Exposure to Herbicides Prime P450-Mediated Detoxification of Helicoverpa armigera against Insecticide and Fungal Toxin

Abstract

With the long-term and large-scale use, herbicides have been well known to influence tritrophic interactions, particularly natural enemies of pests in agro-ecosystems. On the other hand, herbivorous insects, especially the generalist pests, have developed antagonistic interaction to different insecticides, toxic plant secondary metabolites, and even heavy metals. However, whether exposure to herbicides would affect resistance of insects against insecticides is largely unknown, especially in agricultural pests. Here, we first reported that pre-exposure to two widely used herbicides butachlor and haloxyfop-methyl for 48 h can prime the resistance of a generalist agricultural pest Helicoverpa armigera Hübner against insecticide methomyl and fungal toxin aflatoxin B1. In addition, there were no significant differences between control and herbicides-treated caterpillars on weight gain, pupal weight, and pupation rates, suggesting that exposure to herbicides induces resistance of H. armigera accompanied with no fitness cost. Moreover, by determining detoxifying enzyme activities and toxicity bioassay with additional inhibitor of cytochrome P450 piperonyl butoxide (PBO), we showed that exposure to herbicides might prime P450-mediated detoxification of H. armigera against insecticide. Based on these results, we propose that exposure to herbicides prime resistance of H. armigera against insecticide and fungal toxin by eliciting a clear elevation of predominantly P450 monooxygenase activities in the midgut and fat body.