When Monsanto’s Bollgard II XtendFlex cotton system enters the market—possibly as soon as 2015, pending regulatory approval—the technology will offer “another valuable tool” to improve weed control efficiency, especially in light of growing concern over herbicide resistant weed species.

“But it is no silver bullet,” says Monsanto’s John Everitt. “We need to use pre-emergence herbicides, too. We know we have herbicide-resistant weeds in West Texas, so farmers who have relied exclusively on glyphosate need to add additional modes of action into their program.” 

Everitt, speaking to a group of farmers at a recent Deltapine field day near Seminole, Texas, said Monsanto’s new weed management system—transgenic varieties that include tolerance to both glyphosate and dicamba herbicides in soybeans and glyphosate, dicamba and glufosinate in cotton —will offer farmers a new option to manage resistant Palmer amaranth—and other species—but insists that producers must follow a “systems approach,” to control weeds in cotton.

Farmers also heard about two new varieties, scheduled for release for 2014, that are resistant to root-knot nematodes.

Everitt said new weed control technology will allow over-the-top applications of a glyphosate and dicamba pre-mix to increase weed control spectrum, including glyphosate-resistant pigweed.

 

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The new products are designed to provide more consistent, flexible control of “resistant- and tough-to-control weeds” and help maximize yield potential.

Going back to pre-plant incorporated or pre-emerge herbicide applications is an important part of the system. Materials such as Treflan and Prowl will play a crucial role. “It’s cheap insurance,” Everitt said, “and effective against pigweed. But producers have to get it incorporated.”

Applying Prowl one to two weeks before planting with about three-fourths inch of irrigation is one good incorporation method. Farmers can chemigate with Treflan.

From there, growers may choose, based on field history and previous weed pressure, to add other residual herbicides and then spray over-the-top with new Roundup and dicamba products. “We will offer two new chemistries in 2015,” Everitt said, “that include glyphosate and a low-volatility dicamba (Roundup Xtend and XtendiMax).” These will be part of the Roundup Ready PLUS weed management solutions program.

But new products come with new application parameters. Managing drift and maximizing on-target application is a crucial part of the system and requires that farmers follow application requirements including:

  • Use low volatility formulations.
  • Select nozzles that produce very coarse or ultra coarse spray droplets.
  • Wind speed should be between 3 and 10 miles per hour.
  • Boom height should be 20 inches above the crop canopy.
  • Maintain a spray buffer as required by label to protect sensitive areas.
  • Use a drift reduction agent.
  • Apply at least 10 gallons per acre.
  • Triple rinse for adequate tank clean out.
  • Maintain a ground speed less than 15 miles per hour.
  • Spray when weeds are small—less than 4 inches.
  • Use sensitive crop registries such as DriftWatch and others.
  • Use residual herbicides to improve resistant weed management.

Everitt said volunteer cotton control should not be a factor with addition of dicamba to the system. “Most farmers are not spraying dicamba to kill volunteer cotton. Use gramoxone or cultivate,” he said.

He also said that Bollgard II XtendFlex cotton is “not cross-tolerant to 2, 4-D,” so growers cannot spray 2, 4-D on Xtend cotton.