Classical biological control of the Asian chestnut gall wasp in Italy by the introduction of Japanese-sourced Chinese parasitoid, Torymus sinensis Kamijo, since 2003

Dryocosmus kuriphilus Yasumatsu is one of the most dangerous pests of chestnut (Castanea spp.) worldwide. D. kuriphilus has been introduced accidentally to Japan, Korea, USA and Nepal during the last century and at last it was found in Cuneo, Piemonte Region located in northwestern Italy in 2002. Based on the successful classical biological control of D. kuriphilus in Japan by the introduction of its natural enemy, Torymus sinensis Kamijo from mainland China, a trial introduction of Japanese-sourced T. sinensis started in Italy in 2003. After two years of experimental studies, females of T. sinensis were released in the fields of Cuneo, however, number of the next generation seemed to be too small to establish its population until spring of 2007. In 2008 spring, together with the adult parasitoids emerged from the withered galls imported from Japan, we could obtain more than 1,800 female parasitoids. They were released principally as a unit of 100 females in 14 places in Piemonte Region and furthermore three places out of Piemonte, i.e. in Lombardia, Liguria (both adjacent to Piemonte) and Lazio (Central Italy) Regions. In Japan, T. sinensis females were actually released only once in two places, Ibaraki and Kumamoto Prefectures located in eastern and western part of Japan, respectively, in 1982 about 40 years after the invasion of D. kuriphilus and we have observed the results of their release since then. It should be noted the results of multi-place releasing in Italy in 2008 comparing with those of Japanese cases.