Disease impact tends to be underestimated, because repeated attacks by the fungus over 2 or 3 years can seriously weaken trees and predispose them to other stress agents.
Defoliation is also diagnostic.
The anthracnose fungus overwinters as mycelium and acervuli in stems and twigs and as perithecia in fallen leaves. A second, less significant source of primary inoculum is ascospores produced in perithecia. Mycelium, overwintering in stems, may infect developing buds. Conidia are disseminated by wind and splashing rain. The fungus penetrates leaf or succulent stem surfaces via the production of appressoria or through wounds.