| Pieris rapae(Lepioloptera: Pierididae)is an important pest of cruciferous vegetables. In order to realize effective ecological control of P.rapae, the control effects of several non-preferable plant extracts on P. rapae were studied in this paper. The results were as follows:1 Control effects of non-preferable plant extracts on P. rapaeThere were different degrees of interference control effects of twenty kinds of non-preferable plant extracts tested on the oviposition of P. rapae in cabbage fields. The interference effect of the extracts of Cyrtomium fortunei,Rheum palmatum,Apium graveolens,Foeni culum vulgare and Artemisia apiacea on the population of Cyrtomium fortunei,Apium graveolens,Rheum palmatum,Foeni culum vulgare and Artemisia apiacea were relatively great and the interference indices of population control were 0.2813,0.2980,0.3341,0.3362 and 0.3395 respectively. The research results of the effects of above five plant extracts on eating food, nutritional physiology and growth of larva P. rapae showed that the treatment of Cyrtomium fortunei had the best antifeedant effect and Rheum palmatum the second. The food utilization rate and relative growth rate of 2 instar larva P. rapae under the treatments of Cyrtomium fortunei were smaller than those under other treatments. The activities of carboxylesterase and acetylcholine esterase in the body of larva P. rapae under the treatments of Rheum palmatum and Cyrtomium fortunei were relative low and the mortalitives of larva were relative high.2 Control effects of biological insecticides on larva of P. rapaeThe control effects of three kinds of biological insecticides of A, B and Ehen had no significant difference to that of the chemical insecticide. The dropping rates of larva population of P. rapae after 1d, 3d and 7d of the treatments of biological insecticides were all above 90% and the treatments were relative safe to natural enemies. Therefore, the biological insecticides could be used to control larva P. rapae when its occurrence was relatively serious.3 Control effects of natural enemies on egg and larva of P. rapaeThe research results of life table of natural population of P. rapae showed that the control effects of parasitic factors on the population of P. rapae were quite minor. The predatory enemies had significant potential control effects on P. rapae. The major dominant species of predatory enemies were Siticus sinensis, Theridion octomaculatum, Erigonidium graminicolum, Pirata subpriaticus, Dyschiriognatha quadrimaculata, Araneus sia, Misumenopos tricuspidata, Harmonia axyridis and Propylea japonica. The results of the grey relational grade analysis showed that Propylea japonica had the best follow effect to the egg of P. rapae and Siticus sinensis had the best follow effect to the larva of P. rapae. Based on a comprehensive analysis, the Siticus sinensis and Erigonidium graminicolum were the most important predatory enemies of P. rapae.4 Synthetic application of ecological control techniques to P. rapaeBased on the above research results, the ecological control methods of different development stages of P. rapae were suggested that spraying the extracts of Apium graveolens or Melia tosendan or Areca cathecu in the peak period of oviposition of P. rapae; spraying the extracts of Rheum palmatum or Cyrtomium fortunei in small larva period of P. rapae, or spraying the biological insecticides in case the occurrence of P. rapae was serious; spraying biological insecticides in large larva period of P. rapae. The selected plant extracts and biological insecticides had minor effects on predatory enemies could rapidly rise again after the spraying of the preparations and the ratio of the natural enemies to pests could control methods proposed by this paper had effective control effects on P. rapae and well protective effects on natural enemies as well as significant economic, ecological and social benefits.
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