Formerly Polyporus glomeratus, this fungus causes a relatively common canker rot on sugar maple. It reportedly is the most important decay fungus of sugar maple in Ontario, accounting for up to 40 percent of volume losses. It also is found on red maple and beech.

Branch stubs and wounds are the primary entry points for infection. Once the decay is advanced in the stem, the fungus produces a sterile, thick mass of tissue that spreads over the wound area or around the branch stub. This soon turns black, crusty, and cracked. The canker is irregularly shaped and generally becomes elongate with raised margins.

Canker rots produce fertile fruiting bodies or conks only after the tree dies. Canker rots cannot be eliminated from the forest, but maintaining healthy and wound-free trees and removing infected ones should reduce the incidence of these diseases.