Non-Chemical Treatments Failing to Stop Invasive Weed

Published April 1, 2006

Invasive milfoil, a non-native plant species that aggressively takes over and chokes competing life forms out of freshwater lakes, is proving tougher than non-chemical eradication efforts, lakefront communities across the country are learning.

Wisconsin Harvesting Ineffective

Citizens of Pewaukee, Wisconsin are learning weed harvesting is not only expensive but also largely ineffective. In 2005, Pewaukee, a community just west of the Milwaukee suburbs, allocated more than $100,000 to the harvesting of Eurasian milfoil in Lake Pewaukee. Residents have complained the harvesting effort achieved few noticeable results, so the city is allocating another $129,000 in 2006. Residents wonder whether the money is being well spent.

“I think we got the message all through the year that we needed to do a better job along the shoreline,” said city planner Harlan Clinkenbeard for a January 23 Milwaukee Journal Sentinel story.

While residents debate whether a program focusing on the center of the lake or the shoreline would be more effective, the $129,000 will finance harvesting milfoil in about 600 acres of the 2,500-acre lake. Milfoil will continue to grow unabated in non-treated areas, and harvesting efforts will still leave some milfoil even in the treated acres.

Invasive milfoil is particularly problematic for lake communities because it grows on the bottom of the lake, sending to the surface tendrils that form a thick, tangled mat. If left untreated, milfoil chokes out native plants and fish, boats cannot cut through the weeds, swimmers can get their arms or legs tangled in underwater tendrils, and the stench of the overgrown weeds can make even strolls along the shore unbearable.

Maine Town Limiting Access

Citizens of Belgrade, Maine will have limited boat access to Messalonskee Lake this year and no boat access at all beginning in 2007, according to a plan proposed by state conservation officials. The plan, announced February 15, is an attempt to halt the spread of invasive milfoil from Messalonskee Lake to other lakes.

Belgrade citizens already have had their lake access limited. For the past four years, the town’s boat ramp has been open only part-time, and environmental monitors have been hand-inspecting each boat that leaves the water. Each inspection, carried out by a Maine Department of Conservation employee, costs the state $23. Last year, inspectors found milfoil on 46 percent of the boats leaving the lake, up from 35 percent in 2004. The inspectors have not been able to identify and remove all of the milfoil from boats utilizing the ramp.

“I’m heartbroken that they’re going to close that ramp,” Charlie Wilson, a member of the Maine Bass Federation, told the Kennebec Journal for a January 21 story. “It’s a very nice lake, and it’s a shame what’s happening.”

Other Lakes at Risk

With Maine’s 6,000 other lakes at risk if enough of the milfoil finds its way into other bodies of water, Messalonskee Lake Association officials determined that a pervasive milfoil outbreak near the boat ramp left them with no choice.

Area resident Jack Murphy disagrees.

“The methods used [to control the spread of milfoil] so far–personal screening of boat bottoms and hand pulling of the weeds one at a time by divers–obviously have not worked,” Murphy observed in a letter published in the February 16 Kennebec Morning Sentinel. “It is time that the state recognizes that the only way this weed can be brought under reasonable control is by the use of chemicals.”

Herbicides Successful

Murphy, who also resides in Frostproof, Florida, noted in his letter, “In Florida, the weed most heard about is hydrilla. When the state takes action, there is a small news item in the newspaper that on such a day, Lake so-and-so will be treated for hydrilla. That is it. It is done.

“Chemical treatment is capable of delivering a serious setback to this invasive weed which is now growing unabated. Musical chairs with launch ramps will lead to renaming Messalonskee: Lake Variable-leaf Milfoil,” Murphy wrote.

Jim Skillen, manager of formulator issues for Responsible Industry for a Sound Environment, agrees. “Aquatic herbicides are empirically effective and, just as importantly, have been determined by the Environmental Protection Agency to be safe for humans and for the environment,” said Skillen.

“The best time to treat for milfoil and other invasive plant species is early in the infestation process,” Skillen added. “As time passes, the milfoil continues to spread, resulting in a more expensive treatment process–though herbicide treatment is still less expensive than alternative, less effective methods.”

James M. Taylor ([email protected]) is managing editor of Environment and Climate News.