Lake Wilson still shows no signs of the invasive aquatic weed, Salvinia molesta, and state officials say the threat to fish, recreational fishing and boating is gone — for now.

"Although we have declared Lake Wilson Salvinia-free today, tomorrow may be a different story," said Peter Young, state Department of Land and Natural Resources chairman. "We will continue to monitor the lake and act quickly in a coordinated effort should the need arise."

The weed invasion closed the 325-acre lake to the public from January 2002 to November 2003. The state spent more than $1 million in 2003 fighting the weed.

An interagency effort was created to coordinate city, state, military crews and volunteers pulling out salvinia with machines and by hand, and the use of an aquatic herbicide.

Heidi Bornhorst, a consultant on sustainable landscaping, warned that weeds never really go away.

"I haven't been out there to look at it," Bornhorst said. "But with a week, you never really get rid of it. Weeds never sleep."

The solution is to ensure that native species flourish, Bornhorst said.

Last year, the effort continued as the state sprayed the lake with an EPA-approved herbicide and the state's amphibious harvester removed California grass along lake edges, which could harbor Salvinia plants.

Overhanging tree branches were trimmed, to allow crews to get in close to check for the invasive weed. In addition, crews checked the upper reaches of the north and south forks of the lake to make sure no pockets of the weed remained.

DLNR, the Department of Agriculture, and other state departments are part of the Hawai'i Invasive Species Council, which has received $4 million for planning and implementation of urgent actions to prevent alien and invasive species from being introduced to the Islands, and to create a timely response to control species that do appear.

"The effort that it took to organize multiple government agencies to execute the bulk extraction phase, bear the considerable costs, and carry out maintenance for about two years, has been a primary lesson in the importance of swift, serious response to an invasive species," Young said.

Reach Suzanne Roig at sroig@honoluluadvertiser.com.