The old and new weed management challenges for cotton

Oct 17, 2023

Peter Dotray, Ph.D., Texas Tech University Rockwell Chair of Weed Science, speaks about weed management at the Plains Cotton Growers Annual Meeting and Cotton U event. (Journal photo by Lacey Vilhauer.)

Weeds were front and center when Peter Dotray, Ph.D., Texas Tech University Rockwell Chair of Weed Science, spoke at the Plains Cotton Growers Annual Meeting and Cotton U event in March. Dotray listed multiple challenges with managing weeds that have been issues year after year, but emphasized knowing the enemy.

"One of the most important principles of weed management is knowing the pest we’re trying to control," Dotray said. "If you don't already know, if you have a smart phone and you take a picture of a weed and if you see a little ‘I’ in the photo, and you press that button your phone might be able to help you identify the weed you’re trying to control."

Dotray said carefully thinking through which herbicides to use and why, is crucial for controlling weeds and prevent resistance in the future.

"I want to stress the importance of being diversified when using herbicide modes of action," he said. "I would challenge you to think about herbicide modes of action when you’re making decisions as to which chemistries we need. In all else being equal, let's think about the herbicide that has a different mode of action. We need to understand what our herbicides can and cannot do, but also be thinking about them in terms of how they control the weeds."

Apart from the challenges farmers face every year with weeds, Dotray also spoke about the new challenges cropping up and how to handle them. Some recent issues are herbicide availability and product shortages, a side effect of supply chain issues.

"I still feel like some of this has yet to play out this year," he explained. "But are we going to see products that are more difficult to find? We were fortunate in some ways last year because we needed less herbicides because we had less cotton."

Dotray said cotton producers should consider alternative strategies if some of the products they plan to use are in short supply. Additionally, he challenged producers to pay attention to how weeds react to herbicides that are applied and look for other ways to control them if the weeds are not being suppressed. Do not continue with the same routine herbicide applications if they are not successful anymore.

"No doubt we are seeing more and more weeds that are responding differently to herbicides that we’re using," Dotray said. "The first one that comes to mind is glyphosate or Roundup. We’re seeing more weeds and the discovery of different internal mechanisms weeds now possess that are allowing them to withstand sometimes extremely high rates of chemical. But there are also more weeds we’re finding that are resistant to glyphosate and we’re finding some weeds that seem to be responding differently to other chemistries as well—dare I say, 2,4-D and dicamba. We need to be aware of areas in our fields where the control is not as good as what we have seen in the not so distant past."

Producers have to be as adaptable as weeds are to the herbicides they apply—that is the only way to manage populations for the future.

Lacey Vilhauer can be reached at 620-227-1871 or [email protected].

• Weed identification;

• Risk of accidentally causing crop damage;

• Effective incorporation of pre-emergents;

• Timeliness of post-emergent applications;

• Thorough coverage of herbicides to soil and to the plant;

• Controlling perennial weeds and herbicide resistant weeds; and

• Understanding and using a diversity of herbicides.

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