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Presence of birch bark beetle (Scolytus ratzeburgi) in Croatia

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.