First findings of an invasive tandem bark beetle – phytopathogenic fungus in the Middle Ural megalopolis

The four-eyed fir bark beetle (Polygraphus proximus Blandford) and the fungus (Grosmannia aoshimae (Ohtaka, Masuya & Yamaoka) Masuya & Yamaoka) form an extremely aggressive invasive tandem affecting Siberian fir (Abies sibirica Ledeb.) throughout almost its entire range. In spring 2023, the beetle and its fungal associate were first detected in fir plantings at the Botanical Garden, Ural Branch, Russian Academy of Sciences in the city of Yekaterinburg (Middle Urals). At the time of detection, the pest had destroyed and infested more than a third of the fir trees in the area accessible to visitors and had begun attacking the collection of fir species in the arboretum. The phytopathogen G. aoshimae was found in all beetle galleries. Fungi of the genus Geosmithia Pitt were frequently encountered also. The beetles first attacked Siberian fir trees with the smallest stem diameter. Beetles began exiting weakened trees infested in spring and infest live trees as early as late July – early August. From the fir collection, fir trees from the Balsamea section: Siberian fir, balsam fir (A. balsamea (L.) Mill.), subalpine fir (A. lasiocarpa (Hook) Nutt.), Frasier fir (A. fraseri (Pursh) Poir.), Khingan fir (A. nephrolepis (Trautv. ex Maxim.) Maxim.), Sakhalin fir (A. sachalinensis F. Schmidt Mast.), were infested first. Firs of the section Grandis had traces of single attacks, and Manchurian fir (Abies holophilla Maxim.) (the section Momi) was not attacked by beetles at all. Traces of four-eyed fir bark beetle attacks were also found in the park-exhibition, 3.5 km far from the Botanical Garden, which indicates a wide distribution of the invasive bark beetle in the metropolis.