High dose refuge strategies and genetically modified crops – reply to Tabashnik

Cultivating nontoxic conventional crops (refuges) in the proximity to transgenic crops that produce Bacillus thuringiensis (Bt) toxins is widely recommended to delay pest adaptation to these toxins. Using a spatially-structured model of resistance evolution, Vacher et al. (2003) argue that the spatial configuration of such refuge fields can be optimized to minimize pest densities over the cultivated region whilst preventing resistance rather than just slowing its evolution. Implementing refuge fields in such a way could promote the sustainable control of pests. Vacher et al. (2003) show that the percentage of refuge fields required for this sustainable control can be reduced through intermediate levels of refuge field aggregation and by lowering the toxin dose produced by Bt plants. They additionally show that the spatial Correspondence: Michael E. Hochberg, Laboratoire Génétique et Environnement, Institut des Sciences de l’Evolution, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France. Tel./fax: +33 4 6714 3667; e-mail: [email protected]