Key Factors in Delaying Pesticide Resistance Evolution: Modeling Combinations of Active Ingredients and Their Concentration Levels

This review focuses on two potential strategies for pesticide resistance management: mixtures of chemicals with different modes of action, and the optimization of control intensity（i.e., pesticide concentration and the rate of pest exposure to pesticides）. By comparing and re-modeling several theoretical studies, the review elucidates the principles by which these approaches delay resistance evolution and assesses their practical feasibility for pesticide use. The principle underlying mixtures is historically termed “redundant kill,” whereby individuals resistant to one pesticide are eliminated by another. In contrast, the high-dose/refuge strategy in Bt crops delays resistance by applying high concentrations that kill even heterozygotes within treated fields, while maintaining refuges where pests survive regardless of genotype, and utilizing pre-mating dispersal to prevent mating among resistant survivors. Although high doses have been considered impractical for conventional pesticides, a recent dose–response modelling study indicates that mixtures can delay resistance using realistic concentrations（within several times the current label doses）. Furthermore, in mixtures, even without refuges, the fates of the pests within the field are separated into “killed by multiple agents” or “surviving without exposure,” thereby delaying resistance. This proactive containment of resistance alleles contrasts with the postponement of resistance achieved by rotational application.