Czteroletnie badania polowe nad oddziaływaniem kukurydzy BT na zespoły stawonogów (Arthropoda)

The cultivation of Bt maize, i.e. maize containing insecticidal toxin Cry1Ab that is normally produced by Bacillus thuringiensis, spreads rapidly all around the world. Field trials were perfomed in Czech Republic for four consecutive years to verify whether its cultivation would not endanger beneficial arthropods. Bt and non-Bt maize were each grown on 5 plots of 0.5 ha that were distributed checker-wise in a 7.6 ha field in 2002 and a 14 ha field in 2003-2005. To increase the field load of Cry toxin, Bt maize was grown in 2003-2005 on the same plots and in 2003 the plants at the waxy ripening stage were shred to small pieces and ploughed into the soil. The content of Cry1Ab in plants was measured and samples of arthropods dwelling on the plants and of epigeic species caught in the traps were analyzed in 2-week intervals. The results revealed that maize leaves contained 1 ppm Cry1Ab provided full protection against the European corn borer, Ostrinia nubilalis. Toxin content in pollen and grain was negligible. Numbers of aphids, thrips, and other insects on the Bt and non-Bt plants were similar and independent of Cry1Ab. The same is true for the species richness and population abundance of epigeic carabid and staphylinid beetles and spiders. Differences among the plots in the species richness and population abundance depended on the year, date of collection during the season, and to some extent also on plot position within the field. We conclude that cultivation of Bt maize does not threaten arthropods other than the target species.