Witt and graduate student, Blake Patton, have confirmed the weed is glyphosate resistant in several counties and are working to determine if it is resistant to any other herbicides at a trial in Union County.

"Most of the worst cases of glyphosate resistance are in fields along the Ohio River, but glyphosate-resistant weeds are also found farther back from the river," said Rankin Powell, Union County Extension agent for agriculture and natural resources.

Witt believes growers will be able to control both Palmer amaranth and waterhemp, but it will require a different weed-management plan.

"We controlled weeds before we had products containing glyphosate, and we will control them again," he said.

While control trials for this weed are just beginning, growers can do a couple of things to minimize the spread of glyphosate-resistant waterhemp including removing the weeds while small to prevent seed production and rotate the field with corn. There is an effective herbicide against glyphosate-resistant waterhemp, but it's only available for use in corn.

Producers, who believe they have either weed on their property, should contact their county agriculture and natural resources Extension agent, so the weed can be identified.