Indian paint fungus

Indian paint fungus (Echinodontium tinctorium) is a significant wood-decay basidiomycete that primarily infects coniferous trees. Known as a serious heart rot pathogen, it is particularly prevalent in species such as grand fir, western hemlock, and various spruce varieties, leading to extensive decay of the inner stem wood.

The fungus is easily identified by its perennial, shelf-like fruiting bodies that develop on the exterior of the trunk. These structures are hard, woody, and distinctly brownish-grey on top, while the underside features a characteristic, vibrant reddish-orange hymenophore with spiny teeth, which was historically used by indigenous people to create paint.

The biological cycle of the fungus begins when spores settle on branch stubs or deep wounds caused by frost or physical trauma. Once inside, the fungus colonizes the heartwood, slowly breaking down lignin. The infection process is slow, often taking decades before the tree produces external fruiting bodies, by which time significant internal damage has occurred.

Environmental conditions characterized by high humidity and moderate temperatures favor the proliferation of Echinodontium tinctorium. It thrives in dense, old-growth forests where a high concentration of mature trees provides ample substrates for the mycelium to persist for many years, effectively maintaining the disease within the stand.

Economic damage is substantial, as infected timber loses its structural integrity, rendering it useless for commercial lumber production. Management and control strategies focus on reducing the incidence of decay:

• Implementation of selective sanitary logging to remove symptomatic trees.
• Strict silvicultural practices to prevent bark and branch damage.
• Monitoring of old-growth stands to limit the buildup of fungal spores.
• Focusing on younger, healthier stand structures to mitigate the impact of the pathogen.