Diagnosing white leaf spot in canola

A white-spot forming fungal disease that is mainly a problem in wet weather.

White spots appear on oldest leaves
Greyish-white to light brown leaf leaf lesions with a velvety texture, often with a brown rim
Mature sporulating lesions

What to look for


  • Plants with circular to irregular white lesions that may spread after high rainfall.
  • Damage is worse in wetter areas


  • Greyish-white to light-brown leaf lesions up to 10mm diameter often with a brown rim.
  • Lesion can merge and lead to premature defoliation and spread to upper leaves and less commonly, stems and pods

What else could it be

Condition Similarities Differences
Diagnosing blackleg in canola Greyish leaf lesions Blackleg lesions contain dark fruiting bodies

Where did it come from?

Contaminated stubble
Contaminated stubble
  • White leaf spot survives on canola stubble between crops.
  • After prolonged wet weather in autumn/winter ,wind-borne spores are produced that cause primary leaf lesions on canola.
  • These initial lesions produce new wind and rain-borne spores that cause the rapid spread of the disease throughout the crop.
  • The disease is not usually seed-borne but can be spread by infected seeds or infected debris with the seed.

Management strategies

Weed control
Weed control
  • White leaf spot infection is not usually severe enough to warrant control.
  • Crop rotation and isolation from the previous year’s canola stubble will prevent infection from wind-borne spores.
  • Control cruciferous weeds and volunteer canola.
  • Provide adequate nutrition to reduce crop stress

Where to go for expert help

DDLS Seed Testing and Certification
+61 (0)8 9368 3721
Page last updated: Friday, 17 April 2015 - 9:11am