Brown rot is one of the most common and destructive disease of peaches and other stone fruits. The fungus that causes brown rot, overwinters in rotted fruit that remains on the ground, in dried rotted fruit remaining on the troo, and in infected twigs. In spring, wind and rain carry spores to healthy fruit-tree buds. Flowers can be infected from the time buds open until petals fall. Most fruit rot develops the month before harvest. Brown rot is most severe in mild moist weather.
Brown rot begins as a browning and wilting of blossoms and leaves. Dead blossoms may remain on trees for a long time. After killing flowers, the fungus grows into nearby twigs, producing brown, sunken cankers oozing with a gummy substance. During moist weather, small, rotting brown circles appear on mature fruit and spread rapidly to cover it. Light brown or gray powdery fungus spores, sometimes in concentric rings, soon cover the rotten skins. Fruit eventually shrinks, darkens, and dries out. It sometimes drops, but often remains on the tree. Such fruits are known as mummies.
Cultural practices are essential for low risk for a brown rot epidemic. Before growth begins in spring, prune out and dispose of fruit mummies, damaged twigs, and any branches with gummy cankers. Thin trees to encourage good air circulation. Chemicals can also be used if directions followed carefully.