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Presence of birch bark beetle (Scolytus ratzeburgi) in Croatia Prisutnost brezovog potkornjaka bjelikara (Scolytus ratzeburgi) u Hrvatskoj Ivan Lukić, Željko Zgrablić, Vlatka Mičetić Stanković Summary Bark beetles are one of the most important groups of forest pests and in recent years several bark beetle species have significantly impacted two biogeographic regions in Croatia. The Birch bark beetle (Scolytus ratzeburgi) is the only Scolytus species known to infest birch (Betula spp.) and is a potential threat to birch trees in Croatia but its presence has not been recorded for over 100 years. Here we review historical records of this species and examine several forest stands of Silver birch (B. pendula). The last published record of Birch bark beetle was from 1913 and entomological collections from Croatia only have specimens from neighboring countries. Examination of Silver birch forest stands discovered five new locations of Birch bark beetle with signs of its attack. This species in Croatia has a low population density in forests and urban areas. Impacts of this species may be minimal, but research on this bark beetle should not be neglected since it represents valuable part of entomofauna in Croatia. Further research in Croatia should target fungal relationships with this species in order to determine whether the bark beetle spreads tree pathogenic fungi. Assessment of possible long-term mortality trends across the southern range edge of Silver birch and the presence of the Birch bark beetle merits further attention. Key words: Betula pendula, native species, Scolytinae INTRODUCTION UVOD Bark beetles (Coleoptera: Curculionidae: Scolytinae) are one of the most important groups of forest pests primarily due to their ability to kill large numbers of trees (Kurtz et al., 2008; Raffa et al., 2008; Cudmore et al., 2010). In recent years, several bark beetle species have significantly impacted two biogeographic regions of Croatia. In 2015, the European spruce bark beetle (Ips typographus L., 1758) together with the Six-toothed spruce bark beetle (Pityogenes chalcographus L., 1761) killed large numbers of European spruce (Picea abies (L.) H. Karst.) weakened by ice damage in the previous year in the Alpine region of Gorski Kotar (Hrašovec, 2016). In 2017, the Mediterranean pine beetle (Orthotomicus erosus Wollaston, 1857) killed trees in the Marjan recreation forest (Split, Croatia) and also on other locations situated within the Mediterranean region, predominantly on Aleppo pine (Pinus halepensis Mill.) weakened by drought (Spaić, 1964; Pernek et al., 2019a; Pernek et al., 2019b). The Birch bark beetle (Scolytus ratzeburgi Janson, 1859), is the only Scolytus species known to infest birch (Betula spp. L.) and is a potential threat to birch trees in Croatia. This species is one of the largest in the subfamily Scolytinae (4.0 – 6.5 mm). The body is typically cylindrical with black and very finely dotted striped elytra. Males have thick chaetae |