Use of Whole-Lake Fluridone Treatments to Selectively Control Eurasian Watermilfoil in Burr Pond and Lake Hortonia, Vermont

摘要

One method of selectively managing the invasive submersed plant Myriophyllum spicatum L. (Eurasian watermilfoil) in northern lakes is totreat the entire water body with low doses (6 to 8 micrograms/L) of the herbicide fluridone 1-methyl-3-phenyl- 5-(3-(trifluromethyl) -(phenyl)-4(1H)-pyridinone). A 3-year study (1999-2001) was conducted at Burr Pond and Lake Hortonia, Vermont, to determine whether submersed plant diversity and frequency ofoccurrence were impacted by whole-lake, low-dose fluridone applications in the year of treatment, and beyond, when targeting for control of M. spicatum. Bathymetric maps of both lakes were developed using fathometers and global positioning system techniques in May 2000, which was matched with thermocline data (29 May 2000 - Lake Hortonia only) to determine the amount of herbicide required to achieve the target concentration (6 micrograms/L of fluridone) in each lake. On 4 June 2000, Burr Pond (34.5 ha; average depth, 4.4 m) and Lake Hortonia (195 ha; average depth, 5.8 m) were treated to achieve a nominal rate of 6 micrograms/L of fluridone using the aqueous suspension (AS) formulation Sonar(R) AS. Both lakes were subsequently treated with a booster application of Sonar AS on 9 July 2000, 35 days after the initial treatment to re-set the whole-lake concentration to 6 micrograms/L of fluridone. Water samples were collected at various locations on both lakes from immediately prior to application through 116 days after treatment (DAT), and were analyzed for fluridone using immunoassay.