Red-brown butt rot

Red-brown butt rot is a destructive plant disease caused by the fungus Phaeolus schweinitzii. This pathogen is known for causing brown cubical decay in the roots and the butt section of the tree trunk, significantly compromising the structural integrity of the host.

The disease primarily targets conifer species, with significant impact on pine, spruce, and particularly the Douglas Fir. It functions as a root and butt rot agent, entering the tree primarily through the roots and progressively moving upward into the heartwood.

Key symptoms include the emergence of large, bracket-like sporophores (fruiting bodies) at the base of the tree, which display a distinct rusty-brown color with yellow margins. Internally, the wood becomes brittle, darkens to a deep reddish-brown color, and eventually cracks into distinct, characteristic cubes.

Development and spread of the fungus are favored by moist soil conditions and the presence of root damage. It spreads through the soil via root-to-root contact in dense stands, or through spore dispersal by wind, which colonizes fresh wounds on exposed roots or stump surfaces.

The economic and ecological impact is severe, as infected trees often become victims of windthrow and wood quality is drastically reduced. Management strategies focus on sanitation logging, stump removal to prevent spreading through root contacts, and minimizing mechanical injuries to trees during forest operations.