GM pest-resistant crops - opportunities for mis-management of biological control

摘要

So far, all the commercialised GM pest-resistant crops have been based on the Bacillus thuringiensis (Bt) toxin. For biochemical reasons, this toxin has the advantages of complete safety to humans and very selective toxicity even within insects (O'Callaghan et al., 2005). Thus, testing it for effects on biological control agents has revealed that it appears safe for parasitoid Hymenoptera and has low toxicity to lacewings. However, the work on Cotesia parasitoids of diamond-back moth (Plutella xylostella) could only be carried out using a genotype of the pest resistant to Bt, since the toxin otherwise confers on the crop what amounts to complete immunity to the pest (Schuler et al., 1998). Clearly no biological control agents can survive on such a crop, even if they are not affected by the toxin. It is, however, likely that in future other sources of pest-resistance for GM crops will carry a greater danger of direct damage to biological control agents. Almost the only example in the literature to date is that of ladybirds (Coccinella septempunctatd), feeding on the aphid Myzus persicae on partially aphid-resistant GM potatoes expressing the snowdrop lectin, which have their fecundity reduced by just 20-40% (Birch et al., 1999).