The anthracnose fungus lives in the soil for up to two years. Belly rot of cucumber appears as irregular scabby lesions on the underside of the fruit. It develops most rapidly at temperatures over 82 degrees F but is inhibited by wet weather. Belly rot develops rapidly when conditions are only slightly moist. Preventing direct contact with the ground by using plastic or other mulches protects the fruit to some extent because this fungus is soil-borne.
Cultivars differ in susceptibility, but none are resistant.
Downy mildew, potentially a very serious problem in cucurbits, first appears as small yellowish areas on the leaves. When the leaves are wet overnight, spots may appear in the early morning as water-soaked, somewhat angular areas on the lower sides of leaves. The lesions change from yellow to brown as they enlarge, but retain an angular pattern of development. Downy mildew can overwinter in some areas, but usually moves northward from subtropical areas. Unlike powdery mildew, which grows rapidly in dry weather, downy mildew development is promoted by warm to hot, wet weather.