Abstract: In this paper,a life table and an interference index of population control (IIPC) were used to evaluate the effects of spraying the alcohol extracts of non-preferable plants on the dynamics of diamondback moth Plutella xylostella) population.The results showed that the alcohol extracts of Eupatorium odoratum，Lantana camara and Wedelia chinensis were available to protect kidney bean from Plutella xylostella infestation.Their IIPC were 0.110,0.136 and 0.165,and the efficacies of controlling P.xylostella were 89.0%，86.4% and 83.5%,respectively,compared with control.

Key words: Plutella xylostella, Cotesia plutellae, Oomyzus sokolowskii, Interspecific interaction