Coryneum canker

Coryneum canker is a fungal disease caused by the ascomycete Coryneum lanciforme. This pathogen primarily affects the bark and vascular tissues of maple trees, causing localized necrosis and canker formation. It is a significant concern in arboriculture, as it can severely compromise the aesthetic value and structural integrity of landscape trees.

The primary hosts of this pathogen are maple species. The fungus acts as a wound parasite, meaning it predominantly infects trees that have sustained damage to their protective outer layers. Frost cracks, pruning wounds, and injuries caused by wind or human activities serve as the main entry points for the fungal mycelium to colonize the tree.

Symptoms of the infection include sunken, discolored areas on the bark, which eventually become cracked. During the reproductive phase, the fungus produces small, black, cushion-like structures called stromata that break through the surface of the bark. These are key diagnostic features. Over time, the cankers can girdle branches, leading to leaf wilting and eventual dieback of the affected parts.

The development and spread of Coryneum lanciforme are highly dependent on moisture and temperature. Spores are primarily dispersed by splashing rain and wind currents. High humidity levels during the spring and autumn significantly favor the germination of spores and colonization of host tissues. Crowded plantations or sites with poor airflow are particularly susceptible to widespread infection.

To effectively manage and prevent Coryneum canker, arborists recommend a rigorous maintenance program:

• Prune and destroy infected branches to reduce the amount of inoculum in the area.
• Disinfect pruning tools with alcohol or a bleach solution between cuts.
• Apply wound dressings or fungicides to exposed cuts to prevent new infections.
• Improve tree vigor through proper fertilization, mulching, and irrigation to enhance natural defenses.
• Monitor the bark regularly for early signs of canker formation, especially after storm events.