engleski

Native Parasitoid Assemblages of an invasive pest, Dryocosmus kuriphilus(Hymenoptera: Cynipidae), in Slovenia, Croatia and Hungary

The Asian sweet chestnut gallwasp, Dryocosmus kuriphilus Yasumatsu (DK) (Hymenoptera, Cynipidae) considered to be the most important pest of chestnut 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, Italy. Since then DK spread throughout Italy and has also been reported in all European countries where chestnut growth. 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 European countries the attack rates of indigenous parasitoid species vary from 2% to 4.7%, in some regions of Italy occasionally up to 32%. We study the native parasitoid assemblages of DK across its expanding range in Italy (since 2005), Slovenia (since 2010), Croatia (since 2011) and Hungary (since 2013). All parasitoid species are known to associate with oak cynipid galls. Most of them are generalists that can shift hosts more easily and are more successful in colonizing an invasive host and thus a large parasitoid diversity within the DK community can be expected. The aim was to study the source community of parasitoids available to attack the invasive host and the way in which they may associate with D. kuriphilus. Specifically, (i) are parasitoids conservative in their choice of host, jump onto the new invader rarely and track the host after a suitable match between parasitoid and host is established (the Host Tracking hypothesis) or (ii) are parasitoids opportunistic and readily jump onto a new host from their local population when it becomes available (the Local Recruiment hypothesis). We believe that Local Recruitment is the more likely hypothesis to explain interactions between native parasitoids and DK. Around half of parasitoid species associated with DK across its expanding range, were not observing in the original site of invasion, thus the Host Tracking is unlikely to be happened. Since 2005 44 species shifted onto the new pest, DK. Till 2015 in Italy 39 chalcidoid parasitoid species have so far recruited naturally to the new host, in Slovenia 28, in Croatia 20, in Hungary 17. The time lag between the introduction of the new host, DK, and the recruitment of native parasitoid community is short and depends on the longevity of pest’s presence on a particular site. Recruitment of parasitoids to DK depends on actual parasitoid species composition of oak gallwasps to be found in the same locality and vary from year to year.

invasive pest; Dryocosmus kuriphilus; native parasitoids; augmentation; biological control; parasitization rate

nije evidentirano