A sex-specific trade-off between pesticide resistance and thermal tolerance in Tetranychus urticae

Abstract

Current pest management relies extensively on pesticide application worldwide, despite the frequent rise of pesticide resistance in crop pests. This is particularly worrisome because resistance is often not costly enough to be lost in populations after pesticide application, resulting in increased dependency on pesticide application. As climate warming increases, effort should be put into understanding how thermal tolerance will affect the persistence of pesticide resistance in populations. To address this, we measured thermal tolerance in two populations of the spider mite crop pest Tetranychus urticae that differ solely in the presence or absence of a target-site mutation conferring resistance to etoxazole pesticide. We found that developmental time and fertility, but not survival, were negatively affected by increasing temperatures in the susceptible population. Furthermore, we found no difference between resistant and susceptible populations in all life-history traits when both sexes developed at control temperature, nor when females developed at high temperature. Resistant heat-stressed males, in contrast, showed lower fertility than susceptible ones, indicating a sex-specific trade-off between thermal tolerance and pesticide resistance. This suggests that global warming can lead to reduced pesticide resistance in natural populations. However, resistant females, being as affected by high temperature as susceptible individuals, may buffer the toll in resistant male fertility. In addition, the decrease in developmental time of both sexes at high temperature may accelerate adaptation to both temperature and pesticide, which can promote the maintenance of resistant populations under climate warming.