By Daniel Davidson
DTN Contributing Agronomist
This looks like a good year for herbicide options on soybeans compared to corn where the marketing has been relatively quiet in 2014.
Ohio State University weed scientist Mark Loux said weed pressures in soybeans and the increasing threat of weed resistance to glyphosate have led companies to provide a number of premixes that take advantage of currently available chemistries with residual soil activity. Marestail, common ragweed, Palmer amaranth and waterhemp are the main weeds driving management in soybean fields today.
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Pyroxasulfone is a new active ingredient for residual control of annual grasses and small-seeded broadleaf weeds. Pyroxasulfone is effective at controlling waterhemp, Palmer amaranth, lambsquarters, and black nightshade. It also has fair activity on common ragweed and velvetleaf at higher rates.
Zidua (BASF) and Fierce (premix of pyroxasulfone and flumioxazin (Valor) from Valent) are labeled for preplant or preemergence use in soybeans. Loux added that the Valor in Fierce provides residual marestail control.
The last new chemistry released specifically for soybeans was the saflufenacil chemistry (Kixor) from BASF and products include Sharpen, OpTill, OpTill Pro, and Verdict. Loux pointed out that labels still prevent the mixture of PPO-inhibiting herbicides flumioxazin, sulfentrazone, and fomensafen. "Applications of saflufenacil should be separated from application of the other PPO inhibitors by at least 30 days," Loux said.
The other major change for Sharpen (saflufenacil) and Verdict (saflufenacil and dimethenamid) has been the addition of higher rates in soybeans. "Sharpen can be applied at rates up to 2 ounces per acre in a soybean burndown program," Loux told DTN. "And 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." Loux added that similar changes have occurred for Verdict.
Growers need to pay attention to the label of products with Sharpen. For example, in soils with 2% organic matter, Sharpen can be applied at 1 oz. per acre before crop emergence. Increase the rate to 1.5 oz. and planting intervals increases to 14 days and 2 oz., requires a 30-day wait before planting. On coarse soils with 2% or less organic matter, the minimum interval between Sharpen application and planting is 30 to 44 days.
Today's soybean premixes are formulated primarily for their residual capacity to control weeds as they germinate and emerge. Loux explained companies are tweaking their premixes to get better control of problem weeds like Palmer amaranth by changing the rates of active ingredients, adding additional ingredients and/or tweaking formulations to use or as an early post application.
That's causing some growers to add an additional application of residual to their herbicide program. "We are seeing a shift from preemerge to an early- and late-post applications. A residual is being added to the early post to control emerging weeds after planting," Loux said.
Dow AgroSciences is marketing its Surveil co-pack herbicide. Surveil is a tank mix herbicide with residual activity with two chemistries, flumioxazin and cloransulam-methyl. It provides control of giant ragweed, marestail, Palmer amaranth, waterhemp and other broadleaf weeds. It can be applied preplant or preemergence (up to three days after planting). It can also be tank mixed with a spring burndown product.
DuPont is marketing LeadOff and Panoflex for soybeans. LeadOff, a combination of rimsulfuron and thifensulfuron is being marketed for use on soybeans in Southern and Delta states. It controls winter annuals including marestail, henbit, wild radish, chickweed and annual bluegrass (suppression). It can be applied 30 days prior to planting.
Panoflex 50SC, a combination of thifensulfuron (Harmony) and tribenuron (Express), is similar to Harmony Extra, but has different ingredient ratios. It is targeted as tank mix with glyphosate as a burndown in the spring.
DuPont is evaluating two experimental products: Trivence and Afforia. Trivence is a combination of chlorimuron (Classic), metribuzin and flumioxazin (Valor) and is targeted as a burndown with residual control of broadleaf weeds with activity on marestail, giant ragweed, waterhemp and Palmer amaranth. It can be applied preplant or preemergence (up to three days after planting). For additional preemergence broadleaf weed control, Trivence can be tank-mixed with metribuzin or pyroxasulfone. For additional grass control, Trivence can be tank-mixed with pendimethalin or pyroxasulfone. DuPont expects registration during the first quarter of 2014.
Afforia is a combination of thifensulfuron, tribenuron and flumioxazin and is targeted as a preplant burndown with residual control of broadleaf weeds and is focused more for northern growing regions and crop rotations. Registration is expected in 2014.
FMC has a number of products available including, Anthem, Authority Elite, Authority XL, Authority MAXX, and Marvel. Authority Elite, Authority XL and Authority MAXX are residual products containing Authority (sulfentrazone) and Dual (metolachlor in Elite) or Classic (chlorimuron in XL or MAXX). "The ratio of sulfentrazone to chlorimuron is higher in Authority MAXX compared with Authority XL, but the spectrum of control and other characteristics are similar," Loux said. "Due to the lower rate of chlorimuron in Authority MAXX, the crop-rotation restrictions are not pH-dependent, which differs from other chlorimuron products."
Anthem, first introduced for corn in fall of 2012, provides control of broadleaf weeds and grasses. In 2014, Anthem is available for soybeans. Anthem offers an application window from 45 days preplant through V3 with four to eight weeks of residual activity. Applied in-season, growers can combine the concentrated liquid formulation of Anthem with other tank mix herbicides at rates as low as 4 to 11 ounces per acre.
Marvel is a premix of fomesafen and fluthiacet-methyl (Cadet) for postemergence use in soybeans. Loux explained that the rate of fomesafen is fairly low and the spectrum of control for Cadet is narrow. "Marvel is apparently intended for use in mixtures with glyphosate in Roundup Ready soybeans to help control glyphosate-resistant weeds, and primarily Amaranthus species. This product has no activity on marestail," he said.
Loveland (CPS) is marketing Intimidator and Matador. Intimidator is a premix of metolachlor, fomesafen, and metribuzin and labeled for preplant or preemergence use in soybeans. Matador is a premix of metolachlor, imazethapyr (Pursuit) and metribuzin and labeled for preplant or preemergence use in soybeans. Loux said both products have activity on ragweed species, but are less effective than some other soybean residual premix products. He recommends adding a few ounces of metribuzin to improve control of marestail.
MANA is marketing four residual products available including Pummel, Torment, Rumble and Tailwind. Pummel is a premix of metolachlor and imazethapyr and intended for preplant, preemergence or early postemergence. Torment is a premix of fomesafen and imazethapyr and can be applied preplant, preemergence or postemergence. Neither product controls marestail. Loux said when used preplant or preemergence, Pummel or Torment should be mixed with metribuzin to ensure residual marestail control.
Rumble contains fomesafen, can be applied preemerge or postemergence and controls common ragweed, Palmer amaranth and common ragweed. It can be tank-mixed with glyphosate or paraquat products. Tailwind contains metolachlor and metribuzin and is targeted as a preemerge and controls about 40 species of grasses and broadleaf weeds, including those resistant to glyphosate such as waterhemp and Palmer amaranth.
Monsanto's encapsulated acetochlor Warrant has included soybeans on the label, but some label changes now allow it to be applied preplant, preemerge or postemergence and tank mixed with glyphosate. As a preemerge product, it will broaden control of small seeded grasses and broadleaf weeds, including waterhemp and Palmer amaranth.
Syngenta is marketing Flexstar GT 3.5. It is a combination of fomesafen (Reflex) and glyphosate and can be applied preemerge or postemergence on soybeans. It was developed to control weeds resistant to ALS and glyphosate herbicides including Palmer amaranth, waterhemp and common ragweed and it provides partial control of giant ragweed.
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