Morphological Response of Two Mesquite Varieties to 2,4,5-T and Picloram

Abstract

Honey mesquite [Prosopis julifioravar.glandulosa(Torr.) Cockerell] and velvet mesquite [P. julifioravar.velutina(Woot.) Sarg.] seedlings were treated on individual leaves with 20 or 40 μg of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), 4-amino-3,5,6-trichloropicolinic acid (picloram), or a 1:1 mixture thereof. Formulation of herbicides in a DMSO-complex carrier (dimethyl sulfoxide, ethylene glycol, phytobland oil, water: 50:25:15:10, v/v) enhanced activity considerably over that obtained with an aqueous carrier, the degree of enhancement being greater with 2,4,5-T than with picloram. Lack of major varietal differences in morphological or anatomical response suggests that observed varietal differences in sensitivity of field mesquite to aerial sprays are not a function of the variety itself, but are related to climatic or edaphic differences among sites which the varieties occupy.