Herbicide Diversity

July 27, 2012 09:59 PM
Herbicide Diversity

Diversifying herbicide modes of action is important to addressing weed problems.

Use any single herbicide long enough and weeds will eventually figure out a way to grow in spite of it. Historically, farmers could simply use a new herbicide to remedy the problem. That’s not the case today, though some chemical companies do have new herbicides under development.
"There is not a single silver bullet," says University of Minnesota agronomist Jeff Gunsolus. The overarching solution to weed issues today, experts say, involves a combination of different seed varieties, different herbicides, and different tillage and even cultivation practices.
That might mean dramatic changes in farming practices, which will affect the entire industry, including seed providers. "Seed companies will have to figure out what weed problems there will be three to five years from now and gear up their seed production
accordingly," says Ford Baldwin, a consultant and former weed scientist at the University of Arkansas. "Seed companies that diver-sify are going to be the ones left standing at the end of the day.
All of weed control is going through the seed industry."

Mix it up. The mantra that all experts repeat, whether they are seed, chemical or university related, is: Farmers need to diversify their modes of action for control.
For corn, weed resistance is not so much a problem with six or seven different modes of action available. That’s not true for soybeans. The primary modes of action available today for weed control in soybeans are glyphosate (Roundup) and glufosinate (Liberty) herbicides; the latter is licensed to U.S. seed companies by its creator, Bayer CropScience.
Kevin Cavanaugh, director of research for Beck’s Hybrids, says the resistance issue is getting soybean growers’ attention. He notes that in 2011, only 1% to 2% of the company’s soybean seed sales were LibertyLink. This year, it represented 20% of the company’s total soybean sales.
Still, Cavanaugh believes an important role remains for glyphosate use in soybean crops. "It’s just that we’re now past the point where farmers can rely on it alone," he says.
While advocating the LibertyLink system as an option to solve the glyphosate weed resistance challenge, Arlene Cotie, seed and trait marketing manager for Bayer, says farmers need to mix up their modes of action, so weed resistance is less of an issue, and Liberty’s story does not become like that of glyphosate.
Help is on the way beyond LibertyLink. Three new products that are projected to provide control against glyphosate-resistant weeds are HPPD, a herbicide-tolerant trait from Bayer; Roundup Ready Xtend soybeans, which are tolerant to dicamba and glyphosate, from Monsanto; and Enlist, a 2,4-D–based technology from Dow AgroSciences.
Roundup Ready 2 Xtend soybeans are likely to be available for farmers’ use in 2014, pending key global regulatory approvals, according to Michelle Vigna, Monsanto system launch manager. She notes that it’s important for producers to choose traits that support their yield goals as well as address weed control challenges.
As for Dow, the company is hoping for approval of the 2,4-D–tolerant trait called Enlist. The trait is expected to be incorporated into seed traits, stacked with glyphosate tolerance and also feature a new herbicide product. "We’re looking for approval for corn in 2013; soybeans and cotton will follow that," says Damon Palmer, U.S. commercial leader for the Enlist weed control system. He says that Enlist could be used as a foundation herbicide in farmers’ weed control system, as it offers two modes of action.
Bayer and MS Technologies will bring forward an HPPD trait in 2015, pending regulatory clearance. That will add another mode of action to the soybean toolbox for growers to combat glyphosate-resistant weeds, Cotie says. HPPD is a residual herbicide that is known in corn as Balance. Bayer expects to label the herbicide in soybeans as Balance Bean.

Seed companies will have to predict weed problems and gear production accordingly.

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