Treatment of EWM in Noxon sees success

NOXON - Invasive, non-native Eurasian watermilfoil (EWM) was discovered in Noxon Rapids Reservoir, the stretch of water in and around the towns of Heron, Noxon and Trout Creek, in June 2007 – the first confirmed case in Montana.

Knowing that EWM forms dense, inhospitable beds that crowd out native plants in littoral zones -- water less than 25 feet deep -- the Sanders County Aquatic Invasive Plants Task Force was quickly formed to develop a plan to treat and monitor this new infestation. EWM threatens water quality, fisheries, drinking and irrigation water supplies, recreational uses and hydroelectric operations.

In continued work, the task force used a five-pronged approach to battle EWM in 2013. EWM spreads by natural fragmentation as well as fragmentation caused by human disturbance.

“Last year’s program went well overall. We were able to employ multiple control tactics, using varied removal and suppression techniques tailored to site-specific conditions of existing beds and reservoir conditions,” said Task Force Chairman Jason Badger, who is also Sanders County’s Weed Coordinator.

“As with any weed species, an integrated management approach is best,” he added.

The five efforts were: aquatic herbicide treatments, diver dredging (or hand pulling), installation of bottom barriers, boat inspection stations, and education and outreach efforts.

Herbicide treatments

Aquatic herbicides were used in 2013 to treat 188 acres infested with EWM and Curlyleaf pondweed, where the species were intermixed in Noxon Rapids Reservoir.

The Bellingham, Wash. firm Aquatechnex performed pre-treatment surveys and mapped treatment areas using research findings from Dr. Kurt Getsinger of the Army Corps of Engineers, to finalize priority treatment areas.

Clean Lakes, Inc. of Coeur d’Alene, Idaho, used state-of-the-art littoral zone treatment vessels to apply herbicides to the lower portion of the water column, providing adequate herbicide concentration and exposure times for the substances used to control the unwanted aquatic invasive plants.

Six weeks after treatment, Aquatechnex returned to perform a qualitative review of each plot to determine effectiveness of the herbicide treatments.

The company’s recently-released report states “good to excellent” results for the majority of the treated sites. The largest of 11 treated plots was 74 acres in size, while most were between one and nine acres. Two additional sites received spot treatments.

Aquatechnex will return this summer to perform a more detailed 52-week inspection of 2013 plots.

The long-term impact of herbicide treatments are difficult to determine in a short amount of time, and are best evaluated later on, said Montana State University Extension Agent John Halpop, who helped start the task force. Because of the life cycle of the plants, it will be easier to see results next year.

“When we go back in and look at it pre-treatment, we’ll have a better idea,” he said.

Diver dredging

The task force utilized the services of Hanson Environmental to conduct a diver dredging control project for the first time last year. Owner Erik Hanson, a state aquatic plants specialist-turned contract diver and aquatic invasive species consultant, donned a wetsuit and other gear. Using a hose connected to a modified gold dredge, he carefully unearthed and removed 400 pounds of EWM from several sites on Noxon Reservoir.

Without need for diving gear on the dredge equipment, a two-person crew also hand-picked 220 pounds of EWM at a shallow, shoreline location.

At the time of the work, plants had already grown dense and were beginning to fragment, making removal difficult, Hanson noted. He is still confident that diver dredging is a good weapon when used earlier in the year, especially upon plants that are scattered, rather than in dense infestations.

Bottom barriers

“Bottom barriers,” landscaping mesh stretched between specially-made 10-by-10-foot squares of PVC piping, have been installed along high traffic areas of the reservoir bottom since 2008.

Halpop said they are a good tool.

“Bottom barriers stop plant growth from coming through,” he said.

Because the barriers are non-selective in controlling aquatic plants, there was a decrease in native plants there, too.

While in 2012, 250 barriers were installed along the waterway, only 235 were needed in 2013 due to reduction in plant mass at those areas.

“The program worked pretty well,” said Avista Natural Resources Technician Danny MacKay, who supervised the effort done in cooperation by Avista and Noxon-Cabinet Shoreline Association. “The barriers helped landowners access their docks. It decreased fragmentation of EWM plants that were still left in those areas, and they saw a decrease in native plants there, too.”

