Excerpts from an Associated Press article published in the somewhat-agriculture-oriented StarTribune:
A weed strong enough to stop combines and resist many herbicides has been confirmed in South Dakota for the first time, raising concerns it could spread and cut deeply into crop production in the Upper Midwest — one of the few areas it hadn't yet invaded.And a more measured viewpoint from the Wikipedia entry:
The threat from palmer amaranth is so great that officials in North Dakota have named it the weed of the year, even though it has yet to be found in the state.
"If you think you find plants — kill it!" North Dakota State University Extension Weed Specialist Rich Zollinger said. "Don't even think. Just kill it."..
The weed some officials refer to as "Satan" has moved into the Midwest from cotton country, and was discovered in western Iowa soybean fields last year. It's native to desert regions of the southwest U.S. and northern Mexico... The plants can grow as tall as 7 feet, each one producing as much as a million seeds. Its stems can grow as thick as baseball bats...
"The big concern is, in Southern states, it has developed — quickly — resistance to a considerable amount of herbicides," Johnson said.
Amaranthus palmeri is a species of edible flowering plant in the amaranth genus. It has several common names, including Palmer's amaranth, Palmer amaranth, Palmer's pigweed, and carelessweed. It is native to most of the southern half of North America...Photo by FireFlyForest, via Eat The Weeds.
The leaves, stems and seeds of Palmer amaranth, like those of other amaranths, are edible and highly nutritious. Palmer amaranth was once widely cultivated and eaten by Native Americans across North America, both for its abundant seeds and as a cooked or dried green vegetable. Other related Amaranthus species have been grown as crops for their greens and seeds for thousands of years in Mexico, South America, the Caribbean, Africa, India, and China. The plant can be toxic to livestock animals...
Palmer amaranth is considered a threat most specifically to the production of genetically modified cotton and soybean crops in the southern United States because in many places, the plant has developed resistance to glyphosate.