Growers in the Southeast face a scary nightmare that doesn't just occur during Halloween.

The fright is caused by glyphosate-resistant Palmer amaranth—a type of pigweed—and it's a growing nightmare, according to an Alabama Cooperative Extension news release.

“For farmers, it's actually scarier than Halloween,” says Mike Patterson, an Alabama Cooperative Extension System weed scientist and Auburn University professor of agronomy, who has been closely monitoring the rapid progression of the weed.


Desperate to contain its spread, farmers already have hand pulled resistant pigweed off some 15,000 acres of Georgia cropland.


“Workers are pulling up the entire plants—root and all—out of the ground and loading them on a wagon, then piling them up on the edge of the field,” says Patterson.


As farmers have discovered through experience, merely chopping isn't enough. Only root-and-shoot removal will work;  otherwise weeds return with a vengeance as new plants sprout from the roots.


Patterson's Georgia counterparts estimate that more than 1 million acres of cropland are infested with the resistant weeds, which are spread not only through seed but also via pollen.

The resistance is the result of repeated spraying glyphosate, the generic name for the broad-spectrum herbicide that's marketed as Roundup and Touchdown, among other names.

The advent of Roundup Ready crops, such as soybeans and cotton, that can withstand glyphosate applications, hastened the resistance. In most Roundup Ready cropping systems, growers make two glyphosate applications over the crop. In addition, they may use the herbicide as a preplant burndown.

University of Georgia researchers already are working with U.S. Department of Agriculture counterparts to identify other ways to attack the weed. They've discovered that pigweed seed may typically degrade after only three years in the soil.

“That may be one of the weak points of this weed, which is a good thing,” Patterson says. Other weed seed, such as sicklepod and morningglory, may survive for decades in the soil.


Researchers are searching for ways to keep these fields clean—managing them so that germination doesn't occur, leaving pigweed seed to decay in the soil.


“That's the only way we're going to beat this thing, unless chemical companies come up with another weed-control system similar to the Roundup approach,” says Patterson.


“But don't hold your breath on that one, because Roundup represented a once-in-a-lifetime discovery that is not likely to be repeated.”

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