Helpful Herbicide Hints
September 8, 2008 That’s not so easy, is it? That’s why we’ve brought in Reid W. Acker, our fictional but competent in-house herbicide advice columnist, to help you sort through your key questions and concerns. Step aside Dear Abby; Reid the Weed Man’s on the case.
Dear Reid: So, what’s new in herbicides this year?
My Extension contacts around the Midwest say most of the active ingredients (a.i.s) in the new crop of herbicide products aren’t new (see chart), but the a.i. combinations are. “Other than Laudis, all the materials are existing active ingredients in new premixes,” says Chris Boerboom, University of Wisconsin Extension weed scientist, noting that therein lies the trick to knowing the new material. Recognizing the component products you’re well acquainted with will allow you to build on familiar properties. “If you understand the ingredients, you understand the product pretty well,” he says. OK, I’ll follow that advice and try to mention the familiar product names to make this easier.
Dear Reid: How do the new herbicides fit into a glyphosate resistance management program?
Resistance management is quite critical. Bill Johnson, Purdue University Extension weed scientist, says it needs to become part of your growers’ routines, especially where fields are typically sprayed with glyphosate three to four times a season. “They need to take the management approach as if this population is developing a low level of resistance,” he says. “There’s a couple of strategies. The cheapest is to really be aggressive in managing it in corn. Drive it down, using broadleaf herbicides and 2,4-D.”
In soybeans, he recommends starting with a clean field, especially in no-till systems. “If we get them to start clean and use a residual herbicide to try to keep the giant ragweed in check, it allows for timely glyphosate treatments. And get the glyphosate rate up as high as they legally can in that first postemergence treatment.”
Laudis is a bleaching herbicide, with the same mode of action as Callisto and Impact, says Bob Hartzler, Iowa State University Extension weed specialist. “It’s for postemergence control in corn, with activity on grass and broadleaf species, although it is stronger on broadleaves. Laudis has the best grass control of the three post bleachers, but probably not good enough to be a stand-alone grass product, and will provide some residual control of weeds.” The safener in Laudis allows it to be used on all corn types.
Dear Reid: What does this year’s crop of soil residuals offer my growers?
That’s a great question, since using a soil residual product is one of the strongest methods of resistance management. Aaron Hager, University of Illinois at Urbana-Champaign Extension weed specialist, reminds us that these products can be used in more than one way. “The underlying thing is that obviously glyphosate is going to need some assistance for certain species, so several of these new products will be well-suited as tank-mix partners, whereas others would be good residual herbicides. We simply need to continue using residual products from a weed interference standpoint,” he says. “You don’t see any new a.i.s in the postemergence glyphosate arena, for example, so if you run out of options for the postemergence control of, say, waterhemp in soybeans, we don’t have any post options coming in the marketplace. We may have to rely more exclusively and heavily on some of the soil residuals.”
Manufacturers understand all this and continue to bring forth new soil residual products. DuPont‘s Envive and Enlite “are premixes of Classic, Harmony GT, and Valor,” says Christy Sprague, Michigan State University (MSU) Extension weed scientist. Mike Owen, Iowa State University Extension weed specialist, adds that the pair have two modes of action, the PPO inhibitor plus ALS. Envive targets the central and southern soybean growing regions, and Enlite — containing less Classic and with no soil pH restrictions — will be marketed in Minnesota, Wisconsin, and northern Iowa.
“Valor XLT is a good product in the soybean market where growers have glyphosate resistance concerns about stewardship performance,” says Bryan Young, Southen Illinois University weed scientist.
Hartzler notes that Authority MTZ, Prefix, Valor XLT, Envive, and Enlite will compete for the same niche, the preemergence market in Roundup Ready soybeans. “None of them will provide full-season, broad-spectrum weed control,” he says. “However, what they do provide is good early-season weed control/suppression that greatly reduces the likelihood of weeds impacting yield potential prior to the postemergence glyphosate applications. This allows the postemergence application to be delayed long enough that there normally won’t be a need to make a second application to deal with late-emerging weeds.”
“They also can reduce the likelihood that weeds resistant to glyphosate will survive,” Hartzler says. “In research I did a couple years ago, PRE treatments reduced selection pressure by 70% to 95% depending on the species. Envive and Enlite would probably have the best burndown activity on winter annual weeds, but all of them do have some foliar activity.”
“SureStart is a premix intended to capture the preemergence market in herbicide-resistant corn,” adds Hartzler. “It’s a premix of acetochlor and the products in Hornet, labeled at lower rates than used in conventional corn since the intent is to only suppress weeds prior to the postemergence application rather than provide full-season control.”
Dear Reid: It seems like any conversation about herbicides revolves around glyphosate, doesn’t it?
It sure does. MSU’s Sprague says it’s almost inevitable with today’s technology. “When you look at the new seed genetics, almost everything is starting to have glyphosate resistance in it, so it’s to be expected,” she explains.
Dear Reid: We had a nasty frost last spring and had to replant our corn crop. Anything new out there for killing off a failed corn stand?
Actually, yes. Select Max from Valent is now labeled for that very use. The University of Wisconsin’s Boerboom notes that it will be a good product for killing a field damaged by frost or flood before replanting.
Dear Reid: I’ve heard about a few deals between some of the ag-chem manufacturers. How will those affect my dealership?
There have been several recent agreements created with the intent to bring improved herbicide options to the market sooner — and that’s good news for your bottom line. For example, DuPont and Valent formed a flumioxazin pact in early 2007 which allows DuPont access to Valent’s soybean active ingredient. Pending registration, DuPont hopes to have products in the market by spring.
DuPont’s seed company, Pioneer Hi-Bred International, has added several herbicides to its TruChoice Opportunity Program: Syngenta‘s Touchdown Total and Touchdown HiTech and AMVAC Chemical Corp.‘s Impact 2.8SC.
In a similar vein, Valent’s Valor, Valor XLT, and Gangster herbicides have been added to Monsanto‘s Roundup Rewards START CLEAN, STAY CLEAN Assurance Plan for Roundup Ready soybeans.
Dear Reid: Any future products you can tell us about?
Naturally, companies can be nervous about EPA’s view of pre-registration talk, but BASF is excited about a herbicide containing a new a.i., currently named BAS 800. Hager says this product is significant, because it shows that the industry is still working to register new actives.
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