Stutsman County Extension agent Alicia Harstad holds a Palmer amaranth plant. NDSU photo.

This is the time of the year to scout for noxious weeds, especially until harvest is finished.

September turned out to be a menacing month for the noxious weed Palmer amaranth in North Dakota, with three new sightings of weed. The weed has been found in 12 North Dakota counties as of Sept. 16.

The weed has not been found in Montana yet, but it is within two North Dakota counties of arriving there.

Custom combiners may be one of the main sources of the infestation, according to NDSU Extension.

Palmer can also be brought in on trucks, loaders, trailers and more – anything that could carry a seed.

Combiners are in the state finishing grain harvest and will be back for soybean and corn harvest.

While combines are certainly well cleaned between farms and crops, one tiny seed is all it takes for Palmer to establish.

“Palmer amaranth’s seed is so small that it is very difficult to completely clean out of a combine. It takes a thorough job, and usually that time is not available during harvest,” said Joe Ikley, NDSU Extension weed specialist. “I’m not sure that we have any good ways to prevent seed from entering this way (custom combines), but we recommend scouting fields the next year if they were custom combined.”

Palmer amaranth was found in Stutsman, Barnes and Cass counties this month.

During the last week of August, the weed was found in a new site in Benson County, after being initially detected in Benson County in 2018 at a different site.

The North Dakota Department of Agriculture reported that Palmer amaranth was first found in the state in McIntosh County and identified through DNA analysis. A farmer showed the suspect plants to a local crop consultant, who then contacted a NDSU weed specialist.

The noxious weed has also been found in Foster, Dickey, and Richland counties in the eastern half of the state; and Emmons, Sioux, Morton and Grant counties in the western side of the state.

Why can’t producers spray their fields with the labeled rate of glyphosate to get rid of Palmer amaranth?

“Palmer is almost guaranteed to be resistant to glyphosate,” he said. “A farmer could probably spray a 1,000 percent rate of glyphosate and some plants will still be present. This is why we recommend hand-pulling individual plants as it is very difficult to remove with chemicals.”

“Seed rain” is the term Ikley and other researchers use to describe when newly produced weed seed falls onto the ground.

“Managing seed rain means we want to prevent any seed that is on the plant from leaving the plant and returning to the field,” Ikley said.

The best way to get rid of Palmer is to hand weed it, pulling the entire plant out and putting it into a bag.

“We recommend bagging plants so that any seed that falls off would fall into that bag, and not the field,” he said. “Since Palmer amaranth produces a lot of seed, one of the best things we can do is to also remove that seed from the field and burn it/bury it with the plant itself.” 

When hand-pulling Palmer, be sure and call your Extension agent first as he/she will have the latest information.

Palmer can indeed grow to large heights, Ikley pointed out.

“We found 11-foot tall plants at one of the sites. It usually only gets that tall in corn, but we can easily find 8-foot plants in other areas,” he said.

“This is the time of year to be vigilant and look for Palmer amaranth in and around fields. Plants will be setting seed as we get closer to the end of summer, and preventing seed production and seed rain in 2020 are some of the best tools we have to manage infestations beyond this year,” Ikley added.

If you find plants that you suspect are Palmer amaranth, please contact your county agent, local area Extension agronomist, Brian Jenks, NDSU weed specialist, or Ikley, who can be reached by office phone at (701) 231-8157, or by cellphone at (701) 238-6065.

For more information, see https://www.ag.ndsu.edu/palmeramaranth.