The fungi invade the plant’s circulatory system, causing it to rot from within. As the disease progresses, plants flop over and die. Infected plants are inedible.
Make sure plants get good air circulation and plenty of sun, and keep weeds controlled to promote prompt drying after rains. Use mulch to keep soil from splashing onto plants in heavy rains. Avoid using sprinklers or other overhead irrigation methods after cabbage, broccoli, cauliflower or lettuce heads have formed. At the end of the season, pull up and compost plant material so it will be completely rotted by the following summer. In beds where this disease has been seen, grow grains and other non-susceptible crops for three years.
Pull up affected plants, chop them into pieces, and compost them in an active compost pile. Do not turn under diseased plant material, because it may survive winter intact. Managed composting is needed to make sure that cabbage or broccoli stumps rot completely by the following summer.