Xylobolus frustulatus

Pathogen and type of disease. Xylobolus frustulatus is a species of crust fungus in the family Stereaceae. It is classified as a wood-decay fungus that causes a specific type of white pocket rot. As a saprotrophic organism, it secretes enzymes that break down the main structural components of wood—lignin and cellulose—effectively turning solid wood into a brittle, degraded substance.

Susceptible cultures. The fungus primarily infects hardwoods, with oaks (Quercus species) being the most common hosts. It is frequently observed in mature forests where old-growth timber is present. While it predominantly colonizes dead logs or stumps, it can also act as a weak parasite, invading the heartwood of stressed or physically damaged living trees.

Symptoms and signs. The diagnostic sign of this fungus is its perennial fruiting body, which appears as a hard, crust-like growth. As it matures, it cracks into small, distinct, angular, tile-like pieces, which is why it is often referred to as the "parquet fungus." Internally, the infected wood undergoes a process of severe decay, becoming pale, fibrous, and prone to breaking into small, cuboidal fragments.

Conditions for development. Xylobolus frustulatus thrives in environments with high humidity and moderate temperatures. The spores are primarily wind-dispersed and infect the host through wounds, broken branches, or bark injuries where the inner wood is exposed. The presence of decaying woody debris on the forest floor provides an ideal reservoir for the fungus to persist and spread.

Harmfulness and prevention measures. The economic damage is significant as the fungus compromises the structural integrity of timber, rendering it unsuitable for commercial use and increasing the safety risk from falling branches or trees. Management strategies include:

• Regular forest sanitation and removal of heavily infected, dying trees.
• Application of wound sealants to pruning cuts and accidental damage on valuable trees.
• Implementation of proper silvicultural practices to maintain tree vitality.
• Minimizing physical stress and mechanical injuries to stands during logging operations.