Chestnut dendrostomosis

The most visible symptom of dendrostomosis is the development of necrotic areas on the bark. These lesions often appear as sunken, dark-brown or black patches on the trunk or branches.

Black, pimple-like fruiting bodies of the fungus eventually break through the bark, serving as a diagnostic indicator of the infection. In advanced stages, the bark may crack and peel off.

Wilting of the leaves in the upper parts of the crown is common as the blockage of water supply progresses. This dieback eventually moves downward as the branch becomes completely girdled.

When the bark is cut in the infected area, a distinct color change in the cambium (turning brown or orange-red) can be observed, indicating the presence of fungal mycelium.

If the infection girdles the branch or trunk, the affected section will eventually die. Under humid conditions, fungal growth or exudates may appear on the surface of the lesions.

The disease is caused by the fungus Dendrostoma castaneum (formerly Cryptodiaporthe castanea), which belongs to the class of Ascomycetes. It is a parasitic fungus that primarily attacks the bark and cambium of chestnut trees.

The fungus produces stromata containing perithecia, which are fruiting bodies that erupt through the bark surface. This allows the pathogen to release spores into the environment to spread the infection.

It typically enters the host tree through wounds, cracks, or insect damage. Once established, the mycelium spreads through the inner bark, disrupting the vascular system and preventing the flow of nutrients.

The pathogen can survive in dead wood for long periods, making it difficult to eradicate if infected debris is left in the orchard or park. Its development is often linked to the general weakening of the host tree.

Spore dissemination is facilitated by environmental factors such as wind and water splashing, which transport the fungus to new, healthy parts of the tree or neighboring trees.

High humidity and moderate temperatures are ideal for the development of Dendrostoma castaneum. Extended rainy periods provide the necessary moisture for spore germination.

Physical injuries to the bark, such as frost cracks, sunscald, or wounds caused by pests, significantly increase the tree's susceptibility. Stressed trees are much more likely to be colonized by the pathogen.

Poor air circulation within dense plantings or unpruned trees helps maintain a humid microclimate, which encourages the fungus to thrive. Lack of soil fertility and drought stress also contribute to the infection.

The disease persists in infected plant material, including fallen twigs and dead bark. Without regular cleanup of the surrounding area, the infection cycle continues from year to year.

Seasonal weather patterns that impact the tree's sap flow or bark elasticity can create openings for the pathogen. Rapid changes in temperature often weaken the tree's natural defenses.

Dendrostomosis is a destructive disease that can lead to crown thinning and the eventual death of affected chestnut trees. It poses a significant threat to both ornamental plantings and forest stands.

The primary harm is the destruction of the phloem and cambium, which results in the slow death of parts of the tree. If the main trunk is girdled, the entire tree will die.

Infected trees lose their aesthetic value and ecological function. Furthermore, they can become breeding grounds for opportunistic pests and secondary fungal pathogens.

The economic impact involves the costs associated with monitoring, pruning, and, in severe cases, the complete removal of dying trees. Restoration of landscape value takes many years.

In forest ecosystems, the spread of the disease can lead to the decline of chestnut populations, impacting biodiversity. The disease significantly hinders the productivity of chestnut orchards.

The most effective management strategy is regular sanitation pruning. All infected branches must be removed and destroyed to reduce the local spore count.

Disinfection of tools between cuts is essential to prevent the spread of the fungus to healthy parts of the tree. Tools should be cleaned with alcohol or other appropriate disinfectants.

Wounds and pruning cuts should be protected with antifungal pastes or wound dressings. This barrier prevents the fungus from entering the exposed tissues of the tree.

Preventive fungicide applications during the growing season can help protect trees, especially those in high-risk areas. Always follow local regulations regarding chemical use.

Maintaining the health of the tree through balanced fertilization and appropriate irrigation is key. Strong, vigorous trees are naturally more resistant to the invasion of Dendrostoma castaneum.