PLATE II. =z = ~~ => : —— eae 3 a SSS a ere ee SS THE PROPER WAY TO USE PARADICHLOROBENZENE. 1. The soil around the tree is made ready for treatment. 2. The paradichlorobenzene is applied in a continuous ring 2 inches wide and 1 inch from the tree trunk. This is the correct method. 3. Several shovelfuls of soil are placed on the crystals and compacted, to hold the gas and pre- vent surface washing. 4. In the case of young trees, the base is uncovered four weeks after the paradichlorobenzene is applied. Bul. 1169, U. S. Dept. of Agriculture. PRATE LHe IMPROPER WAYS OF APPLYING PARADICHLOROBENZENE. 1. The crystal ring is too close to the tree trunk. It should be at least 1 inch away. 2. The crystal ring is too far from the tree trunk for good results. 3. The soil level should have been raised around this tree before applying the crystals, as there are borers at work above the present soil level. No borers will be kiiled above the crystal ring, as the gas is heavier than air. . teat PARADICHLOROBENZENE ON YOUNG PEACH TREES, 13 should be used to distribute the crystals as evenly as possible, as the action of the gas islocal. Use only pure paradichlorobenzene having a fineness of granulated sugar. One-ounce doses should be used on trees 5 years old and older, and if this material is used on younger trees the three-fourths ounce dose is suggested. After the crystals are placed around the tree, cover them withseveral shovelfuls of soil and compact with a sharp blow or two, using the back of the shovel. This produces a slight mound which prevents the crystals from washing and also serves as a container for the gas. Avoid pushing the crystals against the tree trunk with the first shovelful of soil. If paradichlorobenzene is used on trees younger than 5 years old, the mounds should be opened four weeks later to remove any unspent crystals or to allow any remaining gas to escape. In the latitude of central Georgia it will not be necessary to open the mounds after treating trees 5 years old or older. Plates II and III show proper and improper methods of applying paradichlorobenzene. For best results the chemical must be applied in the peach belt of central Georgia from October 10 to 15. e northern Georgia the material should be applied about October 1, and in southern Georgia, October 15 to 20. The same dates should be applicable for similar latitudes in the other Gulf States. LABORATORY EXPERIMENTS. In connection with the field work on paradichlorobenzene, several tests were made with the material in the laboratory. Field conditions were somewhat different from those in the laboratory, but the two were made as nearly similar as possible. ‘The evaporation of the gas in the laboratory was slower than in the field, as in the latter case the material was subjected to a higher temperature due to its being exposed to the direct rays of the sun. In testing the killing effect of paradichlorobenzene on peach-borer larve, the gas was concen- trated in a small area and the action was somewhat faster than under normal field conditions. RATE OF EVAPORATION OF PARADICHLOROBENZENE CRYSTALS. The paradichlorobenzene crystals used to determine the rate of evaporation were about as fine as granulated sugar. The soils used were red clay and sandy loam. One-half ounce of paradichloroben- zene was used in all tests and was imbedded from 4 to 6 inches in the soil, with the exception of one test, where the crystals were placed on the surface of the soil. Some of the soils were used just as they came from the field; others had various amounts of water added up to the point of saturation. In the sandy loam soils the crystals evaporated at about the same rate, whether 4 or 6 inches below the surface. The evaporation was