Herbicide, Monitoring Reducing Hydrilla Threat to Cayuga

Officials see need for multi-year, multi-million dollar control effort...


By Andrew Casler via The Ithaca Journal, 1/9/12

Hydrilla in Cayuga Lake inlet was knocked down in 2012, but it’s not yet knocked out.

Further eradication efforts are expected this year in the fight against the invasive aquatic plant that was found in the lake in August 2011. Hydrilla can grow into a thick mat that robs oxygen from water and makes boat navigation impossible. Treatment can take years, and the cost for controlling it in Cayuga Lake is expected to run well into the millions.

Craig Schutt, director of Tompkins County Soil and Water Conservation, estimates that it will cost between $700,000 and $1 million annually for an effective five- to eight-year eradication program. Schutt said the county has applied for $304,000 from U.S. Fish and Wildlife Service.

“We’ve got to keep finding money,” Schutt said.

The county will apply for other grants to eradicate hydrilla as they come available, he said.

In 2012, the program received $380,000 in federal funding in June and began receiving $800,000 from New York in December to cover expenses. With the state money, Schutt said paying for hydrilla treatment for 2013 is largely covered.

The federal cash alone would not cover all costs to kill the plant, such as community outreach for hydrilla education, as well as plant, tuber and water quality monitoring, Schutt said.

Robert Johnson, an aquatic biologist working with the county, said the hydrilla monitoring covered about 600 acres on Cayuga Lake’s southern end.

The work included using rakes that scraped the lake bottom near the shore line to gather samples of plant life, and sending in scuba divers to seek out the plant.

Only one hydrilla fragment was found during monitoring in the summer.

“In general, things are going as well, and maybe even a little better, than we expected with the treatment, but it’s a long term process,” City of Ithaca Watershed Coordinator Roxy Johnston said.

Over this winter, Johnston said the hydrilla monitoring data will be reviewed in depth.

“We’ll look over all the monitoring data in depth, so we’ll look at the tuber count through the season, and we’ll be able to really get a handle on how they’re decreasing,” Johnston said. “That’s the ultimate goal, to get zero tubers in the system.”

Herbicide treatments began in late June 2012 with endothall, also known as Aquathol K, and in late summer with Fluridone at a cost of about $346,000.

Both chemicals work by disrupting photosynthesis, the process plants use to convert light into energy.

“The idea of the Aquathol (K) treatment was the knock it back ... and then the fluridone treatment over time, hopefully, will take out some of the tubers,” Schutt said.

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