Weed Control Strategies - 4

OMAHA (DTN) -- It could be the breakout year for soil-residual herbicides in soybeans. Growers are getting the message that it takes more than traits to control problem weeds such as marestail, waterhemp, ragweed and Palmer amaranth.

A full rate of a soil-residual herbicide, coupled with moisture this spring and a planned postemergence program, is a good start toward controlling problematic weeds in most of the Midwest. Southern growers or those located in areas with a persistent weed issue may need to look at more elaborate programs of overlapping residuals.

Mark Loux, extension weed scientist at The Ohio State University, noted that the number of products available has expanded. "Companies now have access to more generic, off-patent products than ever before," Loux said. "The use of residual in soybeans is increasing rapidly and everyone wants to get a product in that market space. And, lastly, herbicide-resistant waterhemp, Palmer amaranth and ragweed continue to present new challenges and new herbicides are needed to target these problem weeds."

NEW CHEMISTRY

Just as in corn, pyroxasulfone is the only new active ingredient coming to market this year for use in soybean. "Mode of action of pyroxasulfone is similar to the acetochlor and controls most annual grasses, pigweed, waterhemp, lambsquarters, and black nightshade, and also has fair activity on common ragweed and velvetleaf at higher rates," Loux reported. BASF will market a pyroxasulfone-only product, while other companies will offer it as a premix.

COMPANY PRODUCTS AND LABEL CHANGES

BASF

BASF continues to market saflufenacil, the active ingredient in Kixor and Sharpen. Loux said the major changes with saflufenacil products within the past year include the addition of higher soybean burndown rates and planting restrictions.

Sharpen can now be applied at rates up to 2 ounces per acre in a soybean burndown program. Loux said higher rates can improve burndown and residual broadleaf weed control. "As Sharpen rates increase above 1 ounce per acre, the minimum interval between application and soybean planting increases. For soils with more than 2% organic matter, the minimum delay between Sharpen application and planting at 1 ounce is any time before emergence; at 1.5 ounce, 14 days, and at 2 ounces, 30 days." Loux added that similar changes have occurred for Verdict (saflufenacil and dimethenamid) in soybeans.

OpTill PRO is a co-pack of OpTill (saflufenacil and imazethapyr) plus Outlook (dimethenamid), which was released in 2012. OpTill PRO can be applied prior to soybean emergence. The addition of Outlook improves control of annual grasses, pigweed, waterhemp and black nightshade.

"There have been some changes in the status of the labels for mixing saflufenacil products with other PPO (Protoporphyrinogen oxidase)-inhibiting herbicides since last spring," Loux noted. New labels state that saflufenacil cannot be mixed with flumioxazin (Valor, Valor XLT, Envive, Enlite, Gangster, Fierce) or fomesafen (Prefix, Intimidator). In addition to the prohibition of mixing, a period of 30 days must separate the application of any of these herbicides and the application of saflufenacil. Several products containing sulfentrazone can still be mixed with saflufenacil, and these include: Sonic, Authority First and Authority XL.

BASF is also expecting registration of Zidua herbicide for use in soybeans this year. It is the only solo pyroxasulfone product on the market, and has a wide application window, from fall through early preplant to early postemergence. This provides adaptability to a wide range of weed control needs and allows for precise placement for the most effective weed control. Zidua herbicide can also be applied at a range of use rates, allowing growers to select the best rate for their specific needs, based on soil texture in their fields.

FMC

Marvel is a premix of Flexstar (fomesafen) and Cadet (fluthiacet-methyl) herbicides for postemergence use in soybeans. Marvel is a contact herbicide to control tough weeds such as Palmer pigweed and waterhemp. FMC received federal registration in February 2013. FMC anticipates registration of Anthem (pyroxasulfone and Cadet) in soybeans in 2013 for use in soybeans in 2014. It provides broad-spectrum weed control with residual for control of grasses and broadleaf weeds.

LOVELAND/CPS

Intimidator is a premix of metolachlor, fomesafen (Reflex) and metribuzin for preplant or preemergence use in soybeans. Intimidator provides broad-spectrum weed control, but will be less effective for residual control of giant ragweed compared with other broad spectrum soybean herbicides. Addition of a few more ounces of metribuzin improves marestail control and burndown of some weeds. Matador from Loveland/CPS is a premix of metolachlor (Dual), imazethapyr (Pursuit), and metribuzin for preplant or preemergence use in soybeans.

MANA CROP PROTECTION

MANA has launched five new soybean weed control products in time for the 2013 season: Torment, Rumble, Vise Outflank and Tailwind herbicides.

Torment combines imazethapyr (Pursuit) and fomesafen (Reflex/Flexstar) for control of more than 65 grasses and broadleaf weeds with up to 45 days of residual activity. Torment can be used as a preemergent or early postemergent application. Torment was designed to be used where grass and broadleaf resistance issues related to glyphosate and HPPD and triazine inhibitors resistant weeds are present.

Rumble is a preemergence and postemergence residual tool containing fomesafen. The formulation has compatibility with glyphosate and paraquat-based products.

Vise herbicide contains fomesafen and metolachlor. The dual modes of action provide up to 45 days of residual control and are an early-season foundational tool and work with a glyphosate postsequential program. Both Rumble and Vise provide residual control of both glyphosate- and ALS-(acetolactate synthase)-resistant weeds such as waterhemp, Palmer amaranth and common ragweed.

Outflank contains the active ingredient flumioxazin that offers broad spectrum residual control in soybeans, cotton, field corn and many other crops. Early season applications can help manage ALS-, sulfonylurea- and glyphosate-resistant weeds while offering crop safety and rotation flexibility.

Tailwind, a residual herbicide, contains the active ingredients metolachlor and metribuzin. Its two modes of action control more than 40 species of grasses and broadleaf weeds, including those resistant to glyphosate and ALS inhibitors.

MONSANTO

Monsanto has expanded the label for Warrant herbicide (encapsulated acetochlor) to include preemergence use in soybeans. The new label will broaden control of small-seeded grasses and broadleaf weeds including tall waterhemp and Palmer amaranth and in either a pre- or postemergence application. Encapsulation improves crop safety and provides up to 30 days residual control. Warrant can be tank-mixed with glyphosate and be applied to Roundup Ready soybeans.

VALENT

Fierce herbicide now has clearance for use in soybeans. Fierce is a combination of Valor (flumioxazin) and pyroxasulfone. It offers preemergence and residual control for tough weeds such as Palmer amaranth, waterhemp, common lambsquarters, velvetleaf, dandelion, marestail, annual nightshade and annual grasses. It should help soybean growers manage weeds with resistance to glyphosate, ALS and triazine resistance.

Daniel Davidson can be reached at daniel.davidson@telventdtn.com

(ES/SK)

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