Ripe peaches infected by coryneum blight just before harvest, showing the sunken rot lesions that developed during two to three weeks of refrigerated storage. Coryneum blight affects peaches, apricots and sweet cherries in Colorado. Economic loss results when fruits are blemished and disfigured by spots and lesions from Coryneum blight. Outbreaks of this disease take place in spring and early summer and in cool, wet periods prior to harvest. Blight is difficult to eradicate because the fungus in infected buds and twigs may produce spores for two to three years.
Control requires chemical sprays and removal of dead wood over a three-year period.
In Colorado it affects mainly peaches and apricots, and to a lesser degree sweet cherries. Severe foliar shot holing may weaken a tree, while the most apparent damage is infection of the fruit. The fungus apparently overwinters in dormant infected leaf buds, blossom buds and small twig cankers. Spore production begins in early spring. The first symptoms of infection are observed on young leaves as small red spots that enlarge and become purple with a white center.