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Jenifer K. Parsons, Kathy S. Hamel, John D. Madsen, and Kurt D. Getsinger

ABSTRACT

A patchy distribution of Eurasian watermilfoil (Myriophyllum spicatum L.) in Loon Lake was treated with the herbicide 2,4-D during July 1998. Aquatic plant biomass and frequency data were collected before treatment, and six weeks and one year after treatment. Aqueous concentrations of 2,4-D increased to 1 to 2 mg/l within one day of treatment, and were below detection limits by one week after treatment. Macrophyte data were analyzed to assess the herbicide's impacts on Eurasian watermilfoil as well as the rest of the aquatic plant community. Results showed a significant decrease in Eurasian watermilfoil biomass and frequency in treated areas 6 weeks after treatment, which continued through the one year post-treatment samples. No other plant species were significantly affected by the herbicide application.

For more information:

Parsons, Jenifer
Washington Dept. of Ecology
15 W. Yakima Avenue
Suite 200
Yakima, WA 98902