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Option and Yukon Receive State Registration

April 12, 2002
In issue no. 1 of the Bulletin, we mentioned two new herbicides that were pending registration. In the last week, both of these herbicides have received state registration. These two new herbicides are Option and Yukon and are briefly described below.

Option 35WDG is manufactured and sold by Aventis CropScience and contains the new active ingredient foramsulfuron. Option is a sulfonylurea herbicide and is labeled for postemergence use in field corn. Use rates range from 1.5 to 1.75 ounces per acre. Broadcast applications may be made when corn is between zero and 16 inches in height or through the V5 growth stage. Drop nozzles must be used when corn is between 16 and 36 inches in height. Applications of Option must include a methylated seed oil and a nitrogen fertilizer (UAN or AMS). The use of non-ionic surfactants or crop oil concentrates will result in unacceptable weed control. Do not make more than two applications or apply more than 3.5 ounces of Option per acre per year.

Option has good activity on several grass and broadleaf weed species. Grasses that Option controls include foxtail, fall panicum, barnyardgrass, shattercane, johnsongrass, quackgrass, and wirestem muhly. Some of the broadleaf weeds that Option controls are common lambsquarter, pigweed, velvetleaf, common ragweed, and eastern black nightshade. Since Option is an ALS inhibitor, it will not provide satisfactory control of ALS-resistant weed biotypes. Tank mixtures with herbicides having other modes of action will be needed to control these species. Labeled tank-mix partners include atrazine, Beacon, dicamba, Distinct, Exceed, Harness, Hornet WDG, Marksman, NorthStar, Prowl, Spirit, Surpass, TopNotch, and Tough. Certain corn hybrids are sensitive to Option, so as a precaution consult seed company hybrid sensitivity charts. Do not apply Option in the same season if Counter, Dyfonate, or Thimet was used. Do not make foliar applications of an organophosphate insecticide within 7 days of an Option application. Replant intervals for Option are 7 days for corn, 14 days for soybean, and 60 days for all other crops; the preharvest interval for Option is 70 days for corn grain and 45 days for corn forage.

Yukon 67.5WDG is marketed by Monsanto and is a premixture of halosulfuron and dicamba. Yukon is labeled for use in field corn, field corn grown for seed, and grain sorghum. The common use rate of Yukon is 4 ounces per acre, which delivers 2/3 ounce per acre of Permit and 4 ounces per acre of Banvel. However, it can be applied up to 8 ounces per acre to control larger weed species in corn (6-ounce maximum rate for sorghum). Applications of Yukon must include either a non-ionic surfactant or a crop oil concentrate but not both. A nitrogen fertilizer (UAN or AMS) may be added to the spray solution; however, it is not required. Two applications of Yukon may be applied to corn per year, with a total application not to exceed 8 ounces per acre. Yukon can be applied over the top or with drop nozzles, from spike through 36-inch-tall field corn and from the two-leaf stage to 15-inch-tall grain sorghum. Yukon controls both large- and small-seeded broadleaf weeds, with the added benefit of yellow nutsedge control. Since Yukon contains dicamba, special precautions need to be taken when applications are made near dicamba-sensitive species.--Christy Sprague and Aaron Hager

Author: Aaron Hager Christy Sprague

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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