Yellow herbicides are back in business — they’ve proved themselves this year, and they may strengthen your cotton weed control plan for 2017.
Pre- and post-harvest control efforts this fall can also help prevent runaway weed flushes next spring, says Peter Dotray, Texas Tech University weed scientist. Even though the 2016 cotton crop is either made or approaching cut-out, herbicide or manual weed control is needed now to prevent weeds from going to seed and lingering until they can germinate and explode after winter,
With a joint appointment at Texas A&M AgriLife Extension, Dotray was part of a recent AgriLife cotton quality tour in Lubbock, and discussed how old school weed control can be merged with new age herbicide programs to manage glyphosate-resistant Palmer amaranth, marestail, and other hard-to-kill weeds.
“I’m seeing the complete gamut of weed control this year,” Dotray says. “Some fields are clean late in the growing season, while others are not. Fortunately, we have tools available to help finish the weed control job and get a good start on next year.”
A good lay-by herbicide program to stop late-blooming weeds is a good start. “We are looking at fall-emerged seed that can come from late weed pressure,” he explains. “We want to eliminate that seed production. Various herbicides can be used in a lay-by program to kill late-season weeds.”
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PROLIFC SEED PRODUCTION
He suggests that farmers consider using Direx, Caporal, Valor, and other herbicides recommended by Extension or crop consultants for a lay-by program. “Weeds that emerge in early September may produce 400 to 500 seeds per plant on the High Plains. Numbers are likely higher the farther south you go.
“If those seeds happen to have herbicide resistance, we aren’t helping ourselves if we let them go. If a field is behind and weeds are still large and growing in the cotton, we need to manually pull them out or hoe them. We need to finish the job.”
Additional pre-2017 weed management should continue as winter approaches, Dotray says. “Herbicide applications should be made 10 to 14 days before the first hard frost, which should provide enough time to get herbicides established below the ground. Dicamba, Roundup, 2, 4-D, and other systemic herbicides can be effective for early control of perennials like bindweed and other weeds common to the region. That’s not complete weed control — but it’s a good start.”
YELLOWS STILL STRONG
Application of yellow herbicides can strengthen a good burndown program for resistant weeds that can no longer be handled by glyphosate, he says. “Because of resistant pigweed, marestail, and other tough weeds, a lot of growers are again using yellows. Some parts of the country have nearly eliminated the use of Treflan or Prowl, but High Plains farmers never got that extreme.”
Dotray encourages farmers to make sure yellow herbicides are well-incorporated to insure the best weed control. “Yellows don’t move in the soil,” he says, “so a lot of growers use a two-pass operation to make sure the herbicide is incorporated. That helps them get a clean start. We don’t want to plant into fields that already have weeds.”
Liberty technology was used this year in many weed control programs and showed success, he says. “An initial application of 43 oz. of Liberty, possibly mixed with Dual or Warrant, followed by a second shot at 29 oz., provided good control in many cases this year. That, plus the potential for new technologies we’ve been anticipating, should provide better weed control options.”
The new technologies, namely XtendFlex dicamba-tolerant varieties and Enlist 2,4-D- tolerant varieties, remain idled while the Environmental Protection Agency slowly ponders the safeness of the varieties.
When approved, Dotray says, the use of these technologies will require specific sprayer nozzle tips, boom height, buffer areas, and other requirements that may differ from what’s in use today.
“I like what I see in these technologies,” he says. “They provide some additional options for weed control. I’m hopeful we have them for next year.”
But until the new weed management techniques are labeled for cotton, “it still comes down to yellows, PREs, post applications, and late weed control programs,” Dotray says.
And if wet weather stalls early and in-season herbicide applications, as in 2016, look for more use of hooded sprayers, cultivators, and hoeing to keep up.