See:
Oak (Quercus spp.) - Ganoderma Root and Butt Rot
Cause The fungus Perenniporia fraxinophila (formerly Fomes fraxinophilus) has been reported in Washington. It causes a heart-rot wood decay of injured trees. Injuries may be due to many factors including broken limbs from storm damage, sunburn, or lightning. Wood decay may also be more common as the Emerald Ash Borer makes its way through the PNW. Presence of conks indicates internal decay, but the extent of decay is difficult to determine from external indicators alone because it often is associated with wounds. Conks are usually located where dead branch stubs were previously present. Trees are rarely killed but more susceptible to failure.
Symptoms The diseased wood is initially brownish with white spots. Later the wood becomes straw colored or white, soft, and crumbly. The fruiting bodies or conks are either hoof shaped or shelf-like. They are perennial, hard, and woody. The upper surface is rough and dark brown or black. The under surface is brownish and covered with small pores. The conks may be a foot or more in diameter.
Cultural control
- Avoid wounding trees to prevent decay.
- Make pruning cuts adjacent to, but not into, the supporting branch, and prune when branches are small to enhance callus formation and wound healing.
- Inspect trees for decay and/or conks to assess tree stability.
- Remove affected trees to avoid damage to surrounding property or spread to other trees.
References Lesica, P., Atthowe, H.E., and Dugan, F.M. 2003. Incidence of Perenniporia fraxinophila and its effects on green ash (Fraxinus pennsylvanica) woodlands in eastern Montana, USA. Forest ecology and management 182:153-159.
Shaw, C.G., and Harris, M.R. 1960. Important diseases and decays of trees native to Washington. Ag Extension Service, WSU. Extension Bulletin 540.