No. 1/March 19, 1998
New Corn and Soybean Herbicides for 1998
Several new herbicides will be available for use in the 1998 growing season.Some are new active ingredients not previously available, while others arepremixes of older products. This article is intended to be a short summary ofnew additions to the market, not an exhaustive description of each product. Besure to read and follow label directions for any pesticide.
New Corn Herbicides
Accent Gold 83.8WDG is marketed by DuPont for postemergence control ofbroadleaf and grass weeds. The product-use rate is 2.9 ounces per acre, andapplications must include a crop-oil concentrate (COC) of petroleum orvegetable base; an ammonium nitrogen fertilizer is recommended in addition tothe COC. Accent Gold may be applied to corn up to 12 inches in height. Do notapply to corn taller than 12 inches or exhibiting six leaf collars, whicheveris more restrictive. Annual grasses should be 3 inches or less in height,while broadleaves should not exceed 6 inches. Accent Gold is composed of fourdifferent active ingredients: Stinger, Python, Accent, and rimsulfuron. Thepremix is similar to Basis Gold, with the atrazine replaced by Hornet to fitbetter in areas where atrazine use is restricted.
Spirit 57WDG (primisulfuron + prosulfuron) contains the same activeingredients as Exceed; however, the component ratios differ between the twoproducts. Exceed is a 1:1 premix, while Spirit is formulated as a 3:1primisulfuron:prosulfuron premix. The reduced amount of prosulfuron isintended to reduce the potential risk of carryover injury to certainrotational crops, soybeans in particular. Spirit will be marketed in the areaof Illinois between Interstate 70 and Interstate 80. The use rate is one ounceper acre for corn between 4 and 20 inches in height, or exhibiting six orfewer leaf collars. Applications of Spirit should include either a COC or anonionic surfactant (NIS) and may also include an ammonium fertilizer. Ifrotating to a broadleaf crop sensitive to Spirit the following season(soybeans), do not apply Spirit after June 30.
FieldMaster 4.25CS, marketed by Monsanto, is a premix of Harness Xtraand Roundup. The product is positioned for use in no-till corn for bothburndown and residual weed control. FieldMaster has similar label restrictionswith respect to mixing, loading, and application as other products containingacetochlor. General rate guidelines are to apply 4 quarts when existingvegetation is less than 6 inches tall; or 5 quarts when weeds are taller than6 inches or when difficult-to-control species, such as fall panicum andbarnyardgrass, are present. Tank mixes with 2,4-D or dicamba are allowed, toimprove burndown activity. Four quarts of FieldMaster are about equivalent to5 pints of Harness Xtra 5.6L and 1.5 pints of Roundup Ultra. FieldMaster isnot to be applied as a postemergence herbicide to glyphosate-resistant cornhybrids, as severe crop injury can result.
Python 80WDG (flumetsulam) may be used as a soil-applied option forbroadleaf control in corn or soybean. Python contains the same activeingredient as the Broadstrike component of Broadstrike + Dual and Broadstrike+ Treflan. Use rates vary according to soil texture, ranging from 0.8 to 1.33ounces per acre. The Python label includes several application restrictionssimilar to those listed on the Broadstrike + Dual label. Python providesgood control of several broadleaf species, including velvetleaf, but isgenerally poor on cocklebur, jimsonweed, and common ragweed.
Dual II Magnum 7.64EC, Bicep II Magnum 5.5L, and Bicep Lite II Magnum 6L(s-metolachlor) contain the same active ingredients (metolachlor ormetolachlor + atrazine) as Dual II, Bicep II, and Bicep Lite II, respectively.The difference resides with the metolachlor component. Products with theMagnum designation are formulated with the active or resolved isomer ofmetolachlor, thus the use rates are slightly reduced. For example, the userate of Dual II Magnum is about one-third less than that of Dual II.
Celebrity B&G (dicamba and nicosulfuron) is available from BASF forpostemergence control of broadleaf and grass weeds. Celebrity is a copack of adry dicamba formulation (70DG) and Accent that may be applied to corn up to 20inches tall, or with six or fewer leaf collars. Applications must include anNIS and UAN (urea-ammonium nitrate solution), but not AMS (ammonium sulfide).Grass sizes are the same as for Accent alone, while broadleaves should be 3inches or less for best performance.
Products with Labels Pending
Balance 75DF (isoxaflutole) may receive a label in 1998 forpreemergence application in corn at 1 to 3 ounces per acre. Balance controlscertain broadleaf and grass species, but the manufacturer (Rhone-Poulenc) willrecommend tank mixes with a grass herbicide, atrazine, or a grass herbicideand atrazine to broaden the control spectrum. Balance disrupts a step in thechlorophyll-synthesis pathway of plants, a mode of action similar to clomazone(Command).
