A Preliminary Introduction and Release of a Parasitoid (Ghalcidoidea, Torymidae) of the Chestnut Gall Wasp, Dryocosmus kuriphilus Yasumatsu (Cynipidae) from China

Abstract

The first infestations of the chestnut gall wasp, Dryocosmus kuriphilus, were observed in Okayama Prefecture in 1941, and since 1946 it spread rapidly and soon became one of the major pests of chestnut trees in Japan. The origin of the pest was not established, but it was thought to have been accidentally introduced from China. In the summer of 1975, 69 galls of the chestnut gall wasp were collected in a grove at a suburb of Hsian, Shensi, China and imported to Japan. In early April, 1976, 4 females and 3 males of Torymus {Syntomaspis) sp. emerged from these galls. Later the galls were opened for examination. The dead adults or pupae of 5 species of parasitoids were found in these galls; i.e., Megastigmus sp., Ormyrus sp., Eurytoma brunniventris, Eudecatoma sp. and an undetermined chalcidoid. Parasitism was estimated to be between 60 and 80 percent in the grove where the material had been collected. A preliminary release test of the Chinese parasitoid, T. (S.) sp. was made on four caged branches on two chestnut trees at the Fruit Tree Research Station, Hiratsuka by using 3 females and 2 males. They produced 10.3 progenies per female on the average. This suggested the possibility of successful establishment in Japan of this parasitoid. Among the Chinese parasitoids so far examined T. (S.) sp. was the only parasitoid which was host-specific and synchronous with the chestnut gall wasp. Therefore, it was recommended that the parasitoid shoud be introduced from China for the biological control of the chestnut gall wasp in Japan. © 1977, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.