Protothelenella

Protothelenella is a genus of lichenized fungi that are often found on the bark of woody plants. While they are not classified as obligate plant pathogens, they act as epiphytes that, under specific environmental conditions, can alter the surface properties of the bark, potentially contributing to the decline of host vigor in sensitive species.

These organisms are typically found on mature fruit trees, ornamental shrubs, and old forest trees. Plants that are already stressed due to environmental factors, such as extreme temperatures or physical bark damage, are significantly more susceptible to colonization by these fungal growths.

The primary symptoms include the appearance of small, crust-like formations on the bark surface, which can vary in color from pale grey to white. In cases of heavy infestation, these patches can make the bark appear thickened or rough, occasionally leading to premature flaking of the outer bark layers.

The development and spread of Protothelenella are heavily dependent on moisture levels. High relative humidity and prolonged periods of wet weather provide the necessary hydration for the fungus to expand. If the canopy of the tree is too dense, it limits airflow and sunlight penetration, which keeps the bark moist for longer periods, favoring fungal proliferation.

Integrated control measures focus on maintaining the overall health and vitality of the trees. Regular pruning is essential to ensure adequate air circulation and light penetration, which naturally dries the bark and suppresses fungal growth. Additionally, cleaning the trunks and applying recommended protective coatings or copper-based sprays during the dormant season are effective ways to prevent and control the spread of these organisms.