Effect of larvae treated with mixed biopesticide Bacillus thuringiensis-abamectin on sex pheromone communication system in cotton bollworm, Helicoverpa armigera.

Abstract

Third instar larvae of the cotton bollworm (Helicoverpa armigera) were reared with artificial diet containing a Bacillus thuringiensis-abamectin (BtA) biopesticide mixture that resulted in 20% mortality (LD20). The adult male survivors from larvae treated with BtA exhibited a higher percentage of "orientation" than control males but lower percentages of "approaching" and "landing" in wind tunnel bioassays. Adult female survivors from larvae treated with BtA produced higher sex pheromone titers and displayed a lower calling percentage than control females. The ratio of Z-11-hexadecenal (Z11-16:Ald) and Z-9-hexadecenal (Z9-16:Ald) in BtA-treated females changed and coefficients of variation (CV) of Z11-16:Ald and Z9-16:Ald were expanded compared to control females. The peak circadian calling time of BtA-treated females occurred later than that of control females. In mating choice experiment, both control males and BtA-treated males preferred to mate with control females and a portion of the Bt-A treated males did not mate whereas all control males did. Our Data support that treatment of larvae with BtA had an effect on the sex pheromone communication system in surviving H. armigera moths that may contribute to assortative mating.