Task force battles Eurasian Watermilfoil

THOMPSON FALLS – The Sanders County Aquatic Invasive Plant Task Force came together for their monthly meeting at the Sanders County Court House last week.

Throughout the meeting the task force discussed their timeline and strategies for treating Eurasian Watermilfoil (EWM) in the Noxon Rapids and Cabinet Gorge Reservoirs.

EWM was first discovered in the county in 2007 and in 2009 there were 364 acres of EWM in Noxon Rapids Reservoir.

Since this point in 2009, EWM control on the reservoir has improved greatly, ranging from 70 to more than 85 percent control rates in the majority of treatment areas.

The mild winter, minimal snow pack, dry spring and a recent spate of warm temperatures in early summer have all contributed to providing EWM with optimal conditions for growth, despite the efforts taken to eliminate the invasive and noxious aquatic weed from the region.

Additionally, this season’s low water levels with reduced water flows and unseasonably high temperatures provided optimum growing conditions for EWM.

Dr. Kurt Getsinger a biologist with the Army Corps of Engineers, who has been assisting the task force with their maintenance plan was on hand for last week’s meeting.

The biologist explained local populations of EWM were able to take advantage of this combination of beneficial growing conditions.

“Weather gave them the best opportunity and they took advantage of it as a weed will do,” Getsinger said.

Getsinger stated the warm temperatures had caused issues for several bodies of water in the Pacific Northwest.

“It wasn’t just here in this valley it was all over the northwest, especially in the inland part,” Getsinger said.

Sanders County is not the only area to see an increase in EWM as similar weather conditions across the state and in Idaho have led to increased EWM growth to the east in the Fort Peck Reservoir by the Missouri River in Glasgow, and to the west with reports of aquatic growth in Lake Pend Oreille and Hayden Lake in Idaho.

Survey and delineation of high density EWM beds in Noxon Rapids Reservoir was contracted July 10, and has been completed with results of the survey indicating about 142 acres of EWM require treatment between Trout Creek and the Marten Creek Bay area.

Getsinger noted efforts to reduce EWM in Sanders County have been quite successful over the years even with the weed’s resurgence in some areas this year.

“That is seven years in a flowing system where you haven’t had to treat it. Anybody in the country would be happy with that whether you are talking about a lake or a reservoir,” Getsinger said.

The task force notes treating EWM that has re-invaded sites on the reservoir will reduce the amount of fragments produced by the weed and limit the continued spread of the plant.  

It is important to note that the ideal growing conditions, which have led to an increase in EWM, has also proved to be a boon for native species of aquatic plants throughout the region.