The breakdown of the triazine herbicide cyanazine in wheat and potatoes grown under indoor conditions in treated soils

The breakdown of the triazine herbicide cyanazine (“BLADEX”,a 2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine) has been studied in spring and winter wheat and potatoes grown under indoor conditions in soils treated at planting with up to 1.5 kg/ha of the radiolabelled herbicide. Breakdown products were mainly those formed by hydrolysis of the cyano group to give an amide (II) and an acid (III) followed by hydrolysis of the chlorine to hydroxyl (IV). De-N-alkylation reactions also occurred although these were less evident in soils. In wheat the chloro acid (VII) formed by the des-ethylation of (III) was more evident than in previous studies with maize. In all of the crops at harvest the residues were mainly of the hydroxy acids (IV) and (VIII); (IV) 2-hydroxy-4-(1-carboxy-1-methylethylamino)-6-ethyl-amino-1,3,5-triazine; (VIII) 2-hydroxy-4-(1-carboxy-1-methylethylamino)-6-amino-1,3,5-triazine, respectively. In potatoes and spring wheat they were present in both free and conjugated forms whereas in winter wheat they were almost entirely in conjugated forms. The compounds (IV) and (VIII) are of a low order of toxicity to animals and are not herbicidal. They are unlikely to present a residue hazard if present in field crops.