Field experiments were conducted to evaluate the effect of five spray-nozzle types and three drift-control adjuvants (DCA) on glyphosate spray drift. The extended-range (XR) flat-fan nozzle at 280 kPa was used as the standard comparison. DCAs were evaluated for drift reduction with the use of the XR and air-induction (AI) nozzles. Wind speed ranged from 1.3 to 9.4 m/s (3 to 21 mph). Lethal drift (D_L) and injury drift (D_I) were determined by downwind visual observation of grain sorghum response. Drift distances were measured from the spray swath edge. The Turbo FloodJet and AI nozzles reduced D_L distance by 34%. All four drift-reducing (DR) nozzles reduced D_I distance by 22 to 32%. Reducing the pressure of the XR flat-fan nozzle from 280 to 140 kPa did not reduce D_L or D_I distance. When applied through AI nozzles, each DCA increased droplet volume diameter, one DCA reduced D_I distance and none reduced D_L distance when applied through XR tips. The DCAs did not affect D_L or D_I distance.

Nomenclature: Glyphosate; grain sorghum, Sorghum bicolor (L.) ‘Topaz’.

Additional index words: Drift-control adjuvant, flat-fan nozzle, flood nozzle.

Abbreviations: AI, air induction; AMS, ammonium sulfate; DAP, days after planting; DAT, days after treatment; DCA, drift-control adjuvant; DG, preorifice flat fan; D_I, injury drift; D_L, lethal drift; DR, Combo-Jet; GR, glyphosate resistant; HRC, herbicide-resistant crops; TD, TurboDrop; TF, Turbo FloodJet; TT, Turbo TeeJet; VMD, volume median diameter; XR, extended range.