MINNEAPOLIS — It's a beast of a weed, creeping north into the Midwest from cotton country.
Palmer amaranth can shoot up as high as 7 feet, and just one plant can produce up to a million seeds. Herbicide is increasingly futile against it, and the weed's thick stems and deep roots make it hard work to clear by hand. It can slash yields and profits when it gets out of control.
Midwestern weed scientists are sounding the alarm because the plant recently turned up in Iowa and can cause deep losses in corn and soybean yields.
"This is not just a nuisance. This is a game-changer," warned Purdue University weed scientist Bill Johnson, whose state has well-established pockets of the plant.
The weed isn't known to have a beachhead as far north as Minnesota, but University of Minnesota Extension researchers have already advised their farmers to be vigilant.
"I'd like to say we're not going to have the problem, but we're not going to say that," weed scientist Jeff Gunsolus said.
Cotton growers in the South already spend about $100 million a year to try to keep it out of their fields, University of Georgia scientist Stanley Culpepper said.
"This is a crop robber," said W.C. Grimes, who farms 1,600 acres of cotton, peanuts and corn near Twin City in eastern Georgia. "It will steal your profit. It will choke your cotton out, and anything else you're trying to grow."
Grimes said he was losing up to 200 pounds of cotton per acre until farmers learned the key to overcoming Palmer amaranth's resistance to glyphosate — sold under brand names like Roundup — was to continuously change herbicides.
His advice to Midwesterner farmers: Keep your eyes open and do whatever it takes to kill the weed as soon as it turns up.