Root Disease
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Ganoderma Root Rot
Artist's Conk
Ganoderma applanatum (Pers.) Pat.

Host:  Aspen

Figure 279. Figure 279. Ganoderma applanatum conks are often found at the base of infected trees.

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. Gandoderma applanatum produces advanced white-mottled decay in the large roots and lower parts of the stem.

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

Figure 280. Figure 280. Trees often topple over due to severe decay of major roots.

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:  39, 93