Drift of Glyphosate Sprays Applied with Aerial and Ground Equipment

Abstract

The potential losses from spray applications of glyphosate [N-(phosphonomethyl)glycine] with and without the inclusion of a polymer thickening agent were evaluated in field tests, applied under identified weather conditions with a boom-nozzle ground sprayer, helicopter, and fixed-wing aircraft. The downwind transport and diffusion of the spray loss was assessed by means of Mylar fallout sheets, high volume air samplers, and 4-leaf wheat(Triticum aestivumL. ‘Anza’) plants. Lowest drift losses occurred, under 0.01 g/ha on fallout sheets at 100 m, with deflector fan nozzles (KGF) operating at a low pressure (7 kPa) on the ground sprayer. Drift losses from a helicopter equipped with micro-jet nozzles were only slightly higher, less than 0.03 g/ha on fallout sheets at 100 m. Drift losses from 8003 nozzles mounted on a ground sprayer and D-6 jet nozzles directed back on fixed wing aircraft produced much higher drift deposits, from 0.2 to 1.0 g/ha on fallout sheets at 100 m. The highest levels of drift losses were obtained with D-4 jet nozzles directed down on a helicopter, 5 g/ha on fallout sheets at 100 m. Some evidence of reduced airborne drift was apparent where the polymer thickening agent was used with aircraft and ground equipment. The test results indicate that significant reduction in drift losses were obtained with proper application equipment; however, the use of a polymer thickening agent reduced drift only slightly for certain applications.