Bacterial leaf spot of cucurbits

Xanthomonas campestris pv. cucurbitae

The disease symptoms are marked on seedlings first. Small spots of brown color (slightly pressed-in, then getting a kind of ulcers) appear on cotyledons. Mass development of the disease is marked usually in the beginning of July, directly dependent on the amount of precipitations. On adult plants, the disease is shown as necrotic spots on leaves and characteristic lesions on fruits. On leaves, the disease begins as chlorosis of light-yellow color along their margins. Later, small round necrotic spots form in chlorotic zone, where they increase in sizes, merge, and soon occupy the most partajority of the leaf surface, forming sites with dead brown tissue. As a rule, the necroses penetrate deeply into leaf lengthwise veins, being limited by the veins. Necrotic spots do not drop out. The described symptoms occur on leaves of any age. On fruits, the disease begins as dimness of tissue of seed chamber, as a rule, at the flower end. Initially, the fruit appears to be completely healthy. Then round oily, slightly pressed-in brown spots, frequently with chlorotic border, appear on its surface. Viscous liquid drops of an amber color are formed on the surface of these spots in damp weather. At strong lesion, the fruits are deformed, becoming covered with cracks, and then rotting.