INFLUENCE OF ORGANOSILICONE SURFACTANTS AND SPRAY NOZZLE TYPES ON THE FATE AND EFFICACY OF CLOPYRALID ON HONEY MESQUITE (PROSOPIS-GLANDULOSA)

Greenhouse and laboratory experiments were conducted to evaluate the influence of two organosilicone surfactants and spray nozzle types on the spray deposition, absorption, translocation, and efficacy of the monoethanolamine salt of clopyralid on honey mesquite. Sylgard 309 or Silwet L-77 added to the spray solution at 0.1, 0.25 and 0.5% by vol did not increase spray deposition, absorption, translocation, or phytotoxicity of clopyralid applied at 140 g ae ha-1 on honey mesquite compared to no surfactant. An air-assist spray nozzle at 9.4 L ha-1 by vol resulted in greater initial clopyralid deposit on honey mesquite than hydraulic nozzles at 9.4 or 187 L ha-1 by vol, but air-assist application did not increase phytotoxicity compared to hydraulic nozzles. Nomenclature: Clopyralid, 3,6-dichloro-2-pyridinecarboxylic acid; Silwet L-77, polyalkyleneoxide modified polymethyl-siloxane copolymers; Sylgard 309,2-(3-hydroxypropyl)-heptamethyltrisiloxane, ethoxylated, acetate EO glycol, -allyl, -acetate; honey mesquite, Prosopis glandulosa Torr.3 PRCJG.