Biscogniauxia nummularia decline of European beech ("Fagus sylvatica") in Sicily and Calabria (Italy) has been linked to "B. nummularia" and experiments have suggested that this ascomycete plays a primary pathogenic role under certain environmental conditions. It typically causes strip‐cankering and general wood decay. Biscogniauxia nummularia Biscogniauxia nummularia is a plant pathogen in the family Xylariaceae, known as the beech tarcrust. The specific epithet is derived from the Latin "nummus" meaning a coin, referring to the often rounded and coin-like encrustations. The fruit body forms a thick and shiny black crust, on beech ("Fagus") bark and is found at all times of the
Fagus sylvatica depends on the location: in forest areas, "F. sylvatica" grows to over , with branches being high up on the trunk. In open locations, it will become much shorter (typically ) and more massive. The leaves are alternate, simple, and entire or with a slightly crenate margin, 5–10 cm long and 3–7 cm broad, with 6–7 veins on each side of the leaf (7–10 veins in "Fagus orientalis"). When crenate, there is one point at each vein tip, never any points between the veins. The buds are long and slender, long and thick, but thicker (to ) where the buds