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SENNETT — Last year's Cayuga Lake hydrilla treatment near the village of Aurora reduced the invasive plant's population significantly, and treatment is set to continue this year. 

Mike Greer, a regional technical specialist with the U.S. Army Corps of Engineers, said hydrilla took up about 57 percent of the identified area when initial surveys were conducted in September 2016. As of a September 2017 survey following the Army Corps's approximately $500,000 treatment and monitoring efforts, that is down to 2.4 percent. 

"That's tremendous progress towards eradicating the plant, but also represents a substantial reduction and risk that hydrilla spread to other portions of the lake based on this infestation," Greer told members of the Cayuga County Water Quality Management Agency meeting Thursday morning. 

The Army Corps, he added, has secured funding to treat for 2018, though eventually the federal agency will have to turn monitoring and management over to local officials. 

Hydrilla is a particularly nasty invasive species because it can regenerate new plants from cuttings. If left alone, it can choke out water bodies making swimming, boating and other recreational activities nearly impossible. It's a sneaky-growing plant, too. Tubers, which Greer said look like little potatoes, can spring up new plants once the water hits about 68 degrees. 

The Army Corps has been using fluridone, a kind of slow-release herbicide, to control the majority of the plants. From July 20 to September 14, staff put seven treatments of fluridone down. The Cayuga County Health Department worked with the Army Corps to test water samples from the Wells College treatment plant to make sure the drinking water was safe. 

Environmental Health Director Eileen O'Connor said levels were detected in three samples, but they were well below those of concern and there was no public health risk. 

Greer said the Army Corps plans to change its strategy a bit this year, as it found some small patches of hydrilla outside the original treatment area. It plans to expand its treatment and monitoring north and south of the approximately 30-acre site. 

"We're going to keep an eye out, and make sure we're looking an appropriate-sized area for the project, and make sure nothing is slipping through the cracks," Greer said.

Hydrilla on Cayuga Lake

A map shows the area where hydrilla was found on Cayuga Lake near the village of Aurora. Red dots show where the U.S. Army Corps of Engineers conduct surveys. The yellow-shaded area shows the approximately 27-acre patch where hydrilla was found and where herbicide treatment is being applied. The darker square in the middle shows where the hydrilla is most concentrated and where scientists used copper to treat the invasive. 

Patches of hydrilla have cropped up at the southern end of the lake, too, near Stewart Park in Ithaca. The Army Corps is looking into helping treat and monitor there as well. 

Greer said he'll also start treatment earlier in the season. The plant's tubers, he said, tend to all bloom at the same time, so there's a greater chance of killing off more of the plants sooner if staff can treat during that window. That could also allow for fewer fluridone treatments throughout the season. 

Though the success of the program was good news to local officials, Greer cautioned that even after five years of hydrilla treatment and monitoring, missing one year could bring a water body back to square one. He said lake monitoring programs will be crucial, and while hydrilla populations may go down to nearly zero, staff time for searching water bodies could go up.

"The needle in the haystack keeps getting smaller and smaller, but you don't want to miss it," he said. 

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Staff writer Gwendolyn Craig can be reached at (315) 282-2237 or Follow her on Twitter @gwendolynnn1.


County Government Reporter