Lenzites betulina

Lenzites betulina, commonly known as the gilled polypore, is a wood-decay fungus that belongs to the Polyporaceae family. It acts as a primary agent of white rot, which involves the enzymatic degradation of lignin and cellulose, fundamentally weakening the structural integrity of the host wood.

This pathogen predominantly attacks broad-leaved trees, with a strong affinity for birch (Betula spp.), but it is also frequently found on species like alder, beech, oak, and poplar. While it primarily colonizes dead or decaying wood, it can pose a risk to weakened or stressed living trees, entering through wounds, pruning cuts, or broken branches.

The most visible sign of infection is the presence of shelf-like, fan-shaped, or semicircular fruiting bodies on the trunk or logs. These fruiting bodies are characterized by a velvety, hairy upper surface and distinct gill-like structures on the underside. Inside the wood, the decay appears as bleached, spongy, or fibrous tissue that becomes brittle and loses its commercial and ecological value over time.

The development of Lenzites betulina is heavily influenced by environmental factors such as humidity and ambient temperature. Spores are dispersed by wind and can colonize wood surfaces within hours if moisture levels are adequate. The fungus thrives in shaded, moist environments, making dense and neglected forest stands particularly susceptible to rapid infestation and spread.

The economic impact of this fungus is significant due to the loss of timber quality and the structural failure of affected trees. To mitigate the risks and protect tree health, forest managers and arborists should implement the following strategies:

• Regular removal of deadwood, fallen logs, and severely infected trees to reduce spore load.
• Avoiding mechanical damage to the bark of healthy trees during thinning or maintenance operations.
• Applying protective pruning sealants to large wounds in areas prone to fungal outbreaks.
• Proper disposal of woody debris away from healthy forest stands to prevent contamination.