Research Report: Weed Wars

George Washington once said, "I know of no pursuit in which more real and important services can be rendered to any country than by improving its agriculture." Today, more than 200 years later, this pursuit continues at a relentless pace. New technologies are pushing U.S.agriculture to a level none of our forefathers could have imagined. But while the solutions may have changed, many of the problems they address are remarkably the same. Tough-to-control weeds, for example, still stand in the way of a corn grower's yield and profitability.

Fortunately, the tools available to manage this problem have vastly improved since the 1700s, when growers would simply walk the rows and weed their fields by hand. Upon EPA registration, Acuron^™ herbicide, the latest in a long line of crop protection innovations from Syngenta, is expected to be one of the most promising new weed-management solutions in 2015. It has four active ingredients, including new bicyclopyrone, and three modes of action that, together, will deliver high-level control of the most problematic weeds in corn, most notably Palmer amaranth, marestail, giant ragweed, kochia, morningglory and waterhemp.

"From a technical standpoint, Acuron is the best corn herbicide I've ever seen because of its superior and consistent weed control, especially of the most difficult-to-control weeds," says Syngenta Technical Development Lead Brett Miller, who helped bring several of the company's corn herbicides, including Acuron, to market. "It will set a new standard for weed control in corn."

Lessons Learned

To fully appreciate the value of a new technology like Acuron, it helps to look back at the circumstances that led to its development. In 1996, glyphosate-tolerant soybeans triggered a revolution in weed control. Annual broadleaf weeds and grasses were finally in the crosshairs of what many in the industry hoped was "the silver bullet."

"At the end of the day, managing problem weeds can help give growers more bushels to sell and preserve their farm legacy for future generations."

But after years of over relying on the Roundup Ready^® trait system, growers began seeing the telltale signs of glyphosate resistance. Fields of glyphosate-tolerant soybeans that were clean the previous season became infested with yield-depriving weeds, so once again, the industry, realizing that not controlling weeds in soybeans leads to more weed-control problems in corn, scrambled for a solution.

In recent years, the incorporation of residual post-emergent herbicides into weed management programs has given growers more options. But resistance is threatening the effectiveness of these and other products, too, making some weeds more difficult to control. In the last four years, infestation of tough broadleaf weeds in corn has increased 50 percent¹.

Fighting Back

It's no wonder growers and retailers agree that continuous improvements in the corn herbicide market are crucial. Syngenta is at the forefront of these improvements by introducing Acuron. It will bring a multitargeted approach that offers built-in weed-resistance management.

"Resistance to post-emergence herbicides will continue to expand," says Gordon Vail, Ph.D., technical product lead, who, like Miller, has played an instrumental role in the development of several market-leading Syngenta corn herbicides. "With Acuron, we are seeing robust pre-emergence performance on some of the toughest-to-control weeds in corn."

Growers like Joe Dierickx (below), from DeWitt, Iowa, are anxious to turn the tide on resistance and fortify their weed control programs with new solutions. "With the

resistance problems that we are having in the Corn Belt now, it's paramount that you use multiple modes of action to control your weeds," he says. "If we don't work to prevent resistance, we are going to have serious problems in our fields."

Four out of five growers are actively seeking new products that will help achieve better weed control². Acuron will offer better, more consistent weed control than industry standards, and season-long residual control will help growers decrease their weed seed bank for the coming years.

"A full rate of a pre-emergence herbicide is an easy sell in my area," explains Jason Weirich, Ph.D., director of agronomy for MFA Incorporated, based in Columbia, Missouri, and 2013 Syngenta Resistance Fighter of the Year. "It's the only option we have. We need to start clean. If we look at giant ragweed, for example, it usually germinates before we even put the crop in the ground. Those annuals will be there all year long. The best goal is to not let those weeds get out of the ground."

The Proof Is in the Trials

Years of formulation testing and more than 700 field trials featuring bicyclopyrone have contributed to the development and extensive evaluation of Acuron. In 2014 alone, numerous trials were conducted at 85 Syngenta locations, 54 university locations and 18 distributor locations. Retailers and growers also were able to see the product's in-the-field performance for themselves at Syngenta-sponsored Grow More Experience sites across the Midwest. These trials repeatedly showed that Acuron delivers improved control over competitors, including Corvus^®, Verdict^™, Harness^® Xtra and SureStart^®. Product development trials in 2012 and 2013 showed similar results, demonstrating that Acuron provided better weed control than competitive herbicides.

"Acuron is going to be a consistent product," says Larry Steckel, Ph.D., a University of Tennessee associate professor and row crop weed specialist, who has included Acuron in several corn studies over the last two years. "When we're talking about controlling weeds like Palmer pigweed (Palmer amaranth), Acuron performed better than Corvus."

Since the early stages of its development, Acuron has stood out as a superior compound for controlling difficult weeds, notes Dain Bruns, Ph.D., a Syngenta R&D scientist who first tested bicyclopyrone in 2001 through his small-plot research in Ohio. "As weeds have developed resistance and become more difficult to control, many current weed-control programs have lost their effectiveness," he says. "One of Ohio's key driver weeds is giant ragweed. It is on almost every acre across the state. Local Acuron trials have shown excellent control of this weed and have given growers new hope that much-needed help is on the way."

Trials from 2014 showed that with a full rate, pre-emergence application, Acuron controlled giant ragweed almost 15 percent better than Corvus and 35 percent better than SureStart.

In an environment where corn prices are low, investing in products that will effectively control the weeds that cost crops yield is especially critical. "At the end of the day, managing problem weeds can help give growers more bushels to sell and preserve their farm legacy for future generations," says Bruns. "Once registered, Acuron will bring a high level of weed control to growers, ultimately making their corn production more sustainable and profitable." That's good news for U.S. agriculture, which, as our first president recognized over two centuries ago, is also good news for the country.

Acuron is anticipated to receive registration for the 2015 growing,season and will be available in limited supply. Visit the Acuron website for more information.

¹2013 Syngenta Market Research. Cocklebur, kochia, marestail, morningglory, ragweed (common, giant), waterhemp (common, tall).
¹2014 Syngenta market research.