Publication Summary

This is a journal article in the July 2004 issue of the Journal of Aquatic Plant Management.

The journal is through the Aquatic Plant Management Society. Their website is: www.apms.org/index.htm.

A dense mat-forming population of Eurasian watermilfoil (Myriophyllum spicatum L.) was interfering with fishing and recreation in a small western Washington lake. A low concentration (1.5 mg/L active ingredient) of the herbicide endothall formulated as Aquathol® K was used in 2000 to attempt to selectively control the Eurasian watermilfoil. Aquatic plant biomass and frequency data were collected before treatment, ten weeks after treatment and during the growing season for 3 additional years. 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 10 weeks after treatment. The Eurasian watermilfoil continued to be present, but at a significantly reduced level through the remainder of the study (3 years after treatment). Of the native plant species, large-leaf pondweed (Potamogeton amplifolius Tucker.) frequency and biomass was significantly reduced after treatment. Common elodea (Elodea canadensis Rich.), muskgrass (Chara sp. Vallaint.) and bladderwort (Utricularia sp. L.) all increased significantly after treatment.