Ascodichaenosis

Ascodichaenosis is a fungal disease caused by species within the Ascodichaenaceae family, most notably Ascodichaena rugosa. This pathogen is specialized in colonizing the bark and periderm of various deciduous tree species, where it acts as a slow-growing parasite that affects the outer protective tissues of the stem and branches.

The primary hosts for this disease include broad-leaved trees, particularly oaks (Quercus), beeches, and hornbeams. The fungus is often found in both forest environments and urban plantings, where it can persist for years on the bark surface without causing immediate catastrophic decline of the tree, although it significantly alters the bark structure.

The visual symptoms of the disease appear as small, ash-grey to black, erumpent fruiting bodies known as apothecia. These clusters often resemble lichen growth, making the disease difficult to identify for non-experts. As the fungus develops, it causes the bark to become cracked, scaly, and noticeably roughened, which disrupts the natural protective barrier of the tree trunk.

Environmental conditions that favor the spread of ascodichaenosis include high humidity, stagnant air, and shaded environments. Spores are primarily dispersed through wind and splashing rain, allowing the pathogen to colonize new areas of the host tree or nearby susceptible individuals during periods of frequent rainfall.

While ascodichaenosis is rarely the primary cause of tree death, its presence is a sign of stress and can exacerbate other biotic or abiotic issues. Effective management focuses on cultural practices such as

• thinning dense forest stands;
• improving air circulation around tree trunks;
• monitoring tree vigor and addressing nutrient or water deficiencies.