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But that doesn’t mean the tiny weevils have pulled a disappearing act in the lake, a lead scientist on the project was quick to point out after spending the afternoon inspecting an area where 12,000 weevil eggs and larvae were released last August.
“The weevils are tiny,” said Michelle Marko, a Concordia College professor joined on the research team by three biology students from the Moorhead, Minn., college. “We’ll have to examine the milfoil under a microscope to check for larvae and weevil damage.”
Laboratory tests of milfoil taken from the lake in June did detect weevil eggs and adults, said state Department of General Administration senior planner Nathaniel Jones.
At the same time, the research team found only sparse numbers of milfoil plants in the three-acre lake lagoon next to the Capitol Lake Interpretive Center, an area where the weevils were introduced and did damage to the milfoil last year.
Adult weevils eat the milfoil leaves and stems. And as larvae, they bore into the stem of the plant, causing the plants to collapse.
It’s also possible that the weevils were unintended victims of the draining and saltwater back flush of the lake in March in an attempt to control another lake invader — the New Zealand mud snail. The lake disruptions did little to dent the snail population.
“A lot has happened with the lake in the past year,” Marko noted.
The state Department of General Administration resorted to the weevils after hand-pulling of the pesky invasive weed failed to curb it in the lagoon in the years after the 2004 herbicide spray. The chemical treatment was considered a success in most areas of the lake.
The three-year, $75,000 project financed primarily by the state Department of Ecology was the first large-scale use of milfoil weevils in the state, according to project officials.
Marko’s research team will be back on the main stem of the lake Thursday, looking for milfoil and weevils. The contract also calls for them to return for a follow-up lake inspection next month.
Left unchecked, the milfoil can choke out other native aquatic plants, hinder recreational use of the lake and serve as a vehicle for floating mats of algae.
The lake has been off limits to recreational use since the mud snails were discovered last fall.
John Dodge: 360-754-5444 jdodge@theolympian.com
