By Darren Hefty

Marestail, dandelions, leafy spurge and several other tough weeds instill fear in our minds. Even talking about them can be a little scary at times. What if you could
permanently rid these weeds from your farm? Read on as we take a shot at three of the toughest winter annuals and perennials in corn, soybeans, wheat, and pastures.

Marestail

  • The first glyphosate-resistant weed in many areas across the country.
  • Fall tillage is a fairly effective control method, but by spring it may take heavier tillage to knock out the larger plants.
  • In corn, use 16 ounces of Verdict as a burndown and follow with 5 or more ounces of Status in-crop.
  • In wheat, Sharpen at 2 ounces with your burndown is effective. Crop canopy in a well-established wheat field may be sufficient to stop further outbreaks, but Huskie as well as a WideMatch/Affinity BroadSpec tank mix are decent options in the spring.
  • In soybeans, burndown is critical, and Roundup alone is not sufficient. Adding Sencor at 1/4 to 1/3 lb. per acre is helpful. Using the maximum labeled rate of Sharpen is good, but you can’t use 2 to 3 ounces like in other crops. The best product may be Authority First, which contains FirstRate. However, I prefer to save the FirstRate for post-emerge applications. Adding Flexstar with the FirstRate broadens the weed control spectrum and adds a little more punch. Flexstar (or Reflex) used in combination with Classic is another lesser alternative for post-emerge suppression.

Dandelions

  • While they sound harmless to those who haven’t had to face them in a field situation, dandelions can be one
    tough weed.
  • Perennial weed with a very large taproot. Very common weed in lawns and reduced tillage fields across the
    country.
  • Controlling dandelions in the fall is by far the best option in nearly every situation.
  • Corn – Banvel at 1 pint or a very strong rate of 2,4-D are the best fall options. Roundup is effective at the highest labeled rate if used before the first hard-killing frost. In the spring, Verdict in combination with Roundup makes a great burndown. In crop, Status is even better than Banvel if used at the full labeled rate, and
    it’s much more crop safe.
  • Soybeans – Fall burndown is a great option that allows you to use some products that would not be okay in the spring, such as 2,4-D. Fall treatments with 3 ounces of Valor plus 2,4-D have worked well while giving fields some residual control into the spring.
  • Wheat – Burndown is key, and Sharpen with Roundup works well. Plus, the Sharpen gives some residual broadleaf control for a couple weeks. In crop, you have to hit dandelion early in the spring while they are smaller and you can still get good coverage. Huskie is the best option, but it will only suppress established dandelions.

Leafy Spurge

  • Mainly a problem in pastures, grasslands, and roadside ditches.
  • Rarely a problem in fields.
  • Fall is the best time to control leafy spurge because the plant moves nutrients down into its root system before the first hard-killing frost to survive the winter.
  • Tordon is the best herbicide option for control. It moves through the plant to achieve a permanent solution. Use 1 quart per acre and spray an extra pass around the outside edges of all patches to account for any rhizomes (underground spreading root systems).
  • Tordon takes a long time to break down in the soil, potentially up to 5 or even 10 years, so only use it where you plan on leaving the ground in pasture or grass.
  • If you’ve already had a killing frost this fall or if you’re planning on rotating to another crop in the next few years, a strong rate of 2,4-D can provide top growth control.

Your job this fall isn’t done yet if you have these tough weeds. Fall herbicide treatments could make your job much
easier next spring, so talk to your agronomist to see which programs fit in your area.