Blackleg Disease: How Can You Prevent It From Destroying Your Canola Crop?
In the early 1970’s, blackleg disease was responsible for destroying the entire canola industry. Unfortunately, once the symptoms of blackleg disease are present, yield loss has already occurred. However, with today’s technology crop producers are able to mitigate the risk that this disease presents to canola crops. There are two types of blackleg
Weakly virulent – This is the less severe type of blackleg. Generally, weakly virulent appears in August and does not cause significant damage.
Virulent – Virulent blackleg is the severe type, attacking canola seedlings as the crop grows in June and July. This is the form that crop producers need to be aware of, as it can result in major yield loss.
How does blackleg spread?
Generally, blackleg infects areas in east-central Alberta. Infected seeds and spores are spread through wind and rain conditions. Once infected, blackleg can be seen in seedlings, which will display lesions from infected spores. The lesions are usually white or grey with a dark border. Spores can spread to healthy seedlings and continue the infection. Moist conditions will further the infection process. Infected canola seed and stubble can produce blackleg until it is buried in the soil and rots. Infected stubble that is two-years-old generally produces the most blackleg spores.
How can you minimize the risk?
Although the risk of blackleg has lessened in recent years, crop producers can lower the risk of blackleg by practicing proper crop rotation
and growing more tolerant species of canola. Ensure that purchased seed has been tested for blackleg spores, and that fungicide is used on the crop. It’s also important that an alternation between canola and cereal growing does not allow enough time for residue to break down.
Even though the time for fungicide application has passed, crop producers should keep these mitigation techniques in mind for next year. To put Alberta crop producers minds at ease, complete yield losses from blackleg are not common in the province.
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