a widely distributed group of plant diseases caused by imperfect fungi of the genus Macrosporium. They are manifested in the form of spots that have various shapes, sizes, and colors and that consist mostly of dead cells with clearly defined concentric zonation. A velvety olive-black film forms on the affected tissue. The most harmful are macrosporioses of potatoes and tomatoes (causative agent Macrosporium solani), macrosporiosis of grapes (M. vitis), and macrosporiosis of cotton (M. nigricantium). The causative agents are spread by conidia and hibernate in plant remains. When there is severe infection the plants die.
Control measures consist of proper crop rotation, cultivation of resistant varieties, destruction of plant remains, deep autumn plowing, sowing and transplanting at optimal times, and spraying with fungicides.