Preliminary selecting of insecticidal activity parts of folium isatidis against Plutella xylostella.

In order to study the insecticidal activity parts of folium isatidis against Plutella xylostella,the active substance of folium isatidis was extracted through ultrasonic wave by using ethanol as the menstruum,the extract was leached respectively by petroleum ether,chloroform,ethyl acetate and n-butanol,and its insecticidal activity was determined by leaf disc method.The larvae of Plutella xylostella fed by cabbage leaves soaked in n-butanol extract were totally dead after 24 hours,and they fed by cabbage leaves soaked in petroleum ether extract were completely dead after 48 hours.There were various degrees of deaths for the larvae of Plutella xylostella within 144 hours after they fed on the cabbage leaves soaked in ethyl acetate and ethanol extracts.The results showed that every extract from folium isatidis had a certain contact toxicity against Plutella xylostella,and the n-butanol and petroleum ether extracts had much more active substance against Plutella xylostella.