Toxic Effects of Five Insecticides on the Development and Enzymatic Activities of Trichogramma ostriniae

As an egg parasitoid, Trichogramma ostriniae (T. ostriniae) exhibits a broad host range and plays a crucial role in controlling various lepidopteran agricultural pests. However, the application of chemical pesticides negatively impacts its development and survival. Therefore, it is essential to assess the toxicity of commonly used insecticides against T. ostriniae and evaluate their compatibility. This study aims to determine the toxic effects of five common insecticides (dinotefuran, abamectin, imidacloprid, beta-cypermethrin, and chlorantraniliprole) on the development, reproduction, and enzymatic activity of T. ostriniae. The contact, lethal, and developmental toxicities were evaluated. Activities of detoxification enzymes, including cytochrome P450 (CYP450), carboxylesterase (CarE), and glutathione S-transferase (GST), and protective enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) as well as malondialdehyde (MDA) and reactive oxygen species (ROS), mitochondrial respiratory chain complex I (MRCC I), adenosine triphosphate (ATP) of T. ostriniae were examined after being treated with the five insecticides. The results showed that the order of lethal toxicity in adult T. ostriniae was beta-cypermethrin > dinotefuran > imidacloprid > abamectin > chlorantraniliprole. The emergence rates of adult T. ostriniae exposed to insecticides during the egg and larval stages were higher than those exposed to insecticides during the prepupal and pupal stages. The activities of CYP450, GST, and SOD were increased, but CarE activity and ROS content were decreased in T. ostriniae treated with the five insecticides compared with the control. Beta-cypermethrin increased the POD and CAT activities. Chlorantraniliprole decreased CAT activity and increased MDA content. The MRCCI of T. ostriniae was not significantly affected by any of the five insecticides tested. The ATP content of T. ostriniae was not significantly affected by chlorantraniliprole but was significantly decreased by the other four insecticides. In conclusion, the toxicities of the five insecticides to T. ostriniae were different, among which imidacloprid, dinotefuran, abamectin, and beta-cypermethrin had a high risk of toxicity to T. ostriniae, and chlorantraniliprole had a low risk to T. ostriniae.