Experimental and theoretical landscape influences on Spodoptera frugiperda movement and resistance evolution in contaminated refuge areas of Bt cotton.
Transgenic cotton plants producing Bacillus thuringiensis (Bt) (Berliner) insecticidal proteins have contributed to the management of key lepidopteran pests. Larval high dispersal rates between non-Bt and Bt plants in landscapes with seed contamination can speed the evolution of insect resistance to Bt plants. We evaluated the effect of Bt and non-Bt cotton plants on the larval dispersal pattern and survival of susceptible, heterozygous and Cry1F-resistant Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) genotypes in pure and contaminated artificial micro-landscape. A computer model was used to analyse the consequences of S. frugiperda larval dispersal behaviour on resistance evolution in refuge areas with different contamination levels and migration of different adult genotype combinations. The biological data from artificial micro-landscape experiments were used in simulations of macro-landscape scales. The Cry1F-resistant genotype avoided non-Bt cotton. The heterozygote had a similar larval dispersal behaviour as the susceptible genotype when non-Bt cotton was the central plant. Our simulations provide evidence that in refuge areas contaminated with Bt cotton plants, the evolution of resistance may be >75-fold faster in relation to a contamination-free refuge. In conclusion, S. frugiperda resistance management practices on regional scales with contamination-free refuges are important to prevent loss in different crops.