Decline of the Chestnut Gall Wasp Population, Dryocosmus kuriphilus YASUMATSU (Hymenoptera : Cynipidae) after the Establishment of Torymus sinensis KAMIJO (Hymenoptera : Torymidae)

Abstract

Prior and subsequent to the release of Torymus sinensis in 1982, galls of Dryocosmus kuriphilus were collected from chestnut ( Castanea crenata) trees in Japan. Populations of the parasitoid increased shortly after its establishment and the number of females in 1985 was 33.4 per 100 galls compared with 3.1 per 100 galls in 1983. The number of females of T. beneficus varied from 2.0 to 31.6 per 100 galls during the study. It is concluded that the introduction of T. sinensis has resulted in biological control of D. kuriphilus.