Anthracnose on cucumber leaf.
Leaf symptoms begin as small, pale yellow or water-soaked lesions that rapidly enlarge and turn tan to dark brown or irregular and black. As lesions merge, large areas of the leaf may appear blighted or entire leaves may die. Defoliation and killing of infected vines are common on cucumber and muskmelon. Young cucurbit fruit may turn black, shrivel, and die if fruit pedicels are infected. Circular, water-soaked spots develop on older fruit. These lesions soon become sharply sunken and then pinkish in moist weather. Lesions gradually turn green to black and vary in size from 1/4 inch to 2-1/2 inches in diameter. Anthracnose lesions occur on both green and red pepper fruit. Lesions often have visible concentric rings that are composed of tiny fungal fruiting bodies. Tomato fruit lesions are very similar to that of pepper fruit.
Frequent showers, heavy dews, temperatures of 68 to 85 F, and overcrowding of plants favor the spread and development of anthracnose. Secondary disease cycles can occur as long as the weather remains favorable.
Crop rotation with non-host crops and clean tillage (for example, plowing) help to reduce the risk of disease by reducing the amount of primary inoculum (spores) in the immediate area. If possible, plantresistant varieties and plant only certified, pathogen-free seed. Fungicide control of anthracnose of vegetables is feasible.