By Darren Hefty

Growing up, there were hardly any post-emerge weed control options in soybeans.  My dad said this “allowed the best managers the opportunity to stand out because they had to be fussy to have a clean field.”  There are plenty of weed control options in soybeans now, but in sunflowers there still aren’t very many.  That leads to an “opportunity” as my dad would say, to stand out with good management.

STEP 1 – FERTILITY

2000 pound flowers take up a lot of nutrients.  They need to pull out of the ground:

  • 110 pounds of nitrogen
  • 24 pounds of phosphate
  • 100 pounds of K2O potassium
  • 17 pounds of sulfur

While the flowers don’t remove all that from the field (some is returned if the residue is left in the field after harvest), they still need to access that many nutrients, so be sure to have them available.  Having a thick, healthy stand gives you your best chance at crop canopy stopping future weed outbreaks.

STEP 2 – VARIETY SELECTION

This is a big deal in all crops.  Yield is important.  Traits are important.  Don’t forget to look at the defensive characteristics of the variety, though, as this often makes an impact on performance from field to field.

STEP 3 – WEED CONTROL

If you aren’t willing to use a pre-emerge herbicide, you probably shouldn’t be raising sunflowers.  It’s that critical.  Here are the most popular and effective choices.

Pre-emerge.  Our recommendation is to use 2 pre’s, one from each of these categories:

  1. Spartan – With the same active ingredient as Authority, this is your best broadleaf weed control option.  Spartan has a long soil residual which helps fight weeds through most of the growing season.  You often get the best deal buying Spartan Charge, which also contains Aim.  Aim adds greatly to the burndown but has no residual.
  2. A Yellow or Dual – The “yellows” include Prowl (for no-till), Sonalan, and Treflan.  These are the best grass control residual herbicides, and they help on small-seeded broadleaves as well.  Dual and the generic versions of Dual are good grass control residuals if you don’t want to use a yellow for some reason.

Post-emerge:

  • Select Max, Poast, and Assure II are among the many contact grass herbicides available for sunflowers.
  • Beyond – With the same active ingredient as Raptor for soybeans, Beyond works well in Clearfield flowers controlling grasses and broadleaf weeds that are not ALS-resistant.  Just watch the carryover issue next year.
  • Express – For use in ExpressSun varieties only, Express has good broadleaf activity but needs help controlling grasses.

Summary of weed control:

No-till – start with a burndown using Gramoxone or Roundup plus your pre-emerge herbicides.  We suggest using Spartan Charge plus Prowl.

Conventional till – Spartan Charge plus Sonalan is recommended.  Sonalan has slightly more weed control and less carryover potential compared to Treflan.  Since there are no good post options, you need maximum weed control pre-emerge, which is why Sonalan is the preferred product over Treflan in sunflowers.

STEP 4 – DISEASE AND INSECT MANAGEMENT

Getting the first three steps right sets the table for a good crop.  Continue scouting through the season and address disease and insect outbreaks timely to maximize yield.