What is in this article?:
- Palmer amaranth resistance spreads in Texas High Plains
- Begins on two fronts
• Glyphosate-resistant palmer amaranth is spreading in west Texas.
• Large areas in central Texas have resistant common water hemp.
• Horror stories are not inevitable.
Begins on two fronts
Baumann said resistance management begins on two fronts: relying on more than a single method of weed control and starting to manage for resistance before the problem arises.
He is not saying stop using glyphosate. Just use it in combination with other herbicides with different modes of action, and 100 percent control is possible with combos of available herbicides.
“Roundup is too good on too many weeds to pull it out of a program, but use it as one of the tools and not the only one,” he said.
This multi-front attack plan begins with a pre plant incorporated, soil applied herbicide.
Trifluralin (Treflan) and pendamethalin (Prowl) are two of the available products that could be used in cotton programs.
Some other approved products that also are soil-active herbicides are Staple, Cotoran, Dual and Warrant. Utilize these with early or mid-season post planting herbicide applications.
“I know farmers don’t want to spend more money fighting a problem they don’t yet have,” he said.
“But my argument is, even if you don’t ever have the resistance problem, you are just ensuring there is no competition to your crop from weeds from day one if you use a soil-active herbicide. Those first eight to 10 weeks are the most critical in keeping (fields) weed-free to prevent competition and yield loss.”
The other option, he said, is to switch to LibertyLink cotton, which is tolerant to the herbicide glufosinate (Liberty). This product has much of the same spectrum of weed control as glyphosate, but has a different effect on the weeds, which makes it a sound alternative to glyphosate.
The application timing on pigweed, however, is much more critical in terms of weed size for treatment with Liberty, Baumann warned, so treatments must be applied to small (less than 4 to 5 inches) Palmer amaranth or common water hemp.
“We have to have more than one mechanism to manage the anomalies,” he said.
“The resistant plants have probably always been there, but when you eliminate the competition with a highly effective herbicide like glyphosate, they begin to flourish.”
The problem can be even worse for producers who plant back-to-back Roundup Ready cotton and Roundup Ready corn, if they continue to use only glyphosate herbicide on either crop, Baumann said.