engleski

Native parasitoid recruitment to chestnut gallwasp, Dryocosmus kuriphilus (Hymenoptera: Cynipidae), across Italy, Slovenia, Croatia and Hungary

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 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 and Spain (Catalonia) in 2012. In Hungary it was detected for the first time in 2009 and was successfully eradicated but in 2013 heavy infestations were found in 20 localities of Zala County in the south-western part of the country and no doubts, the pest successfully settled down in Hungary also. 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, and 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. Possibilities for biological control by meaning of conservation and augmentation are discussed ; classical biological control by using of introduced Torymus sinensis (Torymidae) is emphasised as well.

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

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