Canola School: A two-pass herbicide layering strategy


Herbicide strategy for in-crop applications in canola first requires knowing what weeds are out there, and keeping in mind that two applications is an option.

In this Canola School episode, Jaeda Hoppe, field crop agronomist with UYMI Agronomy at Biggar, Sask., says that two in-crop herbicide applications is likely if the weeds are there and spring conditions have been dry.

Hoppe says that when it comes to tank-mixing, first knowing which group the canola is resistant to  — Group 2, Group 9, or Group 10 — and factoring in the grassy weed population can create a great control strategy.

“If you have a lot of grassy weeds, and you’re solely relying on a contact chemical to actually get the control, I don’t like that, I’m not comfortable with that,” says Hoppe. “If you have a very low grassy population, you’d probably get away with just the contact chemical, but I like to see someone use a Group 1 and just make sure.”

Using proper herbicide rotation with different active ingredients means doing due diligence when it comes to herbicide resistance, adds Hoppe. (Story continues below video)

The time-frame to control weeds? Typically from cotyledon to bolting, which is a wide window, but Hoppe warns that choosing a two-pass systems means the control window is more narrow. Before row closure is ideal, but that also means the weeds can’t be too large — especially weeds that emerged at the same time as the canola crop, such as cleavers or sow thistle.

When the canola crop itself is very “stagey” weed control in those crops is going to be harder, and that’s when two applications will be really helpful — to control weeds that came up with the crop and weeds that came up later.

“Ideally, the best control you’re going to get is with as small a weed as possible, but also with that being said, when you’re waiting for rain, you’re waiting for weeds to come out of the ground, so it makes staging for weeds really awkward, ” says Hoppe.

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Canola School (view all)Season 13 (2021) Episode 15

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