Cabbage Diseases

Black rot on cabbage caused by the bacterium Xanthomonas campestris. Note the large yellow-orange "V"-shaped lesions extending inward from the margin of the leaf. Black rot is favored by warm, wet weather. The bacteria spread by means of water (surface water, irrigation water or splashing rain) and enter the plant through natural openings (stomates and hydathodes) or wounds. Downy mildew is caused by the Oomycete, Peronospora parasitica. Initial symptoms consist of small yellow spots on the leaves that eventually turn brown as the disease progresses. Downy mildew is favored by cool, wet weather and may predispose plants to bacterial soft rot. Image courtesy of Clemson University. Alternaria leaf spot caused by Alternaria spp. Elliptical necrotic lesions with a "bull's-eye" pattern are characteristic of this disease. Infected leaves eventually turn yellow and drop. Image courtesy of Clemson University - USDA Cooperative Extension.

Head rot of cabbage caused by the soil-borne pathogen Sclerotinia sclerotiorum is often referred to as "white mold." The most favorable conditions for disease development are cool, wet weather combined with high humidity and heavy dew.