Abstract:

The chalcidoid wasp Chouioia cunea (Hymenoptera: Chalcidoidea, Eulophidae) is a predominant parasitoid in pupa of the important introduced defoliator Fall Webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae) in China. For understanding the potential of sustainable management of the pest in biological control by mass rearing and releasing the parasitoid, its alternate hosts were investigated in forests. Through two-year investigations, the species of alternate hosts and their life history, as well as biology were figured out. And the parasitism rate, offspring number, and sex ratio of the parasitoid on those hosts were also surveyed. Results showed that there mainly were six other defoliator species (Lepidoptera) as its alternate hosts besides Fall Webworm, I.e. Clania variegeta (Psychidae), Stilpnotia salicis, Ivela ochropoda (Lymantriidae), Semiothisa cinerearia (Geometridae), Clostera anachoreta (Notodontidae), Acronycta increta (Noctuidae). The parasitoid C. cunea developed seven generations in a year compared with only two generations (occasionally three generations) of Fall Webworm. Besides the two (and/or three) pupal stages of Fall Webworm, the wasp could parasitize those alternate hosts in its other generations because the pupal stages of those hosts were existed and just filled the gaps between the pupal stages of Fall Webworm. Thus, it could keep higher population to control the Fall Webworm after it was released. Results of the investigation showed that the parasitoid distributed widely and the population were relatively stable. It was also indicated that certain population of C. anachoreta and A. increta in forest stands is important for the parasitoid to increasing the population. Furthermore, it could be concluded that the tree_species diversity was a main factor for the parasitoid to keep Fall Webworm under control sustainablly.

Key words: Chouioia cunea, parasitoid, alternate hosts, biological control