Life got easier when the Roundup Ready production system came down the road. In fact, many farmers can't imagine doing without the technology.
The good news is you officially have another nonselective herbicide alternative that delivers similar convenience. Ignite herbicide (glufosinate) and the LibertyLink soybean trait technology recently cleared regulatory hurdles in all key markets. The unique mode of action is welcome relief for those coping with or worried about the growing issue of weed resistance to glyphosate.
Big differences. Don't let the fact that this is a comparable technology lure you to think the products are comparable in application techniques. "The only thing similar about glyphosate and glufosinate is they both start with the same letter," says Aaron Hager, University of Illinois Extension weed specialist. "The LibertyLink system is different in how it works, how it's timed and how it is applied."
Glufosinate is a contact killer. Glyphosate translocates or moves through the plant to get the job done. "How each product works impacts timing," Hager says. "With Ignite, weeds need to be a true 3" to 4" tall when sprayed and that might be two to three weeks sooner than growers are used to spraying with the Roundup Ready system."
Recommended timing for the first Ignite application in LibertyLink soybeans is no later than 22 days after emergence in the Midwest and 10 to 14 days after emergence in southern growing areas. Soybean growers in the habit of waiting to finish planting before heading out with the sprayer may have to re-evaluate priorities if the season lingers as it did in 2008.
Because Ignite works on contact, better control is realized if weeds are a consistent size, Hager adds. Water volume is also critical. Plan to use 15 gal. to 20 gal. of water with Ignite, compared with 10 gal. to 15 gal. for glyphosate. Hager prefers to see Ignite applied on sunny days when soil moisture is adequate.
Nozzle selection influences contact coverage, too. "You'll want to make sure the leaf is getting maximum coverage," Hager notes. "The drift retardant nozzles typically used for Roundup may not be the best choice."
Andy Hurst, Bayer CropScience product manager of herbicide tolerant traits and Ignite, says flat fan tips work. "Some of the air induction tips can do a nice job at high pressures," he says. "We suggest growers use their favorite tips—just make sure it delivers a medium spray droplet in the 300 to 350 micron range."
Use a residual. Hurst says Ignite is 40% more concentrated than the Liberty herbicide it replaces. Ignite will be used for all LibertyLink crops (corn, cotton, soybeans and canola), and it controls more than 120 broadleaf weeds and grasses. The standard rate of Ignite is 22 oz. per acre. A single application of up to 36 oz. per acre can be used in LibertyLink soybeans to improve control should weeds exceed recommended height. While Ignite can be used as a stand-alone product, Hurst says the company stresses the use of a residual—either at burndown, pre-emergence at planting or in the first Ignite application.
"The LibertyLink system is more forgiving if weather prevents the pre-emergence product from getting activated," says University of Arkansas weed specialist Kent Smith, who has been studying LibertyLink and Ignite in field trials. "A farmer can come back early with Ignite to remove small weeds that escaped the pre-emergence product. Although it's not my preference, there's also the option of waiting for an early postemergence application and adding a residual with the Ignite."
"I'm excited about the opportunity to manage Palmer amaranth with LibertyLink technology," Smith says. "The varieties we tested in 2008 yielded well. My guess is every [LibertyLink] seed that Arkansas farmers can buy will be planted in 2009. If LibertyLink yields compare with the more traditional Roundup Ready varieties, this technology will be readily accepted.
"The mind-set of how we farm soybeans has to change with this technology," Smith adds. "LibertyLink soybean varieties are not Roundup Ready soybean varieties in a different color bag. Ignite is not glyphosate in a different color jug. We need to learn the Liberty-Link system and manage accordingly for it to be effective."
You can e-mail Pam Smith at firstname.lastname@example.org.
- March 2009