Robust conk

Robust conk (scientific name: Phellinus robustus) is a wood-decay fungus that acts as a pathogen primarily targeting hardwood tree species. It is responsible for causing extensive white heart rot, which progressively compromises the structural integrity of the host tree from the inside out, leading to internal wood degradation.

The primary hosts for this fungus include oaks, beeches, and occasionally other deciduous trees like hornbeam or birch. Phellinus robustus is commonly found in mature forests and urban green spaces, where it specifically exploits older trees that have developed natural wounds or have been weakened by environmental stressors over time.

The diagnostic sign of an infection is the appearance of perennial, woody, hoof-shaped fruiting bodies (conks) on the tree trunk. These conks are typically hard, dark gray or brown, and exhibit characteristic deep cracks on their surface. Internally, the infected wood displays signs of white rot, often accompanied by thin, dark black lines that map the fungal advancement through the heartwood.

The development of the fungus is facilitated by the presence of wounds that expose the heartwood, such as frost cracks, sunscald, or broken branches. Spores are released from the fruiting bodies and disseminated by wind to new infection sites. Humid conditions combined with a compromised bark barrier create the ideal environment for the spores to germinate and colonize the tree.

The economic and ecological impact of this disease is significant, as it increases the risk of stem breakage and windthrow in affected stands. Prevention and management strategies include rigorous sanitary pruning, the removal and destruction of heavily infected trees, and the application of wound dressings to prevent the entry of spores into fresh mechanical damages on the trunk.