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Blackleg is spread primarily by wind, with the heaviest spore fall out normally occurring within 500 metres of any canola residue. Each year canola residue continues to produce blackleg spores at a diminishing rate until the stubble has completely broken down (see Diagram 2). In WA this breakdown could take up to 4 years, and so the recommendations are for long rotations.
The blackleg fungus can attack all the aerial parts of the plant. While leaf infection is the most obvious symptom, high levels of leaf infections do not necessarily indicate that major losses will occur from blackleg. It is the less obvious infection of the crown region (junction of root base and stem) that causes the largest seed yield losses from blackleg.
Canola seedlings of all varieties are susceptible to blackleg until they achieve a degree of adult plant resistance, usually at about the six leaf stage.
Number of Pages
Canola, Fungicides, Fungal diseases, Plant disease control, Western Australia
Agronomy and Crop Sciences | Biosecurity
Department of Agriculture and Food, Western Australia. (2003), Managing Blackleg : A grower's guide to minimising risk from Blackleg disease of canola in Western Australia. Department of Agriculture and Food, Western Australia, Perth. Bulletin 4571.