Palmer amaranth: You have questions, we have answers

Palmer amaranth -- voted the most troublesome weed in the United States by the Weed Science Society of America -- has made its way to North Dakota. The weed, also known as Palmer pigweed, recently was discovered in McIntosh County, the first offi...

Palmer amaranth towers over a row of soybeans just outside of North Platte, Neb., on Tuesday, Aug. 15, 2017. Nick Nelson / Forum News Service
Palmer amaranth towers over a row of soybeans just outside of North Platte, NE on Tuesday, August 15, 2017. Nick Nelson / Agweek
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Palmer amaranth - voted the most troublesome weed in the United States by the Weed Science Society of America - has made its way to North Dakota.

The weed, also known as Palmer pigweed, recently was discovered in McIntosh County, the first official sighting in the state. DNA testing at the University of Illinois confirmed that the weed is Palmer.

The weed already had been found in South Dakota and Minnesota.

In South Dakota, there have been confirmed sighting in Potter, Sully, Hughes, Lyman, Bennett, Buffalo and Douglas counties. The weed could be present elsewhere in the state, too.

South Dakota agriculturalists and agronomy specialists with questions about the weed can contact Gared Shaffer, South Dakota State University extension weeds fields specialist.


In Minnesota, Palmer has been documented in Douglas, Lyon, Todd, and Yellow Medicine counties. Again, it could be present elsewhere in the state, too.

Palmer is listed on Minnesota's Prohibited Noxious Weed Eradicate List. All above and below ground parts of the plant must be destroyed. And no transportation, propagation, or sale of this plant is allowed. More information:

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Though some in Upper Midwest agriculture have worked in the past few years to learn more about Palmer, the weed is still largely unknown by the public, especially in North Dakota. With that in mind, here are some common questions about Palmer, with answers from North Dakota State University extension, the North Dakota Department of Agriculture and weed scientists.

Why is the weed so worrisome?

There are many reasons. Here are the primary concerns:

• It grows rapidly - 2 or 3 inches per day - and can reach 10 feet or taller. Its growth rate and size allows it to "outcompete" crops, including corn and soybeans, America's most commonly grown crops. Yield losses of up to 91 percent in corn and 79 percent in soybeans have been reported.

• It grows so large that it can damage farm equipment.


• Nitrates in its leaves, at high levels, can be toxic to livestock.

• A single plant can produce up to 1 million seeds by some accounts, 1.8 million seeds by others.

• Its seeds are so tiny that farmers can spread them unknowingly.

• It quickly develops resistance to herbicides.

• Unlike other annual weeds that need to be controlled only through early summer, Palmer emerges throughout the entire growing season,

What does it look like?

Palmer's appearance is yet another reason it's so worrisome. It's a summer annual with green, smooth leaves - quite similar, especially in early growth stage, to other weeds such as pigweed and waterhemp. That complicates identification, even by people who know weeds.

Two generally good ways of identifying Palmer: Its leaf stem, or petiole, is longer than the leaf blade. And its long, snaky seed heads can grow up to 2 feet long.


Palmer are either male or female; male plants produce only pollen while female plants produce only seed.

What it's history?

Palmer is native to the southwestern United States and has, over time, expanded east and north. It already has been identified in South Dakota and Minnesota, and experts said its arrival in North Dakota could only be delayed, not prevented.

How does it spread?

It seed can be spread in many ways, including farm equipment, wildlife, water and wind. The Palmer identified in McIntosh County is thought to have been brought in by birds. Migratory birds can eat the weed in one state and carry it hundreds or even thousands of miles.

Any special concerns for North Dakota farmers and ranchers?

A large amount of out-of-state hay came into the state in 2017 because of drought. Some of that hay may have contained Palmer and other weeds.

Any special concerns for North Dakota gardeners?

The potting soil they buy in the state likely was bagged elsewhere and could contain Palmer seeds or other contaminants.

Is Palmer illegal in North Dakota?

The state Department of Agriculture is paying close attention to the weed. But the ag department hasn't put Palmer on the state noxious weed list, so far focusing instead on education and outreach.

How can its spread be prevented or at least slowed?

So-called integrated management - an approach that includes various types of herbicides, crop rotation and even pulling weeds by hand - is strongly recommended by weed scientists.

Experts familiar with the weed urge a zero-tolerance policy.

What can I do?

Study images of the plant to give yourself some familiarity with its appearance. Scout your fields, pastures and gardens for plants that might be Palmer. If you find anything suspicious, check with local weed officers, extension agents or other experts. Or contact the North Dakota Department of Agriculture at 701-328-2250 or NDSU extension at 701-231-8157 or 701-857-7677 to report a suspicious plant.

Where can I learn more?

At NDSU Extension's Palmer amaranth website: .

Palmer amaranth was spotted in a Nebraska corn field. A group of North Dakota officials have traveled to Nebraska to learn more about the weed that is devastating agriculture in parts of the country. (Nick Nelson/Agweek)

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