Growers across the Southeast wondered what would replace Deltapine’s 555 in their cotton fields.
Few figured it would be Palmer amaranth, the worst of the worst pigweed.
The virulent weed that’s now popping up with resistance to both glyphosate and ALS herbicides dominates conversations and cropping decisions in those areas where it’s overrunning fields. In other areas, resistant marestail is a deal breaker.
For some, that’s meant a move away from cotton.
• Growers look to weed control when deciding cropping plans.
• By 2013, 1 in 4 acres may have glyphosate-resistant weeds.
• Agronomics still underpins every seed buying decision.
“The acreage of corn in the South has taken a fairly good-sized jump in the last couple years, not surprisingly in conjunction with a drop in cotton acres,” says Mike Hughes, Pioneer’s agronomy research manager for the Southern business unit. “From my standpoint, corn would be an attractive crop to these guys that have been growing cotton and have seen a rise in resistant weeds.”
Corn is attractive for fields overloaded with weeds in large part because atrazine is a powerful weapon against weeds. Syngenta technical brand manager Chuck Foresman points out that atrazine has high efficacy against the toughest weeds — pigweed, giant ragweed, morningglory — and enhances grass control in pre-mixes.
“Atrazine has great residual performance,” Foresman says. “Without residual, growers would be out there making an application after every rainfall.”
While the heaviest glyphosate-resistant Palmer amaranth infestation is in central Georgia, Foresman cautions growers to take steps now to thwart resistance. Nine glyphosate-resistant biotypes are identified in 22 states at this point, he says.
“We could end up with 1 in 4 row-crop acres infested with a glyphosate-resistant weed by 2013,” Foresman warns.
Growers who haven’t found resistant weeds in their fields still focus their cropping decisions on agronomic performance of a cotton variety.
“If the weed control is there, it’s just having a variety,” says University of Georgia Extension agronomist Jared Whitaker. “If growers use pre- and postemergence herbicides, then they’re already ahead of the ballgame.”
The key is to weigh both factors — regardless of whether those weeds that grow like teenagers are in a given field.
“Growers certainly do not want to give up any agronomic performance or weed control potential,” says Andy Hurst, Bayer CropScience product manager for herbicide-tolerant traits and Ignite herbicide. “They want the best solution for weed management that’s going to yield the most.”
Another factor in choosing cottonseed is price, including technology fees, and herbicide and insecticide costs. The graph offers a comparison of prices for the technology packages offered based on 2009 prices.
As always, growers have a deep bench from which to pull their lineup for the 2010 season.
The list at left includes the top two variety picks from each of the four major cottonseed lines — Deltapine from Monsanto, PhytoGen from Dow AgroSciences, and FiberMax and Stoneville from Bayer CropScience. Expect more releases as the season nears.
DOCTOR OF PALMER AMARANTH: UGA Extension agronomist Jared Whitaker wrote his doctoral dissertation on glyphosate-resistant pigweed. He advises cotton growers to start with a combi-nation of preemergence herbicides. Then, he says, “you still need a Dual or Staple mixed with Roundup or Ignite [depending on variety] applied early for control to last. These early post-[emergence] residuals extend that window of control so that you can get to layby.”
Growers swing at pigweed with Ignite on WideStrike
It’s controversial. It breaks rules, but not laws.
Some call it a rescue operation. Some call it salvation.
It’s the practice of using Ignite on cotton with the WideStrike technology.
Ignite is a glufosinate-based herbicide offered by Bayer CropScience and labeled for cotton and several other crops. WideStrike is a proprietary two-gene insecticide technology offered in PhytoGen cotton varieties by Dow AgroSciences. Neither company endorses using Ignite on WideStrike.
“What we have in the marketplace is a semi-tolerant event to Ignite, but one that’s not up to specifications as far as Bayer’s criteria for commercial tolerance,” says Andy Hurst, Bayer CropScience product manager for herbicide-tolerant traits and Ignite herbicide. “Bayer does not warrant the use of Ignite over the top of PhytoGen, WideStrike, varieties.”
• Growers take risk when using Ignite on WideStrike cotton.
• Ignite burns WideStrike and kills other cotton.
• Ignite kills Palmer amaranth that’s shorter than 3 inches.
Neither does Dow.
Dow General Manager and PhytoGen cottonseed market specialist Duane Canfield says, “All risk of crop damage and loss associated with the use of GA [glufosinate ammonium] herbicides on WideStrike cotton remains solely with the user.”
For some growers in Macon County, Ga., that’s a risk they’re willing to take.
Although neither Macon County Extension agent Jeremy Kichler nor the University of Georgia recommends Ignite on WideStrike cotton, Kichler shares some of the management tactics his growers are adopting.
Growers are using the 29-ounce rate of Ignite, applied with a flat fan nozzle, he says. They’re also using a residual, whether it’s Treflan, Prowl, Cotoran, Staple or Reflex. And some are mixing Dual at 1 1/3 pints with Ignite, even though Kichler notes that mix increases burn on the cotton leaves.
Essentially, he says, Ignite gives “a little wider window to get your residuals activated, which can be very beneficial especially in dryland production.”
“You still have to be timely with it,” he says. “Growers need to spray when Palmer is 3 inches or less.”
Some growers are using FiberMax LibertyLink varieties. The ones who moved to WideStrike did so to be able to continue using Roundup on grasses, Kichler says. “It’s about flexibility,” he says.
Bayer is developing cotton varieties with resistance to glyphosate and glufosinate. Southeast growers can look for GlyTol plus LibertyLink varieties stacked with TwinLink, a two-gene Bt trait, in 2012.
HOME OF G-R PALMER: Jeremy Kichler showed up at the University of Georgia Extension office just in time for the war that threatened to end all cotton fields: farmers vs. glyphosate-resistant Palmer amaranth. An unconventional approach — using Ignite, which is designed for LibertyLink varieties, on varieties with WideStrike, which is a two-gene insecticide technology — is helping growers survive.
This article published in the January, 2010 edition of SOUTHERN FARMER.
All rights reserved. Copyright Farm Progress Cos. 2010.