Impact of biopesticides on the probing and feeding behavior of Aphis gossypii

Abstract

Background Pesticides-induced mortality has traditionally been the toxicological endpoint on which a chemical is selected for pest management strategies. However, the exposure to a pesticide might also cause behavioral alterations that can dramatically affect the dynamics of pest-plant interaction. Understanding these non-lethal effects is crucial for developing comprehensive and sustainable pest control measures. Methods Here, using the Electrical Penetration Graph (EPG) technique, we evaluated whether biopesticides routinely used in organic or conventional pest management might alter the probing and feeding behavior of the cotton aphid Aphis gossypii on treated plants. The post exposure persistence of feeding alterations when moving the insect onto clean plants was also assessed. The tested biopesticides were chosen for being aphicides or because used in those crops hosts of A. gossypii. Generalised linear mixed models were fitted to analyse the effects of biopesticides on the probing and feeding behavior of aphids, using untreated control data as a model baseline. Results Residuals of Bacillus thuringiensis, Beauveria bassiana, and sulfur significantly affected the dynamics of the stylets intercellular route compared to the control (namely, shorter pathways, fewer and shorter brief intracellular stylets probes, higher and longer derailed stylets events). Mineral oil, orange essential oil and pyrethrin delayed or impaired the onset of phloem sap ingestion. On the other hand, copper and potassium salts promoted feeding. Pyrethrin was the only biopesticides inducing persistent behavioral alterations, with insects displaying a higher frequency of occurrence of xylem ingestion events when moved to untreated plants after exposure. Conclusions Overall, this study demonstrates that biopesticides modulate the aphid-plant interactions by impairing or facilitating the exploitation of the host plant, also affecting the patterns conducive to plant pathogens transmission. This study also highlights the importance of considering in toxicological studies the impact of all the compounds the pest could be exposed to within the agroecosystem, including those not designed for that specific pest.