White Blister

White blister is common on cabbage and sprouts.

Raised white pustules are formed on the leaves of infected plants. These become powdery as spores are released, and may turn brown later in the season. The pustules occur mainly on the underside of the leaves and are variable in shape and colour.

The disease is favoured by periods of high humidity and temperatures of 10-20ºC and is usually seen in late summer/early autumn.