Farmers in Illinois, other states too, are struggling to control glyphosate resistant weeds. Marestail can be one of the most challenging under no-till conditions prior to planting soybeans. More often than not farmers are using a tank mix of glyphosate and 2,4-D (two-four-dee). Sometimes the problem is that the weed is already too big to control, at others says University of Illinois Extension Weed Scientist Aaron Hager is its just that the 2,4-D isn’t doing the job any better than the glyphosate.
Quote Summary - Well, there are some alternatives that can be used for control of mares tail in a burn down scenario. A product called Sharpen could be included with glyphosate/2,4-D to try to increase the efficacy on the marestail and if that is the case be sure to include a methylated seed oil with any application that has Sharpen with it. Or alternatively you could switch completely over to something like a glufosinate product, like a Liberty or Interline containing product or something like Gramoxone. Either of those will typically perform better when used in combination with metribuzin and probably 2,4-D in the tank as well.
Tillage is another option, however, Hager says to delay it until field conditions are suitable and be sure to till deep enough to completely uproot all existing vegetation.