Impact des cotonniers génétiquement modifiés sur la biodiversité de la faune entomologique: Le cas du coton Bt en Afrique du Sud

Abstract

For the last three years, CIRAD (Centre de Cooperation Internationale en Recherche Agronomique pour le Developpement, France) and the University of Pretoria led field research to evaluate the impact of transgenic Bt cotton, expressing the Cry1Ac toxin, on arthropod biodiversity in South Africa. The diversity and the density of insect populations were estimated at different crop development stages using traps, sweep-nets, and direct observations on the cotton plants. In untreated plots, the insect diversity in Bt cotton did not show major changes. The toxin was efficient in controlling one of the major bollworm species, Helicoverpa armigera (Hubner), and reduced the population density of specific larval parasitoids. Predators were present in comparable numbers in both cotton types, except for ladybirds. The toxin did not affect pollinators. In small-scale farming fields, where pesticides are still sprayed for controlling sucking insects, the introduction of Bt cotton did not help meet the expected reduction in insecticide use.