Toxicology and Biochemical Basis of Cantharidin Effects onHelicoverpa armigera (Hub.) (Lepidoptera: Noctuidae)

Toxicity of cantharidin, a well known natural compound produced by beetles of family Meloidae and Oedemeridae, was examined on Helicoverpa armigera. Furthermore, its effect on different metabolic enzymes, responsible for resistance towards insecticides, was also investigated. Bioassay results showed that LC50 value of cantharidin was 0.068 mg/g, using diet incorporation bioassay under laboratory conditions. Body weight of insects was also significantly reduced by cantharidin treatment. The LC10 concentration of cantharidin, 0.01mg/g was tested to see its effect on metabolic enzymes such as; alkaline phosphatase (ALP), glutathione S-transferase (GST), cytochrome P450s (P450s) and carboxylesterase (Car-E). Our results showed that cantharidin significantly inhibited the activity of ALP after 48 h, whereas activity of GST was significantly inhibited after 24 h. Cytochrome P450s activity remained significantly high at 12 to 48 h after treatment. Statistically, no significant change was recorded in Car-E activity. It may be concluded from the results that ALPs and GSTs may be target of cantharidin, whereas P450s may be involved in detoxification of cantharidin in insects. In light of our results, we suggest cantharidin as potential candidate insecticide precursor and its scope in pest management needs to be explored further to solve the problem of insecticide resistance.