The weevils bred for U.S.-based EnviroScience Inc. have worked wonders at Puslinch Lake near Cambridge, residents say. Aaron Jacobs, a member of the Puslinch Lake Conservation Association, led the charge against the watermilfoil invasion there, and says two years after treatment wrapped up, he’s delighted with the results. 'Before they introduced the weevils, the lake was 75, 80 per cent covered in weed,' he said. 'This year, it’s 95 per cent open.' (Photo courtesy EnviroScience Inc.)  

Attack of the killer weed:
Weevil battles aggressive intruder choking Ontario waterways

News Archive BY GARY MAY
It sounds eerily like the plot of a blockbuster Hollywood horror flick: An alien invader attacks a small, isolated resort town, its tendrils slowly engulfing everything in its path, until finally, all that’s left is a thick, green mass.  

This creepy scenario is, unfortunately, playing out in waterfront communities across North America. Fortunately, just like Will Smith in Independence Day, a hero has surfaced in the nick of time, armed with a simple little beetle that’s salivating at the prospect of sending this foreign monster packing.  

This time, standing in for Will Smith is Nancy Cushing, agent for a U.S.-based company that has helped residents’ associations at dozens of lakes across the continent fight back against the growing menace of the Eurasian watermilfoil.  

Cushing is leading the charge this summer at Rondeau Bay, a picturesque little inlet on Lake Erie, that is at risk of being taken over by a spreading mass of Eurasian watermilfoil. The invasive weed has settled in on the bay and is threatening residents’ and visitors’ enjoyment of this quiet little oasis in the municipality of Chatham-Kent, southwest of London.  

“It could take three years,” Cushing tells MyNewWaterfrontHome.com. “You can’t eradicate it, but you can control it. You can make the situation a lot more acceptable to the residents.”  

And it can be done without the use of chemicals or herbicides.  

That’s music to the ears of Dean Jones, the Erieau Partnership Association member who is spearheading the battle on the local front. Concerned about the spreading mass of weed that threatens to choke the bay, Jones started research on the Internet and came upon the website of EnviroScience Inc. of Stow, Ohio.  

“The weed is very thick,” explains Jones. “It lays across the top of the water and you can’t boat through it. We have a lot of recreational boating in this area, skiing and tubing on the bay.”  

Weevil has worked wonders in a number of waterways

Jones found the EnviroScience website was filled with testimonials from residents’ associations across Michigan and New York, where introduction of a tiny aquatic beetle or weevil, native to North American lakes, stemmed the expansion of the invasive watermilfoil.  

Places such as Lake St. Helen, Michigan, where the weed was so thick “we had ducks walking on top of it,” says John Bawol. Then there’s what locals are calling floating “islands of weeds” in the St. Lawrence River at Alexandria Bay, New York.  

In Ontario, there’s the 136,000-acre Lake Scugog, one of the Kawartha Lakes that’s part of the Trent-Severn Waterway north of Oshawa. Eric Sager, manager of the Trent University-associated James McLean Oliver Ecological Centre near Bobcaygeon, was called in last year to consult with Skugog lakeshore residents about how to control the watermilfoil that was creeping across the surface.  

As it turned out, Scugog’s particular brand of watermilfoil was a hybrid of the native and imported varieties. Happily, the weevil loves to chow down on both.  

Sager says the Eurasian variety arrived in the Kawarthas in the 1970s, died out and then mysteriously reappeared about five years ago. Just why this happened isn’t known, but it could simply be the natural ebb and flow of nature, he says.  

EnviroScience was called in to apply the first treatment of weevils in July 2009, and the process is being repeated this year on a patch of watermilfoil that’s about 100 metres wide and one kilometre long.  

Sager tells MyNewWaterfrontHome.com, however, the jury’s still out as to whether the weevil will be a successful tool in the long-term, in such a large body of water. The adults over-winter onshore, says Sager, and with such a huge area of lake to choose from, there’s no guarantee they’ll return the next year to where they’re most needed.  

Nevertheless, Sager says interest in the weevil treatment is growing as residents along more Ontario lakes try to grapple with the weeds. “I’m getting dozens of calls from across Ontario,” says Sager. “I tell them I don’t have a whole lot of experience with it.”  

Weed-feeding beetle native to Canada

EnviroScience’s trademarked process was applied at Puslinch Lake near Cambridge between 2006 and 2008. Donna McBrearty, who lives on Puslinch Lake, says the weevil treatment proved highly successful. “Before we started, you could just about walk across the weeds. If you took your canoe out, you were bound to get stuck. It’s made a huge difference.”  

