Effect of DMSO and Surfactant Combinations on Tissue Concentrations of Picloram

Abstract

Over a 2-year period no treatment differences were noted in 4-amino-3,5,6-trichloropicolinic acid (picloram) concentrations recovered from grass and yaupon(Ilex vomitoriaAit.) tissues treated with 1.12 kg/ha of picloram in mixture with dimethyl sulfoxide (DMSO) and surfactant (X-77).⁴Less than 1 μg of picloram per gram of fresh weight of grass or yaupon was present in aerial tissue 6 months after treatment, in yaupon stem tissues 1 month after treatment, and in yaupon root tissue 5 days after treatment. Tissues sampled 1 year after treatment were devoid of picloram residue; tissues sampled 1 year after retreatment had levels ranging from 0.04 to 0.26 μg/g. The April application of 1.12 kg/ha of picloram plus 5.0% X-77 plus 10.0 or 25.0% of DMSO produced more effective canopy reduction of yaupon 1 year after treatment than did other herbicide treatments or dates of treatment. Increased canopy reduction by retreatment the second year suggests that X-77 rather than DMSO was the effective component in the spray mixtures.