Stem Decays and Stains

Red Belt Fungus
Fomitopsis pinicola (Sw. : Fr.) P. Karst.

Hosts: Conifers and aspen

Figure 202. Figure 202. Fomitopsis pinicola on dead Douglas-fir.

Symptoms/Signs: Fomitopsis pinicola forms perennial conks that are corky and shelflike. Its characteristic feature is a red-brown band near the white to cream colored edge. These fruiting bodies form on dead trees and logging slash and not on infected living trees. The decay is a brown cubical rot with shrinkage cracks in which prominent white sheets of mycelium develop.

Biology:  This fungus enters living trees with airborne spores colonizing and infecting through wounds and broken tops. It may be introduced into dying or dead trees by insects, as it has been isolated from Douglas-fir bark beetles captured both in flight and from egg galleries.

Effects:  Fomitopsis pinicola is one of the most important brown rot pathogens of old-growth western conifers, but it acts slowly and is not considered a major decay pathogen of second-growth forests. However, it is an important component of the coniferous forest ecosystem because it decays dead trees and logging slash and leaves a lignin-rich residue that is very stable and is a major component of the organic matter on the forest floor and in the upper layers of soil. This residue enhances water holding and cation exchange capacities of soil and is a favorable habitat for the development of ectomycorrhizae and for nitrogen-fixing bacteria.

Similar Insects and Diseases:  Brown rot caused by F. pinicola is difficult to distinguish from that caused by Phaeolus schweinitizii, a butt rot of Douglas-fir. Since P. schweinitzii is a root and butt rot pathogen, it is found in the lower 3 meters of the trunk and in the roots, and it fruits from the roots out through the soil of live trees. Fomitopsis pinicola only fruits on dead wood material so is frequently observed on stumps.

References:  28, 30, 93