Picloram Enhances 2,4-D Movement in Field Bindweed

Field bindweed ( Convolvulus arvensis L.) was sprayed with a mixture of (2,4-dichlorophenoxy)acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram). A mixture of picloram and 2,4-D each at 0.01 lb and 0.001 lb/A killed tops of plants faster than 2,4-D alone or picloram alone at the same rates. Higher rates of 1 lb/A picloram plus 1 lb/A 2,4-D and 0.1 lb/A picloram plus 0.1 lb/A 2,4-D were not consistently synergistic or antagonistic. The percent of plants which produced new growth were 0 for picloram alone at 1 lb/A, 20 for a mixture of 2,4-D and picloram each at 1 lb/A, and 40 for 2,4-D alone at 1 lb/A. Other rates of 0.1 lb/A, 0.01 lb/A, and 0.001 lb/A did not control regrowth of field bindweed. Application of unlabeled picloram simultaneously with 14 C-2,4-D increased translocation of 14 C-2,4-D, but the reverse was not true.