Insecticides for Suppression of Early-Season Cotton Insect Pests in the Texas Blacklands, 1987

Abstract

Abstract Cotton was planted 16 Apr on 38-inch row spacings. Five insecticide treatments, 2 partially treated check treatments, and a completely untreated check treatment were compared in a randomized block design with 4 replications. Plots were 10 rows wide × 75 ft long, but only the middle 4 rows were sprayed. Applications were made with a high-clearance, self-propelled ground sprayer using TX-8 hollow cone nozzles calibrated to deliver 8.6 gal/acre. Insecticide treatments (including applications of Bidrin to the fleahopper check plot) were applied 29 Apr and 6 May for thrips and aphid control when cotton was in the seedling stage. Thrips and aphid densities were measured on 4 Apr and 5 and 12 May by examining 15 randomly selected cotton seedlings from each plot. The individual cotton seedlings were picked whole, quickly immersed, and shaken in pint jars of 70% ethanol. The sample jars were taken to the laboratory and numbers of thrips and aphids were counted under a dissecting microscope. Estimates of thrips damage to cotton seedlings were made 12 May when most plants were in the 5th true leaf stage. Ten randomly selected cotton plants were subjectively rated on a scale of 1-4: 1, no visible damage; 2, light damage; 3, moderate damage 4, heavy damage (e.g., terminal destroyed). An additional application of insecticide treatments (including Bidrin for the thrips-aphids check plot) was made 22 May for cotton fleahopper. Fleahopper adult and nymph densities were determined 22 May and 8 Jun from 30 randomly selected plant terminals in each plot using a combination beat bucket/visual inspection method. Cotton fruiting rates were monitored over a 5-week period by taking daily counts (Monday- Friday) of white blooms within a designated 20-ft section of row in each plot. Yield data were collected in a stratified harvest from 2 pickings of cotton from the same 20-ft row section used for counting white blooms. All data were subjected to analysis of variance.