Hohenbuehelia

Hohenbuehelia is a genus of fungi within the family Pleurotaceae. While primarily recognized as saprotrophs that decompose dead wood, some species function as opportunistic pathogens. They are capable of invading living trees that have been compromised by environmental stress, mechanical injury, or poor pruning practices, acting as agents of wood decay.

The fungus is known for causing white rot in various deciduous tree species, including willow, birch, poplar, and oak. The pathogen secretes enzymes that break down lignin and cellulose within the host tissue, significantly weakening the internal structure of the tree. This process often begins at wound sites, progressing deep into the heartwood over time.

Symptoms of an infection include the presence of gelatinous, spatula-shaped, or fan-shaped sporocarps appearing on the bark. As the disease advances, structural symptoms such as branch dieback, premature leaf drop, and longitudinal bark cracking become evident. The wood inside becomes spongy and loses its mechanical strength, often emitting a distinct fungal odor.

Development is most favorable in environments with high humidity and stagnant air circulation, which facilitate spore germination and mycelial growth. The fungus spreads via airborne spores that enter the host through exposed wood or existing cavities. Once established, the mycelium can colonize large sections of the trunk, significantly compromising the structural integrity of the plant.

Mitigation of damage requires proactive management strategies to protect tree health:

• Immediate removal and disposal of severely infected woody material.
• Applying protective wound dressings to all pruning cuts to prevent pathogen entry.
• Improving site drainage and air circulation to reduce humidity levels.
• Monitoring trees for early signs of decay and implementing sound fertilization to improve plant vigor.