Timings of treatments determine the effectiveness of insecticides in controlling the cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

Abstract The cryptic nature enabled reduced vulnerability to insecticidal control of the pink bollworm Pectinophora gossypiella (Saunders), a serious threat to transgenic cotton cultivation due to development of resistance against Bacillus thuringiensis (Bt) toxins necessitated determining the critical timings of spray applications on the effectiveness of its control. This study assessed the influence of egg age and location of larvae as exposed vs. burrowed inside the bolls on insecticide control efficacy. The results revealed significant decrease in ovicidal activity of test insecticides with the increase in age of eggs from one day old to three days old (paired t-test, P values 80% mortality) than that of larvae exposed after they burrowed inside the bolls (<49% mortality). The inhibitory effects of test insecticides on the developmental biology were more pronounced in the experiment on pre-larval release insecticide treatment compared to insecticide treatment given post-larval release and entry inside the bolls. Very low fecundity (96%) and higher avoidance index (>0.93) revealed oviposition deterrent activity of test insecticides. The test insecticides also exhibited significant adulticide action on PBW moths. The study has generated information crucial to the development of effective management strategy for cotton pink bollworm.