Testing Bt refuge strategies in the field

Abstract

Bt transgenic plants can greatly reduce the use of broader spectrum insecticides, but there is concern that this technology might be short-lived because of insect resistance. Field tests on managing resistance to Bt-engineered plants using Bt-transgenic broccoli plants and the diamondback moth as a model system have been reported recently. Insects with a known frequency of resistance alleles were released, and the manner in which the refuge influenced both resistance allele frequency and pest population density was examined. The study shows that a separate refuge will be more effective at conserving susceptible larvae than a mixed refuge. When spraying the refuge to prevent economic loss to the crop, insects from the 20% sprayed refuge treatment and the 20% unsprayed refuge treatment showed no difference in changes in allele frequency, indicating that insects do not evolve resistance more rapidly. However, great care must be taken to ensure that refuges produce adequate numbers of susceptible alleles. Nat. Biotechnol. (2000) 18, 339–342.