Herbicide use in the management of roadside vegetation, Western Oregon, 1999-2000: effects on the water quality of nearby streams

Previous studies by the U.S. Geological Survey (USGS) have established that many different herbicides can be found in small Willamette Valley streams. Several of the compounds detected in those studies were known to be used by the Oregon Department of Transportation (ODOT) as part of its integrated vegetation management (IVM) plan to control roadside vegetation. The purpose of this study was to assess whether the use of herbicides in IVM programs could be a significant contributor to the load of herbicides carried by streams in Oregon. Field work was carried out at a site in the Willamette Valley near Colton, Oregon, where ODOT applied the herbicides Krovar (active ingredients diuron and bromacil), Oust (active ingredient sulfometuron-methyl) and Roundup (active ingredient glyphosate) as part of its integrated vegetation management program at the site. This combination of herbicides had not been used previously at this site, but it had been used by ODOT at other sites. The combination