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ŠUMARSKI LIST 11-12/2019 str. 19     <-- 19 -->        PDF

bark beetles colonize dying or weakened trees (Zúbrik et al., 2013) although, they may also attack apparently healthy trees (Löyttyniemi, 1983; Linnakoski et al., 2009). The species is typically with one-year life cycle (Pfeffer, 1995) but may have two-year life cycle depending on the temperature of environment (Sieber & Benz, 1985). Emergence, maturation feeding, mating, and egg deposition occur from May to June, depending on the location (Trédl, 1915a; Trédl, 1915b; Langhoffer, 1915; Kovačević, 1956). Little is known about their relationship with micro-organisms (Ring, 1977; Löyttyniemi, 1983; Sieber & Benz, 1985) but recent studies of the Birch bark beetle have focused on their relationship with ophiostomatoid fungi (Linnakoski et al., 2008; Linnakoski et al., 2009; Jankowiak, 2011) and mites (Kiełczewski et al., 1983; Khaustov & Magowski, 2003; Trach & Kaustov, 2017).
The Birch bark beetle has been little studied and its presence in Croatia is unclear. Here, we (1) review historical records of this species (literature and available entomological collections) from Croatia and (2) examine forest stands with Silver birch (B. pendula Roth) to confirm the presence of the Birch bark beetle in Croatia.
MATERIAL AND METHODS
MATERIJALI I METODE
Published records of the Birch bark beetle in Croatia were collected and specimens in museums and other institutions were checked. Museums in Croatia were the Croatian Natural History Museum (CNHM), Natural History Museum Rijeka (NHMR), Natural History Museum Split (NHMS), Varaždin City Museum (VCM) and National Museum Zadar (NMZ). Additionally, Hensch’s entomological collection at the Faculty of Forestry, University of Zagreb was included in the study.
To determine the presence of Birch bark beetle in Croatia, Silver birch stands were examined throughout Croatia from 2016 to 2017. Logs were sampled at three localities throughout Croatia and analyzed in the laboratory (Croatian Forest Research Institute). Geographical coordinates for each sampling site were collected using a GPS handheld device (Garmin GPSMAP® 78s) and depicted on a map created with Esri® ArcGIS 10.1 software. Illustrations were prepared using Adobe Illustrator CS6. Logs were kept at 20±1 °C, 65 % r.h. and a photoperiod of 16h:8h (L:D). All emerging beetles were collected and identified to species, based on Pfeffer (1995) and Bense (1994).
Photos of killed trees were taken using a Canon® EOS 550D, and photos of Birch bark beetle morphology traits were made with Leica WILD MZ-8 equipped with Olympus SP–500 UZ (combined with Olympus QuickPHOTO CAMERA 2.2 microscopy imaging software).