somewhat faster in red clay when the crystals were only 4 inches down in the soil. The evaporation in the cages to which water had been added was retarded at first, but in about two weeks it was about the same as in normal” soils. It took from 91 to 135 days for all of the paradichlorobenzene to disappear, with the exception of the single cage in which the material was placed on the surface. The 2 The soil used as it came from the orchard without the addition of water is henceforth designated in this paper as normal soil 14 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. crystals disappeared in this cage in 16 days. The two types of soil showed very little difference in the rate of evaporation. It would appear that moisture in the soil in central Georgia soon evaporates and does not decrease the efficiency of the gas to any extent unless continuous rainy weather occurs during the period of the generation of the gas. Table 8 gives a summary of the results obtained on the rate of evaporation of the crystals. TABLE 8.—Rate of evaporation of paradichlorobenzene crystals in the laboratory, Fort Valley, Ga., 1921-22. One-half ounce dose to all cages on Oct. 13, 1921; one-half ounce=219 grains. ] Amount of evaporation, in grains (losses be- tween succeeding dates). Num- | ber of Ge B= a ee ee ee Depth of | days re~- crystals | “Amountof | soit 1921 1922 anotal , | quired Betie" added Och, ds.). She a te eee ee ae soil. : I a : E 5 - | orated. | orate Gigli laislSiesisj«|s]s crys- 2 Bay |B LI (kt = lin) Spee] | So lays 7 | 2 (40 |e i olo;/o}]oao/8/8 616lazizlalalsls§ialsia Surface...| Normal soil...| S rte Gey 122, i SBy io ese eas leece PS Sea a Ee Oct. 30 16. | oam. 4inehes..-:|.. 22. “CLC ees ee Re G60. 2 17 |. 18))\ (8°45? Jttg 48 17 .| Feb. 18 128. 6inches...| uneere 0 V0) elie, See Sart dos. 16) SLO Sia Seal 27 AVG OE le taletes Gores 128 4inches...| 180 cubic cen- dots 7 183) 4s bea e230 ag SOU < Scilly Sees Feb. 4 114 timeters of water added.a Ginches...|..<.. Gowes- 7s 3 do: .-F- 8 | 12 | 12 | 28 | 59 | 39 oT Fe 93 hel yee I | WR ro (a yee 114 4inches...| Saturated @. ‘dott 0} 31]18 | 64 | 61 | 30 2 A aia ae ml plan Jan. 12 91 6inches...|..... 0:6 52 052| 235 0: 4.4: 0!) Doe) ZZ 66 [44 Sl 2S: sete ys Bie eee Jan. 5] . 84 4 inches...| Normal soil. ..| Red clay} 10 | 15 | 13 | 63 | 49 | 35 |....] 34 |....[...1.... Jan. 12 gl Grichesss|. 3 [00s FAS 3 dott és? 8 TE} TO WeB9e] 49 HN) AP) aD [ch sh 22 Le wep sis 128 4inches...| 180 cubic cen- |...do..... OO) ARS ah At U0 i: Hy PR el fet: aa [pepe IE Jan. 12 91 timeters of | water added. Ginchess. doses. -. = yeasts 0) 14) 14 |-S8 180" 33 .|... 21536 [oo Sa" 10 | Heb; 925 135 4inches...| Saturated a....|...do..... Oue2Hl SAWSZHSS aL (27 eee Eat. an. 115 84 Ginehes-.<|....- Gordes 252—- Sexi ee 0 | 18 | 21 | 42 | 58 | 45 cee BS oclisetelose last Jan. 12 91 a This water added to soil in flowerpots 10 inches high and 6 inches wide. These pots were used as soil containers for all of the above paradichlorobenzene evaporation tests. MORTALITY OF PEACH-BORER LARVZ EXPOSED TO PARADICHLOROBENZENE. Peach-borer larve were collected in the field and brought to the insectary to determine the effect of paradichlorobenzene on them. All larvee were placed on peach bark and set in the soil from 3 to 12 inches below the crystals. From one-half ounce to 2 ounces of para- dichlorobenzene was used in the different cages that contained the larve. Each cage had five larve, and all were killed in three weeks’ time. The larve that were placed in normal soil with from one-half ounce to 2 ounces of paradichlorobenzene per cage were all killed within two weeks. The generation of gas was retarded somewhat in the cages where a large amount of moisture had been added, but