Blackleg in Canola – to spray or not to spray?

Things to consider:

  1. Crop rotation – the tighter the rotation the higher the risk of blackleg
  2. Historic levels of blackleg in that field – have you experienced yield loss from blackleg?
  3. Weather forecast – infection requires free moisture (light-moderate rainfall, not soil saturation)
  4. Presence of inoculum –can you see leaf lesions on first true leaves? or pseudothecia present on canola stubble?
  5. Yield potential – what is your target yield, return on investment expected?

If you have made the decision to spray, what else do you need to know?

  1. Application timing – apply at the 2 to 4 leaf stage, later applications are not as effective at reducing disease.
  2. Fungicide type – strobilurin fungicides (Group 11) are more effective at reducing disease than triazoles (Group 3). For more information on what products are registered for blackleg management, see the MB Guide to Field Crop Protection
  3. Yield increase….not guaranteed – while strobilurin fungicides applied at the 2 to 4 leaf stage did significantly reduce the severity of the disease, yield bumps were only observed when a susceptible cultivar was grown.




Reference: Liu, C. 2014. Evaluation of fungicides for management of blackleg disease on canola and QoI-fungicide resistance in Leptosphaeria maculans in Western Canada. Master of Science Thesis. University of Manitoba. 172 pp.


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Over the Course of Time: Manitoba Canola Diseases 2009-2014

Canola is one of the most economically important crops produced in Manitoba and yield robbers such as canola diseases need to be identified in order to apply best management practices. For many years, sclerotinia has been the most significant canola disease in Manitoba. However, in recent years the prevalence (% of fields infested) and incidence (% plants infected per field) of blackleg have been increasing.

Disease incidence and severity will change from year to year based on use of genetic resistance in varieties, environmental conditions, and agronomic practices such as crop rotation and fungicide use. Annual surveys of commercial canola crops provide valuable information on the distribution of disease, impact of farming practices on severity and incidence, help agronomists and farmer prioritize where future resources need to be directed, and can provide an early-warning system that provides information on the occurrence of disease/pesticide breakdown.

For more information on the annual Manitoba canola disease survey including methods, results from 2009 to 2014, and further discussion, please view the attached poster which was presented at the 2014 Manitoba Agronomists Conference:

Over the Course of Time Manitoba Canola Diseases 2009_2014 (Kubinec et al., 2014)

For more information on canola diseases in Manitoba, and information on various types of control methods, please visit MAFRD’s website at
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Assessing Canola for Swathing Timing? Why Not Look for Diseases Too!

Prepared by Anasatsia Kubinec, MAFRI Oilseed Crop Specialist

Once your canola comes out of flower the countdown is on to swathing and then harvest. 

The prime stage to be swathing is at 50-60% seed color change.  On the plants that looks like the bottom 1/3 of the plants pods have mostly black/brown seeds, the middle 1/3 has 50% brown/black seeds and the top 1/3 seeds are firm when rolled between your fingers and at there are some seeds that can be found to have spots started turning brown.

While out there staging for swathing, scout for the diseases your canola field has too.  Scouting at this stage does not mean control, but it will give you and idea of diseases the crop has and how you can plan for your next canola crop in that field.

Examine the plants from root to top.  What do you see:

Leaves – yellowing and lesions – could be blackleg, look also for black pepper spots that could be blackleg (raised black spots that don’t rub off or smear).  No black spots – it could be alternaria which will also have concentric rings in the lesion.  Just yellow but lesion look ‘water-soaked’, that may be the start of sclerotinia

Stems – grey/white lesions – does the spot ‘shred’ when you scratch the lesion, then is is probably sclerotinia.  Does the lesion have black pepper spots and does not shred – then it is probably blackleg. Is there entire portion of the stem that are grey and hollow, but not shredding or no black spots?  Then is may be grey stem. 

Base of plant – see pinching?  It could be a root rot.  If you cut through the base of the stem and see blackening in the base that is blackleg.

Get what you see confirmed by your agronomist or take the plants to your local MAFRI office to be confirmed.  Then write the diagnosis down.  Management options like longer time between canola crops, variety selection and fungicide use can be integrated into your future cropping plans and reduce the amount, and severity of the above diseases in the future.

For more information also see Canola Council of Canada CANOLA WATCH for July 31, 2013

SCLEROTINIA on STEM – note the shredding. Photo from Anastasia Kubinec, MAFRI

BLACKLEG on STEM – see black pycnidia or “pepper spots.” Photo from Anastasia Kubinec, MAFRI

BLACKLEG found when cutting through canola crown.
photo from Anastasia Kubinec, MAFRI


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My canola has a number of dead plants in it. It has been a dry summer here, could I have sclerotinia?

Based on the rainfall in most of the province, the prematurely ripened plants are probably not due to sclerotinia, but there is a chance it could be.  Typically sclerotinia will look like prematurely ripened plants that are dead above a specific infection point on the stem.  Plant material tends to start shredding and may looked bleached.  More likely in 2012, it could be caused by blackleg which also causes premature ripening, but tends to affect the entire plant.  The stem may have lesions, but it will not shred and probably has black dots that look like pepper spots in the lesion.  To confirm diagnosis a sample can be sent to the MAFRI Crop Diagnostic lab in Winnipeg (submit sample through local MAFRI GO office).

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