Blue Planet, Green Ideas / Eurasian Watermilfoil | Unequal struggle against encroachment of lakes

Biologists can tear it apart, suffocate it, poison it, but it is useless; The Eurasian watermilfoil has become an unstoppable invader of lakes in Quebec. Described as a “zombie” plant, it is almost everywhere. Failing to eradicate it, at least to contain it, complex and expensive interventions are on the rise again this summer.

This invasive plant (Myriophyllum spicatum) has taken root in 184 lakes and 22 rivers in the province by 2023, according to the most recent survey by the Ministry of Environment, Combating Climate Change, Wildlife and Parks (MELCCFP). Pres. The most occupied areas are Estrie, Laurentides and Outtavoys resort lakes. The ministry notes that almost all regions are affected, including Montreal. Only the Gaspésie and Saguenay-Lac-Saint-Jean regions are exempt. But this is only a period, say biologists.

With an area of ​​about twelve square kilometres, Lake Papineau in Outois is one of the jewels of Quebec’s resort region. The lake is famous for clear water and swimming. It is popular for navigation and lake fishing. But now this fish’s spawning ground — where it spawns — apparently swallows the Eurasian milfoil.

The biologist and his crew have manually pulled 423 pounds of Eurasian milfoil out of Babineau Lake since last year and put them back on the boat in airtight bags. A tarpaulin covering an area of ​​3,600 square meters made of 25 canvases was laid. A tarpaulin was used to suppress seven beds of invasive plants in the lake.

The procedure alone costs $120,000. It was funded by the coastal community Boileau du lac sector and benefited from a grant from the Nature Conservancy of Canada (CNC). According to studies carried out by MELCCFP experts, the cost of treating one hectare is $200,000. Several factors explain these costs, including the invasive plant’s ability to reproduce on its own from a small fragment of stem.

“It never ends,” notes Jeremy Isabelle, a biologist with the Rappel Cooperative, which conducts operations at Stukeley and Fraser, two freshwater lakes in Mont-Orford National Park, sponsored by the Société des Entreprises. plein air du Québec (SEPAQ).

“A maintenance campaign should be carried out every year, ensuring that the new seagrass beds are gently uprooted. In some lakes, we can hope to get below the detection threshold. For example, we’ve had good results with the small Lake O’Malley near Orford, but we’re not sure about complete eradication. Can never speak »

From one scientific journal to another, the Eurasian watermilfoil is described as a plant with branching stems that can reach up to six meters. The invasive plant has a habit of establishing itself until it reaches the surface. Unpleasantly green, slimy, it should not be confused with algae or other plant species. Milfoil is found in lakes, natural and artificial ponds, swamps and bays with calm waters of rivers and streams.

According to the Ministry of the Environment, the plant was introduced to North America through stagnant water from ships coming from Europe, Asia or Africa. Other hypotheses suggest that it was used as an aquarium plant or carried by migratory birds. In Quebec, it has existed since at least 1958.

Claude Lavoie is Professor and Director of the Graduate School of Land Planning and Regional Development at Laval University. He is an expert in the ecology and management of invasive plants. In this capacity, he collaborated with the Ministry of Environment to draft a reference document listing the Eurasian watermilfoil in 184 lakes.

“There are all kinds of myths, each stranger than the last, surrounding the Eurasian watermilfoil,” explains Claude Lavoie. For example, I hate the expression “zombie”. We decided to call it because it is a naturally rooted fragment. But as far as I know the plant has never eaten anyone. »

Mr. Lavoie studied six methods for combating milfoil in addition to unproven interventions. Hypotheses. One of them introduces a herbivorous insect called the weevil, but experiments in Lac-Supérieur have failed. A particular insect is prized by a particular fish. Another is the installation of an ultraviolet ray-emitting platform, but this is controversial because of its destructive environmental impact. Indeed there will be the introduction of grass carp, a volatile species of this plant, but it is considered invasive, and its introduction is “strictly prohibited” in Quebec.

“I believe that neighboring homeowners need to ask questions about their tolerance level. Maybe they should limit themselves to cleaning swimming areas and ensuring visual inspections of boats? Because there is little data to demonstrate that Eurasian watermilfoil harms ecosystems and fish,” said Mr. Lavoie explains.

In Lake George and Upper Saranac in New York state, a massive grubbing operation was “a wonderful success,” he adds. But this huge investment did not make it possible to completely dismantle the plant, Mr. Lavoie recalls, and the move must be repeated forever.

Access the guide Eurasian Milfoil Prevention and Control 2023