LIBRARY STATE PLANT BOARD December 1949 E-792 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine EARLY-SEASON APPLICATION OF INSECTICIDES FOR COTTON- INSECT CONTROL By K. P. Ewing and C R. Parencia, Jr., Division of Cotton Insect Investigations Experiments in early-season application of insecticides for cotton- insect control conducted on a community- wide basis in Wharton County, Tex., in 1948 (Ewing and Parencia 1949) were so successful that some- what similar experiments, but on a smaller scale, were conducted in central Texas, near Waco, in 1949. Some of the experiments were also designed (1) to determine whether cotton that receives early- season treatment only can mature a full crop without late- season treatment for the boll worm, and (2) to compare the effectiveness of sprays and dusts in controlling cotton insects. The boll weevil (Anthonomus grandis Boh.) is a serious pest of cotton almost every year in central Texas, especially in river and creek bottoms and in areas adjacent to woodlands and other hibernation quarters. The cotton fleahopper ( Psallus seriatus Reut.) and thrips (several species) often cause considerable damage early in the season in this area. The bollworm (Heliothis armigera (Hbn.)) is frequently an important late- season pest and is the most dreaded and most difficult to control of all cotton insects. 1/ Presented at the meetings of the American Association of Economic Entomologists, held at Tampa, Fla., December 13-16, 1949. 2/ In cooperation with the Texas Agricultural Experiment Station. ^ The authors acknowledge the valuable assistance of H. S. Johnson. Jr., and C. B. Cowan, Jr., Division of Cotton Insect Investigations, and of L. W. Lee, McLennan County supervisor of the Farmers Home Administration. -2 - Farmers in two communities cooperated- -the Satin community in Falls County and the Bolton Bend community in McLennan County. Both communities are located in the Brazos River bottoms, where weevils are known to have caused severe damage to cotton for many years. In the entire Bolton Bend area, there are 19 farms, all purchased by their present owners through the Farmers Home Administration. How- ever, all farmers in this entire area did not cooperate in the insect- ^ control program, only the farmers in the western part of the area. Therefore, for the sake of specific identification of the participants, the Bolton Bend community includes only the adjoining farms in the western <^ part of the area that received early-season applications of insecticides. A total of 350 acres in the eastern part of the area received no treat- ment for insect control at any time during the season, and this cotton was a source of weevils for the reinfestation of the early-treated cotton. There were 1,400 acres of cotton that received treatment, 700 in each community. Of this total, 380 acres were planted early(in April), and the remainder was planted late (around the middle of May or later). The early-planted cotton receiv^ed two treatments and the late-planted cotton one treatment. To obtain the maximum amount of information on maturity of the cotton before bollworms appeared, and the need, if any, for bollworm control, detailed seasonal records were made in the early- planted cotton. Comparable check areas, also located in the Brazos River bottoms, were utilized. There were two check areas for the early-treated area of the Bolton Bend community; one received late- season treatments, and the other was untreated throughout the season. The seven late- treated check fields received an average of 3.5 insecticidal applications between July 1 and 25. The check fields of the Satin community were untreated throughout the season. Treatments A total of 380 acres of early-planted cotton in 19 fields on 6 farms received two early- season treatments of one of the new all-purpose insecticides. In some of the fields sprays and dusts were both used for comparison. In the Bolton Bend community two dusts were used. The active ingredients were as follows: (1) 20 percent of toxaphene plus 40 per- cent of sulfur, and (2) 5 percent of DDT plus 40 percent of sulfur plus sufficient gamma benzene hexachloride to give 3 percent of the gamma isomer in the finished dust. One field was sprayed with a toxaphene- DDT emulsion. -3 - In the Satin community the fields were subdivided so that four were dusted and four were sprayed. Three dusts were used. The active ingredients were as follows: (1) 20 percent of toxaphene plus 40 percent of sulfur, (2) 10 percent of DDT plus 40 percent sulfur plus gamma benzene hexachloride sufficient to give 2 percent of the gamma isomer in the finished dust, and (3) 10 percent of chlordane plus 5 percent of DDT plus 40 percent of sulfur. The emulsion concentrates consisted of (1) toxaphene, 6 pounds per gallon; (2) toxaphene and DDT, 4 and 2 pounds per gallon, respectively; and (3) chlordane and DDT, 4 and 2 pounds per gallon, respectively. The dusts used during early- season treatments were applied by 6- or 8 -row ground machines. The rate of application was approximately 10 pounds per acre. Late- season applications were at the rate of about 15 pounds per acre. The sprays were applied by 6- or 8-row tractor attachment machines. The total volume of spray used in the early treatments was 2 1/2 gallons per acre, and it was applied at 60 pounds pressure with one nozzle per row. One quart of the emulsion