Palmer amaranth (Amaranthus palmeri) has been confirmed in Barnes and Cass counties. A crop specialist noticed some suspect plants in a Barnes County field and notified the landowner. The landowner worked with a North Dakota State University Extension specialist, who submitted samples for DNA analysis to the National Agricultural Genotyping Center, where it was confirmed as Palmer amaranth. In the Cass County case, a NDSU Extension specialist found it within the city of Fargo, and it was confirmed in the same way.

Palmer amaranth, the herbicide-resistant species of pigweed known for devastating crops across the South and Midwest, is without question the most prevalent weed concern in the United States according to agronomists and weed specialists alike.

“Palmer amaranth’s prolonged emergence period, rapid growth rate, prolific seed production, and propensity to evolve herbicide resistance quickly makes this the most pernicious, noxious and serious weed threat that North Dakota farmers have ever faced,” Rich Zollinger, retired NDSU Extension weed scientist, said.

These are the third and fourth findings this year, with the other findings being in Benson and Stutsman counties.

“I strongly encourage agricultural producers to monitor fields for weed infestations. If you have cattle that were fed grain screenings, pay particular attention to where their manure was spread or where they may have foraged. Do not assume it is just pigweed or waterhemp,” Agriculture Commissioner Doug Goehring said. “With harvest season in full swing, farmers are also encouraged to scout fields and clean excess dirt and plant debris off equipment between fields to prevent unintentional spread.”

Newsletter signup for email alerts

The weed originated in the desert region of northern Mexico, but subsequently spread through the Mississippi Delta. Within a few years the plant invaded and destroyed crops across Missouri, Kansas, Iowa, Wisconsin, Minnesota and South Dakota.

Palmer amaranth may spread through multiple channels, including: contaminated seed mixes; equipment and machinery movement; animal feed and bedding; and wild birds.

Palmer amaranth has now been found in 12 North Dakota counties. Those sites continue to be monitored for Palmer amaranth. More information on Palmer amaranth and other noxious and invasive weeds is available at nd.gov/ndda/plant-industries/noxious-weeds.

Palmer amaranth poses a significant threat to North Dakota crops because it can grow two to three inches per day in optimum conditions and reach heights of eight feet. A single plant is known to produce up to a million seeds, quickly spreading the noxious weed great distances. With wind conditions notorious in North Dakota, the weed could potentially spread across the state with rapid pace.

The root system has been known to reach diameters equivalent with that of a baseball bat, posing serious risk of combine header damage during harvest, if unnoticed.

Heavy infestations recorded in other states show reductions in yield of nearly 80 percent for soybeans and over 90 percent for corn, according to the North Dakota Department of Agriculture.

Further complicating the issue is that Palmer amaranth is notoriously difficult to control as the weed is prone to resist nearly all common herbicides.

“Palmer amaranth is an extremely rapid-growing species once it emerges,” Greg Endres, NDSU Extension agronomist, said. “It’s easy to calculate that we don’t have much time to make an application, assuming we find it while it’s in its early stages, which is problematic, considering it’s extremely difficult to identify the weed when it’s in its earliest stages of growth.”

Unlike other annual weeds that need to be controlled only through early summer, Palmer amaranth emerges throughout the growing season and into harvest, Endres noted.

Identifying Palmer can be difficult because it resembles multiple other species of weeds, including redroot pigweed, Powell amaranth and waterhemp — all of which can be treated with common herbicide. One of the best ways to distinguish Palmer amaranth from the other weeds is its leaf stem, or petiole, Endres said. Palmer amaranth’s petiole is as long as, or longer than, the leaf blade.

Farmers are urged to work with local weed officers, extension agents and other experts to identify and report suspect plants. Palmer amaranth may spread through multiple channels, including contaminated seed mixes, equipment and machinery movement, animal feed and bedding, and wild birds.

Anyone who sees a plant they believe may be Palmer amaranth should contact a local NDSU Extension agent or agronomist as soon as possible. More information can be found online at www.ag.ndsu.edu/extension/directory.