Which strategy delays insect resistance development?
Resistance evolution to Bt toxins accelerated when transgenic crops grown continuously on large acreage without alternative hosts for susceptible insects. Homozygous resistant insects emerging from Bt fields mating with each other rapidly increase resistance allele frequency. Refuge strategy maintains pool of susceptible individuals by planting non-transgenic crop nearby or mixing seeds. Susceptible moths from refuge mate with rare resistant survivors from Bt field producing heterozygous offspring. High dose of toxin expressed in transgenic plants kills heterozygotes because resistance general
Ref: Gould Annu Rev Entomol 1998 refuge strategy; Tabashnik Annu Rev Entomol 2013 mixing; NCBI NBK131103 insect resistance management; EPA refuge guidance 2001.
