[3] Symptoms are similar to all species of maple and include a canker forming most commonly 2–12 feet (0.61–3.66 m) from the ground.

[3][4] The formation of the canker begins with a small pronounced necrosis of the bark and requires several years to expand.

Although the canker can become quite large, it normally does not kill the tree but does increase the risk of the trunk failing and being blown over by the wind.

As for visible signs of the fungus, if the bark is peeled back at the center of the canker, a mat of white mycelium (fungal tissue) will be revealed.

[7] When conditions are favorable (moderate temperature and high humidity), the perithecium will produce sexual spores called ascospores which are dispersed primarily by the wind.

Each year, the fungus kills the callus material formed by the tree and invades more cambium during the growing season.

[4] During the summer months, the fungus is also able to produce asexual spores called conidia that are dispersed by the wind to be used as secondary inoculum to infect other maple trees in the area.

[4][9] Once they are produced they can be visible with very close observation in the center of the canker, which can give it a speckled, gritty appearance.