Eutypella canker

Eutypella canker is a serious fungal disease caused by the pathogen Eutypella parasitica. It manifests as a slow-growing, perennial bark canker that targets the stems of susceptible trees. Unlike rapid fungal infections, this pathogen establishes itself in the host tissue for many years, progressively causing severe damage to the tree's vascular system.

The primary hosts for this fungus are various species of maple trees, particularly the sugar maple. However, reports also indicate that the disease can affect species such as the plane tree. It is primarily observed in forest ecosystems and landscape plantings where trees have suffered minor bark wounds that serve as entry points for the fungal spores.

The visual symptoms are quite distinct: the fungus creates a depressed or flattened area on the trunk surrounded by a conspicuous ridge of callus tissue. As the canker expands, the bark often sloughs off, revealing the underlying wood. Small, black, pimple-like perithecia (fruiting bodies) emerge on the dead wood within the canker, serving as the source of new infections.

The disease thrives under conditions of high humidity and is spread by wind-borne ascospores that infect wounds. Because the growth of the fungus is incremental, trees may appear healthy for several seasons while the internal decay proceeds. The main threat posed by this disease is the structural weakening of the trunk, which significantly increases the risk of wind breakage.

Effective management focuses on sanitation rather than chemical treatment. The most crucial steps include:

• Identifying and removing heavily infected trees to reduce local spore load.
• Preventing mechanical injury to tree trunks during forest management.
• Maintaining tree vigor through proper site selection and soil care.
• Monitoring vulnerable stands for early signs of sunken bark or callus ridges.