Axiom 68DF (fluthiamide + metribuzin) from Bayer is a soil-appliedpremix herbicide with grass (fluthiamide) and broadleaf (metribuzin)components. Axiom primarily controls grass weeds, but the metribuzin has beenadded to provide some control of certain small-seeded broadleaf species. Proposed use rates vary according to soil texture and organic-matter content,and fall in the range of 13 to 24 ounces per acre. Axiom will also be labeledfor use in soybeans.
Aim 40DF (carfentrazone) is in the same chemical family as Authoritybut is for postemergence control of certain broadleaf species in corn. WhenAim receives a label, it likely will be positioned as a tank-mix partner forother postemergence herbicides.
Distinct 70WG (diflufenzopyr + dicamba) may receive registration during1998. The product is for postemergence broadleaf control in corn.
Other Corn News
Exceed 57WDG (prosulfuron + primisulfuron) labeling for rotational croprestrictions has been changed from the 1997 label. Soybean recrop intervals(soil pH below 7.8) are 18 months for the geography between Interstate 70 andInterstate 80, or 10 months if an STS (sulfonylurea-tolerant) soybean varietyis used. North of Interstate 80, the recrop interval is 18 months regardlessof soybean variety. Additionally, all Exceed applications must be made beforecorn reaches 30 inches in height, and before June 30 if rotating to asensitive crop such as soybeans the following season.
Roundup Ultra (glyphosate) has been labeled for preharvest applicationin corn.
Maximum per acre use rates of cyanazine (Bladex or Extrazine II) havebeen reduced in 1998. The maximum amount of cyanazine that can be applied peracre is 3 pounds of active ingredient. This rate corresponds to 3.3 or 4.4pounds, respectively, of Bladex or Extrazine 90DF; and 3 or 4 quarts,respectively, of Bladex and Extrazine II 4L. Additionally, any application ofcyanazine must be made from an enclosed cab.
New Soybean Herbicides
FirstRate 84DG (cloransulam) is labeled for soil or foliar applicationsin soybeans. Rates for soil applications (PPI or PRE) range from 0.6 to 0.75ounce per acre, while postemergence applications are made at 0.3 ounce.Additives to include with postemergence applications include an NIS + UAN,COC, or COC + UAN. FirstRate controls common lambsquarters and certainpigweeds when soil-applied, but not postemergence. Eastern black nightshade isnot controlled regardless of application method. FirstRate has good activityon several broadleaf species, including common and giant ragweed, cocklebur,and sunflower. FirstRate and Python share a common mode of action, inhibitionof the ALS enzyme.
Raptor 1S (imazamox) received a label late in the 1997 growing season.Similar to Pursuit and Scepter, Raptor is an ALS-inhibiting herbicide forpostemergence applications in soybeans. The spectrum of weed control issimilar to that of Pursuit, however Raptor has less soil-residual activity andis slightly stronger on common lambsquarters and certain annual grasses thanis Pursuit. Use rates are 4 fluid ounces per acre if following a soil-appliedherbicide, or 5 fluid ounces if used as a total postemergence program.
Touchdown 5 (sulfosate or glyphosate-trimesium) is a new formulation ofTouchdown with spray adjuvants added to the formulation. Under certainconditions, an NIS or AMS may be added to improve activity. The Touchdownformulation available in 1997 contained 6 pounds active ingredient per gallon,whereas Touchdown 5 contains 5 pounds; so the use rate will be slightly higher than in previous years.
Products with Labels Pending
Action 4.75WP (fluthiacet) may receive registration in 1998 for use insoybeans. The product also may receive a label for use in corn at a latertime. Action is used at 1.5 to 2.25 ounces per acre and is extremely active onvelvetleaf. The product likely will be positioned as a tank-mix partner forother postemergence herbicides.
Expert 75WG (oxasulfuron) is a postemergence ALS-inhibiting herbicidefrom Novartis. The use rate of Expert is expected to be 1.5 ounces per acreand often may be recommended as a tank mix with Action (also manufactured byNovartis). Expert is primarily active on broadleaf species, with good activityon cocklebur, velvetleaf, smartweed, and sunflower.
Authority First/Synchrony STS was formerly sold as Cover by DuPont in1997. The product is a copack of Authority (sulfentrazone) for soilapplication and Synchrony STS for postemergence application to controlbroadleaf species. Authority First Synchrony STS is for use only in STSvarieties.
Aaron Hager (firstname.lastname@example.org) and Marshal McGlamery (email@example.com), Extension Weed Science, (217)333-4424