It can severely devitalize trees by defoliation and it reduces yield and quality of harvested fruit. Most varieties developed in more humid areas of the country possess fair to good tolerance to the disease. Varieties developed in drier areas of the country are frequently too susceptible to grow successfully in humid areas.
Bacterial spot attacks the fruit, leaves, and current season's twigs.
Fruit infections appear as tiny purple to black flecks on the fruit surface of peaches, and as water-soaked spots on nectarines and other smooth skinned Prunus spp. In about three days, the lesion becomes visible with reflected light. Leaf lesions are much more common at the distal ends of the leaves and around major leaf veins. This occurs because the water film is thicker in such areas and these regions of the leaf dry more slowly. Leaves with as few as two to three lesions turn yellow and fall.