GRAND FORKS. N.D. - When Scott Knoke visited Nebraska in 2017 on a group trip to learn more about Palmer amaranth, he and others on the trip hoped the destructive weed wouldn't reach North Dakota until 2020.

But Knoke, Benson County (N.D.) Extension agent, acknowledges that was too optimistic. The state had its first confirmed case of the weed in 2018.

The task now is to keep Palmer from expanding further and establishing itself in North Dakota, Knoke said.

Knoke and Joe Ikley, North Dakota State University extension weed specialist, spoke Feb. 21 in Grand Forks on the second-day of two-day International Crop Expo. Though focused primarily on small grains, potatoes, soybeans and dry beans, the annual event also provided information on topics, such as Palmer amaranth, of general interest in agriculture.

The weed, which has been spreading north and is firmly established in Nebraska, already had been identified in South Dakota and Minnesota before it was confirmed in North Dakota.

Palmer amaranth - voted the most troublesome weed in the U.S. by the Weed Science Society of America - closely resembles pigweed and waterhemp, especially when small. That complicates proper identification of Palmer. The weed has many other advantages, too, including producing a huge number of extremely small seeds and quickly developing resistance to herbicides.

Given its danger, "We want to get ahold of this plant, stay on top of things and keep it from spreading," Ikley said. "If you find it, let us (Extension) know."

Weed scientists and others familiar with Palmer recommend a "zero-tolerance" policy that includes the use of many tools, including crop rotation.

Knoke mentioned a Nebraska farmer whose zero tolerance includes pulling Palmer plants by hand from his fields and even cutting the weeds with a scissors so it doesn't shatter and spread seed.

Agweek participated in the 2017 trip to Nebraska that Knoke mentioned during his Feb. 21 presentation at the International Crop Expo. Here's one of the news articles from the trip:

To learn more about Palmer and how to control it: