41st Annual Meeting of the Society for Invertebrate Pathology
and 9th International Conference on Bacillus thuringiensis

The Western Corn Root Worm (Diabrotica v. virgifera) first time occurred in Germany in July 2007. Four different maize cultivars including Diabrotica-resistant MON88017, were assessed in respect to its effects on saprophagous Diptera and predators out of Carabidae and Staphylinidae. The methodological approach comprised a hierarchic order of different ecological scale levels (agro-ecosystem, population, organisms). Abundance and species composition of both Diptera and their predators were recorded in the field. Most saprophagous Diptera belong to Sciaridae (fungus gnats), of which the predominant Lycoriella castanescens was used for feeding trials. It was tested whether mortality, pupation, hatching rates, duration of larval development and pupation were affected by uptake of Cry3Bb1-contminated plant tissues. Species of Carabidae and Staphylinidae were fed with Sciaridae-larvae reared on Bt- and non-Bt-maize-litter respectively. In a similar way Diabrotica-larvae were offered as prey. Toxin analyses of saprophagous Diptera and predators reared with Bt-plant parts or feeding on Bt-contaminated prey contained Bt-toxin up to 1.6% (decomposers) and 14.0% (predators) of the toxin level recorded in the source material. Predators collected from Bt-maize fields stated these findings. Thus, Bt-toxin is transferred into the food chain. Predators feeding on prey containing Cry3Bb1-toxin showed a significant delay in accepting the prey in comparison to prey free of Bt-toxin, but this didn't result in higher mortality or less longevity. However, predators which were fed with Sciaridae-larvae containing Bt-toxin produced significantly less offspring than those feeding on prey reared with non-Bt-maize litter. Thus, an uptake of Cry3Bb1-toxin by carnivorous beetles doesn't lead to a higher mortality, but results in subtle effects like lower fertility of the females.