Soybean School: Did the weeds die? The critical weed-free period in soybeans


After a challenging spring that saw getting the crop planted take precedent over pre-seed weed control, soybean growers in Western Canada have had to be diligent in catching up with potentially yield-robbing kochia, lamb’s quarters, volunteer canola, and other weeds in-crop.

To keep yield losses down to less than five per cent, most soybean varieties grown on the eastern Prairies should remain weed-free through the V2 to V4 stages, and as long as R1 — the start of flowering — in some cases, according to research conducted through the University of Manitoba.

“Once we start throwing in other factors like row spacing, we might even be looking at keeping that crop weed-free until V4 or even a little after, especially on some of these wider rows,” explains Jeanette Gaultier, senior technical services specialist with BASF, in this Soybean School episode.

“This year kochia still seems to be a key weed, especially since we’re looking at estimates of 60 per cent of that kochia population being resistant to glyphosate now, according to the Manitoba Agriculture survey that was recently completed,” she says. “So we have to make sure we’re throwing in multiple modes of action to target those weeds that we are really concerned about.”

Now is the time to assess how well herbicide strategies worked, and with plenty of moisture in most of Manitoba’s soybean-growing area, there’s also the question of this being a year where growers might see a return on applying a fungicide.

“It’s something to keep an eye on, and when you’re in your fields doing your post in-crop herbicide scouting, if we keep getting those rains, I would keep an eye on it,” she says, noting disease pressure in soybeans in Manitoba is often quite low or sporadic.

“White mould can be a challenge in years when we do have moisture when we’re in the reproductive stages here, so it is good to check,” she says.”We are also seeing that some of the leaf diseases — frog-eyed leaf spot — for example, are increasing, however they do seem to be low still, so just check out your own crop and make sure you’re not seeing any excessive disease issues.”

Gaultier joins us to discuss weed issues, as well as the fungicide question, as part of this latest Soybean School, filmed near Winkler, Manitoba:

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