WB is a common oomycete disease of weed brassicas that can spread to crops, and is caused by the fungus Albugo candida. WB does not generally cause major damage in brassica crops although radish can be heavily infected.

 

Identification

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.

 

 

Importance

WB is uncommon in leafy turnips.

 

Spread

Spores are readily airborne, with cool wet conditions favouring WB development. Seedlings are particularly susceptible. WB 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.