Abstract:

Releasing parasitoid Chouioia cunea Yang for biological control of the Fall Webworm Hyphantria cunea (Drury), an serious invasive defoliator has been researched in China from 1998 to 2003. Results showed that the Fall Webworm population could be effectively put under control when releasing the parasitoid in the full-grown larval and early pupal stages of Fall Webworm respectively and in two consecutive generations, with release proportion of 5 wasps versus 1 host larva. The infested rates of trees reduced to 1.25%, and total parasitism rates of Fall Webworm attacked by natural enemies reached 92.67% after carrying out the biological control measures for the first year. Occurrence of 10 generations of Fall Webworm has been traced continuously for 5 years after release of C.cunea, it indicated that this chalcidoid parasitoid had excellent sustainable control effectiveness on Fall Webworm. The infested tree rates kept under 0.1% and parasitism rates of Fall Webworm by insect natural enemies were still beyond 92% from the 2nd to 5th year after applying the biocontrol measure, which demonstrated the significant sustainable control effects of C.cunea. In addition, a new regression model ( y =-51.607 95+77.475 12 lg x ) we established on parasitism rates between total insect natural enemies and C. cunea itself has also been evaluated in practice. Results revealed that the total parasitism rates calculated by this model did not significantly differ with those from practical investigation. Thus, the model is usable in the survey of parasitism rates by operating organizations for greatly saving works.

Key words: Fall Webworm, Chouioia cunea, biological control, sustainable control, regression model