A fast-growing superweed that has destroyed soybean and cotton fields in southern states is popping up in Ohio, alarming researchers and agriculture groups who fear its spread.
It’s called “Palmer amaranth,” and commonly used herbicides such as Roundup have no effect on it. It’s been found locally in Mercer and Van Wert counties.
“It goes from a few plants to Armageddon in a couple years,” said Mark Loux, a weed scientist with Ohio State University Extension.
Infestations in Scioto County last year and in Fayette County this year inspired Loux to reach out to researchers in Indiana and Tennessee and to organizations such as the Ohio Soybean Council. This new partnership mailed letters and DVDs to more than 3,000 soybean farmers and agriculture industry firms in September to warn them.
“Palmer amaranth is the worst weed problem that soybean growers in the country have experienced,” the letter said. “It is impossible to overestimate the effect it could have on Ohio agriculture.”
Loux is asking farmers to send in samples of suspect weeds to help identify and destroy infestations before they spread. “We want to get ahead of this.”
‘Weed from hell’
Roundup and other glyphosate herbicides used to kill any plant, including Palmer amaranth. That’s a problem when you just want to kill weeds. So researchers created genetically engineered “Roundup-ready” crops, including soybeans and corn, that are not affected by the herbicide.
But somewhere along the line, Palmer amaranth developed its own resistance to Roundup and evolved into a superweed that Roundup can’t touch. The result is farm fields where nothing but corn, cotton or soybeans grows along with Palmer amaranth.
With a growth rate as much as 3 inches per day, the weed steals nutrients and shades out shorter crops. It competes well with corn, too.
“There is no amount [of Roundup] that you can spray to kill it,” said Travis Legleiter, a Purdue University Extension weed-science specialist tracking Palmer amaranth in Indiana.
Farmers can kill it with other herbicides, but they have to work fast. Many herbicides don’t work once the weed grows past seedling stage, Loux said.
New plants sprout from April through August. This can double to triple herbicide costs because farmers must keep spraying new plants.
An infestation of Palmer amaranth seed in a field can destroy nearly 80 percent of the soybean plants and as much as 40 percent of corn crops, Loux said. In Southern states, farmers have lost entire fields, plowing down crops in attempts to kill the weed.
“It’s the weed from hell,” Loux said.
How it got here
Tiny Palmer amaranth seeds are picked up by harvesting equipment and mix with crop seeds that are sent to other states, Legleiter said. The weed also has been confirmed in Indiana, Illinois, Kentucky, Michigan and Pennsylvania.
In many cases, experts believe that the seed arrived in Ohio and other Midwestern states in shipments of contaminated cotton seed shipped as feed for cattle. Loux said cows pass the seeds through their digestive tracts, and the plants emerge in fields fertilized with manure.
In other cases, Palmer amaranth seeds made their way into prairie grass seed mixes that Ohio farmers planted in conservation areas and buffer strips meant to separate crops from streams and ditches.
Loux said reports and samples he has seen have come from farms in Clark, Clinton, Mercer, Van Wert, Union and Tuscarawas counties. So far, these findings were isolated, and the weeds had yet to produce seeds. Loux said he is optimistic that farmers can wipe it out in those areas.
He also said Ohio has yet to see the bigger infestations reported in northwestern Indiana and southeastern Michigan.
“We are desperately trying not to get to that point in Ohio,” Loux said.
Kirk Merritt, the director of the Ohio Soybean Council, said he hopes Ohio farmers will act quickly and eliminate Palmer amaranth.
“With early detection and with the right tools, farmers will be able to manage this,” Merritt said. “If it’s not managed, it can do severe damage.”