Beaver Lake north of Whitefish Lake was closed to public use Monday evening after Eurasian water milfoil was discovered in the lake.

Signs indicating the closure were posted and the boat ramp has been blocked, Montana Fish, Wildlife and Parks spokesman John Fraley said.

The closure is necessary to prevent the spread of the invasive, noxious weed.

“Milfoil can spread and reproduce itself by fragmenting,” Fraley said. “It’s important to keep it isolated.” The weed could become caught on a boat or an angler’s boot and potentially be carried into another body of water, he said.

A 12-foot-by-12-foot patch of the weed was discovered last week during a field trip and inspection by personnel from the Department of Natural Resources and Conservation. The weed was positively identified by experts at Fish, Wildlife and Parks and the agriculture department.

The closure comes about at the request of Flathead County and the Montana Department of Agriculture. Those two agencies are responsible for determining a plan to deal with the weed, Fraley said.

Jed Fisher, Flathead County weed department director, said a diver will enter the lake soon to pull up the weed and help determine how to control it.

Reporter Shelley Ridenour may be reached at 758-4439 or by email at sridenour@dailyinterlake.com.