Touchdown Labeled for Postemergence Applications in Glyphosate-Resistant Soybeans

June 18, 1999
Last week, a federal label was issued that permits Touchdown 5 (glyphosate trimesium or sulfosate) to be applied postemergence to glyphosate-resistant (Roundup Ready) soybean varieties for control of broadleaf and grass weed species. Postemergence applications can be made up to and including the full-bloom stage of soybeans, at a maximum of 3.2 pints per acre. For many annual weed species, apply 1.2 to 3.2 pints per acre. An application rate of 1.6 pints per acre for weeds up to 6 inches in height is commonly recommended by the manufacturer. Including a spray-grade ammonium sulfate at 8.5 to 17 pounds per 100 gallons of water may improve control of annual and perennial weed species. Repeat applications are allowed up to a maximum per acre application rate of 12.8 pints. Several tank-mix options are included on the new label.

Additionally, Touchdown 5 also may be used as a preharvest treatment in glyphosate-resistant soybean varieties to aid in soybean harvest. Make preharvest applications at least 7 days before harvest, with no more than 1.6 pints per acre. Do not graze or harvest for hay following a harvest-aid application.

The active ingredients (acid) in Touchdown 5 and Roundup Ultra are the same, but these two herbicides are formulated as the trimesium and isopropylamine salts, respectively. Touchdown 5 contains 5 pounds active ingredient/3.43 pounds acid equivalent per gallon, whereas Roundup Ultra contains 4 pounds active ingredient/2.95 pounds acid equivalent per gallon.--Aaron Hager, Marshal McGlamery, and Christy Sprague

Author: Aaron Hager Marshall McGlamery Christy Sprague