Assessing the Influence of Bt Crops on Natural Enemies

Transgenic Bt crops expressing proteins derived from Bacillus thuringiensis (Bt) currently are grown commercially in ten countries on over 20 million hectares. Assessing their environmental safety is a critical part of the regulatory approval process and product stewardship for Bt crops. The environmental safety testing process for Bt crops follows a standard risk assessment approach, and involves multiple tiers of laboratory and field testing. Lower tier testing is based primarily upon pure protein tests, with testing concentrations keyed off of the maximum possible environmental exposure for a variety of non-target species. Test species are chosen based on considerations of the product and region, and typically include insect predators and parasitoids. These laboratory studies have not found any direct toxic effects of Cry1, Cry2 or Cry3 proteins against any generalist predator or parasitoid. The results of these studies agree with other laboratory and field studies conducted prior to and post-commercialization of Bt crops. Collectively, the non-target studies performed to date demonstrate that Bt crops do not have any unexpected toxic effects on natural enemy species, as would be predicted from knowledge of the mode of action and specificity of Bt proteins.