Roller Application of Picloram for Leafy Spurge Control in Pastures

Roller-applied picloram (4-amino-3,5,6-trichloropicolinic acid) at a concentration of 30 to 60 g ae/L gave similar control to leafy spurge (Euphorbia esulaL. ♯ EPHES) as spray-applied picloram at 1.1 to 2.2 kg ae/ha. Leafy spurge control was most effective when the roller applicator was adjusted to treat a maximum amount of stem tissue with a 60 g/L picloram solution. Control was not improved by including a petroleum oil or surfactant additive. Fall applications of roller-applied picloram tended to provide better control than spring applications. When used on dense leafy spurge stands, the roller applicator applied only 40% as much picloram as spray treatments of 2.2 kg/ha. However, picloram residues in soil following roller application were similar to those from picloram at 0.3 to 1.1 kg/ha applied as a spray.