By Brian Hefty

What will you tankmix with Roundup post-emerge in your corn this spring?  Here is a quick rundown on the 3 most popular options, as well as some extra add-ins you commonly see in premixes.

  1. Status – Many people have the misconception that dicamba is the main weed killer in Status.  At the 5 oz rate, there is only about a quarter-pint equivalent of Clarity, so that’s not much.  The main weed killer is diflufenzopyr, which is an incredible product.  Plus, there is a corn safener.  While Status is the most expensive product, it is also the most broad-spectrum of the big three post-herbicide choices.  Status is my favorite tankmix partner for Roundup if you have waterhemp, Palmer pigweed, common or giant ragweed, marestail, lambsquarters, or kochia.
  2. Callisto/Laudis/Impact/Armezon – These are what we call the HPPD products.  They are all very similar to each other, and you’ll also find them in premixes including Halex GT, Capreno, and more.  The HPPD’s are a little weak on wild buckwheat and thistles, but they do have more soil residual than Status or straight dicamba.  They are also relatively safe even to bigger corn.  You will get the best activity from any HPPD, even when tankmixed with Roundup, by using methylated seed oil (MSO) or crop oil concentrate (COC).  However, depending on what else you add to the tankmix you may not be able to use MSO or COC.  The HPPDs offer good control on almost every Roundup-resistant broadleaf, and they are less expensive than Status.
  3. Clarity/DiFlexx – Drift and crop injury.  Those are the two big concerns with a straight dicamba product like Clarity.  DiFlexx has a crop safener, so that takes care of the safety issue, but DiFlexx is considerably higher in price than Clarity on a pound for pound dicamba a.i. basis.  Dicamba pricing is down this year, which is good news, and we expect pricing to go down even more for next year.  Yes, straight dicamba is pretty good on most broadleaves, but personally, I’d save the straight product for Xtend soybeans next year.  Our advice is to use Status or an HPPD in corn instead.
  4. Atrazine – Between potential leaching, carryover, and the constant re-evaluation by the EPA since no one can believe the LD50 of atrazine is equal to table salt, atrazine doesn’t have the best name out there.  However, it is inexpensive and a good helper on both broadleaves and grasses.  Yes, there are some weeds resistant to atrazine, and it’s certainly not a standalone product, but it does provide synergy with many post broadleaf products.  Nevertheless, because of all the other issues with atrazine, we advise you to use it post-emerge only at a rate of half a pound per acre or less in corn.
  5. Dual/Zidua/Harness/Surpass – If you are using Halex (Dual), Anthem (Zidua), TripleFLEX (Harness), or SureStart (Surpass), you are getting one of these products on your ground.  They have zero burndown activity, but do have decent residual on grasses and suppression on broadleaves.  We would prefer to see these Group 15 herbicides pre-emerge, but they do offer some value post.
  6. Cadet – While you may never spray straight Cadet post in corn, you might use Solstice (Callisto/Cadet) or Anthem (Zidua/Cadet).  Cadet is great on velvetleaf, and it has activity on many different broadleaves.  Our concern is crop safety.  We want the corn leaves dry and the plants small when you spray.
  7. Varro – Varro is not labeled in corn, but its active ingredient is in the product Capreno (Laudis/Varro).  Varro is an ALS herbicide that will obviously not help on ALS-resistant kochia, waterhemp, or Palmer pigweed.  The strength of the product is winter annuals and foxtails.  It has some suppression on a number of other weeds and has decent residual.
  8. Stinger & Python – You will find the active ingredients from Stinger and Python in SureStart and TripleFLEX.  If you are spraying those products post-emerge you will be happy with the thistle control, but the combination of Stinger and Python isn’t great on many of the toughest Roundup-resistant weeds.  Python is an ALS herbicide, and Stinger isn’t tremendously broad-spectrum.  Both products do have good residual, though.