Affected leaves are susceptible to sun scorch and may have a scalded appearance following hot weather. Wilt symptoms produced are similar to those caused by black shank. The leaves do not yellow, but wilt suddenly. Discolored tissue will be evident beneath the outer layer of the stem. The central portion of the stem will be darkened but not divided into disks as with black shank.
Blue mold is favored by cool, wet weather and is a problem in plant beds and in the field.
During periods of cool, wet and humid weather, circular yellow spots develop on the upper surface of the leaf and the blue-gray fungus can be seen sporulating on the underside of these areas. Spots later turn brown, die and may fall out giving a ragged appearance to the leaf. The fungus can grow systemically through the leaf and into the vascular system of the stem, resulting in a stunted plant. A brown discoloration will be evident in the stem. On young plants, new leaves will be crinkled, twisted and the bud may be killed.