Field Measurements of Drift of Conventional and Drift Control Formulations of 2,4-D Plus Glyphosate

Recent advances in biotechnology have resulted in crops that are tolerant to the synthetic auxin 2,4-D, expanding the weed management versatility of this herbicide. With potential expansions of use, concerns have been raised about the increased risk of herbicide drift, leading to damage to nontarget crops. A field-scale study was conducted with the objective to measure drift deposition and the potential for drift reduction conferred by a proprietary premixture formulation of 2,4-D choline salt plus glyphosate dimethylammonium salt compared to an in-tank mixture of 2,4-D dimethylamine salt plus glyphosate potassium salt. Treatments were made with field-scale spray equipment under typical application conditions in McCook, NE, using three widely used nozzle tips. Deposition was captured in triplicate downwind collector lines and assayed for tracer dye and 2,4-D. In comparison to the in-tank mixture, the pre-mixture formulation exhibited lower downwind depositions when applied through a flatfan (TeeJet Extended Range; XR) and air induction (TeeJet Air Induction Extended Range; AIXR) nozzles, but not with a pre-orifice (TeeJet TurboTeeJet Induction; TTI) nozzle. Based upon median deposition at 30m downwind, the pre-mixture formulation reduced drift by 62% and 91%, for the XR and AIXR nozzles, respectively. From a drift reduction perspective, the pre-mixture formulation performance with the AIXR nozzle was equivalent to a much coarser TTI nozzle while still offering sufficient foliar coverage for acceptable weed control. Nomenclature: 2,4-D; glyphosate