FL MORRIS / FMORRIS@STARBULLETIN.COM
Working near Lake Wilson's spillway, Harold Komoku used a front loader yesterday to scoop out Salvinia molesta plants.
City and state crews, using heavy equipment, removed less than an acre of a noxious alien weed this week that has covered an estimated three acres of Lake Wilson in Wahiawa, causing it to resemble a golf course. Losing battle feared
at Lake Wilson
By Leila Fujimori
lfujimori@starbulletin.comIf left unchecked, the aquatic fern, Salvinia molesta, could put the reservoir's fish population at risk.
"I think it will be virtually impossible to eradicate this," said William Devick, state Department of Land and Natural Resources' Aquatic Resources Division administrator, who said the plant probably came from someone's aquarium.
The problem is widespread throughout the southern United States, and a single plant could quickly multiply to cover 40 square miles. Herbicides are ineffectual, he said.
The invasive plant has caused angling to decline in Lake Wilson, home to turtles, ducks and 22 species of fish, including largemouth bass.
"My customers tell me it's very hard fishing," said George Tobita, owner of Wahiawa Sporting Goods, who sells tackle and issues fishing licenses. "You imagine like a lot of limu out there. You throw your line, everything gets all fouled up. Even the boats get in trouble because they (plants) get caught in the engine."
The fern, also known as Kariba weed and aquarium watermoss, has become a problem since the beginning of this year and aquatics personnel have been removing it manually. But the Salvinia has been harder to remove than the water hyacinth, which plagued the reservoir four years ago, because it is smaller and breaks up more easily.
Workers hauled out between 24 and 30 cubic yards of it from Wednesday through yesterday. Booms first contained the plants, which were pulled to shore using trucks, allowing a front-lift loader to scoop them out.
Landowner Dole Food Co. hauled the weeds to a nearby field, where it disintegrates into mulch.
Different techniques, including a backhoe, will be tried to speed up the removal. The work continues through next week.
Although there hasn't been a large number of fish dying because of the Salvinia so far, it could block the absorption of oxygen, leading to their suffocation.
The nutrients from treated sewage dumped by the city waste-water treatment facility have caused the fern to proliferate, Devick said.
Tobita has noticed a weed problem since sugar cane production no longer takes a large amount of irrigation water out of Lake Wilson.
"When the water level drops, you'd see the weeds dried up on the banks," he said. "All I know is I haven't seen the water level drop in years. All I've seen is my sales drop."
Devick confirmed his theory, saying, "If the reservoir level would drop like it did, this would provide a natural control for the Salvinia."
Salvinia had been present but brought under control in Enchanted Lake, where the problem was much smaller, Devick said.
