Aquatic invader spotted in lake

State officials scramble to stop milfoil from spreading

JOHN DODGE, THE OLYMPIAN

Originally published November 6, 2001

OLYMPIA -- A pesky, nonnative weed called Eurasian watermilfoil has been detected in Capitol Lake this fall.

The state Department of General Administration, which manages the man-made lake as part of the Capitol Campus, is scrambling to complete a survey to determine the extent of the infestation, the agency's David Schilperoort said.

"We can't leave it alone," he said. "Otherwise it will take over the lake, period."

Left unchecked, milfoil forms dense floating mats of vegetation that crowd out other freshwater plants, rob the water of oxygen and interfere with recreational use of a lake.

Eurasian milfoil has been found in more than 100 lake, reservoir and river sites in the state.

Public agencies and private waterfront owners spend some $1 million a year fighting milfoil, according to the state Department of Ecology.

Options for control include pulling the lacy-leafed plant by hand, spraying it with herbicides or suffocating it with a barrier on infested areas of the lake bottom.

So far, the invasive freshwater plant has been spotted on the eastern shore of the lake between Interstate 5 and Heritage Park.

It may have arrived in the lake clinging to a boat or bird. Small fragments of the plant grow roots and colonize quickly.

Prime habitat

The lake, which is shallow and warm in the growing season, is prime growing habitat for the noxious weed, Schilperoort said.

If the infestation is under three acres in size, the state agency could apply for an emergency grant to rid the lake of the milfoil, said Kathy Hamel, an aquatic plant specialist with the state Department of Ecology. The maximum grant is $50,000.

The lake is a poor candidate for herbicide treatment to combat milfoil, said Mark Swartout, a Thurston County natural resource specialist.

Fluridone, a herbicide often used to kill milfoil, requires several weeks of contact time in the water. Capitol Lake is an impoundment of Deschutes River water that turns over every two to 11 days.

The 1999 state Legislature also approved the use of 2,4-D for limited infestations of Eurasian milfoil where individual plants are targeted for treatment.

Such a use in Capitol Lake would be controversial at best.

"If it were a county lake, we wouldn't allow 2,4-D," Swartout said, referring to the county's vegetation management policy.

"The state may be better off to use hand-pulling and bottom barriers," Hamel said.

Time is of the essence. As the weather cools, the plant leaves turn brittle and break off, making it harder to spot the plants. In addition, the leaf fragments grow roots and create new plants.

"We're trying to get the survey done in the next week or two," Schilperoort said.

In addition, General Administration has posted signs around the lake, showing the public what Eurasian milfoil looks like and how to avoid spreading it.

John Dodge covers the environment and energy for The Olympian. He can be reached at 360-754-5444.

Aggressive species

Difficult to control and quick to spread, Eurasian watermilfoil is considered the most troublesome nonnative, freshwater plant in the state.

In the growing season, the plant produces reddish spikes and pinkish flowers that protrude above the water. In the late summer and fall, the plants turn brittle and break into fragments that produce new plants.

Milfoil can crowd out other plants, rob water of oxygen and foul swimming and boating areas quickly. It can move from one lake to another on boats, boat motors and birds.

Other South Sound lakes with documented Eurasian milfoil infestations include Long and Scott lakes in Thurston County and Mason and Island lakes in Mason County.

Methods used to control milfoil include applying herbicides to infested lakes or hand-pulling individual plants.

It was discovered this fall in Capitol Lake.

The plant features feathery submerged foliage that form whorls around the thin plant stalks.

On the web:

Eurasian watermilfoil

The Olympian Copyright 2001

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