Phytotoxicity and Uptake of Clopyralid in Honey Mesquite (Prosopis glandulosa) as Affected by Adjuvants and Other Herbicides

The addition of surfactant I (trimethylnonylpolyethoxyethanol) or surfactant II (4-isopropenyl-1-methyl cyclohexane) at 0.5% (v/v) to the spray solution or 1:1 mixtures of benazolin [4-chloro-2-oxo-3(2H)-benzothiazole-aceticacid], picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), or triclopyr {[(3,5,6-trichioro-2-pyridinyl) oxy] acetic acid} with clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) each at 0.28 kg ae/ha enhanced the phytotoxicity of clopyralid on honey mesquite (Prosopis glandulosaTorr. # PRCJG) compared to clopyralid applied alone. Addition of surfactant I, surfactant II, picloram, or triclopyr to clopyralid enhanced its absorption into leaves by 4 h after treatment and movement into upper-stem phloem by all additives by 1 day after treatment. When combined at equal rates, more clopyralid than picloram was transported into stems.