クリタマバチ輸入天敵チュウゴクオナガコバチの放飼実験 (4)放飼後6年間の経過

抄録

Trends in gall densities and parasitization of the chestnut gall wasp, Dryocosmus kuriphilius YASUMATSU in an experimental orchard of Kumamoto Prefecture following the introduction of an imported parasitoid, Torymus (Syntomaspis) sinensis KAMIJO were reviewed, and the interim results were discussed. During six years following its release, gall-formed buds fluctuated at a high density level greatly because the parasitization rate remained relatively low. Two possible reasons of low parasitization rate were discussed. One was that the parasitoid might suffer a high mortality caused by hyperparasitism, and the other was that the established parasitoid population did not increase due to its low female ratio.