Realizing the ROI of Managing Glyphosate-Resistant Weeds

Identify mature waterhemp with long, hairless stems

Mature waterhemp in an Illinois field. Photo courtesy of Aaron G. Hager, University of Illinois.

Glyphosate resistance continues to impact corn and soybean growers across the Midwest. Without proper management, aggressively resistant weed species, such as waterhempPalmer amaranth and marestail, can quickly turn productive fields into a lost cause.

But managing glyphosate resistance pays – literally.

Take soybean acres, where glyphosate-resistant weeds are especially prevalent, according to a USDA Economic Research Service study. This research considered a cropping scenario that estimated growers in a continuous soybean system could realize an extra $22.60-per-acre return by managing resistance rather than ignoring it. Growers using a corn-soybean rotation could realize an advantage of up to $55.80-per-acre by managing glyphosate weed resistance, according to the study.1

Increased resistance to glyphosate is part of a larger trend toward growing weed resistance to herbicides, including ALS inhibitors, triazines, PPO inhibitors and HPPD inhibitors. Multiple herbicide resistance in weed population sites, as well as cross-resistance – resistance to herbicides that are from different chemical families, but share the same site of action – is a real concern.

Appropriate management can make the difference at the end of the year. Growers have proven options for fighting back and protecting profits.

Take a Zero-Tolerance Approach

In one university report, Palmer amaranth seeds collected from a St. Joseph County, Michigan, soybean field were confirmed resistant to glyphosate, and some of those resistant Palmer amaranth plants survived a 32X rate of glyphosate.2 This serious threat of economic losses from glyphosate-resistant weeds highlights the need to consider alternatives.

Experts agree that a goal of zero tolerance for the distribution of seeds by resistant weeds can aid in management. Implement best management practices and adopt a zero-tolerance approach.

Select the Right Seeds

The LibertyLink® system is proven to be the simply better solution, providing superior weed control, high-performing genetics, application convenience and peace of mind. Growers who choose LibertyLink corn and soybeans can spray Liberty® (Group 10) herbicide, which boasts a unique site of action to control a broad spectrum of resistant and tough-to-control weeds like marestail, waterhemp and Palmer amaranth.*

LibertyLink soybeans are the highest rated trait platform of the year, according to a 2017 independent market research survey. In fact, 97 percent of growers who planted LibertyLink rated it “good” to “excellent.” 

Additionally, university data shows that LibertyLink delivered a 2+ bu./A yield advantage over Asgrow® Roundup Ready 2 Xtend® soybeans.**

LibertyLink is also enabled on over 50 million corn hybrid acres with Herculex®, Genuity® SmartStax® and Agrisure® hybrids with corn borer protection. All LibertyLink corn hybrids have built-in tolerance to Liberty herbicide, combining excellent crop safety with agronomic performance and yield.

Start with a Pre-emergence Herbicide

For optimal yields, growers should start with clean fields. That means starting with a pre-emergence residual herbicide.

Corn is particularly sensitive to early season weed competition. High-weed-density research during weed competition variety trials recorded a 20- to 40-bushel-per-acre yield loss – even when glyphosate was first applied two to three weeks after corn and weed emergence.3

Corvus® herbicide (Groups 2, 27) has overlapping sites of action to control early season problem weeds.*** A wide application window allows for application from pre-plant to early postemergence at V2, making it an effective, long-lasting first-pass herbicide in a two-pass system.

Pre-emergence residual herbicides are also recommended in soybeans to prevent yield loss and minimize selection of glyphosate-resistant weeds. Choose a pre-residual herbicide with two sites of action that are both effective on the weeds you wish to control.

Stay Clean with a Post-emergence Application

For a zero tolerance approach in corn, include DiFlexx® DUO herbicide in your second pass. DiFlexx DUO provides excellent strong post-emergence control against a full range of tough weeds, especially glyphosate-resistant ones. In addition, DiFlexx DUO delivers built-in resistance management with its two effective sites of action (Groups 4, 27) and exhibits excellent crop safety. Liberty (Group 10) offers another strong second-pass option, as the only broad-spectrum herbicide that effectively controls resistant grasses and broadleaf weeds.*

For post-emergence weed control in LibertyLink soybeans, use Liberty (Group 10) plus a Group 15 residual herbicide, such as Zidua®, Anthem®, Outlook®, Dual®, Warrant® or Prefix®.

Additional Resources

Not every product is suitable for every situation, nor registered in every state, and proper application techniques will help ensure the best results. Before applying any herbicide, please read the entire label and to confirm that the product is effective on the weeds you wish to control. Learn more about using herbicides with effective sites of action with our Herbicide Resistance Management Guide and Trait and Technology Use Manual.


*The active ingredient in Liberty is a Group 10 herbicide, which is the only broad-spectrum herbicide that effectively controls grasses and broadleaf weeds, and it has no known resistance in U.S. broadacre crop. Liberty is not registered for use in all states.

**Yield shown summarizes average of LibertyLink and Asgrow RR2Xtend varieties entered. 2016 University OVT including over 2100 observations (AR, IA, IL, IN, KY, LA, MI, MO, MS, OH, PA & VA) as of 12/7/16. Endorsement or recommendation by the universities is not implied.

***Corvus is a Restricted Use Pesticide. Corvus is not registered in all states.

Work Cited

1. Livingston, Michael, et. al. “The Economics of Glyphosate Resistance Management in Corn and Soybean Production.” April 2015.

2. Sprague, Christy. “Glyphosate-Resistant Palmer Amaranth in Michigan: Confirmation and Management Options.” Feb. 2012

3. Rosenberg, Mark. “Effect of Weed Competition on Corn.” June 2013

Bayer, the Bayer Cross, Corvus, Liberty, LibertyLink and DiFlexx are registered trademarks of Bayer. Asgrow, Genuity, SmartStax, and RoundUp Ready 2 Xtend and Warrant are registered trademarks of Monsanto. Agrisure, Dual and Prefix are registered trademarks of Syngenta Herculex is a registered trademark of Dow Zidua and Outlook are registered trademarks of BASF. Anthem is a registered trademark of FMC.

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