Aaron Jacobs, a member  of the Puslinch Lake Conservation Association, led the charge against the watermilfoil invasion, and says two years after treatment wrapped up, he’s delighted with the results.   “Before they introduced the weevils, the lake was 75, 80 per cent covered in weed,” Jacobs says. “This year, it’s 95 per cent open.”  

At about $1 per weevil, the treatment wasn’t cheap, he adds, but well worth it. The association members probably paid $75,000 over three years, raising funds and collecting donations from local businesses and corporations.  

Because EnviroScience’s process uses a beetle that is native to Canada, few government approvals were required. In fact, it needed only an import permit from the Canadian Food Inspection Agency, because the company breeds its watermilfoil-loving weevils in the U.S. so it must bring them across the border.  

Jones says other federal and provincial officials have been kept advised of the project.  

Sager says at Scugog, the federal fisheries and oceans department, plus the Ontario environment and natural resources ministries are on-side, but caution that there is still a lack of evidence the process is effective in the long-term.  

Scugog was a slightly more complicated case than Puslinch, he says, because as a link on the Trent-Severn Waterway, it came under the authority of Parks Canada, which also required a special research permit.  

Eurasian watermilfoil was accidentally introduced to North America in the early 20th century. It was officially identified in a Washington, D.C., pond in 1942. Boats and waterfowl are primarily blamed for spreading it across the continent and it is believed to have reached Ontario by the 1960s.  

Shallow, nutrient-rich bays, lakes most at risk

Watermilfoil can become entangled in boat propellers, with stems lodged among the parts of watercraft and even boat trailers. Propellers cut up the weed and, when a segment floats to the bottom of the lake, a new plant can easily sprout. Nutrient-rich lakes and bays of four to 10 feet in depth are the perfect place for it to spread. As it does, it can deplete dissolved oxygen and cut out light required for native species.  

Meanwhile, a floating canopy of weed can crowd out important native water plants that local fish populations rely on for their survival. Once it is established, it is nearly impossible to eliminate. In fact, Jacobs says EnviroScience officials were doubtful the treatment would be enough to help save Puslinch, because the weed had taken total control of the waterway.   

Before the weevil procedure, other methods used to stop watermilfoil’s spread have included underwater roto-tilling, hand-pulling, dredging and bottom weed barriers. In the U.S., herbicide use has been common, although it’s difficult to get approval in Canada, and residents are increasingly resistant to it.  

For small-scale applications, such as individual waterfront owners wanting to clear a spot at the end of their dock so the kids can enjoy a weed-free swim, some have laid down light-blocking barriers or mats to kill a patch of the weeds.  

But biological control has become increasingly popular for larger areas. Researchers discovered the North American weevil normally eats Northern watermilfoil, but given the opportunity, it will happily nosh on the Eurasian variety, too.  

The weevil lays its eggs on the plant tips. When they hatch, the youngsters burrow into the weed stem, which slows its growth and weakens the plant. While eradication is virtually impossible, weevils can reduce the numbers to the point where the weed won’t shoulder out native species.  

EnviroScience has been busy. It introduced 19 new projects across North America in 2009 alone.  

Weevils called in to work in Lake Erie's Rondeau Bay

Jones estimates it’s going to cost $24,000 for a full, three-year treatment package on Rondeau Bay. But the Municipality of Chatham-Kent has kicked in $5,000 to cover some of the costs this year, and Jones hopes more will be forthcoming in subsequent years, as the treatment’s effectiveness is proven.  

Cushing says 5,000 weevils are being introduced to a portion of Rondeau’s weed mass this year and, in the fall, the bay will be inspected to find out what the result has been. Another injection is planned for next year and another for the year after.  

While a limited number of the weevils exist naturally in the bay now, says Jones, the colony is too small to cope with the weed invasion. But with the applications planned, it is hoped the weevils will stand a fighting chance to establish sufficient numbers to keep the weeds in check.  

While most of the EnviroScience projects have been in smaller lakes, Cushing says the company has had clients in the upper reaches of Lake Huron off the Michigan shore. Shallow water along the Great Lakes are prime breeding grounds for the weed, she says. Jones points out that Rondeau Bay is no more than 10 feet in depth.  

EnviroScience created its biological approach to treatment through a partnership with Middlebury College in Vermont. The beetle-based treatment now is registered under the trademark name, MiddFoil.   Sager says research is ongoing at Cornell University in Ithaca, New York, to identify other naturally occurring herbivore insects that can help fight back against aggressively invasive weeds.  

Individuals or associations concerned that they may have a Eurasian milfoil problem are advised to first determine whether it is in fact that species. They are instructed to collect sample stems of the weed, pack them into damp paper towel and a zipped plastic bag and send them off to the company by overnight or two-day delivery service. Accompanying information should include the name, location and size of the water body from which the samples were taken.  

MyNewWaterfrontHome.com — July 2010