Despite cold soil temperatures, which has delayed dandelion emergence, managing dandelion in no-tillage soybean will be an issue again this season. Some have inquired about the use of Sharpen. Sharpen or Verdict may kill new seedlings but only burn dandelion leaves of perennial forms of dandelion (plants > 1 year of age) and plants will likely recover later.
If a no-tillage soybean field has dandelion, an effective herbicide treatment is glyphosate at 1.125 to 1.5 pounds acid equivalent per acre (lb ae/A) plus 2,4-D ester at 1 pt/A plus Express SG at 0.5 oz/A plus MSO or HSMOC adjuvant at 1.5 pt/A at seven days prior to planting. If glyphosate-resistant horseweed/marestail, kochia, or common ragweed is present in addition to dandelion, the addition of Sharpen at 1.5 fl oz/A or Verdict at 7.5 fl oz/A should improve the control of horseweed, common ragweed, and kochia and provide additional residual control compared to Sharpen at 1 fl oz/A or Verdict at 5 fl oz/A.
If Sharpen or Verdict is added to the tank-mixture at the high-end use rates mentioned above then soybean planting must be delayed until 14 days after application for all soils having > 2.0% organic matter and finer than a course soil texture. The addition of sulfentrazone (Spartan) products with the glyphosate, 2,4-D ester, and Express will improve control of glyphosate-resistant kochia present at the time of application and improve residual control compared to Sharpen, but it will not assist in the control of horseweed, common ragweed, and may likely reduce dandelion control.
The addition of MSO or HSMOC adjuvant to the sulfentrazone, glyphosate, 2,4-D, and Express SG combination should enhance control of emerged kochia, but likely none of the other glyphosate-resistant weeds. When applying Sharpen, Verdict, or products containing sulfentrazone in a burndown application, the water volume should be greater than 15 gallons per acre, utilize medium-sized spray droplets and reduce travel speeds to maximize spray coverage.