concentrate was used per acre. Late- season sprays were applied at a rate of 7 1/2 gallons per acre with 3 nozzles per row, and 3 pints of the emulsion concentrate was used per acre. The average dates of treatments were May 31 for the first application and June 8 for the second. Boll weevil hibernation records at Waco duringthe past 10 years show that 93 percent of the weevils are out of hibernation by June 5. Therefore, the applications were timed to kill as many of the overwintered weevils as possible before they laid eggs. At the same time, mid- season application of insecticides was omitted to give beneficial insects time to increase in numbers sufficient to help control the bollworm infestations that usually develop sometime between July 10 and 25- -average date July 20. The procedure and methods of recording insect infestations and other field data were essentially the same as had been previously reported in the Wharton County experiments (Ewing and Parencia 1949). Results Rains were frequent during the month of June and the first half of July. From June 9 to July 15 rains fell on 18 days out of the 37. The rainfall during June was twice the normal for that month, and the rainfall for the first 15 days of July amounted to 51 percent more than the normal for the entire month. - 4 - In spite of weather conditions during June and July being extremely favorable for insect increases, excellent control was obtained of thrips, fleahoppers, and overwintered boll weevils. Immediately prior to the first treatment there was a comparatively high infestation of thrips, average of five per plant in both areas. This insect had already stunted the growth of the plants and was causing con- siderable deformity of them in some fields. Many plants had the appear- ance of having been seared with a blow torch. All the insecticides gave excellent control of thrips. Within 4 or 5 days after the first application the plants showed a marked recovery. During the 2 weeks following the first application the treated cotton averaged one and one-fifth thrips per plant, and the untreated cotton averaged six. Results from other experiments at Waco in 1949 showed that, for complete protection against thrips, treatments in the community experiments should have been started about 2 weeks earlier, or about the middle of May. While the fleahopper infestation was relatively light, this insect caused some damage in most of the fields. The maximum initial infestation (before treatment) in any field was 26 fleahoppers per 100 terminals. One of the check fields averaged 22 fleahoppers per 100 terminals for the first 4 weeks that infestation records were made. All insecticides gave ex- cellent control of the fleahopper. BoUworm infestations developed to the point of causing questionable damage in the early-treated fields of the Satin community about the middle of July. These fields were then subdivided and a portion of each field received two late- season insecticidal applications for boll worm control, and the other portion was left untreated to see whether beneficial insects would give control. (See table 1.) The boll injury averaged 4 percent in the late-treated cotton and 6 percent in the cotton that did not receive late treatment. The yields per acre were 489 pounds of lint from the cotton that received no late treatment and 536 pounds from the late-treated cotton, a gain of 9.6 percent. These figures show that the actual damage from bollworms was relatively light. Since there was a fairly heavy infestation of boUworm eggs and young larvae but only a light damage to bolls, beneficial insects were undoubtedly present in sufficient numbers to give valuable assistance in controlling the boUworm. This emphasizes the importance of proper timing of the early- season treatments, that is, of stopping treatments early enough to give beneficial insects plenty of time to build up again before bollworms appear. This time interval should be at least 4 weeks, and more if possible. - 5 - Table 1.-- Yield of lint cotton (pounds per acre) in fields receiving late applications and no late applications of sprays and dusts for bollworm control, following two early- season applications for control of other cotton insects. Satin community. XVJ.X1L1 dllLl LllIlC' \Jx cljLI IJIX^ cL tlvJIl 17 IciU i x* leici o 1 o 1 H A x" leia T i-vver age Spray: Late treatment 593 591 424 521 532 No late treatment 540 600 375 455 493 Average 566 596 400 488 51 2 Dust: Late treatment 594 597 420 553 541 No late treatment 542 584 336 476 484 Average 568 590 378 515 513 Average of dust and spray: Late treatment 593 594 422 537 536 No late treatment 541 592 356 466 489 Immediately before the first treatment there were medium to heavy infestations of boll weevils in every field of cotton in the two communities. The initial infestations averaged 178 weevils per acre in the cotton that was to be treated and 114 in the check fields. Two weeks after the first treatment, 2 percent of the squares in the treated and 34 percent in the untreated cotton were weevil-punctured. For 4 weeks after the second treatment the weevil infestation remained extremely low in both treated communities. The average weevil infesta- tion for the season (June 12 to July 29) was 11 percent in the treated and 42 percent in the untreated cotton. (See table 2.) The two early-season applications of insecticides gave satisfactory seasonal