Mazinaw Lake Property Owners Plan To Use Chemical Treatment On Eurasian-Milfoil

Jeff Green | Sep 04, 2024

The Mazinaw Lake Property Owners Association (MPOA) approved a plan to apply ProcellaCOR FX, an herbicide that was approved for use in Canada in 2023, on over 15 hectares of Lake Mazinaw. In those locations, infestations of Eurasian watermilfoil are extreme and are causing distress for boaters, swimmers and property owners in the vicinity.

The Ontario government website describes the impact of Eurasian watermilfoil in this way: “the plant reduces biodiversity by competing aggressively with native plants. Reduced oxygen levels in the water caused by decomposing plants can kill fish. Thick mats of Eurasian watermilfoil can hinder recreational activities such as swimming, boating and fishing.”

Eurasian watermilfoil prefers shallow water 1-3 m (3.3 – 9.8 ft) deep, but can root in up to 10 m (32.8 ft) of water. Being a fast-growing perennial, it forms dense underwater mats that shade out other aquatic plants. When large stands begin to die off in the fall, the decaying plants can reduce oxygen levels in the water, potentially affecting the fish communities.

Mazinaw Lake is the deepest lake in Eastern Ontario, at 145 metres deep, so the plant is not a threat for most of the lake, but in shallow bays, and near certain islands, it has become a major issue. According to the MPOA, one of the potential impacts of the plant could be to decrease property values by 10-20% on about 5% of the shoreline properties on the lake.

The association has done comprehensive mapping of the lake as part of their Eurasian  watermilfoil mitigation strategy, and has considered and rejected five options for controlling its spread. The first is hand pulling, which is labour intensive, hard to do, impractical for large areas and can cause further spread in some cases.

The second option is called DASH (Driver Assisted Suction Harvesting), but this was found to be cost prohibitive, and there are no businesses in Ontario to do the work.

The third is mechanical harvesting, which has also been shown to be expensive and ineffective.

The 4th is benthic matting, which is also expensive, blocks out all plant life in the lake bed, and while it may be effective in small areas, it is not practical over a 15 hectare area.

The 5th is a chemical treatment called REWARD, which is applied by fire hose and drifts over the surface of the plants, but does not kill them at the root, and has impacts on native species as well as the invasive watermilfoil.

They have concluded that their option 6,  ProcellaCOR FX, is the only viable one. It is also a liquid treatment, applied by weighted drip lines, has been used in Ontario in agricultural applications in the past year, as well as in Farlain Lake and the Bay of Quinte, and is being trialed on the Trent Severn system.

According to the association, cottage owners can pay for the application themselves, subject to receiving an approval from the Ontario Ministry of the Environment, Conservation and Parks, and the Federal Department of Fisheries and Oceans.

Mazinaw Lake is located in both Addington Highlands and North Frontenac, and the MPOA is appearing before Addington Highlands Council this week, asking that the township, along with North Frontenac, take on the contract with the company that will apply the herbicide. The MPOA said they are willing to “do the heavy lifting” in terms of organising and fundraising the estimated $125,000 the project will cost. But if the townships take the lead, they can issue tax receipts for donations, which the MPOA cannot do. 

“Donors have indicated that their donation is contingent on being able to receive an official tax receipt” said MPOA Vice President Vern Haggerty, in his written presentation to Council that was submitted in advance of this week's meeting.

But while ProcellaCOR FX is approved for use in Canada, it has been controversial. Opponents of its use call it a forever chemical that will have as yet, undetermined implications for the environment. 

A debate about the treatment is ongoing in the United States, where the ProcellaCOR FX was approved for use in 2018. It is the subject of an article that was published by the Adirondack Explorer, a not-for -profit online publication, in July.

According to the report, ProcellaCOR FX has been used in Lake George, a major lake in New York State. Regulators in Adirondack  Park, which includes Lake George, and New York State, approved the use even though it was opposed by 4 local townships and environmental groups in the park, as well.

Not far away, on Lake Bomoseen, a smaller lake in Vermont, approval was not granted by Vermont State regulators, and a lawsuit is underway.

Opponents to ProcellaCOR FX cite a recent Minnesota Department of Agriculture Interim Report that classified the active ingredient in Procella COR as a PFAS, or “forever chemical,”  saying that “these substances are difficult to break down in the environment, and some have been linked to causing cancer and disease. The active ingredient is called florpyrauxifen-benzyl.”

In New York, regulators decided that the Minnesota Department of Agriculture report did not negate the background work already completed on the federal level in the United States and in other locations across the country.

Researchers in other parts of the United States, and Europe, also questioned whether florpyrauxifen-benzyl poses a danger, saying that while it satisfies the criteria for a ‘forever chemical’ because of its persistence in the environment, that does not imply that it is a toxic chemical.

If these issues are indeed of concern in Ontario, it will be a matter for provincial and federal regulators to assess. For the MPOA, the goal this week is to get Addington Highlands Council on board, in order to help its fundraising efforts.