[Toxicity and oviposition-deterrence of Vitex negundo extracts to Plutella xylostella].

This paper studied the toxicity of dichloromethane-petroleum ether-and methanol extracts from Vitex negundo seed and leaf to the 2nd and 4th instar larvae of Plutella xylostella, and the oviposition-deterrence effects of these extracts to P. xylostella adults. The results indicated that among the 6 extracts, dichloromethane extract from seed had the highest toxicity to the 2nd and 4th instar larvae, followed by dichloromethane extract from leaf, and methanol extract from leaf had the lowest toxicity. The toxicity of dichloromethane extract from seed to the 2nd and 4th instar larvae was as 2.62 and 3.09 times as that of methanol extract from leaf, respectively, and the toxicity of dichloromethane extract from seed to the 4th instar larvae was as 0.73 times as that of phoxim. The methanol extract from leaf and the dichloromethane extract from seed had higher oviposition-deterrence to P. xylostella adults. At the concentration of 4 000 mg x L(-1), they had a longer residual efficacy, with the oviposition-deterrence ratio being 60.6% and 55.2% after treated for 24 h, and 50.9% and 46.1% after treated for 72 h, respectively.