engleski

Native parasitoid assemblages of chestnut gallwasp, Dryocosmus kuriphilus (Hym.: Cynipidae) in Europe

The chestnut gallwasp, Dryocosmus kuriphilus Yasumatsu (DK) (Hymenoptera, Cynipidae) is considered to be the most important pest of chestnut (Castanea spp.) worldwide. Originating from China, this pest was accidentally introduced to Japan in 1941, colonized Korea in 1958 and the USA in 1974. In 2002 it was detected in Europe (Piedmont, Italy). Since 2002, DK has been established and spread throughout Italy all the way into Sicily, and has also been reported in France in 2005, Slovenia in 2005, Switzerland in 2009, Croatia in 2010, Slovakia and Czech Republic in 2011, Spain in 2012, Hungary in 2013. In 2014 it was detected in Portugal and Turkey. Within the native range in China, 11 parasitoids species were found to associate with DK which kept the host populations at low densities ; in Japan, South Korea, the USA and Italy the attack rates of indigenous parasitoid species vary from 2% to 4.7%, in some regions of Italy up to 32%. We study the native parasitoid complexes of DK across it expanding range in Italy (since 2005), Slovenia (since 2010), Croatia (since 2011) and Hungary (since 2013). Recruitment of parasitoids to DK depends on actual parasitoid species composition of oak gallwasps to be found in the same locality and higher in mixed chestnut-oak forests than in pure Castanea stands. The research has shown that the time lag between the introduction of the new host, DK, and the recruitment of native parasitoid community is short what was already showed for different sites in Europe. In Italy during 2005-2010 thirty-two chalcidoid parasitoid species have so far recruited naturally to the new host, in 2012-2013 the parasitoid species number increased to 39. In Slovenia 7 species were found in 2010, 11 in 2011, 13 in 2012 and 15 in 2013. In Croatia 11 species were found in 2011, 15 in 2012 and 18 in 2013. In Hungary during 2013 11 species were reared from the new host. The most common and abundant species across Europe are: Eupelmus urozonus (Eupelmidae), Eurytoma brunniventris (Eurytomidae), Megastigmus dorsalis, Torymus flavipes, T. geranii (Torymidae), and Ormyrus pomaceus (Ormyridae). The recruitment speed is very impressive, but the majority of parasitoids have two generations each year and therefore their population dynamics are not closely connected to that of Dryocosmus kuriphilus. The attack rates of indigenous parasitoid species are low, typically 2–4, 7%. In some regions of Italy the parasitization rate was up to 32%. Possibilities for biological control by meaning of conservation and augmentation are discussed.

chestnut gall wasp; parasitoids; Italy; Slovenia; Hungary; Croatia

nije evidentirano