Ryegrass and poa control can become more problematic when horseweed must also be controlled. Simply dropping dicamba in the tank with glyphosate and/or clethodim to control the horseweed will compromise the grass control of those two herbicides. So, is there a herbicide that can be added to glyphosate or glyphosate + clethodim that will provide horseweed control while not sacrificing ryegrass control? There is really only one option that is in good supply that would fit the bill.
This option is Elevore, which is an auxin-mimic herbicide with a mode of action similar to 2,4-D. In our research it has provided horseweed control as good as Sharpen or Verdict. One big plus we have seen with Elevore compared to dicamba is the greatly reduced grass antagonism when mixed with glyphosate.
Another option if you can get it would be saflufenacil (trade names Sharpen or Verdict). In short, the saflufenacil tankmix with glyphosate improves grass control. If you can access Sharpen or Verdict they can be effective options in a tankmix with glyphosate + clethodim to provide control of ryegrass as well as horseweed. Please keep in mind the smaller the ryegrass the better chance of control with that tankmix. Poa control from this tankmix is also typically pretty good.
Please keep in mind the plant back to cotton after Sharpen is 1 month and to Verdict is 6 months. However, there is no waiting period to plant corn, grain sorghum or soybeans after a 1 oz/A of Sharpen or 5 oz/A of Verdict.
If the field in question is infested with just scattered horseweed a possible option would be to go with a glyphosate + clethodim burndown to take out the grasses. Then control the horseweed in-crop with Liberty in Xtend crops or Enlist One and/or Liberty in Enlist crops.
