Abstract:

In order to study the insecticidal activity of methoxyfenozide (RH-2485) against the larvae of Lymantria dispar,the pesticide bioactivity of the chemical against the different instar larvae of L. dispar and its effect on the activities of detoxifying enzymes of the insect were assayed using leaf film method, and the expression of proteins in different tissues of the larvae were detected with SDS-PAGE. The results showed that methoxyfenozide had a high toxicity against the larvae,especially 2^nd instar and 3^rd instar, and the toxicity was obviously different with different larva instars. The activities of detoxifying enzymes, such as carboxylesterase (CarE), MFO O-demethylase (MFOD) and glutathione S-transfer (GST), in the 2^nd, 4^th, 6^th instar larvae were significantly induced or inhibited by the methoxyfenozide treatment. The impact of methoxyfenozide on these enzymes was significantly different at different treatment time. After the 4th instar larvae were fed with methoxyfenozide,the protein expression pattern in the hemolymph,midgut and epidermis was different from that in the control. The effect of methoxyfenozide on proteins in the hemolymph and midgut was obvious in 12 h and 24 h, whereas the effect on protein expression in epidermis tissue was more significant in 48 h. These results indicated that methoxyfenozide as a non-steroidal ecdysone had a higher biological activity against L. dispar,and the major detoxifying enzymes in the insect body were significantly interfered,showing that methoxyfenozide had a high toxic effect against L. dispar. The specific proteins were produced in the hemolymph,midgut and epidermal tissue,which might interfere with the normal physiological metabolism of insects and epidermal formation.

Key words: methoxyfenozide, Lymantria dispar, detoxifying enzymes, protein