Studies were conducted on the campuses of Texas A&M University in College Station, TX, and New Mexico State in Las Cruces, NM, to determine the spray droplet size spectra produced by quinclorac and 2,4-D as the liquid, dry, and emulsion formulations during application with various nozzle sizes using a laser spectrometer. Quinclorac and 2,4-D formulations were also sprayed through three different nozzle sizes in a drift chamber and allowed to settle on glass slides placed downwind. The amounts of each herbicide deposited on the slides were quantified using high-performance liquid chromatography/photodiode array (HPLC/PDA) analysis to assess spray deposition of each formulation at different wind velocities. Data from the laser spectrometer suggested that formulations of 2,4-D affected droplet size, particularly when the 380 ml/min flat-fan nozzle was used. Quinclorac droplet sizes were similar to water regardless of nozzle size. Liquid and dry-formulated 2,4-D tended to be deposited downwind in greater quantities than the emulsion formulation when using the 380 and 760 ml/min spray nozzles with wind velocity of 15 km/h.

Nomenclature: 2,4-D, quinclorac.

Additional index words: Laser spectrometer, drift chamber.

Abbreviations: HPLC, high performance liquid chromatography; HSD, honestly significant difference; PDA, photodiode array.