State to open second front at Lake Wilson
| • | Ban on sale of salvinia sought |
| • | Map: New fronts in war on weed |
By Catherine E. Toth
Advertiser Staff Writer
The state plans to open a second salvinia excavation site at the Lake Wilson Recreation Area today in an attempt to speed up extraction of the noxious weed that has overrun the lake.
A week into the counter-attack against fast-growing Salvinia molesta, workers have made "reasonable" progress, state officials say. But the new extraction site and the promise of another this week along with herbicide spraying that began Monday will strengthen the effort.
"Unfortunately it's been a little slower than we wanted," said Eric Hirano, head of engineering for the state Department of Land and Natural Resources, which is heading the salvinia removal effort.
About 200 to 300 cubic yards of salvinia are being pulled out of the lake daily, less than originally anticipated, Hirano said.
Salvinia still covers nearly 300 acres, or more than 90 percent, of the lake's surface.
Yesterday crews set up heavy equipment at the second excavation site — the boat launch in the Lake Wilson Recreation Area, which has been closed indefinitely. Workers also will use the ramp to launch boats equipped with herbicide to kill the plant, which began taking over the lake in November.
Using herbicide is expected to accelerate the removal. Crews are using two boats to spray AquaMaster, or Rodeo, an herbicide specific to aquatic weed control. The state hopes to cover about 50 acres a week with the two boats. It takes almost 100 gallons to spray about an acre; crews will have to use about 5,000 gallons to meet the weekly goal.
"This is essential," said Peter Young, director of the state Department of Land and Natural Resources. "When you're talking about 300 acres of surface area, you can't just clear it out with a 5-foot scoop at a time. It requires herbicide."
Once a plant is sprayed, Hirano said it will take about 24 days for it to die and sink to the bottom of the lake.
Even before it kills the plant, the herbicide retards the plant's prodigious growth, Hirano said.
Hirano said he has not received any complaints from nearby residents about the spraying, which he said is being done away from lakeside homes, apartments and businesses.
The state is also considering bringing in two airboats from the Mainland, operated by the U.S. Army Corps of Engineers.
Initial estimates that the lake would be cleared in less than a month have been changed.
"That was all based on preliminary estimates," Hirano said. "Right now we have a better handle on how much we're extracting and we're recalculating how much time we need. But it will definitely be more than 28 days."
The state is working with the military to open a third site soon. Young hopes to open two more along the lake in the coming month.
Finding a suitable site has been a problem for the state, which needs enough room along the banks of the lake to operate heavy equipment and launch boats to aid in the herbicide effort. Some areas don't have road access; others don't have a gradual incline from the bank into the lake, which is needed to get equipment into the water.
Pending military support, the third site is expected to open on a small peninsula north of the current site behind Kemo'o By The Lake condominiums on Wilikina Drive.
Meanwhile, a statewide group working to close the gaps in Hawai'i's biosecurity said yesterday that a newly developed weed risk assessment procedure could have warned officials of the hazards of salvinia if it had been in use before the aquatic fern was introduced to the island.
A team of Hawai'i scientists has modified a weed-risk assessment system used in Australia and New Zealand. The modified system will allow scientists to identify weeds that could threaten Hawai'i ecosystems, according to the Coordinating Group on Alien Pest Species.
Salvinia molesta ranks 29 on the system — a high ranking that indicates it would be a pest in the Islands. On the same system, the aggressive forest weed miconia ranks 14. The common plumeria flower, which primarily grows from cuttings and seldom sets seed in the Islands, ranks a negative 5. Plants with negative numbers are considered unlikely to become pests.
The Coordinating Group on Alien Pest Species and invasive species committees in the four counties are recommending the state apply the weed-risk assessment system to identify potential pests before they are imported.
"Some of the world's most notorius weeds are not prohibited to import into our state because they are not listed on the state Noxious Weed List," said Curt Daehler, a University of Hawai'i botany professor and member of the team that worked with the weed-assessment system.
Salvinia gained a high ranking in part because it grows extremely fast, has a choking growth pattern, spreads easily and has become a pest in similar Hawai'i habitats, Daehler said.
Staff writer Jan TenBruggencate contributed to this report. Reach Catherine E. Toth at 535-8103 or ctoth@honoluluadvertiser.com.
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