Avista employees joined forces with divers from ACE Diving, to place the aquatic forms of “weed block” at public boat launches, and at private docks where shoreline owners participate financially in the program.

The 2013 barriers were put into place in June, and were dispersed in key areas extending from the public boat ramp at Finlay Flats, to a private dock adjacent to the Heron public boat ramp. Numerous boats emerged from the Flat Iron Fishing Access Site near Thompson Falls covered with aquatic plants which owners didn’t always sufficiently clean before entering the nearby check station. To cut down the time needed to clean boats by check station personnel, two additional bottom barriers were installed at the launch area.

All barriers were removed in September and October.

Boat inspection stations

Three boat inspections existed in and around Sanders County last year, and all boards that drive past them are mandated to stop for inspection. Some boats and/or trailers were found with aquatic vegetation that hadn’t been removed.

Preliminary 2013 data indicates that at the inspection station at the intersection of highways 200 and 56, three cases of EWM were discovered, as well as five samples of vegetation that were not EWM. The site received almost twice as many boaters from out of state (417) than those from within Montana (244).

At the intersection of highways 2 and 56, the inspection station discovered three EWM segments and six samples of “vegetation not EWM” on boats and trailers. The site catches boaters traveling east along Highway 2, as well as those traveling north on Highway 56, leaving Sanders County. A total of 635 Montana boaters stopped at this check station, while 391 came from out of state.

Significantly more Montanans stopped at the Thompson Falls station (350), while 57 were from out of state. At the stop, boats were checked as they headed eastbound. The highest amount of detection of EWM among the three stations in Sanders County – 23 segments – were detected at the site. Further results from the preliminary numbers show that the largest number of other types of vegetation –143—were also discovered.

“The higher proportion of boats with vegetation at the Thompson Falls station could be related to the station’s proximity to boat launches in the area, some of which have vegetation, including EWM, at the ramp,” said Allison Begley, aquatic invasive species specialist for Montana, Fish, Wildlife and Parks.

FWP took over administration of the boat inspection program from Montana Department of Agriculture last year.

Contributing to a successful inaugural year, Begley said successful operations of the inspection stations was in large part due to support and feedback of the task force.

Education and outreach

The number of people who have heard of EWM has risen significantly since the task force’s education and outreach program began five years ago. At that time, 14 percent knew of the plant, compared to 97 percent last summer.

Ninety-eight percent of those surveyed know that EWM is spread by fragments, while 48 percent of people surveyed last year said they could identify EWM.

Ninety percent of boat owners surveyed said they clean, drain and dry their boats before removing them.

Halpop is convinced that spread of EWM and other aquatic invasive species begins with boat owners taking responsibility.

“People need to recognize their role, and check their own boats and their own trailers,” he said.

More of the 2013 survey data is being studied to determine where future education and outreach efforts need to be made.

Funding

In addition to major funding from a Montana Department of Natural Resources and Conservation Reclamation and Development grant and the Montana Department of Agriculture Noxious Weed Trust Fund, other partners were Avista, Montana Fish, Wildlife and Parks, Montana Department of Agriculture, Montana State University Extension, Noxon-Cabinet Shoreline Coalition, Dr. Kurt Getsinger (U.S. Army Corps of Engineers), Sanders County and Sanders County AIP Task Force.

Task force members

The Sanders County Aquatic Invasive Plants Task Force is made up of representatives from Montana State University Extension, Avista, Green Mountain Conservation District, Noxon-Cabinet Shoreline Coalition, Montana B.A.S.S. Federation, Confederated Salish and Kootenai Tribes, Montana Department of Agriculture, U.S. Forest Service, Sanders County Weed board, a statewide weed management representative and an at-large community representative. The task force was established by, and acts as advisor to the Sanders County Commissioners, who hold decision-making authority for aquatic invasive plant control measures in the county. Meetings of the task force are generally held the fourth Wednesday of the month at 2 p.m. in the County Commissioners meeting room in Thompson Falls, and are open to the public.

For more information:

Jason Badger, Sanders County AIP Task Force Chairman, Sanders County Weed Coordinator, 406-826-3487.

Danny MacKay, Avista, natural resources technician, 406-847-1297.

The Clean Lakes report for 2013 is available at www.cleanlake.com/2013noxonrapidsais.html.