The tiered approach to assessing ecological risk of insect-resistant transgenic crops assumes that lower tier laboratory studies, which expose surrogate non-target organisms to high doses of insecticidal proteins, can detect harmful effects that might be manifested in the field. To test this assumption, we performed meta-analyses comparing results for non-target invertebrates exposed to Bacillus thuringiensis (Bt) Cry proteins in laboratory studies with results derived from independent field studies examining effects on the abundance of non-target invertebrates. For Lepidopteran-active Cry proteins, laboratory studies correctly predicted the reduced field abundance of non-target Lepidoptera. However, laboratory studies incorporating tri-trophic interactions of Bt plants, herbivores and parasitoids were better correlated with the decreased field abundance of parasitoids than were direct-exposure assays. For predators, laboratory tri-trophic studies predicted reduced abundances that were not realized in field studies and thus overestimated ecological risk. Exposure to Coleopteran-active Cry proteins did not significantly reduce the laboratory survival or field abundance of any functional group examined. Our findings support the assumption that laboratory studies of transgenic insecticidal crops show effects that are either consistent with, or more conservative than, those found in field studies, with the important caveat that laboratory studies should explore all ecologically relevant routes of exposure.

The gut contents of field-collected, predaceous Heteroptera were assayed for the presence of eggs of the sweetpotato whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) using multiple enzyme-linked immunosorbent assays (ELISAs). Of seven species examined, Geocoris species and Orius tristicolor (Say) were the most frequent predators of sweetpotato whitefly with 32-39% of the individuals tested over the whole season scoring positive for whitefly antigens. With the exception of Lygus hesperus Knight, a major insect pest as well as a predator, the frequency of predation on pink bollworm eggs was much lower (0.7-14.3% positive over the season). Relatively few predators tested positive for both antigens (0.3-12.5%).

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