Optimizing pesticide efficacy: the impact of extreme heat events and timing in a warming climate

Climate change complicates pest management practices, particularly pesticide application, as pests’ responses to pesticides are temperature-dependent. Here, we investigated the effects of extreme heat events on the toxicity of the neonicotinoid imidacloprid to wheat aphid Sitobion avenae, considering factors including temperature, exposure duration, intervals between heat events and pesticide application, and exposure order. We found that toxicity is both temperature- and time-dependent, with longer exposure durations and shorter intervals between heat stress and pesticide treatment generally increasing toxicity. The sequence of exposure (whether heat or pesticide occurs first) also influenced efficacy, with variations observed between adult (F0) and offspring (F1) stages. Both indoor and field experiments demonstrated that factors like the temperature post-application, the interval between stresses, and their order are crucial for pest control outcomes. Based on these results, we proposed several guidelines for farmers: 1) apply pesticides on hotter days; 2) ensure that post-application temperatures are elevated; 3) minimize the interval between pesticide application and heat events. These strategies can optimize pesticide use, enhance efficacy, and reduce overall pesticide application, offering valuable insights for improving pest management in a warming climate. Further field studies are needed to confirm these findings.