LIMERICK (AP) – Biologists applied an herbicide to a small pond Monday in an attempt to eradicate the state’s first documented presence of hydrilla, a fast-spreading invasive plant that can choke the life out of lakes and ponds.

Aboard an 18-foot air boat, biologists with Aquatic Control Technology Inc. of Sutton, Mass., released a total of 2.75 gallons of the chemical fluridone into the 46-acre Pickerel Pond, where hydrilla was detected last year.

The chemical was diluted in water in an on-board tank and released through four pipes off the side of the air boat as it made passes across the pond.

The state the past two years has been fighting variable milfoil, an invasive plant that has been found in 14 Maine lakes and pond. But hydrilla poses a bigger threat because it spreads faster and is more durable, said Paul Gregory, an environmental specialist with the Department of Environmental Protection’s invasive species program.

“It’s considered the worst invasive plant in North America,” Gregory said while standing on the shore of Pickerel Pond. “It will eventually choke out everything.”

Hydrilla is thought to have been in Pickerel Pond for four or five years, but it didn’t become particularly bad until last year. The state considered three ways to get rid of the pest: chemically, mechanically and biologically.

Taking care of the hydrilla mechanically would have involved pulling the weeds by hand or spreading screening or plastic materials on the bottom to suffocate the plant, not particularly effective means. Biologically, the state could have imported grass carp to eat the hydrilla, but that fish is prohibited in Maine.

State officials decided to hire Aquatic Control Technology to apply fluridone, which has been used successfully in a number of other states to get rid of hydrilla.

“Use of a chemical is a last resort,” said John McPhedran, coordinator of the DEP’s invasive species program. “But it appeared to us we needed to take an aggressive stance.”

State officials have expected invasive plants other than variable milfoil to show up in Maine. But they weren’t expecting hydrilla, which in New England has been found in only four ponds – one in Massachusetts and three in Connecticut.

Hydrilla hurts aquatic ecosystems by forming dense canopies that often shade out native vegetation and over time change a lake’s chemical makeup. Once it has established itself, hydrilla is especially difficult to get rid of; Florida spends up to $20 million a year on hydrilla eradication.

McPhedran said fluridone shouldn’t pose any threats to human health, and that Aquatic Control Technology will be back later, probably next month, to apply more of the chemical.

That’s fine with Mike and Kathy Ward of Limerick, who said the hydrilla became particularly bad last year when it created a thick blanket about 4 inches under water on the west end of the pond.

The pond has houses along its shores and is used for boating, swimming and fishing, mainly for bass, pickerel and perch.

“Everybody’s all in favor of it,” Mike Ward said.

State officials will monitor the hydrilla this summer and test nearby ponds and lakes to see if it has made its way there.

But they’ll probably never learn how the hydrilla came here in the first place.

It could have been carried to Limerick on a boat, fishing gear, an anchor line or on sea planes that have used the pond over the years. Hydrilla was once used as an aquarium plant, and somebody may have dumped old aquarium water into the pond. It may even have come from a bird flying overhead.

“We can’t stop hydrilla entirely,” McPhedran said. “But we can reduce the risk of it spreading, which is what we’re trying to do now.”

AP-ES-06-16-03 1545EDT

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