It is prevalent in the southern United States and elsewhere, and damages the leaves of infected apple trees.

Aleternaria mali can overwinter as mycelium on dead leaves on the ground, in mechanical injuries in twigs, or in dormant buds.

[1] Affected plants exhibit circular spots on the leaves that enlarge as the disease advances.

Apple trees seem to have a weak defense to A. mali, base on the fact that no survivors if leaves has been infected.

[5] Apple cultivars can be ranked in order of increasing resistance as follows: Indo, Red Gold, Raritan, Delicious, Fuji, Golden Delicious, Ralls, Toko, Tsugaru, Mutsu, Jonagold, Jonathan.