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Corn+Soybean Digest

The New Soybean Herbicides

With all the Roundup Ready technology, it's not surprising that the “new” soybean herbicides for the coming planting season are actually new names for proven products.

In coming years, soybean growers aren't likely to see many herbicides that offer new chemistry to battle resistant weeds, says Aaron Hager, University of Illinois extension weed scientist.

“The value of the soybean market, from a manufacturer's standpoint, is not as favorable now to bring in a new active ingredient,” Hager adds.

Hager wouldn't be so concerned if he didn't see weed resistance to products that used to be effective. But he is seeing resistance, particularly from waterhemp and especially using postemergent products.

“Essentially, what we've got are four herbicides that have worked very well on waterhemp postemergence in soybeans. Three of them are no longer effective on certain waterhemp populations: Cobra, Flexstar and Ultra Blazer.

“So we've got one option to control that weed postemerge and that's glyphosate,” says Hager.

The weed scientist has, in recent weeks, been speaking to Illinois growers about herbicides and grower practices contributing to potential continued resistance and changes in the weed spectrum.

“We've tried to demonstrate that the weeds are going to continue to combat practices that we use repeatedly. The problem now is that we're not going to have a lot of new tools in the toolbox to take care of these changes,” says Hager, referring to the dearth of new active ingredients.

So what's a grower to do? In fact, what strategy should growers take on most of the 75% of U.S. acres planted to genetically modified soybeans — most of which are probably protected by post-applied glyphosate?

Hager recommends a sequential program — one that focuses on the use of soil-applied herbicides followed by post. Waterhemp is still susceptible to most soil-applied products, except those with ALS chemistry.

“It's a weed that we once were able to control with a lot of different herbicides. We used to be able to control it with ALS products, although not a lot of people believe that. Now it's figured out a way to get around at least three distinctly different chemical classes. And we're seeing much more inconsistency with glyphosate products controlling waterhemp.”

Although Hager recommends a sequential program, he's skeptical that growers will heed that advice.

“Should a farmer do something now to preserve the effectiveness of however many weed control options he's got left?” he questions. “A lot of times that might be more expensive than simply continuing to use what's been effective in the past. And then there's that philosophy of ‘when something happens, it happens, and we'll deal with it.’

“That has worked in the past, but it might not work now,” he warns. “We're not going to see a lot of new active ingredients in the market.”

For more articles on glyphosate resistance, check out

Soybean herbicides introduced for the 2003 growing season include several new names from proven chemistry.

Yet one of these, Spartan, is a soil-applied product like those Hager recommends to help fight waterhemp. Its active ingredient — sulfentrazone — is the same as that in Authority.

“This offers a pre-emerge product that is very good on some small-seeded broadleaf weeds, especially waterhemp,” says Brent Neuberger, FMC research biologist. “It also has very good residual activity, and that's one of the key strengths of this product.”

Spartan also controls broadleaves such as pigweeds, lambsquarters, morningglories, velvetleaf and nightshades, he adds.

NuFarm Americas, Inc., introduces Credit Systemic Extra, a combination of Credit herbicide and a surfactant.

Equivalent to Monsanto's Roundup Ultra, the NuFarm product offers “enhanced uptake without the need for tankmixing additional surfactants” when compared to Credit, says Ted Head, product registration manager.

Speaking of Monsanto, its newest twist on Roundup is Roundup WeatherMax. Its unique potassium salt formulation with TranSorb II technology allows the herbicide to quickly penetrate weed leaves and deliver a lethal dose of glyphosate, says Matt Helms, U.S. Roundup product manager.

“We specifically tested it under tough-to-control conditions — hot or dry or cool weather and early morning and late afternoon applications,” Helms says. “We tested it with growers and retailers on 1.3 million acres this past summer and said, ‘Spray in these tough conditions.’ More than 93% of growers were satisfied.”

Monsanto adds two warranties to its 2003 Roundup Rewards program, he adds. “TranSorb II technology allows for rapid entry of glyphosate into the plant to support the 30-minute rainfast warranty. The Roundup WeatherMax warranty gives growers confidence when forced to spray in challenging conditions.”

Expanding its presence in the U.S. market, Makhteshim Agan North America, headquartered in New York, introduces a trifluralin called Triflurex HFP. The preplant herbicide controls grasses such as crabgrasses, fall panicum, foxtails and johnsongrasses as well as broadleaves such as chickweed, carpetweed, pigweeds and Russian thistle.

Valent USA ganged up two herbicides — its own Valor plus Dow AgroScience's FirstRate — to form the appropriately named Gangster.

“We're taking two products that are good products but have some holes in them; each fills the other's holes,” explains Valent's John Pawlak, a product development manager.

Valor has some weaknesses on cocklebur and ragweed, while FirstRate isn't strong in controlling lambsquarter, waterhemp and nightshades. “And both products could use a little help on smartweeds and velvetleaf. But when you put them together, the whole spectrum is controlled,” Pawlak says. “It really makes things simpler for the grower, in terms of buying one product as opposed to deciding what two products he wants to use.”

Gangster's active ingredients are flumioxazin and choransulam. The product was designed for the conventional acre, but is also a good fit with Roundup Ready beans, Pawlak says.

Syngenta Crop Protection is applying for state registrations on a new glyphosate formulation of Touchdown, called Touchdown CF. It's to be used as a pre- or post-harvest burndown for growers who use fallow ground in their crop rotations.

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