Palmer amaranth, an invasive plant species, was not in Minnesota when researchers began predicting its spread into the state.

The plant is native to the southwest United States and Mexico, but has been moving into southern Minnesota due to rising temperatures. A study about palmer amaranth was published Feb. 20 by researchers at the University of Minnesota's Department of Plant and Microbial Biology, who are part of a larger network looking to address the impending impacts of Palmer. 

“Palmer likes these warmer temperatures and that's something that's very common in the central Midwest that will become more common in the upper Midwest ... that's going to increase habitat suitability over all of Minnesota,” said Ryan Briscoe Runquist, lead researcher of the study. 

Briscoe Runquist said Palmer is resistant to most herbicides, so the tactics to eradicate it remain more old-fashioned — researchers survey the land by hand to find the species. 

“They'll [hand]-pull the plant, put it in plastic bags, destroy it in a way that none of the seeds can survive,” Briscoe Runquist said. “Then they'll torch the area around the plant so that any seed that potentially fell won't survive, and they resurvey those areas where they found it for the next couple years.”

Although Palmer is typically not significantly damaging to prairies and grasslands, researchers are concerned about the damage it causes to farmlands.

“In some places in soybean production, [Palmer has] caused up to an 80 percent yield loss and in corn its been, in the worst case, up to a 90 percent yield loss,” said Robert Venette, director of the Minnesota Invasive Terrestrial Plants and Pests Center at the University. He also said some populations of the weed have developed herbicide resistance.

Palmer is currently limited to southern Minnesota because of its temperature adaptability, but University Extension invasive species researcher Jeffrey Gunsolus emphasized that total Palmer eradication is the main goal to mitigate its spread. 

“Due to the genetic diversity of this particular weed and its adaptability, I think the tactic of keeping it from getting a foothold is still a very valid approach to keeping this weed from becoming a very expensive problem,” said Gunsolus. 

Researchers hypothesize that Palmer spread to Minnesota after unusable farmland was converted into prairies from past conservation efforts. Palmer found its way into conservation plots via Palmer-exposed equipment, livestock and human activity. 

For citizens in areas where Palmer has already been found, Vinette said it is important for people to not be timid about identifying the species. 

“It's very much like public health in the sense that when people report these finds of invasive species, it's actually very helpful because there are resources that can be brought,” said Vinette.

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