Control of Boll Weevil in Cotton, 1982

Abstract

Abstract A full-season study was conducted on the Plant Science Research Farm of the Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS, to determine the efficacy of various insecticides in controlling boll weevils in cotton. Plots were planted on May 22. All plots were replicated 4 times in a randomized complete block design. Each plot was 4 rows (.92 m/row) x 27.4 m long. Plots were separated by 4 rows of DeKalb ST-6 Sudax. The tall-growing grass was used to form a physical barrier around each plot and reduce inter-plot movement of boll weevils. Insecticides were applied by 1 of the following methods: (1) high volume (6.5 gal/acre) through 2 TX-4 nozzles/row in water, (2) low volume (1.4 gal/acre) through 1 Micromax nozzle/row in soybean oil, or (3) low volume (1.4 gal/acre) through 1 Micromax nozzle/row in water. Applications were made at weekly intervals. Treatments were applied on Jun 21 and 28, Jul 2, 6, 16, 17, 19, 22 and 27, Aug 3, 10, 13, 17 and 19. All plots were oversprayed for boll weevil suppression due to wet conditions on Aug 2, 16, 21 and 31 with 0.25 lb ai Guthion, and oversprayed for bollworm suppression on Aug 3 with 0.15 lb ai Ambush. Insect populations and plant damage were monitored at weekly intervals by making whole plant examinations on a consecutive 1.06 m row length. Yield data were taken on Oct 26 and 27 by mechanically harvesting the 2 center rows of each plot. Extremely wet conditions from ca mid Jul to mid Aug confounded test results. These rains washed off and prevented insecticide applications, allowing the boll weevil population to increase to extraordinary levels. After Jul 15 no significant differences were detected between treatments in percent of squares which were weevil punctured. For this reason, we do not consider yield data to be indicative of the efficacy of the insecticide treatments. For evaluation, we considered the percent boll weevil punctured squares on Jul 15 to be more indicative of boll weevil control. Seven treatments had significantly (P = 0.05) smaller percentage weevil squares punctured than the untreated check. Of these seven, 5 were insect growth regulators and 2 were chemical insecticides.