In recent years gummy stem blight and Phoma blight are often the most serious foliar diseases on cucurbits. Symptoms of gummy stem blight on cantaloupe and cucumber leaves are expressed by irregularly circular tan spots. On watermelon leaves, the cucurbit stems near the crown, dark spots are produced with sunken streaks or cracks accompanied by a gummy ooze. The disease usually spreads from the center of the crown outward. The disease on fruits is called black rot.
Lesions start out as water-soaked areas which enlarge to an indefinite size.
Gummy exudates may appear on fruit and stem lesions, and the black fruiting bodies of the fungus may become conspicuous. The spots on cucurbit leaves produced by the Phoma blight are usually more irregular in shape and most often are on the margin of the leaves. The spots are light brown on cantaloupe and cucumber and dark brown on watermelon. Fewer lesions are produced on stems but symptoms also tend to spread from the crown of the plant, giving the plant a blighted appearance. Fruit are generally not affected.