Foliar infections cause formation of necrotic spots on the leaves or leaf edges. These necrotic areas may progress over the entire leaf, but they primarily occur along the veins. Black rot symptoms can develop on pumpkin and squash fruit in the field or storage. Initially, small water-soaked spots develop on the infected fruit surface. As they enlarge, the spots become sunken, discolored and irregularly-shaped.
Pycnidia appear as black specks in the infected areas.
This fungus can also be carried in or on seed. Wounds, such as those resulting from picking, pruning or insects, are important for the fungus' entry into older stems and leaves. Uninjured leaves are less prone to gummy stem blight infections. The feeding of striped cucumber beetles can increase the plant's susceptibility to infection. Powdery mildew and melon aphids may also predispose cucurbit leaves to infection.