Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Proceedings
Publication Acceptance Date: 12/30/2002
Publication Date: 1/15/2003
Citation: WILLS, G.D., HANKS, J.E., JONES, E.J., MACK, R.E. Effect of Drift Control Adjuvants on Glyphosate Applied with Air Induction Spray Nozzles. PROCEEDINGS OF SOUTHERN WEED SCIENCE SOCIETY. Interpretive Summary:
Technical Abstract: Laboratory and field studies were conducted to determine the effect of six drift reducing adjuvants on the spray pattern, droplet size and efficacy of glyphosate herbicide applied both with and without surfactant using TeeJet® Air Induction 110015VS spray nozzles. Glyphosate was applied at 0.4 lb ai in 10 gallons per acre both with surfactant as Roundup Ultra Max® and without surfactant as either Rodeo® or Roundup D-Pak®. Field applications were over-the-top to four rows each of three-trifoliolate-stage non-Roundup Ready® soybeans (Glycine max L. Merr.) 'Pioneer 9594' spaced 38 inches apart, 40 feet long and interspaced with 4- to 6-inch-tall barnyardgrass [Echinochloa crus-galli (L.) Beauv.], 6- to 8-inch-tall pitted morningglory (Ipomoea lacunose Lag.), 2- to 4-inch-tall smooth pigweed (Amaranthus bydridus L.), and 6- to 10-inch-tall velvetleaf (Abutilon theophristi Medik.) replicated four times in a randomized complete block design. Efficacy was determined by visual ratings 2 weeks after treatment (WAT), whereby 0 = no control and 100% = complete kill of shoots. In the laboratory studies, the spray droplet size was determined using an Insitec Measurement Systems® laser particle analyzer in an enclosed chamber with the nozzle installed on a mechanical traversing system. Droplet size was determined both as the volume median diameter in microns (Dv. 5) and as the percentage of the spray volume resulting in fine droplets less than 144 microns (<144 ) in diameter. Each of the drift control adjuvants in this study was effective in reducing the percent of fine driftable spray droplets and increasing the percent weed control of glyphosate both with and without surfactant. Uniformity of spray pattern was not significantly effected by the addition of drift reducing adjuvants.