Comparison of Insecticide Application Schedules for Control of Cotton Insects

Abstract

Results of a 3-year study to determine the most effective and economical insecticide application schedule for control of cotton insects are presented. Three insecticide mixtures were each applied, and 6 different control schedules were used ranging from full-season insect control to schedules begun at the 25% boll weevil infestation level. The insecticide mixtures used in the experiment were: toxaphene-DDT, endrin-methyl parathion, and azinphosmethyl-DDT. This study indicated that yield losses were caused only by the boll weevil, Anthonomus grandis Boheman; the bollworm, Heliothis zea (Boddie) ; and the tobacco budworm, H. virescens (F.). During the years when both the boll weevil and the bollworm complex caused economic damage, the most satisfactory schedule followed was one where control measures were begun at the 10% boll weevil infestation level and continued only as needed. However, in 1963, when bollworms and tobacco bud worms were the major pests, the highest yields were obtained when the insecticide applications were delayed until boll weevil infestations had reached the 25% level. In 2 of the 3 years, the fullseason schedule resulted in the lowest yields of the 6 application schedules. Results of the 3-year study showed that yields obtained from all application schedules were highly significant when compared with the untreated check; however, there were no significant differencesamong the yields from the application-schedule treatments,