Liberty Link cotton producers will face some new wrinkles in 2006, including a new formulation of Ignite, the herbicide that can be applied over the top of Liberty Link varieties.
“One thing that will change is that the formulation we're going to be using in cotton will no longer be the old Liberty formulation,” says Keith Vodrazka, technical service representative for Bayer CropScience. “It will be Ignite 280. The 280 stands for grams per liter, so the active ingredient is going up.”
Vodrazka said the new product will contain 2.34 pounds of the active ingredient glufosinate ammonium per gallon instead of the old 1.67 pounds in the 200 SL product. The change means the Ignite use rates will go down.
“The rates will be 22 to 29 ounces as opposed to the old 32 to 40 ounces,” he told farmers and crop consultants attending the Regional Cotton Pest Management Workshop at the Memphis, Tenn., Agricenter. “The product is formulated with a surfactant and is a non-selective, contact herbicide that should be applied according to weed size.”
Because the herbicide's effectiveness is highly dependent on coverage, Bayer CropScience is recommending a higher spray volume — 15 to 20 gallons of water per acre by ground and 2 gallons by air. Bayer is also making specific recommendations on spray tips and nozzles.
“What we're looking for — and the label will specify — is a medium droplet, not a big droplet that you might get with an air induction tip,” he said. “Some of the air induction tips will work as long as you use enough high pressure to ensure you that you have a medium droplet.
“With a contact herbicide like Ignite, getting coverage on the growing point of the weed is absolutely essential because Ignite has very limited systemic movement.”
Bayer will recommend farmers match the new rates for Ignite to weed size. Growers can now apply up to 58 ounces per season, which will be comparable to the total season use limit of 80 ounces with the old formulation.
“If you have a weed population with mixed species, you can go with the lower rate of 22 ounces as long as the weeds are in the size range on the label,” Vodrazka says. “Go with 29 ounces if you have larger weeds in that mix.”
One of the challenges for the Liberty Link/Ignite system will be controlling pigweed, he notes. “You can't let pigweed get up to your waist or even halfway to your waist before controlling them with Ignite. The label says to spray at 3 or 4 inches, and that's important.”
The other challenges for Ignite will be heavy grass populations and nutsedge, “but there are ways to control them.”
The company will urge producers to follow a “systems” approach to control the weeds in Liberty Link cotton. The approach includes applying a pre-emergence herbicide to help with the timing of the in-season Ignite treatments.
“A pre- herbicide would certainly be a good recommendation because it can improve the grass and pigweed control and make that timing of Ignite at the one-, two- or three-leaf stage less critical,” Vodrazka said. “It can give you a little more time to make that first Ignite over-the-top spray and allow the grower to avoid early season weed competition.”
If the grower does not use a pre-emergence herbicide, Bayer will recommend the first Ignite over-the-top application be made at one- to two-leaf cotton. If the grower applies a pre-, the first Ignite spray could be delayed to the three- to four-leaf stage of the cotton.
“A study by Jim Burlison and John Willcut at North Carolina State University shows that about two weeks after planting you starting running into weed competition that will cost you yield,” he said. “If you delay that application for even 10 days, you have a 30 percent drop in yield.”
Dual Magnum or Staple can also be applied over the top with the first Ignite application. Bayer says the tank mix of the two herbicides will provide residual control of later-emerging weeds and enhance the overall weed control with Ignite.
Bayer CropScience is seeking Section 24(c) special local needs labels and a full federal label for an expanded seasonal use limit for the new Ignite formulation.
“The use limit of 80 ounces per acre was a hang-up for guys who wanted to make more than two applications of 40 ounces of the old formulation,” Vodrazka said. “That would be the equivalent of 58 ounces per acre of the new Ignite 280.”
Company representatives began submitting residue data to EPA last year to support the request for a higher seasonal use ceiling. The agency told them they faced a two-and-a-half-year review process before the request could be granted. “So we've been supporting the submission of special local needs labels by the cotton-producing states for 2006.”
The new label would permit a higher single use rate of 43 ounces per acre for situations where rainfall or other conditions caused delays, and the farmer had to make an application 10 days to two weeks late when the weeds had grown quite large.
“That application of 43 ounces could be followed by an application of 29 ounces, which would give the grower a total of 72 ounces and would exceed the total seasonal use rate of 58 ounces,” said Vodrazka. “The new label would allow growers to make applications of 43 and 29 ounces or three applications of 29 ounces for a total of 87.”
Two states — Arkansas and South Carolina — had granted Section 24(c) labels for the expanded seasonal use rates for Ignite.