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.
Highlights
The application of insecticides is currently the most common control measure against insect pests [1]
Three treatments pre-treated with piperonyl butoxide (PBO) showed slightly lower than the larvae without PBO pre-treating (Figure 3A–C, S-BuCh + PBO vs. S-BuCh, S- HLFM + PBO vs. S- HLFM and F-BuCh + PBO vs. F-BuCh (Figure 3A–C, S-BuCh + PBO vs. S-BuCh, S- HLFM + PBO vs. S- HLFM and F-BuCh + PBO vs. F-BuCh on weight gain; S- HLFM + PBO vs. S- HLFM on pupal weight), most treatments showed no significant on weight gain; S- HLFM + PBO vs. S- HLFM on pupal weight), most treatments showed no differences. These results suggest that exposure to herbicides not affect and development significant differences. These results suggest that exposure todid herbicides didgrowth not affect growth and of H. development armigera andofinduce resistance of armigera accompanied with no fitness cost
We showed that exposure to herbicides butachlor (BuCh) or haloxyfop-methyl (HLFM) can prime the resistance of H. armigera against insecticide and fungal toxin
Summary
The application of insecticides is currently the most common control measure against insect pests [1]. The resistance of insects to chemical insecticides has become a growing agricultural and ecological concern [2]. Since pesticides are widely and cross used in agriculture, one insecticide is known to confer resistance to other insecticides in insects through the cross-resistance mechanism [3,4]. Herbicides have been largely used in agriculture to control weeds around the world. Excessive and inappropriate use of herbicides have lead to serious harmful effects, including breaking ecological chain, increasing environmental pollution, and sanitation concerns [5,6]. The herbicide glyphosate has great infection on the population numbers of non-target
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