NAPLES — Citing increased milfoil problems in the lower part of the Songo River, the Lakes Environmental Association has recommended that the Songo Lock in Casco be closed to through traffic by boats.

Peter Lowell, president of the LEA, said the early spring and warm weather have contributed to a major milfoil infestation in the lower part of the river, a 3.5 mile long waterway between Brandy Pond in Naples and Sebago Lake in Casco.

He said the number of boats passing through the lock has doubled since last year due to pleasant weather, with 690 recorded from May to June compared to 368 during the same period in 2009. A total of 3,980 boats passed through the lock in 2009.

Lowell said that more milfoil and more boats make it impossible to ensure that milfoil from the Lower Songo River will not be transferred to the Upper Songo River, which leads to Brandy Pond and Long Lake. Individual milfoil fragments can take root and grow in the river bottom, forming thick mats that can inhibit recreational water uses and lower property values.

“If things get progressively worse, then August is pretty much going to be a nightmare,” Lowell said.

Town Manager Derik Goodine of Naples said he has met with local and state officials on the matter, and that there is a general consensus that increasing education and possibly increasing fees to support the courtesy inspection programs would contribute to milfoil control. He said he is reluctant to shut down the lock as it is a busy time for boating.

“The biggest solution to the problem of course is to eradicate the milfoil in the southern part of the river,” Goodine said.

The LEA uses divers and suction harvesting to remove the invasive plants, as well as barriers to cover and suffocate them. Lowell said crews have been successful in controlling milfoil in the Upper Songo River and Brandy Pond, but it would not be feasible to attack the infestation on the Lower Songo River.

“The lower river is way beyond our resources,” he said.

The Department of Conservation operates the lock, but the decision to close the mechanism would be made by commissioners from that department, the Department of Environmental Protection, and the Department of Inland Fisheries and Wildlife.

Lowell said he is working with representatives from the departments, the Portland Water District, the town of Naples, and other areas to discuss the issue. He is also urging boaters to voluntarily stay on one side of the lock.

“There’s plenty of water to navigate without going down the river into Sebago,” he said. “From the other way, if someone’s on Sebago Lake, they’ve certainly got plenty of water to navigate.”

Dan Craffey, owner of the Moose Landing Marina on Long Lake, said he thinks closing the Songo Lock would be as detrimental to the local economy. He said milfoil has long been an issue in the area, but that boaters are cautious about checking their watercraft.

“I can understand the concern, but to shut down a 44-mile waterway […] that’s certainly going to affect real estate values, it’s certainly going to affect our business negatively,” he said.

Lowell said a courtesy boat inspector checks for milfoil at the lock, and that the association has added a second inspector due to the greater infestation. However, he said the position is an added cost to the LEA and more boat traffic creates more difficulties for thorough inspections. He said there hasn’t been a visible increase in milfoil on the Upper Songo River, but that it is too early to determine the impact of the growing infestation and its possible transfer upstream.

“Even if they bring five or six fragments upriver it’s going to be a big impact” he said.

Lowell said the lock has been closed in the past, including once in 2008, but in these cases the decision was due to high water creating difficulties in opening and closing the lock.

The Department of Conservation website says there is a  $3 per boat charge for travel through the lock. Craffey said the lock is open during tourist season from May to October and closed at other times.

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