Leaf spot is a common and sometimes serious disease of sour cherries in the Northeast. In wet years, high levels of infection can cause trees to defoliate by mid-summer, leading to inferior crop quality, significantly reduced winter hardiness, poor return bloom the following spring, and reduced ability of blossom buds to withstand spring frosts. Sweet cherry trees also can be seriously affected, but are not as susceptible as sour cherries. Plums are occasionally affected, but seldom seriously.