WBR is a common fungal disease of weed brassicas that can spread to crops, caused by the fungus Albugo candida.
White blisters form on the underside of leaves that produce white spores. Chlorotic spots occur on the upper leaf surface. Infection of the seed stalk and head produces twisting and swelling (called 'stag’s head'). Leaf infection can often be found in association with downy mildew.
WBR is uncommon in leafy turnips.
Spores are readily airborne, with cool wet conditions favouring WBR development. Seedlings are particularly susceptible. WBR over-winters on volunteers and weeds.
Prevention and management
Sowing certified seed minimises infection, while keeping weed populations in check (especially shepherd’s purse) is extremely beneficial. If young crops are infected, a light grazing may be considered to reduce infection.