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Corn+Soybean Digest

Wide-Open Application Window

A lot of noise was made in the spring over LibertyLink cotton and its new over-the-top weed control program. Rickey Bearden was among the many growers who listened.

The Plains, TX, producer planted LibertyLink varieties on a small portion of his 6,000 cotton acres to help get a better handle on morningglory and other broadleaf control. He anticipates seeing an even greater use of Ignite, the new Bayer Crop-Science herbicide for cotton.

When Bayer introduced Ignite to growers at informational meetings and the Beltwide Cotton Conference this year, what opened farmers' eyes was the wide window of application it provided.

“With LibertyLink varieties, we're able to spray over the top of cotton within 70 days of harvest,” says Bearden. “That's virtually a season-wide window of application.”

That compares to Roundup Ready cotton, which can be sprayed up to the fifth leaf of growth. It can also help relieve fears of any possible resistance that may evolve in glyphosate varieties, such as those in parts of Alabama and other regions.

“I like the Roundup Ready varieties,” says Bearden. “Virtually all of our irrigated cotton is Roundup Ready stacked with Bt. About half of our dryland cotton is Roundup Ready. But I believe it's wise to diversify some of your production and try new things. I planted a seed block of LibertyLink in 2003 and it provided good weed control.”

Approved by EPA for use on cotton this year, Ignite is designed for control of a wide variety of broadleaf weeds. That includes pigweed species, morningglory species, johnsongrass, cocklebur, black nightshade, watergrass, barnyardgrass, sunflower and many other weeds. The active ingredient is glufosinate-ammonium. Ignite can also be used as a preplant burndown or as a hooded application on all types of cotton.

It's currently approved for use on FiberMax LibertyLink resistant varieties.

In Alabama, growers are interested in the LibertyLink system because of glyphosate-resistant marestail, or “horseweed.”

“People have been looking for an alternative to Roundup, even though it has a lot of advantages for our growing areas,” says Charles Burmester, Auburn University extension agronomist. “We've seen some weed resistance (to glyphosate) in northwest Alabama. So farmers are learning that they need to alternate the chemistry to help prevent some of that resistance.”

But one problem with adding new herbicide programs is the confusion it may cause when treatment is needed on various fields and time is running short. “Most growers don't want two or three different systems,” he says. “And they have to watch for drift problems (from spraying) on their farms and their neighbors' farms.”

The key to obtaining good weed control is total plant coverage. “It's weed size, not cotton plant size, that determines when to apply Ignite,” says Randy Boman, Texas A&M University cotton agronomist. “Since it's a contact herbicide, thorough coverage is important for maximum performance.”

The Ignite application rate is 32 oz./acre, and up to 40 oz. depending on weed size. Boman recommends mixing the herbicide with 15-20 gal of water. Bearden uses a 20-gal. rate. “We apply the herbicide with a shop-built, 12 row, 40-ft. wide sprayer,” he says. “To obtain maximum coverage, we use three nozzles, one over the center of the row and two at an angle on the side of the row.”

A preplant or pre-emergence application is recommended if there's a heavy infestation of grasses, nutsedge or pigweed. The herbicide can be tankmixed with other complementary herbicides.

For further information on the LibertyLink cotton program, go to the BayerCropscience Web site at

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