| In this paper, fifteen species of compositae were treated for extraction and biological activities of their extracts against Pieris rapae were compared and analyzed. Then Xanthium inaequilatum was singled out and extracted with two traditional methods and three solvents, and biological activities of the ethanol extract from the leaves of it against Phyllotreta vittata, Spodoptera litura and Plutlla xylostella were determined by bioassay. The effects of the extract of different concentrations on the growth and oviposition of Pieris rapae were measured, and field trials were carried out for measuring its effect on controlling Pieris rapae. Active fractions were separated from the extract of Xanthium inaequilatum by silica gel column chromatography, and biological activities of the fractions against Pieris rapae were also determined.The results of bioassay showed that all the ethanol extracts from those 15 plants had biological activity against Pieris rapae, Xanthium inaequilatum showed the highest biological activity against the pest, with its antifeedant rates being 78.31 and 53.13%, after 24 and 48 hours of treatments, respectively, and the corrected mortality being 95.23%, after 7 days of treatment.Different parts of Xanthium inaequilatum , such as its roots, stems, leaves and fruits, were treated for extraction wife ethanol and two extraction methods. The results showed feat fee extract from fee leaves had fee highest biological activity against fee pest. The antifeedant rates of fee extracts from fee roots, stems, leaves and fruits by Soxhlet method were 30,84%, 47.72%, 61.63% and 33.34%, respectively, after 24 hours of treatments, and were 19.94%, 23.68%, 48.15% and 20.58%, respectively, after 48 hours of treatments, and corrected mortalities were 15.01%, 36.26%, 90.71%, and 53.68%, respectively, while fee antifeedant rates of the extracts by cold dipping were 49.19%, 53.87%, 69.17% and 41.22%, respectively, after 24 hours, and were 13.06%, 20.53%, 50.02% and 39.10%, respectively, after 48 hours, and corrected mortalities were 23.17%, 46.74%, 96.37% and 23.45%, respectively. This showed that cold dippingmethod was more effective than Soxhlet method.The extracts from the leaves of Xanihvum inaequilatum with ethanol, acetone and petroleum ether possessed biological activity against Pieris rapae, when the ethanol extract had the highest, with its antifeedant rates being 65.27% and 51.24%, after 24 and 48 hours of treatments, respectively, and the corrected mortality being 95.34%, after 7 days of treatment. While for the acetone extract, the antifeedant rates and corrected mortality were 53.09%, 40.86% and 95.34%, respectively, and for the petroleum ether extract, the rates were 52.31%, 30.37% and 68.36%, respectively.The larvae of Pieris rapae were treated with the ethanol extract of different concentrations and the results indicated that as its concentration decreased, its biology activity was also reduced. With the extract at concentration of 2%, 1% and 0.25%, the antifeedant rates were 61.11%, 51.28% and 45.73%, respectively, after 24 hours of treatments, and the rates were 50.3?%, 44.35% and 34.12%, respectively, after 48 hours of treatments, the corrected mortalities were 93.56%, 85.49% and 43.25%, respectively. Even with the extract at concentration as low as 0.125%, after 24 and 48 hours of treatments, the antifeedant rates were 42.74% and 30.57%, respectively, and the correct mortality was 20.37%.The extract had a strong antifeedant effect not only on Pieris rapae, but also on Phyllotreta vittata, Spodoptera litura and Plutella xylostella. With a extract at concentration of 2%, it had a strong antifeedant effect on Phyllotreta vittata, with the antifeedant rates being 85.06% and 79.78%, respectively, after 24 and 48 hours, and the mortality rate being 43.21% after 4 days of treatment. Under the same condition, the antifeedant rates were 75.75% and 70.69%, respectively, after 24 and 48 hours, and the mortality rate was 62.54% after 7 days of treatment of 3rd-instar larvae of Plutlla xylostella. While for Spodoptera litura, the antifeedant rates were 93.20% and 84.90% respectively, and the mortality rate was 30.72% after 7 days of treatment.With the extract at a concentration of 2%, the weight of larvae increased...
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