BELGRADE — It’s been nearly three years since the state carried out a controversial plan to rid a cove in Salmon Lake of an aggressive, invasive milfoil, and the plant has yet to reappear.

John McPhedran, of the Department of Environmental Protection’s invasive aquatic plants program, said last week that several surveys over the past two years failed to turn up any evidence of Eurasian water milfoil in Kozy Cove on Salmon Lake. Divers most recently checked the cove on July 16.

“We’ve found none of the invasive aquatic plant,” McPhedran said. “That’s good news, but we still have plenty of growing season ahead of us.”

The DEP is planning one more survey in Augusta if there is adequate water clarity.

Divers have focused their attention on Kozy Cove, but the DEP, the Belgrade Regional Conservation Alliance and volunteer organizations have monitored the rest of Salmon Lake and McGrath Pond and Great Pond.

“It’s a big effort by a lot of people to survey the lakes,” McPhedran said.

If there is no sign of Eurasian water milfoil this year, the state would consider removing Salmon Lake from the list of infested waters, McPhedran said.

Even if the lake is removed from the state’s list, however, that does not mean the threat is over. McPhedran said it will be important for volunteers to keep a close eye on the parts of Salmon Lake that provide good habitat for Eurasian milfoil and other invasive aquatic plants.

“While this news is encouraging, I’ll never feel we can turn our back on Salmon Lake,” he said. “It has to be monitored, because some of these plants are very resilient, and there’s no guarantee it won’t come back at a later date.”

Meanwhile, the Belgrade Regional Conservation Alliance continues to lead the effort to remove variable-leaf milfoil from Great Meadow Stream and Great Pond. Tony Pied, who leads the alliance’s milfoil program, said crews have been working to remove the milfoil since the end of May. That work will continue at least through August.

“Because we’ve had such great weather, it’s been really good growing weather for the plants,” Pied said. “They’ve really taken off.”

She estimated crews of divers and those working to hand-pull the plant have removed a little more than half the variable-leaf milfoil from the stream and the lake.

“The good news is we have not found any other infestations yet,” Pied said.

All watercraft are restricted from Great Meadow Stream and that section of Great Pond, which is marked off with buoys, through at least Sept. 21. The plan is to allow nonmotorized craft after that date, Pied said. The alliance will work with the DEP to determine whether those restrictions must be extended.

“That could change,” Pied said. “It all really depends on how much we can get done in the next couple of months or so.”

Eurasian water milfoil, which can form dense mats and congest waterways, was first discovered in Kozy Cove in August 2008. Divers began removing the plant from the 6-acre cove within a week of the discovery, but it continued to swell.

Divers removed 325 plants in the summer of 2009, which was nearly twice what was collected in 2008.

The DEP announced in July 2009 that it was seeking a permit to spread a chemical — best known by its trade name, Navigate — to control the milfoil in the cove, which is near the Salmon Lake outlet stream.

The department held two public hearings, during which residents expressed concern that the chemical might harm other plants and wildlife in the lake. The DEP applied the chemical in September 2009.

McPhedran said he has noticed no harmful effects from the chemical in Kozy Cove.

“I don’t know about the remainder of the lake. I haven’t surveyed it thoroughly,” he said. “In the area that had the target concentration, I haven’t observed anything.”

State officials said at the time that they hoped the herbicide would push the milfoil back to a level where it could be controlled through dives and other harvesting methods. The chemical has at least met that objective.

“It hasn’t shown up; but if it did, I feel like we could control it manually at this point,” McPhedran said.

Craig Crosby — 621-5642

ccrosby@centralmaine.com