NDSU: Check pollinator, habitat plots for Palmer amaranth

FARGO, N.D. -- North Dakota State University officials are asking anyone who has planted wildlife plots, to enhance honeybee and other pollinators, to ensure that seed sources didn't bring in a dreaded invasive weed -- Palmer amaranth.

Palmer amaranth (Photo courtesy University of Minnesota)
Palmer amaranth (Photo courtesy University of Minnesota)

FARGO, N.D. - North Dakota State University officials are asking anyone who has planted wildlife plots, to enhance honeybee and other pollinators, to ensure that seed sources didn't bring in a dreaded invasive weed - Palmer amaranth.

It's not too late to check plots, says Tom Peters, an Extension Service sugar beet weed specialist for NDSU and University of Minnesota.

In 2015, many people in Iowa and Minnesota stepped up to plant the pollinator plots to help honeybees and other insect habitats. Unfortunately, scientists and weed officials later found Palmer amaranth weeds that came from contaminated seed sources. The contaminated seeds showed up in the plantings in seeds for everything from household pollinator plots, to hunting habitat plots and Conservation Reserve Program mixes.

"It isn't our intent to tell people to discontinue using the pollinator mixes," Peters says. He says officials are trying to gain access to lists of people who received cost-share and technical assistance through the Natural Resources Conservation Service or the Farm Service Agency.

"Our idea is, why don't you go out and walk," he says. "If there's something that looks similar to what these pictures, we want to know that and want to help you deal with that."


The closest Palmer amaranth has been confirmed in west-central Minnesota counties, and suspected but not confirmed in north-central South Dakota.

Experts can confirm the difference with DNA testing, by spines in the axis of the leaves or an elongated petiole. The seed head of Palmer amaranth is large and "bristly to the touch."

A wicked cousin

Palmer amaranth is the wicked cousin of another weed pest - waterhemp - which is invading much of the region and developed strains that are resistant to glyphosate, the active ingredient in Roundup herbicide. A program of the United Soybean Board program says Palmer amaranth has seen resistance in up to four other herbicides classes, in addition to glyphosate.

"That adds to the mystique you can't kill it with herbicides," Peters says. "In the south - Arkansas, Georgia, Mississippi - they hire crews to go out and rogue (pull) it and remove it."

Waterhemp is bad enough - typically growing four to six feet tall, and producing 250,000 to 500,000 seeds.

Palmer amaranth looks similar to waterhemp but grows much faster. The plant grows 2.5 inches per day, or four inches in less than five days, in some southern areas. A mature plant can grow eight to 12 feet tall, with a six-foot diameter, and can produce 1 million seeds per plant each year.

"This is a massive plant," Peters says. The plant is native to the Southwest - New Mexico and Arizona - so it's interesting the desert-loving plant is having an impact in temperate climates.


Peters says anyone who finds it - from farmers to homeowners - who have Palmer amaranth should pull it and put it in a plastic bag to ferment or turn to silage, or let it dry out and burn it. "By pulling it and letting it drop in the field you haven't accomplished a thing," he says. "You don't want to plow it out because that keeps the seeds in play for subsequent years. Seed is viable for four to six years."

In a related issue, officials are investigating whether and how to make Palmer amaranth a noxious weed in North Dakota, making it subject to enforcement by county weed officials. Currently there are 11 noxious weeds in North Dakota. If approved, Palmer amaranth would be the first annual weed. Weeds currently on the list are perennials, or grow year after year without reseeding.

Farmers have a lot to fear from Palmer amaranth, Peters says. In states that have become infested, farmers have to spend $30 to $50 per acre more than what they otherwise would spend for weed control. In soybeans, it reduces yields up to 80 percent.

People with questions can call NDSU Extension agents for information, Peters says.

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