Cotton farmers have a new option for effective weed control this spring with the approval of FiberMax LibertyLink varieties and Ignite herbicide, but weed size and thorough spray coverage will play crucial roles in the new system's success.

“I'm excited that we have a new player in weed control for 2004,” says Peter Dotray, a weed scientist with joint appointments with both Texas Tech and Texas A&M. Dotray, who works out of Lubbock, offered recommendations for using Ignite on tolerant varieties during a recent Bayer CropScience crop consultant seminar at South Padre, Island, Texas.

Weed species, weed size and thorough coverage will be essential for adequate control, Dotray says.

Tolerance excellent

“I've had quite a bit of experience with the LibertyLink varieties and have found that tolerance to Ignite herbicide is excellent with the FiberMax varieties available for 2004.”

Growers can apply Ignite over LibertyLink cotton through most of the growing season. “We don't have a window of application based on the cotton stage, but we need to make timely applications based on weed stage,” Dotray says.

He says Ignite's main target will be annual broadleaf weeds. “But it has activity on annual grass as well. It has limited translocation ability but is fast-acting.”

Ignite is a broad-spectrum herbicide but Dotray still recommends a preplant incorporated treatment with a dinitroaniline or other residual herbicide, “for consistent season-long control. With tough weeds, we may need a little help from residuals.”

Weed size, coverage

Dotray says weed size and coverage are critical because of Ignite's limited translocation. “The smaller the weed and the more active it's growing, the more successful Ignite will be.”

He rated the herbicide's activity against several troublesome weed pests.

“Palmer amaranth is susceptible to Ignite, but it could get away from a farmer without timely applications. We've seen good activity with the 32-ounce and 40-ounce rates but timeliness is critical.” He said devil's-claw is also susceptible.

He said the herbicide has good activity on annual morningglories, “but don't wait for the weed to reach 10 inches. It is difficult to get good coverage on weeds this size.”

Cocklebur susceptibility is similar to morningglory.

“Lanceleaf sage did not respond as well to Ignite as we had hoped,” Dotray said. He suggested an application before the weed grows past one-fourth inch. “That's a key. Also, a residual herbicide will improve control. Some residuals have good activity on lanceleaf sage.

Dotray says a systems approach augments the Ignite and LibertyLink program. He says something like Staple pre-emergence followed by Staple and Ignite early postemergence may be a good option for several weeds. He said Caparol pre-emergence followed by Ignite postemergence also provides good control of weeds like ivyleaf morningglory.

Key to system

“The key to make this system work consistently includes using a PPI herbicide, and maybe a pre-emergence, depending on the weed species. He recommends a 40-ounce rate on larger, tougher weeds.

“We can use two 32- or 40-ounce applications of Ignite over-the-top. Timeliness and thorough coverage, with 15 gallons of water per acre, are essential.”

Dotray cautioned farmers against assuming that LibertyLink and Roundup Ready are similar in their tolerance against the other herbicide.

“Ignite is not Roundup and Roundup is not Ignite,” he says.

Applying Roundup to LibertyLink cotton varieties will kill it as will putting Ignite on Roundup Ready varieties.

“Each of these herbicides have strengths and weaknesses,” Dotray says. “We get faster control with Ignite but Roundup is a systemic and translocates. Neither has residual activity. Depending on the weed species present, the ability to make timely applications, and the need for 15 gallons of water to apply the herbicide, one system may be more appropriate than the other.”

Both, he says, have a place in cotton weed control programs, with the proper varieties or precautions to prevent non-target injury.

e-mail: rsmith@primediabusiness.com