Weed watch

Palmer amaranth could become a major problem for ND farmers

Palmer amaranth is starting to pop in the region and can cause serious problems for growers and their yields. Photo courtesy of Chandra Langseth/NDSU

As the days get warmer, farmers are prepping their fields for the next round of crops. With the birds chirping and insects buzzing, it’s good to be mindful of what might be lurking in the fields — weeds.

Weeds to watch

In 2019, farmers’ biggest challenges are going to be palmer amaranth, wild oats, green foxtail, kochia and horseweeed, according to Brian Jenks, a weed scientist at the North Dakota State University North Central Research Extension Center south of Minot.

“In wheat, we have a number of growers that have resistance to the wheat herbicides we use,” Jenks said. “In fact, there’s quite a few growers that are very limited on what they can use.”

Wild oats and green foxtail are giving growers trouble as they are resistant to Group 1 and Group 2 herbicides.

Crop consultants have also come to Jenks from the Rugby area to report that controlling kochia and horseweed has become a “disaster.”

“They’re resistant to glyphosate, or Roundup, so they’ve got to find other ways to control it,” Jenks said. “Those are very widespread now across the state, it’s very common to have resistance to glyphosate.”

The weed that has been looming for some time now has been palmer amaranth, and with the type of crops being grown in the area, the options to control the weed becomes very slim.

Looming threat

In January, palmer amaranth was added to the noxious weed list because of the potential economic hazard it can be. What was typically found in the southwest region of the United States has made its way to the Midwest and has been found on farms in North Dakota.

“It just grows so fast and, for a number of reasons, is hard to control,” Jenks said. “It’s not in this area but it could be.”

To help get growers familiar with palmer amaranth before it becomes a problem, NDSU Extension Service puts out a weed guide every year and made palmer amaranth the “Weed of the Year” in 2014 and 2015. They wanted the awareness out there to help stop the spread and save growers time, energy and money when they could stumble upon it in their fields.

“Since 2014, we’ve been talking and preaching to people about palmer,” Jenks said.

In the five counties they found palmer amaranth last year, growers and crop consultants that found it were aware enough to bring it to their research center and ask questions.

“That’s what we want to happen here in the northwest part of the state is people be aware so that if we catch it early, we can respond rapidly and have a chance to eradicate it,” Jenks said. “If a grower has it but he doesn’t say anything to anybody, it can spread over his whole farm.”

The weed has been found as close as Leeds, about 90 miles east of Minot, and throughout the southeast part of the state. So far, it has been spread from feed screenings or equipment coming from within the Midwest.

The most important thing growers can be doing to prevent palmer amaranth is to ask questions. It’s important to ask where the equipment or screenings are coming from and if they have been in an area with palmer amaranth.

“The big challenge with it is that it grows so fast and … it is very prone to resistance,” Jenks said. “This weed became very resistant very quickly to many of the herbicides we use or if we get it, it may already be resistant.”

According to Jenks, there was a grower in McIntosh County that had one palmer amaranth plant in his millet field that was able to spread. There are others that have witnessed the spread of palmer amaranth through screenings they receive for their livestock.

“We’re shooting ourselves in the foot by purchasing these screenings that are already contaminated,” Jenks said. “The Minnesota Department of Ag did an inspection and they found up to 250 seeds of palmer per one pound of screenings.”

In optimum conditions, palmer amaranth can grow one to three inches per day and can grow to be around 6 to 8 feet tall. It has reduced the yield up to 91 percent in corn and 79 percent in soybeans.

“One plant can produce up to a million seeds,” Jenks said. “So it spreads easily and fast.”

Jenks noted once the weed reaches about 3 feet tall, it becomes almost impossible to control. If palmer amaranth is seen in a grower’s farm, the best thing they can do is contact their local NDSU Extension agent.


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