Progress Reported in Battle Against Hydrilla

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Tompkins Weekly  6-9-14

By Sharon Anderson

A fight that began 2 years ago is about to resume. A group of scientists, educators and water enthusiasts are winning the battle against one of the world’s most aggressive waterweeds, hydrilla. They, the Hydrilla Task Force of the Cayuga Lake Watershed, modeled their battle plans on successful work in California and Washington. California eradicated hydrilla, Hydrilla verticillata, from a lake as big as Cayuga. The Hydrilla Task Force is holding a free public meeting July 8, 6:30-8:00 p.m. in the large pavilion at Stewart Park to share details about the campaign against this noxious weed.

The fight is a long one. This will be the third year of using herbicides in Cayuga Inlet, the place where hydrilla was found in 2011. All the success stories to get rid of hydrilla include use of herbicides, which disrupt photosynthesis, the plant’s ability to convert sunlight to food energy. Two herbicides are used. An air boat will apply the first herbicide, endothall, in Cayuga Inlet sometime after the Fourth of July weekend. How fast hydrilla grows determines the exact date.

The inlet will be closed to boat traffic for a day or two so that the herbicide can be spread evenly. Swimming in the treatment area is prohibited for one day after endothall application. Swimming is not affected outside the treatment area. Fishing is not restricted. A special drip unit steady releases low levels of a second herbicide, fluridone, later in the summer. The inlet will remain open. Together the herbicides deplete the plant reserves stored in the underground tubers, small potato-like structures. Hydrilla sprouts from some of the tubers as the water warms. Herbicides will likely be used yearly until at least 2020 since the tubers can lie dormant for many years. Visit to learn more.

The Task Force found hydrilla in Fall Creek in 2013 and applied endothall. Endothall will be used in Fall Creek again this year, possibly earlier than it will be applied to Cayuga Inlet. Closing Fall Creek is less disruptive than closing the inlet.

Hydrilla could form a solid mat of weeds from the shore to where the water is 20 feet deep if left unchecked. “A 15-acre infestation found in Florida spread to 3,000 acres in just two years – a tribute to hydrilla’s fast growth and its ability to spread”, according to the Weed Science Society of America (italics original). Native waterweeds are good for fish, ducks and the lake in general. Hydrilla is not. If left alone, it chocks out beneficial plants. It obstructs boating and swimming. It hurts tourism and waterfront property values, which harms the larger community through reduced tax revenue. It blocks intakes at water treatment and power generation plants. It clogs flood control channels. In comparison, using herbicides is far less damaging to the aquatic ecosystem and to humans.

After application of endothall or fluridone, the Tompkins County Health Department monitors the amount of herbicide near and at Bolton Point’s water intake to ensure that it stays below the drinking water limit set by NYS law. Endothall detections at Bolton Point have never exceeded the legal limit. Fluridone, the herbicide used later in the summer, is applied at very low levels. It has never been detected in any Bolton Point sample. NYS Department of Environmental Conservation samples water upstream and downstream of the treatment areas. Monitoring these locations verifies that the herbicide is not spreading beyond the treatment area.

Education is another weapon against hydrilla. Hydrilla may have entered Cayuga Inlet accidentally on a boat or boat trailer. All who use the lake and nearby waters are urged to clean, drain and dry all watercrafts, equipment and gear. Visually inspect the same and remove any plants or mud before entering and after leaving the water. Neighbors are helping neighbors learn through the Hydrilla Hunters program. Hydrilla Hunters are trained volunteers who teach clean boating practices, share why hydrilla is a menace and search the lakeshore in case hydrilla has spread. Educate yourself by visiting

Sharon Anderson is the Environment Team Leader for Cooperative Extension of Tompkins County.


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