The invasive weed Palmer amaranth was recently found in a fourth Minnesota county.

Minnesota Department of Agriculture officials confirmed finding the weed in Douglas County. MDA also has found the weed in Lyon, Todd and Yellow Medicine counties.

MDA officials discovered the Douglas County infestation while investigating plots in Todd County that were confirmed Palmer-positive two weeks prior. MDA’s investigation is currently focusing on the source of the weed seed, according to Allen Sommerfeld, MDA communications.

The three sites found to contain Palmer amaranth in Douglas County were planted this year by one individual, Sommerfeld says, and were mowed in September. To contain the weed’s spread, MDA is considering some spot burning yet this fall and additional eradication efforts next year.

Geir Friisoe, director of MDA’s plant protection, says the department was fortunate to find the infestations early on. “Through early detection, we can develop an effective eradication plan and manage these small, isolated sites before the weed spreads beyond the plantings," he says.

MDA officials note that all of the Minnesota infestations have been found in conservation plantings. None of the weeds have made their way into row crop fields, which MDA says could be economically harmful. Palmer amaranth can cause substantial yield losses and greatly increase weed management costs in soybeans and corn.

It is illegal to sell any seed in Minnesota that contains Palmer amaranth, MDA officials say. Dealers must test seed lots before putting them on the market. Proper seed labeling laws must also be followed.

Friisoe says landowners should buy seed mixes from reputable seed dealers to help curb the spread of Palmer.

“Ask the dealers to see the blending paperwork and lab certification results,” he says.

MDA officials say they are having success in eradicating the Palmer amaranth that was found in Lyon and Yellow Medicine counties in 2016. Thirty-three sites were identified with the invasive weed. Last fall and this year, MDA worked to eradicate it with burning and herbicide treatments, Sommerfeld says.

“We’ve since recovered a small number of Palmer plants on just three sites,” he adds. “Work will continue on eradication next year.”

MDA officials expressed confidence in managing the new Palmer amaranth sites in Todd and Douglas counties, based on their experiences thus far in Lyon and Yellow Medicine counties.