control of the boll weevil in 13 of the 19 fields. Four fields received two late- season applications for weevil control, one field received one, and one field three. These fields were all in the Bolton Bend community. They were adjacent to or near undusted cotton and were subjected to more weevil migration than other fields. The treated cotton in the Satin community had more buffer area immediately surround- ing it and needed no late- season treatments for weevils. - 6 - o 0) a w XJ c o a OS c o w (D CO 03 > T3 13 o a; o +-> a 0) in <\) U cr cn 1 ^ 1 03 (M July CM CM July! I— I 1 July CO 1 July! T— 1 June] CM •-3 0) in B o s ^: OS T) o U tn in ■-H 00 ifi I— I CD t> 03 00 in ^ in in CO in CM £> CO o CM CO o o CO CM CM CO r-H CO x: o -t-j (D CO c t> 03 CM ^ to CO CM rH CD CO ^ CO CM CM 00 in CO rt< O OO CO in <— I in CM CM in 03 CD CO CO Tt* C33 03 CD CM CO CM CM C33 I CO O 03 CD CM »-l I> t> in oo T3 O -t-; a; O cc -t-> t-i CO >> I 7- CD 03 Cfl S W J P c PQ c o ox: 03 > 03 O -a _ _ ;o ^ -WD - 7 - The treated cotton retained its early squares and began fruiting heavily several weeks earlier than the untreated cotton. It was ready for harvest approximately 3 weeks earlier. The seasonal average number of blooms per acre was 1,044 in the untreated fields and 4,201, or slightly more than four times as many, in the treated. In the early- season applications both sprays and dusts gave approx- imately 100 percent control of all insects present, such as thrips, flea- hoppers, and boll weevils. One field with cotton in the presquare stage had 145 weevils per acre on the day before the first spray treatment. Infestation records made 24 hours after treatment showed no weevils, or 100-percent control. In fact, records were made every 24 hours in 7 of the 11 fields in the Bolton Bend community, 6 of which had been dusted, and each of them showed 100 percent kill of overwintered weevils. Such results would be expected, since weevils are killed more easily while cotton is in the presquare stage or while they are feeding on the outside portions of the plant than after they have begun feeding inside the squares and bolls. Table 1 shows that sprays and dusts were equal in their effectiveness against all insects. In the two communities the average production of lint cotton per acre was 178 pounds from the untreated and 415 pounds from the treated cotton, a gain of 133 percent. (See figures 1 and 2.) The profit, after deduction of all expenses of poisoning, picking, and ginning, was $54.42 per acre. Summary All adjoining fields of cotton in two communities near Waco in central Texas were dusted or sprayed with two early- season applications of one of the new all-purpose insecticides for control of cotton insects. Detailed seasonal records were made in 380 acres, or 19 fields, of early-planted cotton, in order that information might be obtained on maturity of early- treated cotton before boUworms appeared. There were heavy infestations of thrips, light to medium infestations of cotton fleahoppers ( Psallus seriatus Reut.).. and medium to heavy infestations of overwintered boll weevils (Anthonomus grandis Boh.) in every field. Rainy weather in June and July was favorable for insect multiplication, especially for weevils. The two early- season (about May 31 and June 8) applications of insecticides gave satisfactory seasonal control of the boll weevil in 13 of the 19 fields. The average seasonal infestation was 11 percent in the treated and 42 percent in the untreated cotton. The fields that needed late- season treatnnent for boll weevils were adjacent to or near un- treated fields. Two late- season treatments for bollworm control were made in four fields. The increased production from control of the bollworm (Heliothis armigera (Hbn.)) was only 9.6 percent. In most fields a full crop of cotton was produced before boUworms appeared. The importance of stopping treatments early enough to give beneficial insects time to build up again is thus emphasized. This interval should be 4 weeks or more. There was a seasonal average of four times as many blooms in the treated as in the untreated cotton. The early- season treatments hastened the fruiting and maturity of the cotton by approximately 3 weeks. The average production of lint cotton per acre in the two communities was 178 pounds from the untreated and 415 pounds from the treated cotton, a gain of 133 percent. The net profit was $54.42 per acre. The low-gallonage, low-pressure sprays gave insect control equal to that given by the dusts. The average yields were 512 and 513 pounds of lint cotton per acre from sprayed and dusted fields, respectively. Literature Cited Ewing, K. P., and C. R. Parencia, Jr. 1949. Experiments in early- season application of insecticides for cotton-insect control in Wharton County, Tex., during 1948. Bur. Ent. and Plant Quar. E-772. - 9 - Figure 1.-- Field of cotton in Satin Community- -W. D. Walker farm-- showing benefits of insect control. This field received early- season insecticide applications on May 31 and June 8 and late- season appli- cations on July 18 and 23. It was ready for picking by August 15, and the yield was 594 pounds of lint per acre. :ifci Figure 2. --Field of cotton in the untreated area- -Warner farm- -showing severe insect damage, mostly from boll weevils. This field was typical of this untreated area which produced 178 pounds of lint cotton per acre.