Boundary News
Herbicide 'Test' Planned for Kootenai River Milfoil
Mar 3, 2008, 08:54

Stretching 55 river miles from Bonners Ferry to the Canadian border, 504 Eurasian water milfoil beds discovered last fall in the Kootenai River are spreading to quickly. Officials fear the invasive weed could permanently alter the ecosystem of the once-pristine river.

If unchecked, state and local weed experts believe the fast-growing aquatic weed could infest more than 700 acres next year and will continue to spread.

They say chemical application on a 20-acre test site proposed for October could be the ray of hope they're looking for to prevent milfoil from gobbling up more of the Kootenai's precious shoreline.

Approximately $75,000 has been requested from the state to test herbicide 2,4-D on five, four-acre sites at public boat ramp areas this fall. It is the third-most widely used herbicide in North America and the most widely used herbicide in the world.

"Another piece of the puzzle is destroying our river's ecosystem, and unless we do something Eurasian milfoil will keep multiplying," Boundary County Weed Control Superintendent Duke Guthrie told a group of local and state officials. "Few places along the shoreline running the entire distance to Canada have virtually no vegetation to speak of because of milfoil. The plant will definitely change the ecosystem of the Kootenai."

If results show that 2,4-D - which has proven effective in fighting milfoil - have no toxic effects on sturgeon, then chemical treatment of the herbicide will be administered in the fall at the five test sites.

"The plants bloom in late September and October, and flows from the Libby Dam are reduced then, which make treatment more effective," said Guthrie. "So far, tests have shown 2,4-D is not harmful or toxic to sturgeon."

Backing the fight against milfoil is the Idaho Legislature, which has made $4 million available to county weed departments throughout the state.

Matt Voile, noxious weed section manager for the Idaho Department of Agriculture said 7,000 acres of milfoil infestation currently exist in Idaho, including shoreline along the Snake, Kootenai and Pend Oreille rivers. That amount, said Voile, has grown from 4,200 acres in just one year.

"Usually, we don't see milfoil infestation in pristine northern rivers," he added. We dont know what the long-term effects are or why its happening here. In one season, a section of shoreline on the Kootenai has been taken over and completely infested with milfoil. You're also looking at a lot of desirable habitat for fish along with recreation areas that are now affected."

First discovered in the Kootenai River in 2006, officials say the submersed, invasive plant degrades water quality, out-competes native vegetation while reducing native plant diversity and abundance.

"There's probably 2,000 acres that support vegetation between Bonners Ferry and Porthill, and a quarter of that amount is already infested with milfoil," said Guthrie. "To do a successful treatment of the Kootenai River, it would cost about $500,000. In comparison, Bonner County has requested $1.6 million to treat roughly 2,000 acres."

Though other options for fighting milfoil exist, both Guthrie and Voile agree that chemical application has been the most viable solution.

"Realistically, it has been the best answer," said Guthrie. "Dive-dredging runs about $1 per square foot and is just not cost-effective. It's not practical on a large scale."

About $3,500 of county labor will be used as an in-kind contribution towards the $75,000 project, which will be coordinated by Boundary County's weed department. Approximately $5,000 in state funding is earmarked for developing an educational outreach program for the public later this year.


February 29, 2008

Why aren't you/they considering the milfoil weevil, a natural long term solution that has been used successfully for 10 years? Your story only mentions herbicides and dredging, both are costly approaches that require ongoing treatment, season to season. The milfoil weevil is self sustaining.

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Lynne Abramovich

March 03, 2008

The milfoil weevil may be a control option in some parts of the U.S. It has not proven to be effective in Idaho waters. The State Department of Agriculture will not fund the introduction of weevils as a viable control measure for its Eurasian milfoil control program. Weevils are present in the Pend'Oreille lake and river system.

The acres infested by Eurasian water milfoil has nearly doubled there in the past three years.

Duke Guthrie
Boundary County Weed Control Superintendent

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