Controlling Palmer amaranth will require timely sprays of herbicides in the future


Back in the good ole days, farmers could spray 12-inch to 18-inch tall Palmer amaranth or pigweed with Roundup and expect 95 percent or greater control. Those days are gone and probably will never return. Instead, growers must be prepared to spray early and with a combination of herbicides to have a chance of controlling those weeds in the future. Monsanto’s Greg Ferguson talked about timely sprays at a Monsanto Learning Experience event at Scott, Miss.

"The one thing we're not able to do is go in here like we used to with Roundup and kill pigweeds that tall," said Ferguson, pointing to a line between his hip and thigh. "This is not going to do that. We are going to recommend spraying at the smaller (1 to 2 inches) stages of weeds.

"We cannot go back to doing what got us into this situation to begin with, and that's spraying big weeds with only one product. And, again, we're always going to recommend these treatments following another pre herbicide or possibly in a tank mix with another post herbicide. But always with other modes of action in there besides dicamba and Roundup."

Ferguson, territory agronomist in the Mid-South for Monsanto, noted that other plots at the Monsanto Learning Center at Scott, Miss., provide ample evidence that sequential treatments of a residual herbicide such as Valor or Warrant or even XtendiMax, a new formulation of dicamba alone, followed by Roundup Ready Xtend (a pre-mix of glyphosate and the new dicamba formulation, can be extremely effective.

"There's nothing but dead weeds down there," he said. "Those treatments work very effectively."

In the video, Ferguson can be seen walking among Palmer amaranth plants that are taller than he is. As he moved to the back of one of the weed control plots to illustrate a point, one member of the audience can be heard to say "Don't get lost."

For more information about Monsanto's new dicamba-tolerant trait, go to



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