Refuges of conventional host plants counter dominant resistance of cotton bollworm to transgenic Bt cotton

Transgenic crops have revolutionized insect pest control, but evolution of resis-tance by pests threatens their continued success. The primary strategy for combating pest resistance to crops producing insecticidal proteins from Bacillus thuringiensis (Bt) uses refuges of non-Bt host plants to allow survival of suscepti-ble insects. The prevailing paradigm is that refuges delay resistance that is rare and recessively inherited. However, we discovered refuges countered resistance to Bt cotton that was neither rare nor recessive. In a 15-year field study of the cot-ton bollworm, the frequency of a mutation conferring dominant resistance to Bt cotton surged 100-fold from 2006 to 2016 yet did not rise from 2016 to 2020. Computer simulations indicate the increased refuge percentage from 2016 to 2020 is sufficient to explain the observed halt in the evolution of resistance. The results also demonstrate the efficacy of a Bt crop can be sustained by non -Bt refuges of other crops.

Automated summary

Transgenic crops have revolutionized insect pest control, but the evolution of resistance threatens their success. The primary strategy for combating resistance is using refuges of non-Bt host plants, which was believed to delay rare and recessively inherited resistance. However, a 15-year study found that refuges countered neither rare nor recessive resistance to Bt cotton. Computer simulations also showed that increased refuge percentage can explain the observed halt in resistance evolution.