It’s been dry in parts of Western Canada heading into canola flowering, but has it been dry enough to hold off on spraying for sclerotinia?

That’s a question many growers and agronomists in drought-affected areas have been asking themselves over the last week or two.

There are really two basic factors to consider in the decision process: disease potential and yield potential; and moisture availability impacts both, notes Nate Ort, agronomy specialist with the Canola Council of Canada in this Canola School episode.

“If you walk your fields in the morning, and you come out with wet pants, that means the micro-environment within the crop is probably optimal for disease pressure, but with a thinner stand you’ll get air-flow going through the canopy and it may reduce disease pressure,” he explains.

In addition to environmental conditions and the weather forecast, it’s important to assess to what extent the pathogen is present, by looking for apothecia bodies on the ground, says Ort. Crop rotation is another disease potential factor, as sunflowers, soybeans, dry beans, and other brassica plants are all sclerotinia hosts.

Yield potential, on the other hand, depends on factors such as plant stand, genetic resistance, and the extent to which the plants have suffered from stresses such as drought, flea beetles, frost, and heat.

If yield potential is decent, there doesn’t need to be a lot of sclerotinia to justify a fungicide application, as the Canola Council says a 10 per cent infection rate in a 50 bushel/acre canola crop equals the cost of fungicide.

Ultimately, there are a lot of moving parts to consider in making the fungicide decision. “It definitely helps to ask around, reach out to extension specialists, retails, agronomists, neighbours. See what they’re doing and that can provide ease of mind,” notes Ort.

The Canola Council is also working with Agriculture and Agri-Food Canada to build a sclerotinia risk calculator with an algorithm for assessing risk and economic thresholds. The CCC is currently looking for beta testing volunteers, with plans to launch the calculator in 2022. (You can sign up to participate by emailing [email protected]).

Check out the full conversation between Nate Ort and RealAgriculture’s Kelvin Heppner, below:

Watch past episodes of the Canola School here.

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