Ecotoxicological risk assessment of combined insecticidal and thermal stresses on Trichogramma chilonis

Trichogramma chilonis (Ishii) is an important biocontrol agent that is widely used around the world to control numerous lepidopteran pests. The overuse of pesticides in agricultural systems causes lethal and sublethal effects on biocontrol agents. In ectothermic organisms, temperature influences the toxicity of insecticides. In the context of global warming, it is crucial to assess the effects of pesticides on beneficial arthropods under temperature stresses. The toxicity of bifenthrin, carbosulfan, chlorantraniliprole, dimethoate, fipronil, flubendiamide, imidacloprid, lambda-cyhalothrin and lufenuron was studied on T. chilonis at 18, 25 and 32 & DEG;C constant temperatures. The temperature coefficient was calculated as the ratio of higher LC50 values to lower LC50 values of an insecticide at different temperatures. The temperature coefficient of imidacloprid, bifenthrin and lambda-cyhalothrin was negative at 25 & DEG;C when compared to 18 & DEG;C and became positive at 32 & DEG;C, while dimethoate and lufenuron had an opposite trend. For carbosulfan and fipronil, the temperature coefficient was positive and for chlorantraniliprole and flubendiamide the coefficient was negative at all tested temperatures. Insecticides having a negative temperature coefficient become less toxic at higher temperatures; this might help reduce non-target insecticide risk to T. chilonis. The risk quotient (RQ) estimated as the ratio of field doses to the LC50 of beneficial organisms indicated that chlorantraniliprole at 25 & DEG;C and 32 & DEG;C and flubendiamide at 32 & DEG;C are harmless to T. chilonis and can be used a component of the integrated pest management (IPM) programs while the other tested insecticides should be avoided. This research can help develop successful pest management systems by reducing the adverse effects of insecticides on non-target species.