Whatever
Happened To...
An update on past news
Salvinia fight at Lake Wilson
continues on small scale todayQuestion: Whatever happened to the infestation of Salvinia molesta, the fast-growing waterweed that choked Lake Wilson last spring?
Answer: At the height of its invasion a year ago, the invasive plant covered almost the entire surface of the 300-acre Central Oahu lake.
U.S. Army Corps of Engineers specialists brought in to survey what was called a "green carpet" expressed doubt that it could ever be eradicated because conditions for its growth were so favorable in Lake Wilson.
Salvinia can reproduce from pieces of plant so rapidly that it can double in size in two to eight days in ideal conditions.
"The guys from Australia (who have battled it) called this the world's worst weed," said John Barko, a Corps director of environmental sciences, as he looked out over acres of salvinia in Lake Wilson last February. "A single bud smaller than a pen-point will generate a new plant."
But by Memorial Day, the salvinia was almost gone and the fish in the lake were saved from smothering. Public fishing on the lake was reopened.
The success story came from an ambitious partnership among state, city and military workers who physically removed tons of salvinia from the lake. Spraying with a herbicide was also part of the treatment.
The battle against salvinia cost about $1 million -- less than originally projected, but still a tidy sum, said Eric Hirano, engineering director for the state Department of Land and Natural Resources, the state agency that coordinated the efforts.
Today, the state still checks the entire lake once a month, looking for remnant pockets of salvinia and treating them while they are still small, said Francis Oishi, DLNR recreational fishery program manager.
Other than some stubborn pockets of the weed below the county sewage treatment plant, "the lake is clear," Oishi said recently. "But I think we have to be vigilant from here on in. I don't think we can say OK, the lake is clear now and the biomass is so low we don't have to worry about that."
After all, fishermen originally reported seeing small amounts of salvinia around Thanksgiving 2002, and just two months later the weed was at disastrous levels.
"The whole experience was a learning one for everyone involved," Oishi said. "I don't think we'd want to make that mistake again."
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