Anthracnose (Ash) (Discula fraxinus) - Anthracnose diseases are caused by a group of morphologically similar fungi that produce cushion-shaped fruiting structures. Symptoms of anthracnose vary considerably from host to host. Most anthracnose fungi cause blotchy, necrotic spots on leaves associated with veins and sometimes cause leaf distortion and premature defoliation. On oak and sycamore, the disease also impacts twigs, shoots, buds, and fruits and occasionally causes stem cankers and brooming. When leaves are infected in early spring, they often turn black and may be confused with frost-damaged leaves.