DIFFERENTIAL RESPONSE OF HERBICIDE DRIFT REDUCTION NOZZLES TO DRIFT CONTROL AGENTS WITH GLYPHOSATE

Abstract

Field and wind tunnel studies were conducted in 2001 and 2002 to evaluate characteristics of the spray producedwith four nozzle types (extended-range flat fan [XR], pre-orifice flat fan [DG], turbo flat fan [TT], and venturi flat fan [AI])used alone and in combination with 1/2X and 1X rates of two drift control agents (DCAs) (47 and 94 mg ai/L of polyacrylamide[PA], and 300 and 600 mg ai/L of hyrdroxypropyl guar [HPG]). Water-sensitive cards were used to evaluate spray coverageand droplet density at the top of the weed canopy in field studies and 4 m downwind from the nozzle in wind tunnel studies.Total physical drift was also calculated in wind tunnel studies by quantifying the portion of the released spray volume thatwas deposited within a designated target area. In field studies, spray coverage at the weed canopy was reduced with the useof low-drift nozzles (XR > DG > TT > AI). Spray droplet density was also generally reduced with the use of low-drift nozzles.However, the addition of a DCA influenced nozzle performance differentially. For instance, spray droplet density was reducedby up to 64% with a DCA when combined with TT nozzles, while no significant reductions occurred when combined with AInozzles. Total physical drift in the wind tunnel study was reduced with these technologies used alone or in combination. However,the resulting spray characteristics were dependent on the specific nozzle and the type and rate of DCA. For instance,the addition of a DCA with XR nozzles did not reduce downwind spray coverage relative to the no-DCA standard (29%),regardless of the type or rate of DCA used. However, downwind spray coverage was 1% or less when AI nozzles were used.Overall, the greatest reductions in downwind spray coverage, spray droplet density, and total physical drift were observedwith AI nozzles.