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INFORMATION
NewsCalendarPublicationsLinksLake and Reservoir Management
18 (3) 181-190, 2002
"Whole Lake Fluridone Treatments for Selective Control of Eurasian Watermilfoil: I. Application Strategy and Herbicide Residues"
Kurt D. Getsinger, John D. Madsen, Tyler J. Koschnick, and Michael D. Netherland
ABSTRACT
The herbicide fluridone is being used in northern lakes and reservoirs to control the exotic species. Eurasian watermilfoil. Since quantitative information linking changes in plant communities following fluridone applications is limited, particularly with respect to water residue records, a study was conducted to investigate the effect of low-dose treatments on the submersed plant communities in four Michigan lakes. The overall study objective was to determine whether plant species diversity and frequency of occurrence were affected by low-dose fluridone applications in the year of treatment. The primary objective of this portion of the overall study was to provide an application strategy that would maintain a threshold dose of fluridone 5ppb declining to 2 ppb in the treated lakes to selectively control Eurasian watermilfoil. Study lakes were 55 to 220 ha in size and contained an average of nine species of submersed plants. Big Crooked, Camp, Lobdell, and Wolverine lakes were treated in mid-May 1997 with the formulation Sonar AS to yield an initial concentration of 5 ppb flurdone in the upper 3.05m of each lake. A sequential application of Sonar AS was conducted on each lake at 15 to 21 days after initial treatment (DAIT), intended to further establish a fluridone concentration of 5ppb in the upper 3.05m of each lake. Bass, Big Seven, Clear and Heron lakes received no fluridone applications and served as untreated reference sites. Water residue samples were collected at prescribed intervals on each fluridone-treated lake from pretreatment up to 81 DAIT. Samples were collected from six littoral and from 2 deep locations throughout each lake, and temperature profiles were measured at the deep stations. Fluridone residues were analyzed using two separate techniques, the newly developed enzyme-linked immunosorbent assay and the standard high performance liquid chromatography method. Fluridone levels on three of the treated lakes met the laboratory-derived criteria for achieving good control of Eurasian watermilfoil by providing a peak concentration of approximately 5 ppb during the first 2 weeks posttreatment, and by maintaining a concentration >2 ppb through 60 DAIT. Residues became well mixed in the water column under isothermal conditions, and thermal stratification, or the lack thereof at the time of herbicide application can affect target herbicide concentrations. Using the volume of a pre-selected depth zone to calculate the amount of fluridone needed to achieve a particular target concentration can result in an over- or under-dosing of a water body.
For more information:
Kurt Getsinger
USAERDC Vicksburg
CEERD-EP-P
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
Email: getsink@wes.army.mil
