Insecticide activity under changing environmental conditions: a meta-analysis

The effect of environmental change on activity of insecticides against insects has been greatly debated, and it is of significance to evaluate general patterns of change and explore the potential mechanisms that drive the changes in the context of global climate change. To that end, we constructed three multilevel meta-analyses and phylogenetically-corrected models based on 810 individual effect sizes of insecticide activity from 95 studies with variable levels of temperatures, humidities, and CO₂ concentrations. We found that increasing temperatures could overall increase the insecticidal activity of insecticides by 1.33 times. Increasing temperatures will boost the activity of some types of insecticides (e.g., acetylcholinesterase inhibitors), but decrease the activity of some other types (e.g., sodium channel modulators). Activities of stomach toxicants and fumigants are overall more sensitive to increasing temperatures than other insecticides. The sensitivity of insects in Hemiptera, Coleoptera, and Diptera to insecticides will also tend to increase significantly due to increasing temperatures. The magnitude of warming was found to have strong interactive effects with both insecticide class and insect group. Although moisture changes were showed to have no significant effects on insecticidal activity overall, our meta-regression analyses identified a positive relationship between insecticide activity and the magnitude of humidity change. No significant relationships between changes in CO₂ concentrations and insecticide activity were identified. Our results are critical in adaptation of insecticide application and pest management strategies, and forecasting insecticide risks (e.g., resistance development) across global climate regions under future warming conditions.