Influence of adjuvants and plant growth regulators on herbicide performance in honey mesquite

Addition of surfactant I (trimethylnonylpolyethoxyethanol) or surfactant II (4-isopropenyl-1-methyl-cyclohexane) at 1.0 and 0.6% (v/v) of the spray solution enhanced the phytotoxicity of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), the triethylamine salt of triclopyr {(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid}, picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), and 2,4,5-T (2,4,5-trichlorophenoxy)acetic acid)] applied at 0.14 kg ae/ha to greenhouse-grown honey mesquite (Prosopis glandulosa Torr.). Application of benazolin 4-chloro-2-oxo-3(2H)-benzothiazolacetic acid] increased the phytotoxicity of all herbicides, but ethephon (2-chloroethyl)phosphonic acid] and mefluidide {N-2,4-dimethyl-5-(trifluoromethyl)sulfonyl]amino]phenyl]acetamide} were usually ineffective. Clopyralid + picloram, triclopyr, or 2,4,5-T applied in 1:1 combinations at 0.07 + 0.07 kg/ha were usually equally or more effective than any one of the herbicides applied alone at 0.14 kg/ha. Adjuvants did not enhance the phytotoxicity of picloram, triclopyr, or 2,4,5-T on field-grown honey mesquite but sometimes did with clopyralid.