Contamination of Refuges by Transgenic Bt Cotton: Implications for Pink Bollworm (Lepidoptera: Gelechiidae) Resistance

Refuges of non-Bt cotton are used to delay Bt resistance in the pink bollworm (Pectinophora gossypiella, Lepidoptera: Gelechiidae), a pest that eats cotton seeds. Contamination of refuges by transgenic Bt cotton could threaten the efficacy of such refuges by increasing the relative survival of larvae that carry alleles for Bt resistance. Here I compared contamination levels in refuges of varying configuration and distance from Bt. I found two types of contamination at low rates in refuges: outcrossing by Bt pollen and adventitious Bt plants. Unexpectedly, outcrossing did not differ between refuge configurations, and did not decrease as distance from Bt fields increased, perhaps because Bt plants in refuges acted as the main Bt pollen source. Bioassays, conducted to evaluate the impacts of contamination on pink bollworm resistance, indicated that Bt plants in refuges may increase the frequency of resistance alleles at a higher rate than outcrossing by Bt plants