RESIDUES OF 4-AMINO-3,5,6-TRICHLOROPICOLINIC ACID IN GRASS FROM APPLICATIONS OF TORDON HERBICIDES

Residues of 4-amino-3,5,6-trichloropicolinic acid, picloram, were determined in grass from seven locations at various time intervals after application of Tordon herbicide. Four formulations of the herbicide were used, three liquid and one granular. Liquid formulations deposited residues on grass up to 200 p.p.m. for each pound per acre applied. In all experiments, the residue level decreased within one or two weeks after application, then remained relatively constant for 8 to 16 weeks. Residues from a granular formulation generally increased through a maximum near the eighth week after application, and dropped to a lower level within the following eight weeks. Residue of the herbicide in samples of grass collected the year after application generally showed a 90 to 100% decrease over the “mid-season” level. No bound form of picloram was found. © 1969, American Chemical Society. All rights reserved.