Holding Their Ground Against Pigweed
July 7, 2015 From Cotton Grower Magazine – July 2015
The rolling hills around northeastern Alabama and south central Tennessee have a long history with cotton production. Families have farmed this area for generations – proud people who are determined to stay with cotton, even when the odds may not be stacked in their favor.
“There are some stubborn folks in this part of the world,” laughed Nathan Silvey. “All they do is grow cotton.”
Silvey, a sales agronomist with Madison County Co-op in Hazel Green, AL, knows the area and its growers well. He’s spent roughly 25 years working closely with them to help solve production issues and tease the best yields out of their fields.
Most recently, the challenge has been glyphosate-resistant Palmer amaranth, or pigweed. It’s a continuing battle – one well suited to the stubborn nature of the area’s growers.
“I started seeing some issues with pigweed around 2003,” said Silvey, “even though we weren’t completely sure what we were dealing with at the time.”
Marestail was the primary problem for years, and Silvey admits that growers now have a good handle on that problem. But in the last five years, pigweed has become such a dominant issue in the area that growers have been forced to adjust everything from variety selection to their weed control programs to help keep it in check.
Randy Brown and his father, Noel, farm 2,200 acres around New Market, AL, with 1,400 acres devoted to cotton. Pigweed pushed them to look at all options for control.
“We used to be all cotton, but we added some wheat and soybeans to help us diversify a bit,” said Brown. “It helps us with the pigweed control, and I think we’ve started seeing better cotton yields since we started the rotation. We’ve consistently done two bales, but have also seen some 2.5 to three bale cotton in the last few years.
“We first noticed the pigweed issue about four to five years ago,” he continued. “We’ve been aggressive with our treatments for the last three years.”
That aggressive approach starts with a first burndown, which featured LeadOff, Sharpen and Roundup this spring. A second burndown of Gramoxone, Cotoran and Caparol behind the planter helped clean up any small escapes and gave young cotton a chance to get up and ahead of the pigweed growth.
The Browns – like many growers in the area – also now rely on varieties that are tolerant to glufosinate, or Liberty, as part of their total production program. It allows them to spot treat pigweed hotspots with an over-the-top application of Liberty as needed. They have also used Gramoxone under a hood for in-season cleanup. And there’s always a sharp hoe handy.
“The Gramoxone, Caparol and Cotoran tankmix behind the planter is the great equalizer,” said Brown. “We’ve had fewer weed issues since we started that, and it’s a common practice around this area now. Two burndowns is a necessity. Otherwise, you’ll spend a fortune trying to control this stuff.
“I’d rather stay ahead of the pigweed than try to clean it up,” he added. “Later on, you’re pretty much suppressing weeds instead of killing them. If you start clean, it makes everything much better, and you have so many more options.”
Jimmy Brannon – who grows 2,200 acres of cotton in and around Elora, TN, with his son, David – agrees.
“We probably had crews out hoeing for three years before we started doing something about the pigweed,” he recalled. “We do a little bit of everything for weed control. We’ll try anything that we think will help.”
That “anything” includes two rounds of burndown, strategic applications of Liberty, other post-emergent treatments under a hood, and hoeing. The Brannons also pull out a wick bar to spot treat their acres as needed. It all seems to work.
“We expect to see 1,200 to 1,500 pound yields in our better fields,” added Brannon. “We did it last year.”
Exploring New Options
Silvey admits that the renewed reliance on residual herbicides caught some growers off guard.
“Roundup Ready made us forget about the cotton injury that goes along with some residuals,” he said. “At first, people were getting a little excited about it. Now they know that after a week to 10 days, it’s all okay.”
The biggest change for the area has been the widespread shift to Liberty-tolerant varieties. This is the first season that growers have had the choice to plant PhytoGen, Stoneville’s GLB2 or GLT varieties, or the new Bollgard II XtendFlex options from Deltapine.
“We’re finding that we just can’t use Roundup Flex varieties anymore,” said Silvey. “It’s hard to sleep at night if you don’t have the glufosinate tolerance out there.”
Another complicating factor for growers is Verticillium wilt, which, says Silvey, is “pretty bad” throughout the area. With that factor in mind, he planted a test plot to help judge cotton varieties for Verticillium tolerance. The plot contains 28 different glufosinate-tolerant varieties side by side, including all available Stoneville and PhytoGen varieties, the Deltapine XtendFlex options and several new Deltapine experimental varieties still under evaluation.
“We decided we had an opportunity to also look at glufosinate tolerances in these cottons and see what these varieties could take,” explained Silvey. “We tried to hurt it – by the label, of course.
“All varieties showed some degree of damage after seven days,” he continued. “We looked again at 14 days and saw that most of them tolerated the higher rates pretty well. That tells us that if we have a problem, we can get aggressive.”
However, he noted, the Verticillium ratings will be equally important for many growers. “For some fields, the seed choice may be made based on the severity of Verticillium wilt first, then weed control,” he said.
The ongoing battles with pigweed will continue to try growers’ patience. Yet there are also concerns about the longer-term impact on cotton in the area.
Brannon also operates Elora Gin, which ginned about 25,000 bales last year. “From a ginning perspective, there is a concern that pigweed could continue to run cotton acres out of the area,” he said.
But the prospect of additional weed control options for pigweed raises hope for the near future. Although growers rely on all three cottonseed companies, it’s no secret that the northeast Alabama area has historical ties to Deltapine. And the prospect that dicamba will be approved for over-the-top use in the Bollgard II XtendFlex varieties for next season feeds their anticipation.
“Growers in this area are as excited about dicamba use as we were about Roundup Ready cotton,” said Silvey. “I think this technology will change the way we burn down weeds in cotton. We still have a few problems with certain types of morningglories, and the dicamba will also help with that.”
For now, using the tools they have at hand, Silvey is pleased with the fight his “stubborn” growers are putting up against pigweed.
“Last year, I knew where the weeds were,” he said. “I’ve gone back this year to see how bad the pigweed pressure might be, and it’s not there yet. We’re holding them back.”
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