By Craig T. Kojima, Star-Bulletin
Water hyacinth plants cover the surface of Lake Wilson.
Government officials, boaters and fishermen are trying
to develop a plan to control the infestation.

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So, where’s the lake?

The state battles a green and purple
monster overrunning Lake Wilson

By Alan Matsuoka
Star-Bulletin

It's green and purple and can double in number every 10 days, smothering plant and animal life as it spreads.

Sounding like a villain from a "Star Trek" episode, the menace actually is the water hyacinth -- and it is threatening Lake Wilson reservoir in Wahiawa, where the plant in some areas is growing shore to shore, laying a leafy carpet so thick the water is hard to see.

"We have a problem," said William Devick, acting administrator of the state Aquatic Resources Division. "We have to get all of this stuff out, and we have to to it relatively fast because of the rate of growth."

To find a way to do that, state officials and freshwater fishing groups held an initial brainstorming session yesterday at the Kalanimoku Building. Michael Wilson, who heads the state Land and Natural Resources Department, said the target date for removal is the end of summer. A draft plan could be ready in three weeks.

According to those at the meeting, the problem started about a year ago. Fishermen pulled the hyacinths, the standard control practice, but the plant grew faster than their efforts. Devick said about two months ago it became apparent the growth was "getting out of hand," and the state tried spraying with Rodeo, an herbicide certified for use on water. The infestation was temporarily checked, but not knocked out.

"In this case, the stuff appeared too rapidly for the surveillance that was going on, and the control efforts that were in place weren't adequate to stop them," he said.

The hyacinths now cover about eight acres, of a total lake surface area of 350 acres. Because of the configuration of the narrow and meandering reservoir, most of the infestation is jammed near a sewage treatment facility that pumps out a rich source of nutrients for the plants. Longer summer days could spur their growth even more, and winds could propel patches to start colonies miles away, as they already have.

Ben Outram, a board member with the Hawaii Freshwater Fishing Association, said the problem is so bad that his nine-foot motorboat couldn't reach a weigh-in station during a fishing tournament this month. He was helped by a friend with a more powerful boat. Howard Araki, an association vice president and owner of Kilani Rod & Tackle, said bank fishermen also are being affected, since there is only limited access to the reservoir, a public fishing area, with one of the most popular spots across from the treatment facility.

"The thing is, with the growth rate, I don't know," Araki said, when asked about the target date. "The problem needs a massive effort right now, but knowing that the lake doesn't really get high priority, we'll take what we can get."

The water hyacinth originated in South America, where insects and disease limit growth.

It has been a serious environmental problem in the southern United States and tropical areas where the natural controls don't exist.

The floating hyacinth can block sunlight to plants below that oxygenate the water, and suck available oxygen needed by fish. The worst-case scenario is a massive die-off of the largemouth bass, channel catfish and other species that populate Lake Wilson.

Officials are worried about the cost of the upcoming operation. They had budgeted $10,000, but Devick said the lowest contractor bid was some $22,000 -- and that was based on manually removing just 0.7 acres of the plant. Since then, the problem has increased by more than 10 times.

Volunteers consequently will be part of any plan, and the military will be approached for help.

One scenario involves moving the plants to an area where they can be stacked on land and dried, reducing their volume by 90 percent. Glenn Higashi, a state aquatics biologist, said prototype development has started on a vessel to push the growth away.

Massive spraying is not considered an option, since decaying plants could kill fish.

The infestation also could lead to an increase in mosquitoes, partly because small fish can't make it to the water's surface to eat larvae. Wilson said the problems point to the need for a long-term plan for the reservoir, which last saw a similar hyacinth growth in the 1950s.

"It's clear we have to change the approach that we've had in the past because we don't want this to end up happening again," he said.