the larve in these cages did not live more than a week longer than those placed in normal soil. One cage had no crystals in it, and all the larvee in this cage were alive and feeding at the close of the experi- ment. The standard 1l-ounce doses killed all larve in two weeks, although the larve did a little feeding before death. The odor of gas was noticeable in one week at the bottom of all cages except those to which 360 and 540 cubic centimeters of water had been added, in which it did not become strong until the end of the second week. Table 9 summarizes the results obtained and shows that the paradichlorobenzene is effective in killing the larve as far down as 1 foot, under normal conditions and standard dosage. PARADICHLOROBENZENE ON YOUNG PEACH TREES. 15 Taste 9.— Mortality of peach-borer larve exposed to paradichlorobenzene in cages at insectary, Fort Valley, Ga., 1921. [All larvee exposed to the gas October 19, 1921. Sandy loam used in all cages.] | | | | Condition of larve. | oa } Oct. 26. Nov. 3. Nov. 10. Num-| Depth) Condition of R les Dose. | berof| in sail emarks. larve. soil. : a id = | | a|¢ a|g¢ e|g dialelslateisl ate | g15/S/s/F/E18 i512 | Ala 4i/Alalia~al|Alal< i | | NCES Inches. | ae 5 3 | Normal Sid 8 8 oa Cee ee ee _...|....| Odor and crystal at close. 5 Yo ot £4) OpeOr) ich 0:1; 1170 | 0 | Few crystals Nov. 10. H 5 My a do Se Pete ree LO [ac [eoec | eae Many erystals left Nov. 3 5 3 See OY ee Shi Ol aio. LB BRD ORS ee Crystals left at close of cage. 1 5 ag C See Ce 2g ae Se yh ie es a ah (eR SR 1 larva fed before death. 1 5 dF ee O02 2 as Se pe Se a a a Ee ee | 2 larvee fed before death. 1 5 i? Rae do-. 2: #2 a) Sh -2? 8 1G, 15... | Joc. t.2s 2 larvee fed before death; many crystals left at. close. 14 5 3 j...-- des 022 AG ub eos SSA RR RS Be some 5 dead at 1 week’s expos- ure; over 1 ounce para- | dichl orobenzene left 17 "| Oct. 26. 1} 5 ® hea. do. Bee Ue Ee Ait olla} «fo eel oe aclaes 4 dead at 1 week’s expos- | ure; over 14 ounces para- dichlorobenzene left | Oct. 26. 14 5 . 8 ee Be at Nihee CPacr) =e’ Seed Pees ager erode 3 dead at 1 week’s expos- ure; over 14 ounces para= | dichlorobenzene _ left Oct. 26. 2 5 | es ee Ey tie ') ee RE ee ARE Fon 4 dead at 1 week’s expos- ure; over 14 ounces para- dichlorobenzene left. Oct. 26. 1 5 6 | 180cubiccen-; 5] 0] O pee pees eee eee bees cee Larve fed before death. timeters of water add- ed. 1 5 6 | 360cubiccen-} 1} 4] 0} 2; 2) 0} 1] 1 | 0 | Larve fed before death; timeters of no odor at bottom of |} Water add- cage Oct. 26; last larva ed. died Nov. 17. 1 5 6 MO0cubiccen-| 1] 0; 4] 3} 1] 0} 1] O]| O| Larve fed before death; timeters of no odor at bottom of cone add- cage Oct. 26. Check. 5 3 | Normal...... 0; O| 5| O}11] 4| O} O|} 5] 1 larva away from food Nov. 3. : i i | 1 Sluggish. Note.—All larv@ confined in flowerpots or battery jars 10inches high and 6inches wide, except several that were in cages 12 inches tall. Odor stronger than around treated trees in the field. . EFFECT OF TEMPERATURE AND ss et oe THE EFFECTIVENESS OF PARADICHLORO- NZENE. In determining the killing effect of paradichlorobenzene on peach- borer larve, with different degrees of temperature and different amounts of moisture, the standard 1-ounce dose was used through- out the experiment. In November and December, 1921, at a maxi- mum temperature of 69° F. and with the moisture in the soil ranging from 9.15 per cent (normal soil) to 20.15 per cent, all larvee were killed in 13 days. At 64° F. maximum, and 1.24 per cent moisture (normal soil), 5 larve were killed in 7 days. At 64° F. maximum, with from 8.34 per cent to 11.44 per cent moisture, all larvee were killed in 15 days. In the cage with no paradichlorobenzene, 4 larvee remained alive and fed continuously throughout the experiment, and one died, probably from lack of food. Table 10 gives a sum- mary of the results obtained. 