Herbicide Stewardship

DR. LARRY STECKEL

 JACKSON, TENNESSEE 

It is crunch time for weed control in our row crops.  When every minute counts to get herbicide applied it is tempting to cut corners on herbicide stewardship.  The forecast would suggest that Tennessee will be entering a bit of a dry spell.  Herbicide drift is even harder for crops to recover from when drought stressed so please take time to use best management practices applying all herbicides but particularly products that contain dicamba and 2,4-D.

 The 2,4-D Ester formulation is fine to use when it is cold outside but should not be used in the now.  Under hot conditions the ester formulation of 2,4-D can readily get up and move as a gas often long after the sprayer has left the field. The title on the jug “Low Volatile Ester” can be misleading and is referring to the ester formulation being less volatile than older 2,4-D formulations from back in the 1950s.  The amine or choline salt 2,4-D formulations are much less volatile than the older ester formulation and are the safest to use but even they should be used with caution.  Never apply them if a crop downwind is sensitive to 2,4-D.

 Likewise, be good stewards when applying dicamba.  There are a lot of best management practices (BMPs) to keep in mind when using this herbicide and include using the labeled formulations Engenia, Tavium and XtendiMax only over the top of Xtend crops. Some folks forget but not just any glyphosate formulation can be tankmixed with those labeled dicamba formulations.  Only approved K-salt glyphosate formulations can be tankmixed with Engenia, Tavium and Xtendmax.  It is also very critical to utilize the correct nozzles, drift control agents and boom height.  Other BMPs are just common sense like be aware of wind direction and what is growing on the landscape down wind. Please remember that some of the BMPs for dicamba stewardship can be found here at the Tennessee Department of Agriculture’s Dicamba Resources page.

 If a sensitive crop is down wind Liberty is a good alternative to dicamba for Palmer amaranth control in XtendFlex crops.  In Xtend soybeans the best option would be Ultra Blazer or Cobra. Those two herbicides will likely control some but not all of the pigweed present though. ∆

DR. LARRY STECKEL: Weed Specialist, University of Tennessee