Petty, D.G., K.D. Getsinger, J.D. Madsen, J.G. Skogerboe, and W.T. Haller, 1998. Aquatic Dissipation of the Herbicide Triclopyr in Lake Minnetonka, Minnesota, U.S. Army Corps of Engineers, Waterways Experiment Station

The aquatic fate of the triethylamine (TEA) salt formulation of triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) was studied in Lake Minnetonka, Minnesota. This study determined dissipation rates of triclopyr and metabolites, TCP (3,5,6-trichloropyridinol) and TMP (3,5,6-trichloro-2- methoxypyridine) in water, sediment, finfish, and shellfish. Two plots containing Eurasian watermilfoil-dominated plant communities were treated at 2.5 mg/L triclopyr. The dye rhodamine was applied with triclopyr to provide water- exchange information during the study. Water and sediment residue samples were collected from within and outside of plots. All nontarget animals were caged in the center of each plot. Water and sediment samples were collected through 6 weeks posttreatment, while non-target organisms were collected through 4 weeks posttreatment. Triclopyr and TCP dissipation half-lives in water were 3.7 to 4.7 days and 4.2 to 7.9 days, respectively. Small amounts of TMP (<5 nglml) were measured in the water in treated plots. Triclopyr sediment values were 257 to 335 ng/g (mean half-life = 5.4 days). TCP sediment levels were 27 to 65 ng/g (mean half-life = 11.0 days). TMP was found in sediment at trace levels. An untreated reference plot tested ND for triclopyr, TCP, and TMP in water and sediment. Triclopyr and TCP cleared from animals in relation to concentrations found in water (triclopyr half-lives <11 days; TCP <14 days) and were generally higher in inedible viscera tissue. IMP levels were two to three times higher than those of triclopyr or TCP in viscera tissue. Eurasian watermilfoil was controlled in the treatment areas. Native plants recovered, and no adverse effects on water quality were found following treatment.

Contact: David Petty, Waterways Experiment Station, U.S. Army Corps of Engineers, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA
Key Words: Eurasian_watermilfoil, Chemical_control, Aquatic_plant_management
Product Type: Publication, Report
User Type: Resource Management