Glyphosate-resistant kochia confirmed in 12 municipalities in 2018

Testing is the only way to confirm how widespread glyphosate-resistant kochia is in Manitoba

When Tammy Jones’ phone rang last year as often as not it was farmers fed up with kochia spreading in their fields.

The Manitoba Agriculture weeds specialist dubbed the tumbleweed ‘weed of 2018,’ in a talk at St. Jean Farm Days last week.

“We saw a lot of it,” she said. “It felt like anyone who called me was swearing about kochia.”

And for good reason. The aggressive weed that thrives in dry conditions, tolerates salinity and spreads across fields has also been confirmed glyphosate resistant in a dozen municipalities — and counting.

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Why it matters: Learning to manage for kochia will help us deal with even more devastating weeds in future.

Manitoba Agriculture’s 2018 in-season survey now documents 12 municipalities with glyphosate-resistant kochia, a jump from five in 2016, which then included RM of Emerson-Franklin, RM of MacDonald, RM of Grey, RM of Dufferin and the RM of Brenda-Waskada. A further survey conducted post-harvest with Agriculture and Agri-Food Canada, will test another 300 samples.

But even this newest map isn’t telling the whole story, said Jones. If your farm isn’t in one of these 12 RMs, don’t assume all is well, she said.

“There is no dome of resistance protection. It doesn’t happen.”

[AUDIO CLIP] Tammy Jones, Manitoba Agriculture weeds specialist tells producers at St. Jean Farm Days to scout several times a year, and keep a close eye out for signs of glyphosate resistance. 

She’s aware of more sites with glyphosate-resistant kochia and as more data is processed, they’ll be added.

“The limitation to this map is the dataset, not the amount of glyphosate-resistant kochia that’s out there,” she said.

Her talk in St. Jean last week touched on Manitoba’s most worrisome or “most unwanted” weeds, herbicide resistance developing in common weeds such as wild oats and foxtail, and detailed descriptions of how to recognize those ‘ugliest weeds of all’ — namely tall waterhemp and Palmer amaranth whenever it starts to show up.

Her emphasis on kochia during her talk, she said, was to illustrate a point, which is that how we manage kochia is learning for how we’ll handle potentially much more devastating weeds in future.

“If we get something like waterhemp or Palmer amaranth we’re going to have to be even more vigilant about how we do this,” she said.

Her advice to her St. Jean’s audience — if you have kochia in your fields, have it tested to know for sure if it’s glyphosate resistant or not.

A lab in Winnipeg — Pest Surveillance Initiative (PSI) — will do an in-season test using leaf material for about $100. Another option is to collect seed in the fall to submit to a lab for testing. Either of those tests will assist with individual farms’ management practices, and will help inform a bigger picture for Manitoba, too, said Jones.

“The reason we don’t have more yellow (indicating herbicide resistance) on these maps is because we don’t have more testing. And a lot of guys are assuming a level of resistance. But you don’t know what you don’t know. So get it tested.”

As for how to deal with ever-spreading patches — that’s the reason for all the swearing.

Hand pulling and burning, if only a few plants are present, is one option, although “farmers might need to have a few more kids” to tackle it that way, she said.

She doesn’t recommend burning larger areas, but mowing, baling, or spot tillage can be used. The key is minimizing seed set.

However, cutting doesn’t stop the plant from growing, or setting seed either. “It just shortens up and grows more horizontally instead of vertically, so it still has the potential to set viable seed.”

Post-harvest controls with tank mix partners aren’t recommended either, she said. “The problem there is that when kochia is at this age or stage it is harder to kill. Just because we’ve cut it off and it’s now four inches tall, it doesn’t now think it’s an eight-leaf kochia. It’s still a mature plant.”

Her main message at St. Jean with respect to this particular weed, was remain constantly vigilant for it and to use a complement of tools to manage for it.

Scouting is critical, and just once is never going to be frequent enough, she said.

“When I say scouting your fields I don’t mean just once. I would like you to do it about five times. Once to know what’s in the field and that it’s at the right stage. Once after you’ve sprayed, to know that it’s worked. And if it hasn’t worked, go back in and do something else. And prior to harvest make sure you’ve gone in again to make sure that you don’t have to do a pre-harvest. Then post-harvest is yet another time to be looking at weed control or be prepared for next year.”

Use herbicides effectively but along with other practices, such as managing field perimeters, drowned-out spots and non-crop areas, she said. All these practices will be necessary as we face more herbicide resistance in general.

“We’re not going to manage herbicide resistance with herbicides alone,” she said.

About the author


Lorraine Stevenson

Lorraine Stevenson is a reporter and photographer for the Manitoba Co-operator with 25 years experience writing news and features. She was previously a reporter with the Farmers Independent Weekly and has also written for community newspapers in Winnipeg and Manitoba's Interlake.



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