Weed foes to watch in 2023 include the familiar: Palmer amaranth, kochia, water hemp

DEVILS LAKE, N.D. — Formidable weed foes that compete with crops were the topic of several presentations at the 2023 Lake Region Extension Roundup in Devils Lake.

The annual event, sponsored by North Dakota State University Extension and the Crop Improvement Associations in Benson, Cavalier, Nelson, Ramsey, Rolette and Towner counties, included featured speakers who focused on topics such as emerging weed issues, insects that have potential to affect producers’ bottom lines in the next 10 years and a roundtable discussion on resistant weed challenges.

The weeds that farmers should watch for in their fields in 2023 include several that are familiar, such as Palmer amaranth, kochia and water hemp.

Kochia, which NDSU Extension named 2022 “Weed of the Year,” has become resistant to several herbicides. In North Dakota’s Walsh and Nelson counties, for example, kochia is the most herbicide-resistant of all weeds, said Traci Lagein, NDSU Extension agent for agriculture for Nelson County. The weed is resistant to four groups of herbicides including glyphosate.

Herbicide resistance to kochia also is a problem in western North Dakota, said Kyle Okke, a Dickinson based agronomist.

“This kochia thing is continuing to be a bigger and bigger issue,” Okke said.

Another familiar weed that has become herbicide-resistant is wild oats. In Walsh County, near Lankin, North Dakota, there is a particularly bad infestation of wild oats that likely resulted from a dry bean and wheat rotation, said Brad Brummond, NDSU Extension agent for Walsh County.

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Three other weeds that farmers should be vigilant about monitoring their fields for are Palmer amaranth, Powell amaranth (also known as green amaranth) and water hemp, which are all types of pigweed.

Jason Hanson, an agronomist based in Webster, North Dakota, found water hemp in six new locations in his service area in 2022, he said.

“Every new location was either in a low area, slough, ditch or next to a lake,” he said.

The only strategy that will effectively control water hemp is to hand-pull the weeds like was done in Illinois and Iowa during the 1970s, said Jeff Stachler, NDSU Extension Agent for agriculture in Griggs County.

“Herbicides are not the solution to the problem,” Stachler said.

Farmers will take different approaches to controlling water hemp and other weeds, depending on their agronomists’ recommendations, Hanson said.

One thing that is clear, though, is that a diverse crop rotation is an effective part of the control, he said.

“The more crops I have in my rotation, the less issue I have with things that keep me up at night,” Hanson said.