Evaluating pesticide mixtures for resistance management in asexual insect pests

Many economically important insect pests reproduce through asexual or partially asexual life cycles, yet how reproductive mode influences insecticide resistance management remains unclear. The choice of resistance management strategy has been suggested to differ for sexual and asexual pests. For instance, current IRAC guidance suggests that pesticide mixtures are less effective in non-mating pests than in sexually reproducing populations. Here, stochastic evolutionary simulations are used to compare resistance evolution under sequences and mixtures across four reproductive modes observed in pests of economic importance: sexual reproduction, obligate parthenogenesis, cyclical parthenogenesis and haplodiploidy. Contrary to current expectations, mixtures are not disadvantaged in asexual populations and, in some cases, lead to delayed resistance evolution compared to sexually reproducing populations. These differences arise as the result of reduced genetic recombination which constrained the assembly and spread of multi-resistant genotypes. Overall, these findings suggest that mixtures remain a viable resistance management strategy for pests with asexual reproduction.