Controlling Volunteer Corn (Zea mays) in Soybeans (Glycine max) with Diclofop and Glyphosate

We compared diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid}, as an early over-the-top spray treatment, and glyphosate [N-(phosphonomethyl)glycine], applied twice in repeated applications with a rope-wick applicator, for control of simulated volunteer corn (Zea maysL.) planted in clumps at various intervals in rows of soybeans [Glycine max(L.) Merr.]. Uncontrolled corn at the lowest density (clumps 2.4m apart in the row) reduced soybean yields an average of 31%. Both herbicides were highly effective in controlling corn, but when corn densities were high, diclofop treatments often resulted in greater soybean yields than did glyphosate treatments — presumably because corn interfered with the soybeans for a longer time before glyphosate was applied.