While Montana Fish, Wildlife and Parks uses a combination effort to eradicate noxious Eurasian watermilfoil from Beaver Lake, the popular boating spot has been closed to watercraft.

The lake north of Whitefish was temporarily closed last week by the Montana Department of Agriculture after some of the milfoil weeds were found to be tall enough to possibly get caught on boats. The closure is to all watercraft, but not to anglers or swimmers. Lease holders on the lake were notified of the closure Thursday.

FWP recently completed a final decision notice on a plan to manage and possibly eradicate the noxious aquatic weed from the lake.

A group of agencies prepared a draft environmental assessment to address the invasion. FWP received three written comment letters from private individuals, all in support of the proposal.

The plan includes using barrier mats, mechanical removal, herbicide treatments, or a combination to remove the weed.

A diver-operated dredge was set to be at Beaver Lake today. The dredge sucks the weeds from the bottom of the lake. The lake will reopen to watercraft once the milfoil is removed.

A 25-by-25 foot patch of Eurasian watermilfoil was found near the boat ramp at Beaver Lake last fall. Barrier mats were placed on the weeds to limit growth and control further expansion in the lake, but officials say the mats aren’t killing the weeds as planned.

Watermilfoil roots itself to the bottom of water bodies and forms dense mats at the water surface, crowding out native plants and interfering with boating, swimming and fishing.

Beaver Lake is the only known water body in the Flathead infested by watermilfoil. The aquatic invasive species spreads by stem fragments and seed. It grows as water temperatures rise in summer.

In 2011, mechanical removal of the watermilfoil was attempted, but did not completely remove it as observed by divers this spring.

Further work to remove the weed is estimated to begin this month with completion set for Nov. 1. Monitoring and additional treatments could occur over a five-year period.

Recreationists are advised to avoid the infested area near the boat ramp, which has been designated by buoys and signs.