Canola School: Mitigating flea beetle pressure through consistent seeding depth

(Kara Oosterhuis/RealAgriculture)

When it comes to seeding depth of canola, there are many different opinions and recommendations out there.

While there may not be a right or wrong answer — did you know you can potentially mitigate flea beetle pressure through seeding depth?

Flea beetles can be one of the most detrimental insect when it comes to yield impacts on the canola crop. What is the magic number then? Turns out it’s not so much about the depth itself — but rather the uniformity of the depth across the field.

“Let’s look at a scenario,” says Jack Payne, agronomy solutions manager with South Country Co-op Ltd, in this Canola School episode. “Much of southern Alberta right now is dry. I’ve seen growers that have put their canola in to two inches deep, and they get emergence, because they’ve got it down into moisture. The one thing I have noticed over the past few years is when I get digging around in a field, is I’m finding quite variable depth in the same field. So within the same field, I’ll find canola at half to three quarters of an inch deep, and in other places its two inches deep. So some of the seed is shallow, some of the seed is deep.”

As Payne explains, if you are in a dry situation, and you strand your seed at a half inch of dry soil, the canola that is two inches down will germinate, and emerge to the surface. The canola that is not in moisture will be behind, creating an uneven stand. The flea beetles will move in, and they’ll have half as many plants to attack, making it even easier to clear out the crop.

“They’re hungry, and that’s what they are going to go after,” he says.

This situation can also work in the reverse if you are in an area that has had excess moisture, and the seeds closer to the surface emerge first, leaving the deeper seeded canola behind.
Check out the full conversation on stressful growing conditions, the importance of seed treatments, and more:

The other consideration with flea beetles, says Payne, is taking a step backwards and looking at what happened in the fall.

“I had quite a few calls coming in from agronomists saying farmers are encountering high populations of flea beetles in the fall on crops that were maturing, and it’s too late to control them. I would mark those fields from last year and say, okay, keep an eye on that area. If there were a lot of flea beetles in that area last year, they’ve probably overwintered. Any canola that’s been seeded close to that area is probably ripe for the picking for the flea beetle — so there’s a high risk there.”

Another thought you can keep in mind when seeding, and trying to keep those future pest attacks down is seeding rate. The old seeding rate guidelines suggested seven to 12 plants per square foot, which has now been dialled down to about five to seven or eight plants per square foot.

“If you’re targeting on the low end of the plant population spectrum, it’s all a numbers game,” explains Payne. “Fewer plants mean the potential for more flea beetles per plant. So if you’re seeding on the low end of that spectrum of target, you have to be on the lookout to scout for flea beetles, and monitor to see what’s going on.”

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