2024 Volume 71 Pages 71-75
The control effect of an introduced parasitoid wasp, Torymus sinensis Kamijo, on the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu, was evaluated at the release site in Nagano Prefecture. The parasitoid (a total of 720 females) was released at a chestnut orchard in Obuse town in 1992. T. sinensis increased every year and became dominant after 1995. The proportion of chestnut shoots damaged by the gall wasp was considerably high (over 50%) in 1992, but it decreased to less than 20% in 1996, and to less than 1% in 2002. Thus, the introduced parasitoid was considered to effectively control the chestnut gall wasp in the site. Dynamics of indigenous parasitoids after the release of T. sinensis were also discussed.