16 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. TasLe 10.—Effect of temperature and moisture on larvicidal actton of paradichloro- enzene, and time required to cause death, 1921. Per Condition of larve. Maxi- | cent of mum mois- Date eee gee ire e tem- | turein| joevm ov. 10. ov-17. | Daysre- | Per were fo lta. lu | icsclan a hued to; || cont Remarks. exposed vv Zz kill larvee. ; killed. during | larve to gas s 3 ' 1 3 expos- | were a Ses ied al DS ure. |exposed a| & S| 3 ee 3 to gas. Ala|/<|Alal< | 2 oR. | Percent." 119217 | Per ct i 69 16.75 | Nov. 4) 3) 2) 0) 2% Oj O} 5 killed in 100 | Average temperature 13 days. 59.9° F.; larve did no feeding. II | 69 Fa Uy ba Eo CoB 3; 1} 1} 2} Of] OJ]...do.......| 100] Average temperature 59.9° F.; larve fed a . | little. Tit 697 Leo thoes 1} 4/ 0; 4] O| OJf...do.......| 100] Average temperature | 60.1° F.; larve did Dae. 8 Dec. 16 no feeding. EV, 64 Ee eWec: iy oon Oy 0, | ptsc) ssp 5 killed in 100 | Average temperature 7 days. 55.9° F.; larve did no feeding. V 64 URE ll eer (ore 3/'2).0). 2] ©} Of 5.Killed in 100 | Average temperature 15 days. 55.2° F.; larve did no feeding. VI 64 fl lege © | PR oy oa 2.1°3)5] SO) ttle BOL BOs a dok=ce ase 100 | Average temperature 55.2° F.; larvee did no feeding. Viilieaen see (1) Check Of BOARS y} Sa KON CASI E Le oe See) ees 4 larve fed continu. ously. 1 Normal soil. NotTe.—Cages contained 1 ounce of paradichlorobenzene and 5 larve each. All larve were placed 6 inches below the crystals. in January and February, 1922, experiments were conducted on soils in which different temperatures were maintained and to which different amounts of moisture were added at the beginning of the tests. The higher temperatures were maintained by keeping the cages indoors and the low temperatures by icing the cages in the insectary. The highest outdoor temperature recorded during the course of the experiment was 70° F. At a maximum temperature of 90° F. and a moisture content of from 7.6 to 27.6 per cent, all larve were killed in from 11 to 13 days. At a maximum tempera- ture of 80° F. and a moisture content of from 7.6 to 30.3 per cent, all larve were killed in from 11 to 13 days. Atamaximum temperature€ of 70° F. and a moisture content of 7.6 per cent (normal soil), 5 larvee were killed in 11 days. At the same temperature and a mois- ture content of 19.8 per cent, 5 larve were killed in 17 days; and with moisture 27.6 per cent, 1 larva was killed in 17 days, and the remain- ing 4in 21 days. At amaximum of 54° F. and 6.4 per cent moisture (normal soil), 5 larvee were killed in 23 days. At the same tempera- ture and a moisture content of 20.7 per cent, 5 larve were killed in 29 days. The larve in the untreated cage were all alive and feeding at the close of the experiment. Table 11 summarizes the results. This table shows that the lower the temperature and the higher the moisture content, the slower is the rate of evaporation of the para- dichlorobenzene, and this naturally influences the effectiveness of the treatment. Fairly high temperatures,? however, such as occur in Geor- gia during the period of treatment for the borer, even though the soil has a high percentage of moisture, will kill the borers within afew weeks. 3 Average maximum daily temperature for the six-week period following the applications on October 10, 1921, was 73° F. f PARADICHLOROBENZENE ON YOUNG PEACH TREES. i TABLE 11.