Diaporthe birch necrosis

The disease is caused by the fungus Diaporthe betulae, which is a significant pathogen responsible for bark necrosis and canker formation in birch trees. This fungus colonizes the cortex and cambium, disrupting the tree's vascular system and causing severe physiological damage to the host plant.

The primary hosts of this pathogen are various birch species (Betula spp.). It is particularly prevalent in ecosystems where trees are already stressed by environmental factors, such as drought, poor soil quality, or mechanical damage caused by insects or human activity, which act as entry points for fungal spores.

Symptoms of the infection typically include localized bark discoloration, which eventually turns into sunken lesions or cankers. As the fungus matures, small black fruiting bodies appear on the surface of the necrotic bark. Over time, these lesions can expand and girdle branches or even the main trunk, resulting in wilting and dieback of the distal parts of the tree.

The development of Diaporthe betulae is closely linked to climatic conditions. High humidity and prolonged wet periods create an ideal environment for spore germination and colonization. Warm temperatures significantly accelerate the growth of the mycelium, making spring and early summer the most critical periods for infection and spread within the stand.

Effective control strategies focus on sanitation and preventive maintenance to reduce the pathogen load. Removing dead or symptomatic branches is essential to prevent the spread of inoculum to healthy trees. In nursery or landscape settings, chemical control using appropriate fungicides may be required during the susceptible growth phases, combined with good silvicultural practices to ensure tree vigor.