Good management practices can help control clubroot. Common practice is to use a combination of long plant rotations with non-hosts, maintenance of a soil pH at 7.3 or above, fumigation, sanitation and maintenance of a high soil organic matter. Farm hygiene is very important because it helps prevent the movement of clubroot from infected soil into clubroot-free areas. Future control measures may use combinations of chemicals, nutritional programs, rotation and clubroot resistant varieties. Infected leaves develop purple, yellow or brown patches on the upper surfaces and white to grey downy fungal growth underneath.
Older leaves show signs of small necrotic areas that look like small black specks.
During moist conditions the specks may enlarge to form large black patches. Plants should be kept well ventilated to reduce the humidity and the risk of downy mildew. Overhead irrigation should be avoided where possible. Cruciferous weeds should be controlled. Symptoms include small circular spots raised on both sides of the leaves.