Toxicity of hexaflumuron and its effects on chitin and chitinase of cotton bollworm,Helicoverpa armigera

【Objective】This study investigated the toxicity mechanism of hexaflumuron to improve the development and application of benzoylphenylureas(BUPs)based pesticides.【Method】Helicoverpa armigera was used as test insect in this research.The toxicity of hexaflumuron against the larvae of H.armigera was studied,and the effects of exposure to hexaflumuron on chitin content and chitinase activity were analyzed.Additionally,the influence on chitinase gene expression levels was investigated by quantitative Real-time PCR.【Result】3rd-instar larvae of cotton bollworm treated with hexaflumuron showed symptoms including slow response,abnormal molting and abnormal development of cuticle,and dead with malformation finally.Hexaflumuron caused a great contact toxicity and abnormal activity against H.armigera with the lethal concentration of 50%(LC50)of 226.43mg/L 96hafter treatment.The chitin content of larvae 72hafter being treated by 120and 240mg/L hexaflumuron decreased significantly,while the chitinase activities of larvae exposed to 120mg/L hexaflumuron were significantly activated.It took longertime for 60mg/L hexaflumuron to activate chitinase activities.Quantitative Real-time PCR analysis showed that the expression levels of chitinase gene(HaCHA)mRNA were significantly decreased after the treatment with hexaflumuron.【Conclusion】Hexaflumuron had strong toxicity against larvae of H.armigeraby decreasing the chitin content and increasing chitinase activity.It was inferred that the changes of chitinase may be related to the toxicity of hexaflumuron against H.armigeralarvae.