Adverse effects of Bacillus thuringiensis bioinsecticide on non-target Drosophila species

Biopesticides based on Bacillus thuringiensis kurstaki ( Btk ) and israelensis ( Bti ) spores and toxins are widely used to control insect pests, increasing environmental risks to non-target biodiversity. Here, we tested for potential effects of larval ingestion of Bt commercial formulations on Drosophila species. Doses equivalent to those recommended for field application (⩽10 6 CFU/g of fly medium) had no effect whereas Btk doses 10 to 100-fold higher (10 7 -10 8 CFU/g) altered the development (decreased emergence due to larval mortality and increased development time), and moderately influenced adult fitness-related traits. At the highest Btk and Bti dose (10 9 CFU/g), all larvae died before pupation. The impact of Btk formulations resulted from the spores/cleaved toxins synergy, but also additives. While recommended doses had no effect on non-target Drosophila species, the accumulation of Bt bioinsecticides in the environment could have adverse side-effects on the populations of these species and therefore their associated communities.