Corn Growers See Rewards for Managing Glyphosate Resistance

As more cases of glyphosate-resistant weeds are reported on new acres in the Corn Belt each year, growers are integrating resistance management into their production strategies. Increasingly, growers are discovering that solid resistance management programs can be agronomically sound in the long run and economical in the near term, as they find ways to get rewards immediately with higher corn yields and even cash incentives.

To achieve higher corn yields, growers are exploring their options with pre-emergence herbicides that help minimize early weed competition that can obstruct the way.

Bob Hartzler, extension weed specialist at Iowa State University, says, “An important component to resistance management is the use of alternative weed control chemistries, such as pre-emergence herbicides.”

Richard Thooft, a grower in Lakefield, Minn. includes pre-emergence weed control as part of his AgriEdge® Corn weed control strategy. He uses a full-rate of Lumax® herbicide from Syngenta for early-season weed control and sprays Touchdown Total® glyphosate herbicide on corn hybrids with the Agrisure® GT trait if needed.

Hartzler adds, “Herbicide diversification is important, but to be fully effective at reducing selection pressure the alternative herbicides must control weeds at least as well as glyphosate. If weeds are not effectively controlled by the alternative herbicides, the likelihood of resistance appearing in these weeds would be just as great as if no pre-emergence herbicide had been applied.”

By following his AgriEdge Corn weed control strategy, Thooft has been able to successfully control a wide spectrum of weeds, including lambsquarters, common ragweed and Canadian thistle. Thooft says, “I also get a cash incentive as an additional bonus for following a recommended AgriEdge Corn weed control program.”

The AgriEdge Corn Program is a crop management system that encourages growers to follow agronomic solutions that help maximize corn yield potential. Growers get cash incentives for selecting the best seed genetics, traits, seed treatment, herbicides, fungicides and insecticides from Syngenta.

To further manage resistance, Thooft makes it a point to rotate corn and soybeans so he limits dependence on glyphosate. “After planting corn hybrids with the Agrisure GT trait in one year and planting NK® Brand Soybeans with the Roundup Ready® trait the next year, we’ll switch to conventional corn the year after. We also never plant glyphosate tolerant (GT) crops on the same field more than two years in a row,” Thooft says.

Brent Woodman of Kenesaw, Neb. takes a similar approach and says, “We use a full-rate of Lexar® herbicide to minimize weed competition on the corn acres early in the season.” Like Thooft, Woodman also rotates corn and soybeans every year, planting corn hybrids with the Agrisure LL trait – which tolerates glufosinate herbicide – on the field that was planted to NK Brand Soybeans with the Roundup Ready trait the previous year.

“Syngenta developed the AgriEdge Corn Program with solutions for the grower in mind,” says Pat Steiner, AgriEdge Corn Program manager with Syngenta. “We know that a grower’s strategy may vary from year to year or field to field. The variety of weed control solutions in the AgriEdge Program helps growers address their agronomic challenges while gaining an economic advantage through higher yields and incentives.”

For growers who are committed to a post-only herbicide system, the 2009 AgriEdge Corn Program added incentives for using Halex™ GT herbicide, a one-pass post-emergence herbicide that combines glyphosate with residual control. In Syngenta and university trials, Halex GT gave growers a 7 bu/A and a 5 bu/A advantage over one application of glyphosate and two applications of glyphosate, respectively.

“For growers who plant soybeans as part of their rotation, the AgriEdge Program provides incentives for using Prefix® pre-emergence herbicide on NK Brand Soybeans that are treated with a CruiserMaxx® Beans brand insecticide/fungicide seed treatment,” Steiner adds.

Neither Woodman nor Thooft has seen resistant weeds in their fields yet, but they strongly believe that being proactive is paying off in their fields.

“By the time you get resistant weeds, managing the problem will be as difficult as it is expensive. Following good agronomic practices now will save me from the more expensive costs of potentially needing to combat resistance later on,” says Woodman. “In the near term, the strategy protects the yield potential of my crops.”

For more information about the 2009 AgriEdge Program or to download a Program Use Guide, growers should visit Use guides are also available from authorized Garst®, Golden Harvest® and NK Seeds dealers or crop protection retailers