Everyone knows blackleg has been all over canola crops throughout Western Canada this year — but producers will still have to wait a bit to find out just how much the fungal disease has impacted Prairie crops.
That’s why Clint Jurke, agronomy director with the Canola Council of Canada, is waiting until survey data is published this month before answering “Has 2024 been a bad year for blackleg?”
“It’s not until the official canola disease survey data comes out at the end of October that we have a sense for ‘Well, was this year worse than last year?’
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“We try to avoid speculating until we actually have some data in hand.”
The council has previously noted the wet spring and subsequent hot and dry stretch on much of the Prairies this year were “ideal” for the disease to develop.
Past that, visual inspections and farmer reports have made their case.
“We’re getting reports from from all parts of the Prairies in Manitoba, central Alberta, southern Alberta, Peace River, all parts of Saskatchewan — blackleg is ubiquitous,” Jurke says.
That’s not necessarily unusual, though. Blackleg’s high degree of variability tends to that, he says.
“It’s never that you’re going to see whole regions where every field has infection. It’s going to be ‘This field is infected’ and then the three neighbours around it are not. And then it’s another couple fields here and there.
“So it really just depends upon what’s happening within a given field.”
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For producers who suspect they have blackleg in their fields, probably the best course of action this time to year is to send samples to a lab to find out if it actually is blackleg (verticillium stripe appears similar to blackleg).
This lab testing is also an opportunity to identify the race of the blackleg — a growing method of matching blackleg-resistant canola genes to the right blackleg target.
“So with that, then you can take your blackleg, your blackleg diagnosis, and then you can look for varieties that will manage that particular race,” Jurke says.
This is a time of year when farmers can scout stubble and look for signs of the disease in stubble, for example, he says.
This will put you in a good position to manage the disease next growing season. In that case, Jurke recommends an array of integrated pest management (IPM) methods.
“You can’t just rely on resistance to manage the disease,” he says. “We are lucky that with blackleg we’ve got quite a few tools that we can use as part of that integrated pest management approach.”
And if you guessed crop rotation would be one of those methods, you’d be right.
“Crop rotation is definitely one of the most effective tools,” Jurke says.
“The pathogen survives in a field on old canola stubble. When that old canola stubble is gone then the pathogen is gone. So if you can remain out of canola in a rotation for at least two years, then the majority of that old canola residue will be gone.
“And so your risk for blackleg really goes down. You still might get a little bit that blows in from a neighbour’s field, but it doesn’t really go that far.”
Fungicides are another option but timing is key. Jurke pointed to new seed treatments that work in the early days of a canola crop’s life, such as the cotyledon through two-leaf stages.
“If you can protect the canola crop during that cotyledon into two-leaf stage, that seems to be the critical period of infections. If you get blackleg infection then it’s usually going to be bad.
“So if you can protect the crop up to that stage, then that really reduces the amount of disease.”
Foliar fungicides are another option, he says.
“In those high-risk situations where you think that your resistance isn’t going to be working (and you’re) seeing a lot of lesions on seedlings, then a foliar fungicide will clear that up.”
Blackleg samples can be sent to any accredited seed lab. Trevor Blois, a disease diagnostician with 20/20 Seed Labs at Nisku, Alta., walks farmers through the process of submitting samples to that lab in the likely event they have to send it a long distance.
Blois recommends collecting between 12 and 20 samples per field. Rather than taking a traditional random sample using the “W” formation, he suggests looking for the most severe infections and cutting the stems just above the soil line.
There are a few ways to package the samples, Blois says, but he recommends a Ziploc bag or an imitation brand. Label it with the information you want to know from the samples, including race if that’s a priority.
Blois also suggests using a courier service like Purolator or Canada Post to ship the sample. 20/20 will accept samples sent by regular mail but he warns it will likely be slow.
“Usually that’s going to be your seed samples and that’s OK, but with plant specimens it’s much better to send by courier.”
