Beefsteak fungus

The beefsteak fungus (lat. Fistulina hepatica) is a wood-decaying fungus that acts as a pathogen, causing brown heart rot in various tree species. While often noted for its resemblance to raw meat, in the context of arboriculture, it is regarded as a parasitic organism that compromises the structural integrity of mature trees.

This fungus primarily attacks broad-leaved trees, with a strong preference for oak (Quercus) and sweet chestnut species. The pathogen enters the host through wounds, broken branches, or improper pruning cuts, eventually colonizing the heartwood. It operates as a white-rot or brown-rot agent, depending on the host's chemical composition.

The most visible sign of an infection is the appearance of fleshy, tongue-shaped fruiting bodies that exhibit a deep red color and a gelatinous texture. On the inside, the affected wood exhibits a distinct reddish-brown discoloration, becoming brittle and prone to structural failure over time as the mycelium breaks down the lignin and cellulose.

Environmental conditions, particularly high humidity and moderate temperatures, significantly influence the spread of the fungus. Spores are disseminated by wind and rain, infecting susceptible areas of the tree through open lesions. Once established, the fungus can survive for many years, progressively weakening the host from the inside out.

• Properly seal all pruning cuts with appropriate tree wound dressings.
• Practice regular sanitation to remove dead or dying tree branches.
• Minimize bark damage during gardening and maintenance operations.
• Monitor tree trunks for the early development of red fruiting bodies.

The economic and ecological damage caused by Fistulina hepatica is significant, as it leads to the degradation of timber quality and reduces the overall lifespan of the tree. Infected trees become hazards due to the increased risk of stem breakage or windfall, necessitating professional assessment and potential removal if decay is advanced.