Side effects of Bacillus thuringiensis toxins on spiders

Abstract

While insecticidal crystal (Cry) proteins produced by Bacillus thuringiensis (Bt) have been used for pest control for almost a century, genetically engineered (GE) plants producing Cry proteins are commercially grown since 1996. For toxicity, Cry proteins need to be ingested, gut environment needs to be suitable, and specific receptors need to be available. Cry proteins have a narrow spectrum of activity and target lepidopterans, coleopterans, or dipterans. Cry proteins produced in Bt crops get diluted when transferred from plants to tissue-feeding herbivores to higher trophic levels. Phloem-feeding herbivores (e.g., aphids) contain negligible amounts of Cry protein. The prey spectrum of spiders living in agricultural fields includes phloem and tissue-feeding herbivores as well as species of higher trophic levels. Therefore, spiders ingest various amounts of Cry protein via prey in Bt crops. In addition there is evidence that spiders can ingest Cry protein when feeding on pollen of Bt crops. Laboratory experiments have demonstrated that spiders are not affected directly by Bt formulations or plant-expressed Cry proteins. Also, no deleterious effects of Bt proteins on spiders were reported from numerous field studies conducted with Bt formulations and Bt crops.