• White to creamy yellow pustules develop on the lower leaf surface. The pustules, later coalesce to form patches on the lower leaf surface.
• Tan-yellow spots develop on the upper leaf surface opposite the pustules.
• Pustules may also form on the pods. Infected flowers develop a "staghead" in which the flowers are sterile, malformed and green, and various flower parts may be thick and club-shaped and greatly enlarged.
• Most turnip or Polish varieties of canola as well as brown and oriental mustard are susceptible.
• Yield losses are about 1% for each 1% of staghead observed in a field. Yield losses in Manitoba are usually less than 10%.

Management

• Argentine varieties are resistant. If growing Polish type canola, select resistant varieties.
• See current variety recommendations for information on susceptibility.
• Use at least a three year crop rotation. Control volunteer canola and susceptible mustard-type weeds in the rotation.