The fungus causes spotting and premature drop of leaves in most plants in the Pomoideae group of the rose family. Hosts include apple, crabapple, evergreen pear, hawthorn, loquat, photinia, pyracantha, quince, Rhaphiolepis, serviceberry, and toyon.
Tiny, reddish spots, sometimes surrounded by a dark red, purple, or yellow halo, appear on infected leaves. Spots darken and enlarge as the leaves mature. Later, a spore-forming body develops in the center of the spots; these cream-colored specks may appear to be covered with a glossy membrane, beneath which white masses of spores are visible under magnification.
Life cycle
On deciduous plants, the fungus overwinters mainly as spores or mycelia on fallen leaves. On evergreen hosts, the fungus can also remain on leaves on the plant year-round. Raindrops and overhead irrigation splash spores from infected plant tissue or contaminated leaf litter to healthy leaves. Fungal infection and disease development can be severe when wet weather or overhead irrigation coincide with new plant growth.
Solutions
Remove and dispose of spotted leaves on plants and the ground near plants. Use drip, flood, or low-volume sprinklers instead of overhead irrigation. Consider removing ground covers beneath infected shrubs and mulching or maintaining bare soil instead. Where the problem is severe, a copper fungicide or chlorothalonil can reduce damage if thoroughly sprayed on plants before they are damaged.
