U of MN Extension thinks aggressive weed has reached Minnesota

An aggressive southern weed called Palmer amaranth apparently has turned up in Minnesota for the first time, University of Minnesota Extension experts said Wednesday.

Palmer amaranth has been spreading northward in recent years from the south, where it's been a frustrating scourge for farmers. The weed can shoot up as high as 7 feet, and just one plant can produce 500,000 to 1 million tiny seeds. Herbicide is increasingly futile against it, and the weed's thick stems and deep roots make it hard to kill by hand. It has already turned up in Iowa, Wisconsin and South Dakota.

Integrated pest management specialist Bruce Potter said he saw it Tuesday after a crop consultant spotted suspected Palmer amaranth in a field in Yellow Medicine County in western Minnesota and gave him a call.

Extension agronomist Jeff Gunsolus said he was waiting to receive a plant sample Friday before officially confirming the finding, but he said he's confident it's Palmer amaranth. He said he decided to put out the information now so that farmers can check their fields before they get busy with the fall harvest.

"I know what it looks like. I've been in Tennessee. I've been in Arkansas. I've seen the plant. This is pretty definitive," Gunsolus said.

They think some seeds for the dreaded weed were in a native seed mixture that was planted in the field to benefit pollinators. Minnesota Department of Agriculture officials will be looking into whether the same seed mixture was planted elsewhere, Gunsolus said.

Gunsolus declined to identify the farm where the weed was found. He said there were just a couple plants and there's no need at this point to treat the field with herbicides. He said mowing should be sufficient and that competition from the native plant cover should help keep it from spreading much. Corn and soybean fields are mostly bare in comparison, he said, and that allows the weed to grow much more quickly in them.