Environmental impact of Bt-corn on non target entomofauna: Synthesis of field and laboratory studies

Laboratory tests and field experiments were conducted to determine the effects of corn (Zea mays) expressing Cry1Ab protein derived from Bacillus thuringiensis Berliner subsp. kurstaki, on non-target insects and on soil fauna. Chrysoperla carnea Stephen was fed with the aphid Rhopalosiphum padi L. reared in laboratory on Bt and on traditional corn. No detrimental effects of transgenic Bt corn on preimaginal development and mortality of C. carnea were observed. The abundance of aphids was not affected by the presence of transgenic corn crops. The statistical analyses revealed no significant differences in the abundance of this sucking insect in isogenic corn and Bt corn crops. In field Coleoptera Carabidae were studied, as typical soil fauna, comparing community structures and degree of specific biodiversity in transgenic and isogenic corn crops. The ground beetle assemblages were quite similar, and any differences appeared to have no correlation with the presence of Bt maize. The biodiversity of the Carabidae communities was quite low for both types of crops and, on comparing the two types of hybrid corn crops, no significant differences were found in any of the indices analysed. Reasons for differences or lack of them are discussed.