Diurnal Temperature Fluctuation Alters the Toxicity of Insecticides: the Role of the Temperature Coefficients of Insecticide
Climate change and insecticides have a complex relationship as environmental stressors that negatively impact organism development and reproduction. Previous insecticide toxicity studies on the climate change have focused on average temperature while disregarding diurnal temperature fluctuations. Therefore, we conducted a study on Sitobion avenae, a global pest, and examined effects of temperature amplitudes (TAs) ( +/- 0, +/- 6, +/- 12 °C) using the average temperature (22 °C). In addition, effects of two insecticides (beta-cypermethrin: negative temperature coefficient NT, imidacloprid: positive temperature coefficient PT) on longevity, survival, early fecundity, fecundity, daily nymph reproduction, and the intrinsic rate of increase were investigated. The findings revealed that wide amplitude significantly decreased adult fecundity, daily nymph reproduction, and the intrinsic rate of increase, while it significantly enhanced early fecundity. Medium amplitude significantly lowered the intrinsic rate of increase. Insecticides mitigated or even reversed the harmful impact of wide amplitude on adults. Following PT treatment, longevity was significantly higher than those under 22 °C. Following NT treatment, survival was noticeably greater than that under 22 °C. The interaction between insecticide and medium amplitude positively affected adult phenotypes. Both PT and NT treatments revealed that survival, longevity, fecundity and daily nymph reproduction were higher under medium amplitude than those under 22 °C. These results corroborate the theory of climate-induced poison sensitivity, provide a theoretical basis for insect resistance under long-term low-dose insecticide residues, and indicate that insecticide temperature coefficients are crucial in assessing insecticide safety risks under current and future climate change scenarios.