Interaction of glyphosate with chlorimuron, fomesafen, imazethapyr, and sulfentrazone

Field experiments were conducted on eight weed species to determine if chlo rimuron, fomesafen, imazethapyr, or sulfentrazone at two races (labeled and one-half the labeled rate) were complementary tank mixtures with glyphosat e at 210 and 420 g ai ha(-1) Laboratory experiments were conducted on barny ardgrass, pitted morningglory, Palmer amaranth, and velvetleaf using radiol abeled glyphosate, chlorimuron, and imazethapyr to determine the absorption and translocation pattern of these herbicides applied alone and in combina tion. In the field, glyphosate plus chlorimuron tank mixtures were generall y additive. Adding chlorimuron did not decrease absorption or translocation of C-14-glyphosate by barnyardgrass, pitted morningglory, or velvetleaf. A dding glyphosate increased absorption of C-14-chlorimuron by Palmer amarant h and velvetleaf. All four fomesafen plus glyphosate rate combinations were antagonistic to goosegrass, sicklepod, Palmer amaranth, and velvetleaf, an d three of the four were antagonistic to barnyardgrass and entireleaf morni ng glory. Fomesafen decreased absorption and translocation of C-14-glyphosa te in barnyardgrass, pitted morningglory, and velvetleaf. Ninety percent of glyphosate plus imazethapyr combinations were additive or synergistic, wit h all rate combinations synergistic for pitted morningglory. Adding glyphos ate to imazethapyr increased absorption of C-14-imazethapyr by Palmer amara nth and velvetleaf. Glyphosate plus sulfentrazone tank mixtures were antago nistic at all rate combinations for barnyardgrass and Palmer amaranth and a t three of the four combinations for goosegrass and entireleaf morningglory , indicating that these herbicides are not complementary in tank mixtures.