Graze stubbles heavily to reduce fungus carryover. Plant canola as far as possible from previous canola crops to reduce the risk of infection by wind-borne ascospores. Avoid planting in areas downwind from old stubbles where the prevailing winds are likely to blow air-borne spores. White leaf spot White leaf spot disease can be found in most plantings, but is not usually a cause of heavy yield losses. Symptoms Symptoms include greyish-white to brown leaf, stem and pod lesions .
Lesions often have a brown margin.
Leaf lesions can be up to one centimetre diameter, often joining up to form large dead areas. White leaf spot can cause complete loss of leaves in highly susceptible varieties, with yield losses as high as 30 per cent if the disease is severe. However, losses are unlikely to exceed 5 to 10 per cent with current varieties. Nitrogen deficient crops seem to be more severely affected by the disease. Cause White leaf spot is caused by the fungus Pseudocercosporella capsellae .