Impact of transgenic Bt soybean (Cry1Ac) on the biological and reproductive cycle and the hervibory ability of Spodoptera cosmioides (Walker) and Spodoptera eridania (Stoll) (Lepidoptera: Noctuidae)

Abstract

The Spodoptera cosmioides (Walker) and Spodoptera eridania (Stoll) populations have increased in the central soybean crop zone of Argentina during the last years. Besides being polyphagous, these species are tolerant to the insecticidal toxin Cry1Ac, which is expressed by genetically modified Bt soybeans. The aim of this study was to determine the effect of Bt soybeans on the consumption, biological cycle and reproduction of both Spodoptera species. The Cry1Ac protein had not consequences in the biological and reproductive cycle of S. cosmioides, except in the pupal period duration. It was not observed the same response in S. eridania, which recorded a shorter duration of the larval and adult stages, total cycle and oviposition period. However, both species of Lepidoptera completed their reproductive cycle successfully and the herbivorous ability was not altered. The genetically modified soybean with the event MON89788xMON87701 that expresses the Cry1Ac protein does not control S. cosmioides and S. eridania, and farmers must appeal to chemical control with insecticides when high densities occur in the field. The results obtained in this work are very useful to understand the biology of these species, which have the potential to become important pests in Bt soybean crops in Argentina.