POTENTIAL ANTAGONISM OF SULFENTRAZONE AND FENOXAPROP TANK-MIXES FOR GOOSEGRASS CONTROL. A.J. Patton*, D.V. Weisenberger, J.T. Brosnan, and G.K. Breeden, Purdue University, W. Lafayette, IN (104)


Several herbicides are known antagonize grassy weed control when tank-mixed with fenoxaprop. The objectives of this research were to evaluate sulfentrazone and fenoxaprop applied alone and in combination with one another for postemergence goosegrass (Eleusine indica) and smooth crabgrass (Digitaria ischaemum) control. Initial experiments were conducted on separate stands of goosegrass and crabgrass at the W.H. Daniel Research and Diagnostic Center in West Lafayette, IN in 2010. Treatments included the factorial combination of fenoxaprop (0.05 and 0.075 kg/ha) and sulfentrazone (0.28 kg/ha). An untreated control was included for comparison. Experimental design was randomized complete block with three replications and plot size measured 2.25 m2. Treatments were applied to 2 to 3 tiller goosegrass and 4 to 5 tiller crabgrass in 814 L/ha water with a CO2-pressurized sprayer at 207 kPa. In 2010 in West Lafayette, goosegrass coverage was lowest from treatments containing fenoxaprop. Goosegrass was not effectively controlled when sulfentrazone was applied at 2-3 tillers. When sulfentrazone was tank-mixed with fenoxaprop, higher goosegrass coverage was present following applications than when fenoxaprop was applied alone suggesting that antagonism was occurring when these products are tank-mixed. No antagonism was observed with these treatments on crabgrass. Experiments were replicated in 2011 at the W.H. Daniel Research and Diagnostic Center (West Lafayette, IN) and the East Tennessee Research and Education Center-Plant Sciences Unit (Knoxville, TN). Treatments included the factorial combination of fenoxaprop (0.05, 0.075, and 0.1 kg/ha), and sulfentrazone (0.28 kg/ha) with an untreated control also included for comparison. Results in 2011 in Indiana mirrored those observed in 2010.  In Tennessee, no antagonism was observed with fenoxaprop and sulfentrazone tank-mixtures applied to goosegrass or smooth crabgrass. Additional research will be conducted in 2012 to determine the reason for the inconsistent response between locations.