Diatrypella

Diatrypella is a genus of ascomycete fungi that causes specific bark and branch diseases in various deciduous tree species. As a plant pathogen, it often acts as an opportunistic fungus, targeting weakened or stressed trees by colonizing the bark tissue and penetrating deeper into the phloem and cambium layers.

The fungus commonly infects tree species such as alder, hazel, and birch. It tends to establish itself in areas where the bark is thin or has been damaged, using these points of entry to develop its mycelial network, which eventually causes localized or extensive necrosis of the living plant tissue.

Symptoms are identified by the presence of small, black, erumpent stroma that break through the epidermis of the bark. Other noticeable signs include the wilting and yellowing of foliage distal to the infection site, cracking or splitting of the bark, and the eventual death of branches that have been girdled by the fungal growth.

Development and spread are facilitated by environmental conditions, particularly high humidity and temperate climates which favor the discharge of ascospores. These spores are dispersed by wind currents and rain splashes, allowing the pathogen to move from infected branches to healthy tissues or neighboring trees within a forest stand.

Management and prevention focus on reducing the fungal inoculum. This involves prompt sanitary pruning of infected limbs, ensuring that all pruning waste is removed or burned to prevent spore dispersal. Maintaining tree vigor through proper site selection and adequate spacing can significantly decrease the susceptibility of the stand to Diatrypella infection.