Translocation of Different 2,4-D, Bentazon, Diclofop, or Diclofop-Methyl Combinations in Oat (Avena sativa) and Soybean (Glycine max)

Oat ( Avena sativa L. ‘Elgin′) and soybean ( Glycine max L. ‘Evans′) were treated with 14 C-diclofop-methyl {methyl ester of 2-[4-(2,4-dichlorophenoxy)phenoxy] propionic acid]} or 14 C-diclofop alone or in combination with 2,4-D [(2,4-dichlorophenoxy)acetic acid] or bentazon [3-isopropyl-1 H -2,1,3-benzothiadiazin-4(3 H )-one 2,2-dioxide] and 14 C-2,4-D alone or in combination with diclofop-methyl or diclofop. More radioactivity was recovered in the treatment zone after 14 C-diclofop-methyl applications, alone or in combination, than after similar 14 C-diclofop treatments in oat and soybean. Basipetal movement of radioactivity was 4 and 1% and acropetal movement was 1 and 4% in oat and soybean, respectively, regardless of the diphenyl ether treatment or time. Addition of 2,4-D or bentazon did not reduce translocation of radioactivity from 14 C-diclofop-methyl treatments in either plant species. Basipetal movement of radioactivity from 14 C-diclofop-methyl was greater than from 14 C-diclofop in both oat and soybean. The addition of diclofop-methyl or diclofop did not affect the pattern or amount of 14 C-2,4-D radioactivity translocated. In oats, radioactivity appeared to accumulate within the intercalary meristematic region with 14 C-2,4-D and 14 C-diphenyl-ether applications. Diclofop-methyl at 1 kg/ha applied either to an entire oat plant at the three-leaf stage or the apical meristemic region resulted in plant mortality. The extent to which transport contributes to diclofop-methyl efficacy is questioned.