Droplet size and spray volume effects on honey mesquite mortality with clopyralid

The effects of droplet size and spray volume (spray-mixture application rate) on honey mesquite (Prosopis glandulosa Torr.) mortality were evaluated using 0.55 to 0.58 kg ae (acid equivalent) ha-1 clopyralid (3,6 dichloro-2-pyridinecarboxylic acid). A factorial combination of 3 spray volumes (19, 37, and 75 liters ha-1) and droplet sizes of 325 +/- 25, 475 +/- 25, and 625 +/- 25 micrometers nominal volume median diameter were replicated 3 times at both Andrews and Big Lake, Tex., during June 1989. The experiment was repeated in 1990 at Big Lake and Campbellton, Tex., without the 75 liters ha-1 spray volume. Honey mesquite mortality and canopy reduction 16 months after application were significantly less on the 625 micrometer droplet treatments in 2 of 4 experiments, when compared to plots treated with smaller droplet sizes. Mortality increased with larger spray volumes, particularly with 625 micrometer droplets. Relative mortality data from the 4 experiments clearly demonstrated that larger droplet sizes require larger spray volumes for greatest efficacy.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.Migrated from OJS platform August 202