Junglerice control with glyphosate and clethodim as influenced by dicamba and 2,4-D mixtures

Junglerice has become a major weed in the mid-south and other areas of the United States. Glyphosate resistance has been documented in junglerice populations and is part of the reason for the increase in its prevalence. However, reduced junglerice control with glyphosate + dicamba and clethodim + dicamba mixtures has been observed in many production fields where glyphosate resistance has not yet evolved. Therefore, research was conducted to assess reduced junglerice control with glyphosate and clethodim when applied with dicamba. Adding dicamba to the spray tank with glyphosate reduced junglerice control by 27%. Adding dicamba to the spray tank with clethodim reduced junglerice control by 11%. The use of Turbo Teejet Induction (TTI) nozzles reduced junglerice control an additional 8% compared to applications with an air induction extended range (AIXR) nozzle. When a drift reduction agent (DRA) was added to dicamba mixtures with glyphosate or clethodim, junglerice control was reduced 36%. Junglerice control was similar with the glyphosate + dicamba treatment compared to the glyphosate + 2,4-D mixture. There was no interaction between nozzles and herbicide treatment. Regardless of herbicide treatment junglerice control was always lower when applied with the ultracourse TTI nozzle. Many applicators in Tennessee prefer to make one application of glyphosate + dicamba in a mixture to save time (authors' personal experience). These results show that the addition of dicamba to glyphosate or clethodim applied with labeled nozzles and a DRA results in reduced junglerice control and should be avoided.