August 14, 2019

Canola Watch quiz – Pre-harvest disease scouting

The best time to survey canola fields for disease incidence and severity is just before swath timing – which is 50-60% seed colour change on the main stem. If not swathing, you can still use this crop-stage timing to check for disease. Some fields across the Prairies are at this stage. The rest will follow over the coming weeks.

At the swath-timing stage, any diseases present will be near peak intensity and fairly easy to identify. This will provide an accurate assessment of disease, which can be used to enhance long-term management decisions (such as disease-resistant seed choices, crop rotations and fungicide use). It could also be used to make harvest timing decisions for this year.

The following quiz questions (and detailed answers) will help you identify the disease symptoms you’re seeing.

1. Fill in the blank. ____________ goes through petals to leaves to stems, annihilating tissue with acid as it goes, drinking in the death of plant cells.
2. Fill in the blank. _________ goes through leaves and stems via the xylem without causing much damage, until it hits the crown. Then it leaves the xylem and destroys all host tissue there.
3. Fill in the blank. __________ infects roots, traveling up the xylem feeding on xylem sap as it goes, multiplying until it chokes the plant mid-stem. Once plant begins to die it fills the xylem with microsclerotia which eventually busts out of the epidermis.
4. When scouting for blackleg severity, you want to clip through the canola crown to see what percentage is blackened. What is the ‘crown’?
5. While doing the pre-harvest scout for disease incidence and severity, take a look for anything else unusual. In moist conditions, you might see symptoms like those shown in the photo below. What caused these symptoms?

Powdery Mildew symptoms on canola plants 
6. If a patch of canola is drying down prematurely but shows no other above ground symptoms, it could be:

 

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