Insecticidal Activity and Active Components of Cynanchi auriculati against Plutella xylostella

The contacting bioactivity of ethanol extract, different polar-solvent extracts and silica gel column sub- fractions of Cynanchi auriculati have been tested against 3rd larvae of Plutella xylostella by method of topical application. The result showed that the 72 h virulence of ethanol extract of Cynanchi auriculati against 3rd larvae of Plutella xylostella was 2.13 g/L, stronger than phoxim(3.93 g/L), dichlorvos(4.36 g/L) and cyhalothrin(4.51 g/L). Different polar-solvent extracts from ethanol extract have tested on 3rd larvae of Plutella xylostella gave a result as following: petroleum ether(97.95%) chloroform(42.17%) ethyl acetate(28.57%) distilled water(18.37%) n-butanol(11.53%). Petroleum ether extract was separated and pured by silica gel column and analysed by GC-MS gave a result that the main components were sitosterol(18.26%), ergostane(16.69%) and β-sitosterol(15.35%).