Metabolism and fate of [C-14] ethametsulfuron-methyl in Rutabaga (Brassicanapobrassica Mill.)

The metabolism and fate of ethametsulfuron-methyl (methyl 2-[[[[[4-ethoxy-6 -(methylamino)-1,3,5-triazin-2-yl]amino]carbonyl]amino] sulfonyl]benzoate) in rutabaga were investigated. Alter 72 h, absorption and translocation of [C-14]ethametsulfuron-methyl in rutabaga did not change for the duration of the study (50 days). Less than 4% of recovered radioactivity was present i n the rutabaga root. Ethametsulfuron-methyl was metabolized through a propo sed unstable alpha-hydroxy ethoxy intermediate that dissipated 3 days after treatment to two major metabolites, O-desethylethametsulfuron-methyl and N -desmethyl-O-desethylethametsulfuron-methyl, as determined by liquid chroma tography-mass spectrometry. It was estimated that at a spray dose of 30 g o f active ingredient ha-l and a harvest weight of 0.5 kg, the edible portion of the rutabaga root would contain no ethametsulfuron-methyl and similar t o 1.3 ppb total of both identified metabolites. Residue analysis and toxico logical assessment show that ethametsulfuron-methyl;md its metabolites shou ld pose little or no risk to consumers of rutabagas.