ÃÞ »¨ ѧ ±¨ Cotton Science 2009£¬21(3)£º212-217
Sublethal Effects of Methoxyfenozide on Spodoptera litura (Fabricius) Abstract£ºMethoxyfenozide (RH-2485) belongs to a new group of insect growth regulators, bisacylhydrazines, which mimic natural insect moulting hormone by binding competitively to ecdysteroid receptors and inducing a premature larval moult. Although acute toxicity tests have shown that methoxyfenozide is the most potent non-steroidal ecdysone agonist to date against larval Lepidoptera, and exhibits a high degree of safety to non-target insects, knowledge about the sublethal effects of methoxyfenozide is still limited. Considering that non-lethal impacts of insecticides on various life history parameters may affect pest population dynamics, we investigated the sublethal effects of methoxyfenozide on Spodoptera litura (Fabricius), a worldwide-distributed agricultural pest. Based on the bioassay results, 3rd instar larvae of S.litura were treated with methoxyfenozide at concentrations corresponding to LC30 and LC10 by the artificial diet incorporation method. Higher rate of deformed pupa and lower eclosion rate were observed, and the fecundity and egg hatchability were significantly decreased compared with control, suggesting that methoxyfenozide at sublethal concentrations had a negative effect on population development of S. litura . The sublethal effects of methoxyfenozide on detoxification enzymes were also studied. After exposure to methoxyfenozide at LC10 for 24 h and LC30ªfor 48 h and 96 h, the activities of esterase £¨EST£© were significantly increased compared with control. The activities of microsomal multifunctional oxidase £¨MFO£© and glutathione S-transferases £¨ GST £© were also significantly enhanced when 3rd instar larvae were treated with methoxyfenozide at LC10 for 24 h and LC30 for 96 h, respectively. These results indicated that detoxification enzymes of S. litura could be induced by methoxyfenozide depending on the concentration and the time after treatment. Finally, the importance of sublethal effects of insecticides on development, reproduction and detoxification enzymes of pests were discussed.
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