Phytotoxicity, Absorption, and Translocation of Five Clopyralid Formulations in Honey Mesquite (Prosopis glandulosa)

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Abstract
Foliar sprays of the monoethanolamine salt, potassium salt, free acid, and 1-decyl ester of clopyralid were more effective in killing greenhouse-grown honey mesquite than the 2-ethylhexyl ester at rates of 0.28 ae/ha or less. More clopyralid was transported to the lower canopy from application of the monoethanolamine salt and potassium salt than the 2-ethylhexyl ester of clopyralid at 4 h or 1, 3, or 8 days after treatment. Application of the monoethanolamine salt and the 2-ethylhexyl ester to leaves with a pipet indicated that about twice as much clopyralid was absorbed within 15 min from the ester form (26%) than from the amine form (12%) of the total recovered. However, after 24 h, absorption of the ester was less than the amine. More than twice as much clopyralid was transported from the treated leaf after application of amine than the ester. Only the acid form of clopyralid was transported away from the site of application of either ester or amine.