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Issue No. 1, Article 4/March 25, 2011

Product Updates for Weed Management in 2011

With the dawning of a new season of newsletter articles, here is a brief overview of some changes in herbicide options available to Illinois weed control practitioners. Currently, the list includes no new herbicide active ingredients. This article is not intended to provide a complete summary of all label changes, and all who use herbicides are encouraged to carefully consult their product labels.

Authority XL 70DG (sulfentrazone + chlorimuron) is the newest addition to the Authority family of products. These active ingredients were previously paired as Authority Broadleaf/Canopy XL, but the active ingredient ratio in Authority XL differs from the earlier premixes. Authority XL may be applied following fall harvest through preemergence for burndown and residual control of broadleaf weed species in soybean. Use rates vary according to soil texture, organic matter content, and length of desired residual weed control. Recommended rates range from 5 to 9.6 ounces per acre, or reduced rates of 3 to 5 ounces per acre when used in conjunction with a planned postemergence application of glyphosate or glufosinate. Do not apply Authority XL if soybean have begun to emerge or if soil pH is greater than 7.6.

Callisto Xtra 3.7SC (mesotrione + atrazine) is a premix product for postemergence control of certain broadleaf weed species in corn and as 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 NIS in combination with an ammonium nitrogen fertilizer (such as UAN or AMS).

Flexstar GT (fomesafen + glyphosate) has become Flexstar GT 3.5.

Peak 57WDG (prosulfuron) can be applied postemergence in field corn or corn grown for silage. Peak, at rates ranging from 0.5 to 1 ounce per acre, can be applied to corn between 4 and 30 inches tall for control of certain broadleaf weed species sensitive to ALS-inhibiting herbicides. To ensure good spray coverage and to reduce the potential for corn injury, applications to corn between 20 and 30 inches or that exhibits more than 6 leaf collars should be directed with drop nozzles.

Prequel 45WDG (rimsulfuron + isoxaflutole) contains the active ingredients of Resolve and Balance Pro. Prequel may be applied from up to 30 days before corn planting (include either MSO or COC for control of existing vegetation) until prior to corn emergence (do not apply after corn begins to emerge). If existing vegetation exceeds 3 inches, a tank-mix partner (such as glyphosate, paraquat, or 2,4-D) is suggested. 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 positioned as a set-up treatment preceding a postemergence herbicide application. 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.

Realm Q 38.75WDG (rimsulfuron + mesotrione) can be applied at 4 ounces per acre to corn up to 20 inches tall for control of small grass (less than 2 inches) and broadleaf species. The 4-ounce application rate, which provides the equivalent of 1.2 ounces of Resolve 25DF and 2.5 ounces of Callisto 4SC, can also provide some residual control. Applications of Realm Q should be made in a minimum of 15 gallons per acre and must include a COC or NIS and an ammonium nitrogen fertilizer. Tank-mix partners can help broaden the spectrum of weeds controlled.

TripleFLEX 4.16SE is a premixture of three active ingredients (flumetsulam + acetochlor + clopyralid) in the same ratio as SureStart. TripleFLEX, at rates ranging from 1.5 to 3 pints per acre, may be applied before corn planting/emergence, or postemergence until corn reaches 11 inches tall.

Verdict is the new name for last year's Integrity. While the formulation has not changed, the maximum application rate in corn has been increased from 16 to 18 fluid ounces per acre. Additionally, Verdict at 5 fluid ounces per acre may be applied as a preemergence burndown in reduced or no-till soybean.

Warrant (acetochlor) is an encapsulated formulation of acetochlor (3 lb ai/gallon) labeled for postemergence applications in soybean and corn. Warrant 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 corn, apply 1.5 to 3 quarts per acre before corn exceeds 30 inches. In glyphosate-resistant crops, glyphosate may be tank-mixed with Warrant if emerged weeds are present at the time of application.--Aaron Hager

Author:
Aaron Hager

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