—Effect of different marimum temperatures and different amounts of moisture in the soil on the time required to kill peach-borer larvx, 1922. INDOOR CAGES. | Condition oflarve. Per cent} Maxi- | of mois- at SLagpy Cees ESB mum | turein ate = temper- soil larve Jan.11. Jan.15. Jan.17. pares Per Cage | ature | when | were , ae mill |.cent Remarks. No. | during} larvee | exposed | [u! | |= Ey larvae. _ | Killed. ex- were to gas. Sal lle! |e posure. | exposed bed 2ee2Flgeit hae Sis S(Sisisisisis Alas Ajai<|A |S | °F. | Percent Pp. I} 90 17.6] Jan. 4 | 1/4 0) 4) 1) 0} 5) 0] 0] 13 days....| 100} Average temperature 80.9° | F.; strong odor of gas 6 inches down on Jan. 5; larve did nofeeding. Il 90 18.1 4 | 0} 5; 0] 5) 0) 0 .| 11 days.... 100} Average temperature 80.3° F.; strong odor not noted | until Jan. 9; larve fed faa before death. Til 90 27.6 4 | 0} 5} 0} 5| 0}. 0}. .|..]..] 11 days... 100} Average temperature 80.3° | F.; strong odor not noted until Jan. 11; larvee fed of before death. IV 80 17.6 4 | 11 4) 0) 4/1 5! 0} 0) 13 days... 100} Average temperature 69.5° F.; strong odor Jan. 5; larve did no feeding be- fore death. Vv 80 21.1 4 { 1| 4] O} 5} O} O}..)..]..| 11 days... 100} Average temperature 69.5° F.; strong odor Jan. 11; larvee fed before death. Vi 80 30.3 40a) 4) OF 5) G] GO}... -| 11 days... 100; Average temperature 69.5° F.; strong odor Jan. 11; | larvee fed before death. VII | Check (2) 4/00 5| if ey Cmaa, ie eee ee 0} Larvee fed continually. OUTDOOR CAGES. | Jan.11.\Jan.17. Jan. 23. Vu 70 17.60) Jan. 6 | 0} 5) 0 s| 0} 0j)..|..]..} 11 days.... 100) Strong odor noted Jan. 11; larve did no feeding be fore death. Ix 70 19.8 6 | 0} 0} 5] 1] 4) 0) 5) 0} O} 17 days... 100) Strong odor noted Jan. 19; ; larvee fed before death. x 70 27.6 6 | 0} O} 5} 1) 2! 2) 1) 4) O| 1 Killed in 20/ 100 per cent killed in 21 17 days. days; larve fed before death; strong odor Jan19. eS ET t@lsoeke [452525 }5-f2<.'3-2h524 | 0| 0 5| 0| 0 5| OQ) Ohl3. 23.5. £35: 494 --| Larve fed continually. ICED CAGES. Jan. 20.|Jan.28.|Feb. 4. xi i 16.4) Jan. 13 | 0 5 0} 0} 5) 0} 5 a 0) 23 days.... 100| Strong odor noted Jan. 28; larvee fed before death. XU | 34 20.7 13 | 0| 0| 5| 0} 4| 1] 0| 5| G| Nonekilled 0| 100 per cent killed in 29 in 23 days. days; larve fed before death; odor of gas re mained mildin this cage. DL OMe a OO a Or Gla Ol Ol aiceasess caeael- oc. ss Larve fed continually; made cases and entered bark furnished for food. 1 Normal! soil. NoTE.—AI]I cages contained 1 ounce of paradichlorobenzene and 5 larve each. All larvee were placed 6inches below the crystals. i 18 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE SUMMARY. Large doses of paradichlorobenzene, ranging from 14 to 24 ounces, to which the tree is exposed for 4, 8, or 12 days, are not as effective against the peach borer as three-fourths ounce or 1-ounce doses with an exposure of from 4 to 6 weeks. The cambium layer of all peach trees ranging in age from 1 to 5 years treated with paradichlorobenzene for experimental purposes was uninjured in the summer following the application in the fall. Brown lesions were observed in the outer bark leetrs on afew trees, however, at a point near which the ring of crystals had been placed. No injurious results from not tearmg down the mounds within six weeks after making the application to peach trees in Georgia could be discerned. During a normal fall in Georgia l-ounce doses of paradichloro- benzene will entirely spend themselves, leaving little if any odor six weeks after the application. In Georgia it is not necessary to uncover the base of the older trees four to six weeks after applying the chemical. It is advisable, however, to use this precaution against tree injury if the fall is abnormally cool, or if the material is applied late, or if it is used on young trees. If the treatment is given to trees 4 years of age or younger, use three-fourths ounce doses. For trees 5 years of age