Black rot is caused by the bacterium, xanthomonas capestris.
It is a plant disease that affects all members of the cabbage family including broccoli, brussels sprouts, cauliflower, chinese cabbage, collards, kale, kohlrabi and of course the common cabbage. Black rot can occur at any stage of growth of these plants. Black rot caused young plants to die in stages, going from yellow to brown to a wilted, dry death. Black rot causes older plants to die by yellowing areas on the edges of leaves, then progressing inward in a v shape. Older leaves drop off and die quickly.