Edwad J. Sikora, Extension Plant Pathologist, Auburn University Plant Disease Notes Gummy Stem Blight of Cucurbits Gummy stem blight, caused by the fungus Mycosphaerella melonis, is a common disease of cantaloupe, watermelon, and cucumbers. The symptoms of gummy stem blight first appear as grayish green circular spots between the veins in the lobes of leaves.
Spots turn a dark brown to black with age.
Spread of the disease begins in the center of the plant and moves outward. Lesions develop first on the vines at the nodes and elongate into water-soaked streaks that become pale brown to gray with time. Stem tissue often cracks and a characteristic gummy ooze is exuded from the wound. Infected vines die eventually, and entire plants die occasionally. The disease, unlike anthracnose, does not attack fruit.