Bacillus thuringiensisbioinsecticide influencesDrosophilaoviposition decision

Abstract

Behavioural avoidance has obvious benefits for animals facing environmental stressors such as pathogen-contaminated foods. Most current bioinsecticides are based on the environmental and opportunistic bacteriumBacillus thuringiensis(Bt) that kills targeted insect pests upon ingestion. While food and oviposition avoidance ofBtbioinsecticide by targeted insect species was reported, this remained to be addressed in non-target organisms, especially those affected by chronic exposure toBtbioinsecticide such asDrosophilaspecies. Here, using a two-choice oviposition test, we showed that female flies of threeDrosophilaspecies (four strains ofD. melanogaster,D. busckiiandD. suzukii) avoided laying eggs in the presence ofBtvar.kurstakibioinsecticide, with potential benefits for the offspring and female's fitness. Avoidance occurred rapidly, regardless of the fraction of the bioinsecticide suspension (spores and toxin crystals versus soluble toxins/compounds) and independently of the female motivation for egg laying. Our results suggest that, in addition to recent findings of developmental and physiological alterations upon chronic exposure to non-targetDrosophila, this bioinsecticide may modify the competitive interactions betweenDrosophilaspecies in treated areas and the interactions with their associated natural enemies.