Biological control of chestnut gall wasp (Dryocosmus kuriphilus Yasumatsu, Hymenoptera: Cynipidae)

Abstract

The chestnut gall wasp, Dryocosmus kuriphilus (Hymenoptera: Cynipidae), is considered to be one of the most important pest of chestnut (Castanea sp. and Castanopsis sp.) worldwide. The larvae of chestnut gall wasp feed on plant tissue, causing formation of galls on the shoots and leaf veins, resulting in severe reduction of fruit yield and vitality of plant. The wasp is of Chinese origin and it invaded Europe and the rest of the world with infected plant material. In Slovenia, chestnut gall wasp appears in Goriška region in 2004 for the first time, but in Italy it appeared three years earlier and is yet widespread in chestnut orchards and forests causing great damage. Introducing parasitoid wasps of chestnut gall wasp seems to be the most promising biological control method to reduce this pest and its damage. The most effective parasitoid species is Torymus sinensis (Hymenoptera: Torymidae), which originate from China and it has been yet successfully introduced and widespread in Japan. The chestnut gall wasp has many parasitoids, but they are not that effective in reducing the population of the pest. 15 species of chestnut gall wasp are presented in Italy. In Slovenia, we have not found any native chestnut gall wasp parasitoids yet, but the research is in process, because of the danger of spreading this important pest throughout Slovenia chestnut orchards and forests.