Diagnosing white leaf spot in canola
A white-spot forming fungal disease that is mainly a problem in wet weather.
What to look for
Paddock
Plants with circular to irregular white lesions that may spread after high rainfall.
Damage is worse in wetter areas
Plant
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
Where did it come from?
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
Rotation
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
