Effect of Various Insecticides on Beneficial Insects and Spiders in Cotton, 1982

Abstract

Lockett 77 cotton was planted on 4 June in a randomized complete block design replicated 4 times. Plots were 12 rows wide by 100 ft long. One irrigation was applied on 22 to 23 July and plots were sidedressed with 72 lb N/acre on 8 July. Numbers of beneficials were determined semiweekly with 50 sweep net samples in each plot. Insects were taken to the laboratory, frozen and counted. Insecticides were applied with a John Deere Hi-Cycle 6000 Ground Sprayer employing drops and three nozzles per row, and at a rate of 10 gal/acre. Adults and nymphs were included in counts of insects with piercing-sucking mouthparts. An extremely heavy Heliothis spp. egg lay occurred on 5 Aug.; but 0.86 in. rain fell on 7 to 8 Aug.; and spraying was delayed until the field dried sufficiently for entry of equipment. All plots wer sampled on 11 Aug and treatments were applied early morning on 12 Aug. Heliothis spp. 3rd-to 6th-stage larvae were collected from plots on 20 Aug. Larvae could not be found in all plots, so collections from each treatment were grouped together. Larvae were fed in the laboratory on pinto bean diet and observed for parasite emergence. Dead pupae and larvae were dissected to determine if they were parasitized. Heliothis spp. larvae and damage were sampled semiweekly before and after insecticide application.