Arthopyreniaceae fungi

Arthopyreniaceae is a family of fungi, often associated with crustose lichens, that can colonize the bark of trees and shrubs. While often considered benign epiphytes, in high concentrations or under specific environmental conditions, they can behave as opportunistic pathogens that hinder the physiological functions of the host plant's bark.

The disease is caused by fungal spores that germinate on the surface of tree bark. These fungi are typically characterized by the development of perithecia, small fruiting bodies that embed into the bark tissues. They thrive in environments with high humidity and limited airflow, making them more common in older or poorly maintained orchards.

The primary hosts for Arthopyreniaceae include various deciduous fruit trees such as apple, pear, and stone fruits. They are particularly drawn to trees with rough, aged bark that retains moisture, where the fungi can establish a stable colony that interacts with the tree's outer layer.

Symptoms appear as small, dark spots or crust-like patches on the surface of the bark. Over time, these patches can spread, leading to a dull appearance of the bark and interfering with gas exchange through the lenticels. This can cause the bark to become brittle and increase the susceptibility of the tree to secondary infections and wood-boring pests.

Preventative measures are essential for long-term control. Gardeners should focus on improving tree vigor through proper fertilization, irrigation, and regular pruning to ensure the tree canopy remains well-ventilated. Mechanical removal of excess dead bark and the application of white-wash or copper-based treatments during the dormant season are standard practices to limit the spread of these fungi.