Ostrinia nubilalis parasitism and the field abundance of non-target insects in transgenic Bacillus thuringiensis corn (Zea mays)

¹ Unité de Recherches de Lutte Biologique, INRA La Minière, 78285 Guyancourt, France
² SRPV Rhône-Alpes, 165 rue Garibaldi, BP 3202, 69401 Lyon Cedex 03, France
³ SRPV/DRAF, Cité Administrative Bât E, Bd A. Duportal, 31074 Toulouse, France
⁴ AGPM, route de Pau, 64121 Montardon, France
⁵ SRPV Poitou-Charentes, 13 route de la Forêt, 86580 Biard, France
⁶ FREDEC, Cité Administrative Bât E, Bd A. Duportal, 31074 Toulouse, France
⁷ FREDEC Rhône-Alpes, 165 rue Garibaldi, BP 3202, 69401 Lyon Cedex 03, France

Corresponding author: bourguet@jouy.inra.fr

Abstract

In this study, we evaluated in field trials the effects on non-target species, of transgenic corn producing the Cry1Ab toxin of Bacillus thuringiensis (Bt). In 1998, we collected Ostrinia nubilalis (Hübner) larvae from transgenic Bt corn (Novartis Hybrid 176) and non-Bt corn at four geographical sites. We found a significant variation in parasitism by the tachinids Lydella thompsoni (Herting) and Pseudoperichaeta nigrolineata (Walker) 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, comparing the temporal abundance of non-target arthropods in Bt corn (Monsanto Hybrid MON810) and non-Bt corn. The non-target insects studied included the aphids Metopolophium dirhodum (Walker), Rhopalosiphum padi (L.) and Sitobion avenae (F.), the bug Orius insidiosus (Say), the syrphid Syrphus corollae (Meigen), the ladybird Coccinella septempunctata (L.), the lacewing Chrysoperla carnea (Stephens), 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 corn. The only exception was thrips which, at one site, was significantly more abundant in Bt corn than in non-Bt corn. 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.