Onnia subtriquetra

Onnia subtriquetra is a significant wood-decaying fungus that primarily targets the root systems and the butt of conifer trees. As a pathogen of the Hymenochaetaceae family, it plays a critical role in forest dynamics, often acting as a primary agent of rot in various pine species.

The fungus typically enters trees through root injuries or wounds at the base of the trunk. Once the infection is established, the mycelium spreads throughout the sapwood and heartwood, gradually compromising the structural integrity and nutrient uptake capacity of the host.

Signs of an infestation often manifest as a noticeable decline in crown density, yellowing of needles, and reduced annual shoot growth. In more advanced stages of decay, the presence of the pathogen is confirmed by its fruiting bodies, which appear as clustered, triangular or fan-shaped caps at the base of the tree or on adjacent roots.

The development of the fungus is favored by moist environments and the presence of old stumps, which act as reservoirs for the pathogen. It spreads effectively through root contact in dense stands, allowing the disease to move from an infected tree to its neighbors over several growing seasons.

• Removal of infected trees and stumps during sanitation harvesting.
• Avoiding mechanical damage to roots and lower trunks during forest maintenance.
• Monitoring forest stands for early signs of decay.
• Promoting diverse, resilient forest stands to slow disease spread.
• Regular inspections in high-value park and plantation areas.

The economic and ecological damage caused by Onnia subtriquetra is severe, as it leads to significant wood volume loss and predisposes weakened trees to windthrow. Furthermore, these trees become hotspots for secondary infestations by bark beetles, further complicating forest management efforts.