Abstract
Although theoretical studies have shown that the mixture strategy, which uses multiple toxins simultaneously, can effectively delay the evolution of insecticide resistance, whether it is the optimal management strategy under different insect life histories and insecticide types remains unknown. To test the robustness of this management strategy over different life histories, we developed a series of simulation models that cover almost all the diploid insect types and have the same basic structure describing pest population dynamics and resistance evolution with discrete time steps. For each of two insecticidal toxins, independent one‐locus two‐allele autosomal inheritance of resistance was assumed. The simulations demonstrated the optimality of the mixture strategy either when insecticide efficacy was incomplete or when some part of the population disperses between patches before mating. The rotation strategy, which uses one insecticide on one pest generation and a different one on the next, did not differ from sequential usage in the time to resistance, except when dominance was low. It was the optimal strategy when insecticide efficacy was high and premating selection and dispersal occur.
Highlights
Insecticides have a long history in the struggle against resistance evolution
There has been a long-standing debate about whether the rotation or mixture strategy will be most effective for pesticide resistance management
Our results support the robustness of the mixture strategy for non-high-d ose insecticides when insecticide application is imperfect or a refuge supplies susceptible insects to the mating pool and the initial resistance frequency is low
Summary
Insecticides have a long history in the struggle against resistance evolution. For more than 100 years, people have recognized how insects can acquire resistance if the insecticide continuously kills the majority of the target population, thereby selecting resistant individuals (Melander, 1914). Genotype x ∊ G at patch i ∊ {T, N} at the τ-th generation and the corresponding density after the first step of their life cycle, that is, juvenile selection, respectively Both state variables contain the population of males and females at a 1:1 ratio, and the sex is assumed to have the Juvenile selection sjuv. Postmating selection is defined the same way as Equation 1, nVII x,i,T. where i ∊ {T, N} denotes the mating patch of females, which does not affect postmating selection survival, and in the same manner as juvenile selection, selection survival is 0, h, and 1 for susceptible homozygotes, heterozygotes, and resistant homozygotes, respectively (we assume the same efficacy and dominance for both pesticides).
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