Idaho Lakes Spared Infestation So Far

Idaho may be one of just eight states in the nation where lakes aren’t infested with Eurasian milfoil.

But even if the exotic weed isn’t in the Gem State yet, chances are it eventually will come, experts said.

Most years, at least one state gets added to the list of those where the aquatic weed is known to exist, said Sandy Engel of the Wisconsin Department of Natural Resources. This year, it was found for the first time in New Mexico and Utah.

The plant is so tenacious that just a small sprig left clinging to a boat trailer or motor can establish a new colony in the next lake where the boat is used. Studies show that isolated lakes without launches are less likely to be infested, said Engel.

Engel said there have been no reports of the plant in Colorado, Montana, South Dakota, Wyoming, Maine, Alaska or Hawaii. That doesn’t mean it doesn’t exist in those states, just that no one has yet found it.

Milfoil infests many lakes in Washington, and is thick in the Pend Oreille River, just across the border from Idaho. In a test scheduled for late June, the Washington Department of Ecology will use herbicides to fight milfoil in Loon Lake, north of Spokane.

Engel lists Idaho as having the weed, based on a report written in the 1980s by two noted botanists who since have retired. But the report doesn’t list the lake in which they found the weed, and officials for the state Division of Environmental Quality said they don’t know of any confirmed cases.

A plant found in Big Payette Lake last year was sent to a California laboratory, said Craig Shepard, DEQ’s water quality supervisor. Tests to determine whether it was Eurasian milfoil or a nearly identical - and easily controlled - native species were inconclusive.

Experts don’t know exactly when milfoil showed up in North America, but it was confirmed here in the mid-1940s, said Kurt Getsinger, an expert from the U.S. Army Corps of Engineers.

In Europe, where the plant is native, it isn’t overabundant, he said, probably because other native plants are better adapted to competing with it than are those in North America.