No Adverse Effects of Stacked Bt Maize on the Midge Chironomus riparius.

Material from genetically engineered (GE) maize producing insecticidal Cry proteins from Bacillus thuringiensis (Bt) may enter aquatic ecosystems and expose non-target organisms. In this study, we investigated effects of SmartStax maize leaves that contain six different Cry proteins targeting Lepidoptera and Coleoptera pests, in two plant backgrounds, on life table parameters of the midge Chironomus riparius (Diptera: Chironomidae). For development and emergence, 95% confidence intervals for the means of six conventional maize lines (Rheintaler, Tasty Sweet, ES-Eurojet, Planoxx, EXP 258, EXP 262), were used to capture the natural range of variation (NV). For reproduction, lowest and highest means were used. The NV allows to judge if observed effects between Bt maize and the closest non-Bt comparator are likely to be of biological relevance. No adverse effects on C. riparius were observed with both Bt maize lines compared to the respective non-Bt counterparts. Female development time was shorter when fed Bt maize than when fed non-Bt maize, but this effect was not considered adverse. Development time, emergence ratio, sex ratio, and larvae per egg rope measured for Bt maize were within the NV. Fecundity for the Bt lines was equal or higher than for the conventional lines. Future risk assessment studies may consider plant background effects and the NV to judge the relevance of observed differences between particular GE and non-GE plants. This article is protected by copyright. All rights reserved. © 2022 SETAC.