Beech canker

Beech canker is a destructive fungal disease caused by the ascomycete Neonectria coccinea. It primarily manifests as necrosis of the bark and cambium layers of tree trunks and branches. As the infection progresses, it disrupts the flow of nutrients and water, eventually leading to dieback of the canopy and, in severe cases, the death of the entire tree.

The disease is most commonly associated with European beech (Fagus sylvatica), but other deciduous species can also be affected. The fungus acts as a secondary pathogen, often infecting trees that are already compromised by environmental stressors such as drought, frost damage, or infestations by insects like the beech scale (Cryptococcus fagisuga).

Initial signs of the infection include discolored, sunken patches on the bark, often oozing a dark fluid. As the infection deepens, the bark may split or fall away, revealing blackened necrotic tissue beneath. During favorable weather conditions, clusters of small, bright red fruiting bodies, known as perithecia, become visible on the surface of the infected bark, signaling active reproduction.

Spread of Neonectria coccinea occurs primarily through airborne or splash-dispersed spores. Moisture is a critical factor for successful germination and colonization. Economically, the disease is highly damaging as it significantly lowers timber quality and reduces the aesthetic and ecological value of forest stands, often leading to large-scale mortality when conditions favor pathogen development.

Management of beech canker focuses on silvicultural practices that maintain tree vigor and reduce the spread of spores. Key protective measures include:

• Regular sanitation to remove and destroy infected wood.
• Managing insect populations that cause initial bark wounds.
• Selecting resistant varieties where applicable in forest plantations.
• Minimizing physical disturbance and wounding of trunks during maintenance.
• Promoting diverse forest structures to enhance ecosystem resilience.