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 http://www.canolawatch.org/

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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