Absorption, Translocation, and Metabolism of Picloram and 2,4-D in Leafy Spurge (Euphorbia esula)

The absorption, translocation, and metabolism of14C-picloram and14C-2,4-D applied alone and together to leafy spurge was evaluated. Leafy spurge absorbed 34 and 24% of the14C-2,4-D applied alone and with picloram, respectively, and 14 and 10% of the14C-picloram applied alone and with 2,4-D, respectively. More14C-2,4-D was translocated in leafy spurge than14C-picloram, and adding picloram to14C-2,4-D decreased14C translocation to the roots. Adding 2,4-D to14C-picloram increased the percentage of absorbed14C that translocated in leafy spurge from 28 to 48%. Generally,14C-picloram and14C-2,4-D remained as the parent acid in leafy spurge whether applied alone or together. Of14C-picloram recovered from the roots, 83% was unmetabolized picloram when applied alone compared to 95% when applied with 2,4-D, which probably is the reason for increased leafy spurge control when these herbicides are applied together.