Cream colored tufts of spores are sometimes present. Infection occurs in the orchard around petal fall or just before harvest. The perennial canker fungus is a wound parasite, entering the tree through pruning wounds, frost cracks, or wooly aphid injuries. In Washington, pruning wounds and wounds from frost cracks are frequent infection courts. The fungus survives the winter as mycelium and conidia in cankers and as conidia on rotten fruit left on the orchard floor.
Sporulation occurs throughout the year, peaking during fall and winter.
Host susceptibility is highest between October and February. The annual reactivation of cankers is due to conidial infection of the callus ring surrounding the canker. The wooly aphid is attracted to the succelent callus tisue around the canker margins and feeds on it. The galls produced as a result are more sensitive to low temperatures than normal bark tissue. Gall tissue ruptures at -17.8 C or lower.