Small, black spots form on leaves and heads. When leaf spots merge they can form somewhat irregular-shaped spots resembling downy mildew. Different fungicides are recommended for managing these diseases, therefore accurate diagnosis is critical. This disease also affects cabbage (most commonly affected crop), Brussels sprouts, radish, turnip, and collards. It is usually not important except in wet seasons. However, the pathogen does cause spots on cauliflower heads that could affect marketability. Copper fungicides are reported to provide minimal control. The causal pathogen survives in seed and in infested crop debris, and like many other bacterial pathogens, is dispersed by splashing water. Avoid overhead irrigation, or use when foliage is dry and will have ample time to dry afterwards. Other control practices include crop rotation (at least one year) and selecting seed that is pathogen-free or treated with hot water.