The Parasitoids of Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) in Japan and the Introduction of a Promising Natural Enemy from China (Hymenoptera : Chalcidoidea)

Abstract

Dryocosmus kuriphilus is one of the most serious pests of chestnut trees in Japan which entered from China about 1941. Among 15 species of native parasitoids, Torymus (Syntomaspis) beneficus is the most important natural enemy but it has not been recognized as an effective natural enemy capable of regulating the pest population under an acceptable economic injury level. Recently 10 species of the parasitoids were recorded from China. Among them a promising natural enemy, Torymus (Syntomaspis) sp. was imported into Japan and was released for propagation. The Chinese species is very closely related to the Japanese beneficus but distinguishable by the length of the ovipositor. The emergence period of the Chinese species is more synchronous with the host than is beneficus .