In Colorado, it affects mainly peaches, apricots, and, to a lesser degree, sweet cherry.
Spore production begins in early spring and continues until fall.
Severe leaf infections produce numerous holes and give the affected leaves a very tattered appearance. Economic loss from coryneum blight results from infection of fruit. The purple-red spots on the epidermis blemish or disfigure the fruit. Spot development depends on the occurrence of wet weather periods, and spots may appear on the fruit from 10-12 weeks before harvest to throughout the postharvest period. Late infections on apricots when the fruit is large generally produce smaller red spots, but these also reduce fruit quality and increase cullage.