Bioactivity of extracts from the plants of Artemisia ordosica against the armyworm Mythimna separata

Bioactivity experiments were conducted with five kinds of extracts from a sand plant,Artemisia ordosica Kraschen,using Mythimna separata Walker as tested species.The results showed that Ethyl acetate extracts of Artemisia ordosica Kraschen had the highest bioactivity mainly in anti-feeding,contacting and inhibiting growth activities of the armyworm,but its stomach poison action was weak:In the treatment with Ethyl acetate extracts,the anti-feeding ratio of 3rd instars larva of the armyworm at 24 h after treatment reached 93.75 %,and the AFC50 was 8.4 mg/mL.The extracts also displayed a highest contact efficiency against the armyworm,and the 72 h mortality with a dipping treatment reached 89.29 %.Ethyl acetate extracts also had significant inhibition to growth and development of the armyworm,the inhibition rate at 24 h and 48 h after treatment were 91.78 %,86.32 % respectively,and a pupation rate was only 43.33 %,the progress of growth and development of the armyworm was delayed.Other extracts,such as petroleum ether,chloroform,n-hexane and acetone,also showed biological activity in certain degree.