It's an underwater menace that could overtake a waterway in just a few years. Now officials in Tompkins County have begun the latest round of treatment against the hydrilla plant. YNN's Tamara Lindstrom tells us about the battle in Cayuga Lake.

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ITHACA, N.Y. -- It's been nearly one year since the first signs of the invasive hydrilla plant were discovered in Cayuga Lake. Officials have taken decisive action.

"If this gets out of hand, we could lose the use of this waterway," explained Craig Schutt, Tompkins County Soil and Water Conservation.

This week, the latest round of herbicides is going into Cayuga Lake to help stop the spread of the aggressive invader.

"This is a more long term treatment. Today, they're putting slow release pellets into the backwaters and area that don't get good mixing. So those will break down over time," said Schutt.

The fluridone pellets will sit low in the water, and help kill any new growth from the tubers. Two weeks ago, a treatment of the herbicide called Aquathol K destroyed most of the existing growth.

Schutt said, "The plants are gone, so we don't have to worry about the boats getting tangled up in them or moving them around. Now the fluridone comes in and that should kill off anything that starts up from those tubers again. This is a systemic herbicide."

Three injection sites have been set up to keep liquid fluridone flowing into the inlet. Fortunately, unlike last fall, the inlet will not have to close. Experts said the treatment is safe for humans and wildlife.

"It's really low levels. About three to five parts per billion is what we're aiming for. So it's really a very low concentration," said Schutt. "Not really harmful to anything else."

The chemicals going into the water have raised some eyebrows. However, experts said the treatment is working, with nearly 100 percent of the existing plants eradicated for now. But this is a treatment that will take several years to finish the job.