Blackleg in Canola
Blackleg in canola is caused by a fungus called Leptosphaeria maculans, which attacks the cotyledons, leaves, stems and pods. This is the most serious disease found in canola and it is found in two forms in western Canada. Avirulent blackleg appears on the leaves and stems in August and causes very little damage. Virulent blackleg causes severe damage by killing the plants and seedlings in the early season.
Symptoms: The most noticeable symptoms of blackleg will be found on the leaves and stems. Leaf lesions are greyish white, round to irregular and usually is speckled with black pycnidia. When the plant is severely infected, the base of the stem will develop dry sunken cankers often with a black border. When your plant is affected with virulent blackleg the leaves, pods and seeds will have dirty-white lesions speckled with tiny black spores. On the stems and crowns light tan lesions will start to develop into the sunken cankers. When your plant is affected with avirulent blackleg, the symptoms on the leaves and stems are similar to the virulent blackleg but less severe. The lesions will appear more shallower, without the black borders and pycnidia.
Disease Cycle: Blackleg is is spread by infected seed, transfer of spores that are spred by wind or splashed of rain from one plant to another and by special spores that form over-wintered stubble and can be air-borned for long distances.
Control: Canola should be grown once planted once every four years on the same field, it also very important that you control wild mustard and volunteer canola. Using disease free seed is very important, a first time canola farmer should test the seed before he plants to make sure the seed doesn't hold any virulent diseases, so that it doesn't contaminate his land.
Symptoms: The most noticeable symptoms of blackleg will be found on the leaves and stems. Leaf lesions are greyish white, round to irregular and usually is speckled with black pycnidia. When the plant is severely infected, the base of the stem will develop dry sunken cankers often with a black border. When your plant is affected with virulent blackleg the leaves, pods and seeds will have dirty-white lesions speckled with tiny black spores. On the stems and crowns light tan lesions will start to develop into the sunken cankers. When your plant is affected with avirulent blackleg, the symptoms on the leaves and stems are similar to the virulent blackleg but less severe. The lesions will appear more shallower, without the black borders and pycnidia.
Disease Cycle: Blackleg is is spread by infected seed, transfer of spores that are spred by wind or splashed of rain from one plant to another and by special spores that form over-wintered stubble and can be air-borned for long distances.
Control: Canola should be grown once planted once every four years on the same field, it also very important that you control wild mustard and volunteer canola. Using disease free seed is very important, a first time canola farmer should test the seed before he plants to make sure the seed doesn't hold any virulent diseases, so that it doesn't contaminate his land.