and older use the 1-ounce dose. Spring treatments of paradichlorobenzene in Georgia are not as effective against the peach borer as the early fall treatments. Spring applications gave a borer mortality of 72.4 per cent, compared with from 95 to 100 per cent mortality from using the material in middle October. Very poor results were obtained in Georgia by applying the crystals during late November or ry December. The most satisfactory results are obtained in central Georgia by applying the chemical October 10. In the laboratory 91 to 135 days were required for the evaporation of one-half ounce doses of paradichlorobenzene imbedded from 4 to 6 inches below the soil surface. One-half ounce doses placed on the soil surface evaporated in 16 days. One would conclude from this © laboratory experiment that the soil mounded on top of the crystals to prevent surface washing and to serve as a container for the gas should not be deep, as the deeper the crystals from the top of the soil the slower the gas will generate. Of course the normal rate of evaporation of paradichlorobenzene around peach trees in an orchard is much faster than it would be in the laboratory—the latter being at a lower temperature. Laboratory tests show that the gas is liberated at about the same rate in both sandy loam and clay soils. Laboratory experiments show that the gas will kill peach-borer larvee as far down as 1 foot below the soil level, and under laboratory conditions the gas killed all larve at that depth within three weeks. The lower the temperature and the higher the moisture content -of the soil, the slower is the action of the gas on the borers. ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE. muamemmmmnmr Agriculiure......../:------..-.--- HENRY C. WALLACE. ee C. W. PuGsLey. Meee sereniific Work..........--...-.--- E. D. Batt. Director of Regulatory Work........----.----- 2 5 See Se as CHARLES F. Marvin, Chief. Bureau of Agricultural Economics........-.--.- Henry C. Taytor, Chief. Bureau of Animal Industry.......-.-...------- JoHN R. Monter, Chief. remap? lant Indusiry........-.-......--- Wiiiram A. Taytor, Chief. 0 W. B. GREELEY, Chief. NE RMPMMISETY =. 52. == 2 WALTER G. CAMPBELL, Acting Chief. I 20%, Ee ew os ee Mrzton Wuirney, Chief. rem Fimtemologiy.....-.--..------------- L. O. Howarp, Chief. Bureav of Biological Survey.......--...------- E. W. Netson, Chief. memeerranne miler Pods: 2-2. 3....22...-.....- THomas H. MacDonazp, Chief. Fixed Nitrogen Research Laboratory......-..-- F. G. Corrrety, Director Division of Accounts and Disbursements....-... -4 A. ZAPPONE, Chief. rman of fublications..........------.----- Epwin ©. Powett, Acting Chief. a ee CLARIBEL R. Barner, Librartan. peemen deerartoms Service. .......-....:......./ A. C. True, Director. Federal Horticultural Board.............------ C. L. Maruatt, Chairman. Insecticide and Fungicide Board................3. K. Haywoop, Chairman. Packers and Stockyards Administration........ CHESTER Morritu, Assistant to the Grain Future Trading Act Administration. . . } Secretary. Rm CE IEIEO 22S. R. W. WiuraMs, Solicitor. This bulletin is a contribution from Pures a Psemology=........--..-....---.--- L. O. Howarp, Chief. Fruit Insect Investigations.........-...-.-- A. L. QuainTance, Entomologist in Charge. 19 ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS COPY FOR PROFIT.,—PUB. RES. 57, APPROVED MAY 11, 1922 V SHE tO Word Nt aide ec SOTA . ann ee AD et tg staan “9 Saat AS TAN AWA 6 vols \3 oll ‘otal aE IS > iat sts rate ae cHetrte Bek. TOR AY ey hy AD ihe re ite be} Janathay th \o aoe m3 Aalst Sis Nig Sister it. cena La7- WOOK Ay yiog ‘ mr a ae tae Sloe ves, OG a wd) re acwoP Cn Tigienedy <). 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