By Brian Hefty

Since almost every farmer now has Roundup-resistant (or at least tolerant) weeds, post-emerge tankmixing with Roundup is more popular than ever.  Below are some products you should consider adding in this summer.  By the way, spray nozzle selection and adjuvant choice are also big keys to getting better control.  If you want a better kill, use flat fan nozzles and crop oil or methylated seed oil.  If you want less off-target movement and more crop safety, use drift reduction nozzles and nonionic surfactant.  Either way, always use real ammonium sulfate for the best weed control, but if you are willing to sacrifice a little control for convenience, there are plenty of AMS-replacement products available.

  • Waterhemp: Best=Flexstar, 2=Marvel (Flexstar/Cadet premix), 3=Cobra or Cadet
  • Lambsquarters: Best by far=Harass ($1/acre), 2=Resource, 3=Pursuit
  • Kochia: Best (and by best I mean awful, but better than nothing)=Cobra, 2=Marvel, 3=Cadet
  • Common ragweed: Best=FirstRate (IF the ragweed is not ALS-resistant), 2=Flexstar, 3=Cobra
  • Marestail: Best (here again everything is terrible, so I’m talking best of the worst)=FirstRate, 2=Marvel, 3=Flexstar/Classic tankmix
  • Wild buckwheat: Best=Pursuit, 2=Harass, 3=Flexstar
  • Volunteer corn: Best=Fusilade, 2=Se-Cure, 3=Clethodim

I’ve just given you MY rankings on the best products to use agronomically, and for the most part economically, too.  Please keep in mind that prices and programs may drastically change the economic factors for you, and if you only have a few weeds it may be worth it to go with the less expensive option and sacrifice a little on the control side.  Also, crop rotation certainly plays a factor, as products like Pursuit, Flexstar, FirstRate, and Classic can all carryover to damage your next crop, depending on which crop you plant.  Harass, Cobra, Resource, and the volunteer corn herbicides have no residual left after a couple of weeks.

If you want to learn more about these weeds and the proper herbicide choices, download the Ag PhD Field Guide App for your smartphone or tablet.  Darren and I have put together the best weed control programs in corn, soybeans, and wheat for all the weeds I have listed above, as well as many more.  Plus, we give you some tips on identification along with pictures and other helpful information.