Impact of genetically modified cotton plants on insect biodiversity: The case of Bt cotton in South Africa [Impact des cotonniers génétiquement modifiés sur la biodiversité de la faune entomologique: Le cas du coton Bt en Afrique du Sud]
International Journal of Tropical Insect Science
CIRAD, Département des Cultures Annuelles, Programme Coton, Montpellier, France; Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
For the last three years, CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement, 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 (Hübner), 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. © ICIPE 2005.
Arthropoda; Coccinellidae; Gossypium hirsutum; Helicoverpa armigera; Helicoverpa zea; Hexapoda; Insecta