Ostrinia nubilalis parasitism and the field abundance of non-target insects in transgenic Bacillus thuringiensis corn (Zea mays).
In this study, we evaluated the effects of transgenic maize producing the Cry1Ab toxin of Bacillus thuringiensis (Bt) on various non-target species. In 1998, we collected Ostrinia nubilalis larvae from transgenic Bt maize (Novartis Hybrid 176) and non-Bt maize at four geographical sites in France, i.e. Rieumes, Lavelanet and Bérat (Midi-Pyrénées region) and Salaise-sur-Sanne (Rhône-Alpes region). We found a significant variation in parasitism by the tachinids Lydella thompsoni and Pseudoperichaeta nigrolineata among sites, and more parasitism in non-Bt than in Bt fields. The Bt effect did not vary significantly among fields. In 1999, we performed a field experiment at two sites (Montesquieu-Lauragais and Aussonne), both located in the Midi-Pyrénées region, comparing the temporal abundance of non-target arthropods in Bt maize (Monsanto Hybrid MON810) and non-Bt maize. The non-target insects studied included the aphids Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae, the bug Orius insidiosus, the syrphid Syrphus corollae [Eupeodes corollae], the ladybird Coccinella septempunctata, the lacewing Chrysoperla carnea, thrips and hymenopteran parasitoids. For all species but one, the number of individuals varied greatly over the season but did not differ between the types of maize. The only exception was thrips which, at one site, was significantly more abundant in Bt maize than in non-Bt. However this difference did not remain significant when we took the multiple tests into account. Implications for pest resistance management, population dynamics and risk assessment are discussed.