The call of the spring and now well into the summer is on failed attempts to control junglerice and goosegrass in Xtend crops. The most recent rash of calls have been from very frustrated folks who have not controlled one of those grass species even after three applications of glyphosate and/or clethodim. Most of these failed applications are coming from tank mixing Engenia or XtendiMax in the tank with either glyphosate, clethodim, or both. Our preliminary research funded by the Tennessee Soybean Promotion Board shows that adding a dicamba herbicide to the tank, reduces grass control by ± 30 percent (Figure 1). Even without dicamba in the tank we only get about 80% control with glyphosate or clethodim. Please note this is the junglerice that is considered glyphosate “susceptible”. We are conducting research at one location where the junglerice is glyphosate resistant and are seeing at best 30% control with glyphosate applied alone.
Another factor in the junglerice escaping glyphosate+dicamba tankmixtues is using the Engenia/XtendiMax labeled nozzles (TTI nozzles) rather than a flat fan nozzle. In addition to the ~30% control loss from Dicamba in the tank, we lose an additional 4% control from using these TTI nozzles (Figure 2).
The best option moving forward would be to spray a quart of glyphosate plus a pint of 2 lb clethodim WITHOUT either Engenia or XtendiMax in the tank. Then follow up with another shot of glyphosate or clethodim two weeks later. Those that still have Palmer amaranth and junglerice and/or goosegrass in your field, these data would suggest the best approach would be to spray Engenia or XtendiMax alone and coming back 5-7 days later with glyphosate and clethodim in order to acquire the best junglerice control.