QUIZ – Sclerotinia stem rot

With highly variable moisture this year, some areas definitely will not need to be sprayed, some areas should be sprayed and some are a definite maybe. When considering fungicide cost ($25 to $30 per acre, including application), a fungicide would have to preserve 1.5 to two bu./ac. of yield to break even (based on $15 to $18 per bushel canola prices). This economic threshold should be easily achieved in a high-risk, high-yield field.

Here are three quiz questions and a poll question on sclerotinia stem rot management.

1. The Canola Council of Canada is beta-testing a new sclerotinia stem rot risk assessment tool. Rainfall is a major risk factor. The tool also asks the user to rate sclerotinia severity in the previous host crop. Four of the following are host crops for sclerotinia. One is not. Which is not a host?

Canola

Peas

Potatoes

Soybeans

Wheat

2. A canola crop with uneven staging presents a challenge for fungicide timing. Which of the following would be the most accurate agronomy statement for fungicide timing on an uneven crop?

Consider spraying when the earliest plants are at the right stage because early infections usually cause the most yield loss.

Consider spraying when the latest plants are at full flower as this will provide a curative response for the greatest number of plants.

Uneven crops are too much of a bother. Just ignore them.

Uneven crops should be sprayed twice because a single application timing is too hard to judge.

3. The window to apply fungicide to protect canola from sclerotinia stem rot is 20 to 50 per cent flower. Kelly Turkington, plant pathologist with Agriculture and Agri-Food Canada, uses this guideline to identify 20 per cent flower....

Just before petals start to drop

The field is at its most yellow

Side branches are just starting to flower

10 open flowers on the main stem

4. Spores have to be present for infection. Apothecia (in the photo) are a sign that spores will be present. However apothecia are not always easy to find or distinguish from other mushroom-like fungal bodies that may be present. Other options for spore detection are petal tests and new tools, like the Spornado (20/20 Seed Labs) or DNA-based petal testing kits (Quantum Genetix and Discovery Seed Labs). Have you ever used spore detection or petal testing? 

Yes

No

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