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.
Highlights
Pesticides provide a primary and non-substitutable method to control pests so that crop yield potential is conserved [1]
A Bacillus thuringiensis and abamectin (BtA) concentration of 2 mg/g resulted in 20% mortality and subsequent experimentation was done with this concentration compared to control
From 0.5 h to 2.5 h and 8 h to 9 h, there were no significant differences in percentages of calling between control females and female survivors (Figure 4)
Summary
Pesticides provide a primary and non-substitutable method to control pests so that crop yield potential is conserved [1]. Pesticide abuse is a serious problem all over the world and pesticide residue in fields can increase risks of threats to human health, inducing pesticide resistance, and killing of non target species [2,3]. There are many studies that focus on the sublethal effects of pesticides on target pests and beneficial arthropods. A median lethal dose (LD50) or lethal concentration (LC50) estimate has been the classical laboratory method for assessing the side effects of pesticides on beneficial arthropods for decades but do not address sublethal effects [2]. The longevity of Microplitis mediator, a parasitoid of the cotton bollworm (Helicoverpa armigera) decreased significantly after being fed with 10% honey water containing a sublethal dose of a Bacillus thuringiensis and abamectin (BtA) [10]
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