Glyphosate resistance has become a widespread problem across the US. In Oklahoma this includes glyphosate resistance in Palmer Amaranth, Kochia as well as some other weeds. As a result Roundup is being used on a lot less acres than five years ago. Noseworthy said he is seeing multiple glyphosate resistant weeds in a single field. This is leading to the use of alternative herbicides to control those weeds as well as the development of new technologies to fight back.
The Xtend and Enlist technologies, marked by Monsanto and Dow AgroSciences, respectively, are likely to be available to Oklahoma cotton and soybean farmers in the near future. The Xtend technology will allow for in-crop use of dicamba and glyphosate (Roundup) in soybean and these same herbicides along with glufosinate (Liberty) can be used in cotton. The Enlist technology will provide both soybean and cotton tolerance to a premix of 2, 4-D and glyphosate (Enlist Duo) and glufosinate. Another technology that is likely to soon be available is Inzen grain sorghum which has tolerance to nicosulfuron (Zest), a herbicide that has traditionally been used in corn for johnsongrass control as well as annual grasses. For each of these technologies, strengths of the weed control programs will be emphasized as well as the ways these technologies can be protected from the development of herbicide resistance.
In looking at weed control going forward, Noseworthy recommends a integrated approach to managing resistance. It starts with a clean field by using pre-emergence herbicide as well as post emergence application with a residual herbicide. He also emphasized the need to prevent seed production.
"If you have a 24D resistant Pig Weed or Kochia or whatever the weed might be, if it sets seed you are going to quickly lose the technology and there is no way to get back in front of it once you have a few of those plants escape and produce seed," Noseworthy said.
Seed production is at the crux of the situation. Noseworthy said seed production ultimately leads to resistance. If there is no seed production in the field, there is ultimately no risk of herbicide resistance. While its not feasible for farmers to walk fields, he said its important farmers have a very robust weed control program and hopefully there will be only a few escapes and those can be hand removed before they produce seed.
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