Downy mildew

Constraint - Downy mildew

Description

• A fungal disease that affects foliage of canola and is both seed and soil borne 

• It is favoured by cool wet conditions when leaves are in contact with the soil or other leaves

• Rarely found beyond the rosette stage

Symptoms

• Yellow areas on the upper leaf surface of young seedlings are the first symptoms

• A white powdery fungal growth can be seen on the underside of the leaf beneath these spots

• Individual spots join to form large irregularly shaped blotches that die and cause a large part of the leaf to dry out, with the upper surface becoming yellow-red

• Infected cotyledons die prematurely

• Severely affected plants may be stunted

Damage

• Downy mildew does not usually affect yield so control measures are not generally warranted unless plant densities are severely reduced on a regular basis

Management

Links and Resources

DAFWA - Diagnosing downy mildew in Canola Introduction, what to look for in paddock and plant, where did it come from, and management strategies. Page last updated 2014.

DEPI VIC - Canola diseases. Downy mildew The section on downy mildew contains introduction, symptoms, disease cycle, and management. Published 2008, page last updated 2009, reviewed 2010.

DEPI VIC - Identification and management of field crop diseases in Victoria. Downy mildew Page 146. Table 11.1 gives a key for canola diseases at different stages of plant growth. Downy mildew is referenced. Page 153. Contains information on introduction, symptoms, disease cycle, and management. Published 2012.

GRDC - Best Practice Management Guide. Downy mildew Page 65. Introduction, symptoms, disease cycle, and management.  Page 59. Table of common disease of canola. Published 2009.