Abstract: It has been shown that the natural product, (-)-polygodial extracted from Polygounm hydropiper L. prossesses very good antifeedant activity to instects. Methods of extraction, purification and content measurement of this natural product are reinvestigated in our laboratory.The content of polygodial in the leaves of the plant in China is about 0.08%. The half-life of　synthetic polygodial in air, under light and in heat (55-60℃) are 34.6 days, 33.8 days and 15.6 days respectively. The results of indoor and field tests showed that the nature polygodial extracted from the plant by ethyl ether can be used against aphids.

Key words: Polygonum hydropiper L.——polygodial——aphid——antifeedant