Influence of Dicamba on Development of Range Grass Seedlings

Abstract

Seedlings of switchgrass(Panicum virgatumL. ‘Blackwell’), sideoats grama(Bouteloua curtipendula[Michx.] Torr. ‘Premier’), and native vine mesquite(Panicum obtusumH. B. K.) tolerated 0.28 kg/ha of 3,6-dichloro-o-anisic acid (dicamba) applied preemergence. After emergence, sideoats grama tolerated 0.56 kg/ha dicamba. Preemergence or postemergence applications of 1.12 and 2.24 kg/ha severely retarded shoot production of all three species. Soil residues in the surface 2.5 cm reduced root production of grass seedlings, whereas placement of dicamba 7.6 or 15.2 cm deep was not detrimental. All grass species germinated and grew for 21 days in soil containing up to 63 ppb of dicamba without reduction in shoot production. Overall order of susceptibility to dicamba was ranked as vine mesquite > switchgrass > sideoats grama.