Root-prune with spade or trowel or twist the stalk to break some of the roots and reduce water uptake. Common disease problems include black rot, wire stem, damping-off, downy mildew, Alternaria leaf spot and watery soft rot. Cabbage is more susceptible to wire stem and downy mildew than Chinese cabbage. Chinese cabbage is more susceptible to Alternaria. Black rot causes the most serious damage and appears as V-shaped lesions down the leaves and spreads into the water conducting system of the plant.
Black rot is caused by a bacterium that is seed-borne or that can be transmitted by transplants.
Warm, moist weather favors the disease. There is no control for black rot once it is established in a planting. Prevent black rot by purchasing transplants that are marked with a tag indicating that they are certified or plant western-grown chemically treated seed. Revision of Growing Cole Crops in the Home Garden, HGL 2, 1989. Prepared by Powell Smith, Lexington County Extension Agent, and Nancy Doubrava, HGIC Information Specialist, Clemson University.