Abstract: To investigate the new methods and tools of alien weeds usage， effects of essential oil extracted from Praxelis clematidea on enzyme activities （carboxylesterase and glutathione\|s\|transferase） of diamondback moth （DBM）， Plutella xylostella， and its toxicity by using topical methods of application and fumigation were studied in this paper. Results showed that LC50 after 48 h of P. clematidea essential oil against DBM larvae was 2102×105 mg·L-1 by topical application methed and was 1404×105 mg·L-1 by fumigation treatment. The median antifeedant concentration （AFC50） of P. clematidea essential oil against DBM larvae was 269×104 mg·L-1. The antifeedant rate could reach 100% when treating concentration was 100×105 mg·L-1. Treating time had no significant effects on AFC50. The activities of carboxylesterase and glutathione\|s\|transferase of DBM larvae treated with P. clematidea essential oil were changed significantly but not in a regular pattern.

Key words: Praxelis clematidea essential oil, diamondback moth, toxicity, carboxylesterase, glutathione\, s\, transferase