Watch out for Palmer amaranth weed this year

FARGO, N.D. -- South Dakota farmers have discovered Palmer Amaranth weed and North Dakota officials are urging farmers to keep a sharp eye for a "spawn of evil" during harvest.

Palmer Amaranth
Officials suggest watching for the Palmer Amaranth weed in unexpected places. Here, it grows this year in a straw bale stack in Indiana. Photo courtesy of Purdue University, West Lafayette, Ind.

FARGO, N.D. -- South Dakota farmers have discovered Palmer Amaranth weed and North Dakota officials are urging farmers to keep a sharp eye for a "spawn of evil" during harvest.

South Dakota State University weed scientists say the weed was found in a sunflower field in Buffalo County next to the Missouri River in central South Dakota.

"Palmer Amaranth is a vigorous weed that is a member of the pigweed family that also includes common water hemp, redroot pigweed, prostrate pigweed and others," says Paul O. Johnson, SDSU Extension Weed Science Coordinator.

The weed is native to the southwest U.S. It is an annual and reproduces only by seed. Scientists don't know whether seasons are long enough in North Dakota for it to produce viable seed, or whether that seed can overwinter, Olson says. The weed has already reproduced in Pennsylvania, Iowa and Michigan.

Olson is concerned that the area next to the Missouri River might provide a favorable microclimate for overwintering. He's not alone.


"It is certainly the most formidable weed that the American grower has ever encountered," says Richard Zollinger, North Dakota State University Extension weed specialist. "The only refuge where this weed has not been reported is Minnesota and North Dakota. It appears that once established eradication is impossible."

Zollinger adds that no state has been able to return the land to a weed-free status for the weed after it is discovered.

"Knock on wood, no one has told us they have found this miserable, wicked spawn of evil in North Dakota," Zollinger says.

Zollinger is encouraging harvest time combine operators and truck drivers to keep an eye out for the weed this year. He suggests people go to Page 137 of the North Dakota Weed Control Guide, available at Extension Service offices.

He notes that Bob Hartzler, an Iowa State University counterpart to Zollinger, has been watching the weed's progression and reports that farmers range in vigilance from "very concerned to little interest."

Zollinger endorses these three suggestions from Hartzler:

•Look for infestations on roadsides, around grain bins and storage areas and along field edges. He has discovered it in "the most unexpected places."

•Eradicate small infestations where discovered. Hand pulling is the most obvious because it's resistant to glyphosate.


"You burn it to make sure that the whole plant gets combusted and that no seed is transported by birds or any other method back to the field," Zollinger advises.

•Be careful not to confuse water hemp with Palmer amaranth. The main difference is that Palmer amaranth has slender 2-foot-long seed heads, versus water hemp and other similar weeds that have seed heads of six inches or less.

"That's the most easily identified," Zollinger says.

Mikkel Pates is an agricultural journalist, creating print, online and television stories for Agweek magazine and Agweek TV.
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