Rust-red stringy white rot

Rust-red stringy white rot is a serious forest disease caused by the fungus Echinodontium tinctorium. This basidiomycete is a significant wood-decay pathogen that systematically breaks down the heartwood of living trees, leading to the formation of a fibrous, rust-colored mass in the center of the trunk.

The disease primarily impacts various conifer species, with the Douglas Fir (Pseudotsuga menziesii) being one of the most susceptible hosts. The fungus enters the tree through wounds, fire scars, or dead branch stubs, gradually colonizing the core wood and compromising the structural integrity of the tree over several decades.

External symptoms are often subtle until the infection is advanced. The most distinct sign of the disease is the appearance of perennial, hoof-shaped conks on the underside of branches or the main stem. These fruiting bodies are dark, woody, and possess a bright orange-red hymenium covered with spine-like teeth, which is a diagnostic feature of the species.

The development of the fungus is favored by moist environmental conditions and the presence of susceptible, older trees. Because the infection process is slow, the disease typically manifests in mature or old-growth forests. The spread of the fungus is mediated by wind-borne spores released from the fruiting bodies, which land on fresh wounds and initiate new decay columns.

Economic damage is substantial, as the infection renders the timber unfit for lumber production. Management strategies are focused on long-term forest health. Preventive measures include:

• Removing heavily infected trees during thinning and sanitation cuts.
• Avoiding mechanical injury to healthy trunks during forest operations.
• Promoting stand diversity to reduce the rate of pathogen spread between hosts.

Effective control of rust-red stringy white rot requires a proactive approach to forest management. By identifying and addressing decay symptoms early, foresters can mitigate losses and maintain the productivity of valuable timber stands such as those dominated by Douglas Fir.