Stem Decays and Stains
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS

Indian Paint Fungus
Echinodontium tinctorium (Ell. & Ev.) Ell. & Ev.

Hosts:  True fir, and occasionally Douglas-fir and spruce

Figure 201. Echinodontium tinctorium conk showing orange inner-tissue. Symptoms/signs:  Echinodontium tinctorium produces woody, perennial hoof-shaped conks, 4-20 cm in diameter, usually at the undersides of branch stubs. These fruiting structures sometimes form at wounds or on limbs. The upper surface is dark gray-to-black, rough and cracked. The lower surface is gray-brown to black, composed of thick, blunt, tooth-like spines. The interior tissue is brick red to rust red, from a pigment that extends into the adjacent decayed wood. The common name for Echinodontium tinctorium, “Indian paint fungus,” is derived from the Native American’s use of conks in the preparation of red paint pigments.

Biology:  The spores of Echinodontium tinctorium are dispersed during cool, wet weather in the fall. They remain viable during winter, germinating best after a period of freezing temperatures. The fungus enters branchlets between 0.5 mm to 1.5 mm in size and spreads through the pith to the main branch. Here the fungus can remain in a dormant condition for 20, 50, or even 100 years. When the main branch dies or breaks off, the fungus becomes active again, and decay of the heartwood portion of the main branch begins, eventually spreading to the main stem of the tree.

Effects:  This fungus is the main cause of heart rot and volume loss in mature true firs. Conks are reliable indicators of defect and are associated with substantial volumes of decay. One fruiting body usually indicates that the entire cross section of the log is decayed for a distance of 2 m above and 2.5 m below the conk. Decay may also be present in trees that do not bear sporophores. The rot is most common in the mid-trunk but may also extend into the butt or down from the top. In very late stages of decay, the trunk may become completely hollow. Infected trees that break or are windthrown are important sources of hollow logs for wildlife habitat and act as nurse logs for regeneration.

Similar Insects and Diseases:  Advanced stages of decay closely resemble equivalent stages of rot associated with Stereum sanguinolentum. However, S. sanguinolentum fruiting bodies are completely different, as they form thin, crust-like layers with a grey to light brown gilled lower surface that turns blood red when bruised.

References:  21, 29, 92, 100