Texas High Plains cotton farmers recently took advantage of a day too wet for field work to stop by the annual Deltapine field day on Steve Chapman’s Lorenzo cotton farm – where it was too wet and muddy to ride through the demonstration plots.
Organizers moved presentations inside where the sound of rain beating on a tin roof had Deltapine and Monsanto representatives speaking a bit louder than usual but also reminded growers that the drought, at least for a time, has been interrupted.
Speakers discussed the increasingly difficult problem of controlling glyphosate-resistant weeds, water-efficient cotton variety research, the Roundup Ready Xtend crop system (including concerns with drift and tank cleanout) new varieties in the pipeline and an ongoing search for root-knot-nematode-resistant varieties.
“Weed management has been the No. 1 topic in cotton this year,” said Dallan Maas, Monsanto area business manager. He said glyphosate-resistant weed problems, mostly pigweed, showed up in the Southwest later than they did in the Southeast and Mid-South, which gave farmers, weed specialists and industry representatives a little time to learn from other areas’ experience.
“We also have new tools to manage weed issues,” Maas said. Tools will include new technology with varieties tolerant to Roundup, Liberty, dicamba and 2, 4-D herbicides. Dicamba and 2, 4-D tolerance will not be included in the same varieties.
Monsanto’s package is the Roundup Ready Xtend Crop System. “It’s not a silver bullet,” Maas said. “It has to be part of a program.” That program will include pre-emergence and preplant incorporated herbicides, multiple modes of action products for postemergence treatment and the new technology.
“For the immediate future, however, most growers will rely on “existing technology,” said Larry Martin, area sales manager. “We will not have enough Xtend seed to meet demand for 2015, so we will have to make existing technology work, and we can’t just depend on Roundup.”
Martin surveyed the audience and found that “most had trouble controlling weeds this year.” In addition to new tools on the horizon, Martin recommended that growers get back to basic weed control strategies, beginning with: “Start clean. Use a burndown in February or March and then a pre-emerge material behind the planter.”
He said incorporation is critical for yellow herbicide efficacy. “Yellow herbicides are still as effective as they were years ago but you have to incorporate them.” He said incorporation may take a little more time and cost a little more money. Chemigation and rainfall are alternatives to mechanical incorporation.
He said weeds sometimes germinate “in the drill where we can do little about it.”
At 30 days after planting, producers apply their first Roundup treatment. “By then, pre-emerge (white) herbicides are tapering off. But yellows are still active. Roundup should kill everything but resistant weeds. If we leave it out, we will see grasses.”
Around Aug. 1, the second Roundup application goes out, “maybe under a hood,” Martin said. “That should take us all the way to harvest, and we expect to see improved harvest efficiency and fewer weed seeds to germinate next year.
“Even with the new technology, we want to do the same thing,” he added. “We don’t want to over-rely on one technology; we need to rotate chemistry.”
He said managing weeds should be a community effort. “If 80 percent of farms follow an effective program but 20 percent do not, we will continue to see a resistant-weed problem.”
He also noted that Monsanto offers rebates on some “endorsed herbicides,” including Warrant, Valor, Dual Magnum, Gramoxone SL, Caparol, Cotoran 4L, Direx 4L, Pyrimax 3.2L and Chateau (labeled for use in Arizona).
John Everitt works with Monsanto’s Xtend chemistry and says the new technology will offer farmers new options for dealing with glyphosate-resistant weeds. “Weed resistance problems have grown every year as growers continued a reliance on Roundup only,” Everitt said.
Anticipated recommendations for Bollgard II Xtend Flex weed management in West Texas would include:
- Burndown or tillage in early spring with a yellow herbicide such as Prowl;
- At planting application of Warrant plus Direx or dicamba;
- Post application 1 of dicamba/glyphosate pre-mix 10 to 14 days after planting;
- Post application 2 with dicamba/glyphosate pre-mix 14 to 20 days after post 1;
- Layby with Roundup PowerMAX plus Direx prior to crop canopy closure.
East Texas recommendations include these options:
- Burndown or tillage. Herbicide options would be Reflex or Valor plus dicamba or 2, 4-D in early spring, preplant;
- At planting application of Warrant plus Cotoran or dicamba;
- Post application 1 with dicamba/glyphosate pre-mix or dicamba plus Warrant 10 to 14 days after planting;
- Post application 2 goes on 14 to 20 days after post 1 with Liberty plus Dual Magnum or dicamba;
- Layby with Roundup PowerMAX plus Direx prior to crop canopy closure.
“We are not taking out any of the residual herbicides,” Everitt said.
Growers and other industry observers have expressed concern over potential for spray tank contamination with dicamba or 2, 4-D, putting other crops or non-tolerant cotton in jeopardy. “Triple rinse is crucial,” said Chet Cook. “If the sprayer is not thoroughly rinsed, herbicide residue can remain in various sprayer components,” he said. He also cautioned growers to pay close attention to screens, nozzle tips and hoses.
The triple rinse procedure includes the seven steps below:
- Drain the spray tank, sump and boom immediately after spraying;
- Clean using a commercial cleaning solution, agitate and recirculate;
- Flush hoses, spray lines and nozzles with clean water;
- Repeat step 3 two more times;
- Remove and clean nozzles, screens and filters with a commercial cleaner;
- Drain sump, filter and lines and (properly) dispose of all rinsate;
- Rinse complete sprayer system with clean water.
Spray drift precautions
Spray drift to vulnerable crops, such as peanuts and non-tolerant cotton, also causes concerns. Droplet size is a crucial factor in reducing potential for drift. Choosing nozzles that produce large droplets, while maintaining adequate coverage, is critical, say Monsanto experts.
Also, sprayer speed should be 15 miles per hour or less; wind speed should be between 3 and 10 miles per hour; boom height should be 20 inches above the crop canopy; a labeled buffer should be used to protect sensitive areas; nozzles and operation pressure should produce coarse droplets; spray weeds that are 4 inches tall or less; and use low volatility formulations.
Aerial application is not approved for Xtend.
Xtend technology also includes VaporGrip technology, which reduces potential volatility of dicamba. Producers can’t use ammonium sulfate products, however, because they negate VaporGrip.
Variety updates included presentation on water use efficiency trials. Doug Jost said Monsanto has been working since 2008 to determine “how varieties perform based on the amount of water they receive.” He’s working with replicated trials comparing various water regimes—dryland, 30 percent of evapotranspiration (ET) replacement rate, 60 percent ET and 80 percent ET—with several Deltapine varieties to determine how those varieties respond to various levels of moisture stress.
He said three new releases show no significant differences but all three topped the best Deltapine dryland variety currently available. He said 1410 and 1421 also responded well when they received more water and reduced the cost of irrigation by about $15 per acre.
Agronomist Eric Best said four or five varieties are awaiting regulatory approval for 2015. “Bollgard II Roundup Ready Flex will take the lion’s share of acreage across the board next year,” he said.
Jorge Cuarezma, Monsanto technology development, said two varieties currently in trials are promising options for root-knot nematode resistance. “We’re using molecular marker technology,” he said. “These are not transgenic varieties.”
He explained that resistance comes through “interrupting the nematode’s life cycle. We are looking for resistance; we do not have immunity. The challenge,” he said, “is to achieve resistance and maintain yield.”