No. 1 Article 2/March 26, 2010

Herbicide Updates for 2010

We begin the 2010 season of weed-related articles for the Bulletin with a broad overview of changes in herbicide options. This is not a complete summary of all changes, and we encourage all who use herbicides to consult current product labels for additional information.

Sharpen 2.85SC (saflufenacil) is a new active ingredient developed and marketed by BASF. Sharpen can be applied prior to planting corn, small grains, grain sorghum, and soybean to control existing vegetation and provide residual control of annual broadleaf weed species. (The length of residual control will depend on application rate.) Application rates range from 1 to 3 fluid ounces per acre, depending on crop. Sharpen belongs to a new chemical family that inhibits the PPO enzyme (similar in action to other soil-applied PPO inhibitors such as sulfentrazone and flumioxazin). For optimal burndown activity, include MSO or COC plus AMS with Sharpen. Sharpen is particularly effective on emerged horseweed/marestail, including biotypes resistant to glyphosate or ALS inhibitors, and has good burndown activity against several other winter annual weed species. Tank-mixes with other products, such as glyphosate, will improve control of other winter annual weed species, including common chickweed and henbit. Sharpen will not control annual grass species. Do not tank-mix Sharpen with other soil-applied PPO inhibitors (such as flumioxazin or sulfentrazone) within 30 days of soybean planting, and do not apply after crop emergence or severe injury will result.

OpTill 68WG (saflufenacil + imazethapyr) combines the active ingredients of Sharpen and Pursuit into a premix that can be used in soybean and Clearfield corn hybrids, although most use of this product in Illinois will be in soybean. OpTill, applied at 2 ounces per acre, provides the equivalent of 1 fluid ounce of Sharpen and 1.4 ounces of Pursuit 70DG. Expect residual weed control from this premix to be contributed primarily by the imazethapyr component, as 0.022 lb ai saflufenacil (equivalent to 1 fluid ounce of Sharpen) provides very limited residual weed control. OpTill may be applied before or after planting but before soybean emergence, and it can provide burndown control of several weed species when used in combination with an MSO or COC and AMS.

Integrity 5.57EC (saflufenacil + dimethenamid), containing the active ingredients of Sharpen and Outlook, can be applied preplant or preemergence in corn for control of annual broadleaf and grass weed species. Application rates range from 10 to 16 fluid ounces per acre, depending on soil texture. The 16-ounce rate of Integrity provides the equivalent of 3 fluid ounces of Sharpen and 16 fluid ounces of Outlook. Expect longer soil-residual control of broadleaf weeds with this rate of Sharpen, but a follow-up application of a postemergence herbicide may be needed to achieve satisfactory weed control later into the growing season.

Capreno 3.45SC (tembotrione + thiencarbazone) combines the active ingredient of Laudis with a new ALS-inhibiting herbicide that improves control of fall panicum over Laudis alone. Capreno, at 3 fluid ounces per acre, can be applied postemergence to corn from the V1 through V6 growth stages. Applications should include an additive package consisting of COC and AMS. Similar to Laudis, tank-mixing 0.5 lb ai/acre atrazine with Capreno will improve the consistence and speed of weed control. Capreno is formulated with a safener (isoxadifen) to reduce the potential for adverse crop response. Several Bayer active ingredients and safeners appear in more than one herbicide; following is a brief summary:

Prequel 45WDG (rimsulfuron + isoxaflutole) is a new corn herbicide premix containing the active ingredients of Resolve and Balance Pro. Prequel may be applied from up to 21 days before corn planting (include either MSO or COC for control of existing vegetation) through prior to corn emergence (do not apply after corn begins to emerge). Preplant applications of up to 30 days are allowed when used in a planned sequential application program (i.e., with a postemergence herbicide application). Applications of Prequel at 1.66 ounces per acre provide the equivalent of 1 ounce Resolve 25DF plus 0.66 ounce Balance 75WDG. Prequel is likely to be positioned as a setup treatment preceding a postemergence application of glyphosate or glufosinate. The label includes several precautionary statements related to conditions conducive for corn injury and use restrictions based on soil types and depth to ground water.

The grazing restrictions for several DuPont cereal herbicides have been changed. The old grazing restrictions for Harmony SG, Harmony Extra SG, and Express SG specified not to graze or feed forage or hay from treated areas. New grazing restrictions approved by EPA allow the following:

Callisto Xtra 3.7SC (mesotrione + atrazine) is a premix product for postemergence control of certain broadleaf weed species in corn and a tank-mix partner with glyphosate for use in glyphosate-resistant hybrids. The application rate ranges from 20 to 24 fluid ounces per acre; the 24-fluid-ounce rate will provide the equivalent of 3 fluid ounces of Callisto and 1.2 pints of AAtrex. Applications must be made before corn exceeds 12 inches and must include either a COC or an NIS in combination with an ammonium nitrogen fertilizer (such as UAN or AMS).

MON 63410 (acetochlor) is an encapsulated formulation of acetochlor (3 lb ai/gallon) labeled for postemergence applications in soybean. MON 63410 must be applied postemergence to the crop but preemergence to grass and small-seeded broadleaf weeds, as acetochlor will not control emerged weeds. Applications, at rates ranging from 1.25 to 2 quarts (depending on soil texture and organic matter content), should be made after soybean are completely emerged but before they reach the R2 growth stage. In glyphosate-resistant soybean varieties, if emerged weeds are present at the time of application, glyphosate may be tank-mixed with MON 63410.--Aaron Hager

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