Residues of 2,4-D and dicamba in wheat following postemergence field application as a tank mixture

In a 2-yr study, residues of 2,4-D and dicamba were monitored in wheat at several times over a complete growing season following postemergence application as a tank mixture at 420 and 140 g ha−1, respectively. Both herbicides were gas chromatographically analyzed as their respective methyl esters using electrolytic conductivity detection. Initial residues immediately after application decreased rapidly and, at 5–6 wk after application, residues of both herbicides were less than 0.1 mg kg−1. Residues of 2,4-D were not detectable in the straw or seed at maturity in either year. However, residues of dicamba in the order of 0.03–0.04 mg kg−1 were detected both years in the mature straw. Residues of dicamba were not detected in the seed in the first year of the study, but were detected at 0.065 ± 0.014 mg kg−1 the second year.