Degradation of Betula spp. under the influence of biotic factors in the forests of Ukrainian Polissia

The paper examines the impact ofbiotic factors – mainly pests and pathogens – onthe degradation ofBetulaspp. inthe forests ofUkrainian Polissia. The taxonomic structure ofthe identified mycobiota includes representatives of9 genera, 8 families, 5orders, 4 classes, and two divisions (Ascomycota 44.4%, Basidiomycota 55.6%). Xylotrophic Basidiomycetes, particularly Fomitopsis betulina and Fomes fomentarius, pose the greatest threat due totheir ability todestroy wood tissues. The bacterial pathogen Lelliottia nimipressuralis, the agent ofwetwood, also plays amajor role, impairing xylem water transport and causing systemic physiological imbalance inaffected trees. Entomofauna significantly contributes todegradation processes. Atotal of31 insect species were recorded, belonging tofive orders, 24 families, and 29 genera, with Coleoptera being the most numerous (32.3%). The most harmful are xylophagous species (e.g.Agrilus betuleti, Rhagium mordax) and phytophagous species (e.g.Geometra papilionaria, Parornix betulae), which cause mechanical tissue damage and facilitate secondary infections. The results indicate that pathogenic complexes intensify under environmental stress, accelerating the decline ofBetula spp. stands. These findings underscore the necessity for ongoing phytosanitary monitoring and adaptive management measures to mitigate further degradation risks in the birch forests of Polissia.