Birch prosthemium

The most prominent sign of infection is the appearance of numerous small, dark-colored bumps on the surface of the bark, which represent the fungus's pycnidia.

Affected areas often display localized discoloration, appearing darker or grayish compared to the surrounding healthy, white, or silvery birch bark.

As the infection progresses, the bark in the affected areas may crack and peel, exposing the inner layers of the tree to further damage.

The disease can affect branches of various sizes, and in severe cases, it may spread across the main trunk, hindering the tree's overall structure.

Visually, the canopy may begin to show signs of decline, including the wilting and drying out of individual branches, signaling that the vascular system is compromised.

The causal agent of this disease is the imperfect fungus Prosthemium betulinum. This pathogen is known to attack the bark and wood of deciduous trees, specifically targeting the birch genus.

The fungus develops its fruiting bodies, known as pycnidia, within the bark tissue. These structures eventually rupture the epidermis to release spores into the environment.

As a facultative parasite, the fungus typically exploits weakened trees, finding entry points through damaged bark or natural fissures in the tree's surface.

Dissemination of spores occurs primarily via wind currents and rain splashes, which transport the fungus to healthy branches or neighboring trees.

The biology of Prosthemium betulinum is closely linked to the physiological status of the host, meaning it thrives when the birch tree is under stress from environmental factors.

High humidity and moderate temperatures are the most critical environmental conditions that facilitate the germination of fungal spores.

Trees weakened by prolonged droughts, waterlogging, or insect infestations are significantly more susceptible to colonization by this pathogen.

Dense plantings with poor air circulation create a localized microclimate with high moisture, which is ideal for the rapid proliferation of the disease.

Mechanical injuries, including frost cracks, pruning wounds, or damage from storm debris, provide easy access for the fungus to penetrate the inner tissues.

Wet spring and autumn seasons are high-risk periods when the fungus is most active in producing spores and infecting new bark areas.

The fungus causes bark necrosis, which disrupts the flow of nutrients and water, ultimately leading to the dieback of branches and limbs.

Chronic infections weaken the tree's natural defenses, making it increasingly vulnerable to secondary attacks by wood-boring insects and other opportunistic pathogens.

In landscaping and urban forestry, the disease causes significant aesthetic damage, reducing the ornamental value of birch trees.

In forest stands, the disease can lead to growth suppression and the loss of individual trees, negatively impacting timber quality and yield.

Failure to manage the disease in nurseries can result in the loss of significant portions of young stock due to infection spread.

The primary control measure involves regular sanitary pruning to remove and destroy all infected branches, which helps reduce the local spore load.

Maintaining optimal tree vigor through appropriate fertilization and watering is essential to help the tree naturally resist fungal colonization.

Fungicidal treatments applied to the bark during the dormant season can be effective in reducing the prevalence of the pathogen on the tree surface.

It is vital to seal any open wounds or pruning cuts with appropriate wound dressings to prevent spores from entering the inner bark layers.

• Sterilize all pruning tools to prevent cross-contamination
• Remove and dispose of dead or dying trees from the site
• Ensure adequate spacing between trees to improve airflow