The Minnesota Department of Agriculture (MDA) has found a new route for the invasive weed Palmer amaranth to enter and spread through Minnesota in grain and seed screenings that are used as feed.

After an investigation into a Palmer amaranth find in Redwood County, the MDA determined the weed found its way into a soybean field through cattle manure. The cattle had been fed screenings from contaminated sunflower seed. The MDA has since sampled screenings throughout the state and has found Palmer amaranth seed in numerous screenings. 

Some of those discoveries have contained as much as 250 Palmer amaranth seeds per pound of screenings.

“This newly discovered path for Palmer amaranth shows the difficultly in stopping the spread of invasive weeds,” said Thom Petersen, MDA commissioner, “However, the MDA is committed to continuing our monitoring of screenings, educating crop and livestock farmers about this development and helping eradicate any new finds.”

Palmer amaranth was first discovered in Minnesota in 2016. Since then, it has been found in six counties in the state. However, because of eradication efforts at confirmed sites and a strong partnership with the U of M Extension Service, no Palmer amaranth has been found in subsequent growing seasons. Palmer amaranth can grow two to three inches a day, typically reaching six to eight feet, or more, in height.

Left uncontrolled, a single female Palmer amaranth plant typically produces 100,000 to 500,000 seeds. It is resistant to multiple herbicides, can cause substantial yield losses and greatly increase weed management costs in soybeans and corn. The MDA is encouraging farmers, especially those who have manure from feedlots on their land, to report suspect plants.

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– Photo courtesy of the Minnesota Department of Agriculture