In the spring, healthy callus again is formed at the margin of the canker and the cycle is repeated resulting in another ring of dead tissue. In addition to the presence of woolly aphids and low winter temperatures, any factor that produces excess succulent growth, such as high nitrogen fertilization or overirrigation, or that weakens the tree, increases the severity of perennial canker. Bull's eye rot is a postharvest disease that is usually observed when infected fruit are removed from storage. The disease gets its name from the lesions that frequently are comprised of concentric rings of necrotic tissue. 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.