The effect of linkage disequilibrium on the evolution of resistance to multiple pesticides.

Pesticides play a crucial role in agricultural pest management and crop yield preservation, yet their extensive application has led to rapid resistance evolution among pest populations. To address this challenge, insecticide resistance management (IRM) strategies aim to prevent or delay resistance evolution. Among the proposed IRM strategies, mixtures are promising but controversial. A key concern with mixtures is the potential for the accelerated evolution of multiple resistance, where selection builds linkage disequilibrium (LD) that leads to a disproportionate number of individuals carrying resistant alleles to both pesticides. In this study, extensive simulations are used to assess the impact of LD on mixtures as an IRM strategy across stochastic and parameter variation. The results demonstrate that LD does not accelerate resistance evolution for mixtures, and analytical predictions explain why resistance alleles are expected to spread independently, even when two pesticides are concurrently applied. These findings suggest that pesticide mixtures can serve as an effective resistance management strategy, outperforming the alternative rotations strategy, particularly when pesticide efficacies are high and exposure is incomplete.