Ascodichaena rugosa

Ascodichaena rugosa is a fungal pathogen that specifically colonizes the bark of various deciduous trees. As a member of the Rhytismataceae family, this fungus functions as a bark-inhabiting parasite that can persist on host trees for many years, affecting the aesthetic and physiological condition of the bark.

The primary hosts for this pathogen include species of the genus Quercus (oaks), as well as Fagus (beech) and Carpinus (hornbeam). The fungus is widely distributed in temperate forest ecosystems and ornamental plantations, often found on mature trees where bark texture provides suitable micro-habitats.

Symptoms of the disease are characterized by the appearance of dark, crusty, or rugose (wrinkled) patches on the bark surface. These patches are the fungal stromata, which eventually develop small cracks to release spores. The bark often appears blackened and roughened, which can significantly alter the tree's natural appearance and surface structure.

The development and spread of Ascodichaena rugosa are favored by high humidity and moderate temperatures. Spores are primarily disseminated by wind and water splash, allowing the fungus to colonize adjacent trees within a stand. Moist conditions are essential for spore germination and the successful establishment of new infections on the bark.

While this disease is generally considered to have a slow impact on host health, heavy infestations can contribute to the overall decline of the tree by weakening the protective bark barrier. Management strategies primarily focus on silvicultural practices, including promoting tree vigor, proper site selection, and the removal of heavily infested or deadwood to reduce inoculum pressure in the environment.