Hosts:  Aspen

Symptoms/signs: Infected trees often break or fall before death, however, a fruiting body or conk can be found at the base of most infected trees. The tough semicircular conk is usually found near ground level. It has a brown upper surface with a white rim and an undersurface that is white and stains when touched or scratched. The latter trait allows for artistic expression that is permanent if the conk is allowed to dry. G. applanatum produces advanced white-mottled decay in the large roots and lower parts of the stem.

Biology:  G. applanatum infection occurs at wounds and the fungus attacks sapwood, heartwood, and cambium. The white-mottled rot is usually concentrated in large roots (larger than 5 cm in diameter) and basal part of the stem, but can extend up into the trunk for a meter or more. The larger roots are believed to act as avenues of spread to new hosts.

Effects:  G. applanatum is found in almost all aspen stands but is more abundant on moist sites with deep soils. Windthrow is common.

Similar Insects and Diseases:  Although there are other root decay fungi of aspen, G. applanatum is the most prominent and the only one that produces a tough woody-conk at ground line in live trees in the Southwest.

References:  38, 92