Anthracnose of maple

Anthracnose spots on a leaf Claude Moffet

French disease name: Anthracnose de l'érable
Pathogen name: Aureobasidium apocryptum (Ellis & Everh.) Hermanides-Nijhof.
Kingdom: Fungi
Phylum: Ascomycota
Class: Dothideomycetes
Order: Dothideales
Family: Saccotheciaceae
Partial list of synonyms:
- Gloeosporium apocryptum Ellis & Everh.
- Kabatiella apocrypta (Ellis & Everh.) Arx
- Microstroma apocryptum (Ellis & Everh.) W.B. Cooke

Distribution

Eastern Canada

Damage, symptoms and biology

The pathogen produces spots on the leaf blades and veins early in the growing season, in early spring. At first the spots are irregularly shaped, the centre is pale brown and the margins are darker in colour. The necrotic zones (spots) grow and end up covering the entire leaf. Once entire leaves have been infected, the brown areas often develop concentric lines radiating out from the margins. Later on, the infected leaves curl up and become deformed before falling. The fungus gains entry to the tree through a bud or a leaf and then moves to the intersection of a larger branch.

Other information

Whereas cool, wet weather in spring favours the disease, hot, dry weather stops its spread. Even with repeated outbreaks of the disease over successive years, anthracnose is usually not fatal. However, the weakened trees become more susceptible to other stresses. The symptoms of anthracnose can be confused with the effects of a major summer drought.