Staying Ahead of the Weed Resistance Curve

Growers in the Southeast and Mid-South have been battling glyphosate resistant weeds for several years. Some of those resistance issues are now beginning to pop up in parts of the Southwest Cotton Belt.

According to Wayne Keeling, growers in the High Plains of Texas seem to be ahead of the curve when it comes to prevention.

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“For West Texas, Palmer amaranth has always been here, and it’s always been the number one weed,” said Keeling, professor of weed science with Texas A&M University in Lubbock. “The bad news is we started seeing pockets of resistance in 2011, and it has become more widespread during the past two years. The good news is that growers have realized what a potential problem this is.”

Keeling noted that many growers have done a good job with residual herbicides this year, especially since a high percentage of cotton varieties planted in the area still rely on glyphosate technology. LibertyLink varieties are also gaining ground, especially in irrigated fields where growers have morningglory problems.

“Use of residuals has been more common this year,” he said. “Growers have used something like Treflan or Prowl incorporated, followed by a preemerge behind the planter and a possible residual mixed with glyphosate in season. By doing that, resistance should be managed pretty well and not become a crisis.”

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Dry conditions through much of the early planting period kept many dryland growers on the sideline waiting for moisture. Memorial Day weekend brought 4 to 5 inches of rain to many parts of the state, improving the outlook for this year’s crop.

“We’ve come a long way to building back some moisture reserves in the soil,” said Keeling. “From a weed control standpoint, later planting is generally cleaner than early planting.”

In spite of the clean start, Keeling says growers need to keep a constant eye on weed control.

“We don’t know what kind of year it will be in terms of severity,” he stated. “Irrigated ground will have weed emergence throughout the season. But overall, the weed problems we’ll have will be based on how much rain we get between now and September.”

Fight Weed Resistance

FiberMax and Stoneville cotton varieties stacked with GlyTol and LibertyLink are the first-ever cotton varieties with full tolerance to both Liberty and glyphosate herbicides. With multiple-herbicide tolerance, growers can rotate two herbicide modes of action to control weeds and reduce potential for weed resistance.  

GlyTol trait technology delivers season-long, in-plant tolerance to glyphosate herbicide. The LibertyLink trait allows growers to spray Liberty herbicide in-crop for nonselective postemergence weed control before they jeopardize yield potential, even on tough-to-control weeds like Palmer amaranth, giant ragweed, waterhemp and marestail.

Liberty Application Tips

As a contact herbicide, follow application guidelines to ensure adequate coverage and maximum weed control.

  • Use nozzles and pressure that generate a medium-size spray droplet.
  • Apply Liberty at 15 GPA of water. Increase water if dense weed canopy exists.
  • Apply at ground speed of less than 15 mph to attain adequate coverage.
  • Apply when wind speeds are less than 10 mph.
  • Add tankmix partner, if needed.

For more information, visit the BayerCropScience website.

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