Actions and methods

The first action to consider is, undoubtedly, to limit its exponential growth by by restricting traffic in the affected areas.Traffic (even at low levels) is at the root of fragmentation. Boating in the milfoil beds is definitely the best way to lose the battle. This simple and not overly restrictive action attacks the problem at the source. It will not eradicate established milfoil, but it will reduce its growth and reproduction in other areas.

Any direct intervention in aquatic plant beds requires a permit (you can find the Permit Application Form here) from the Ministère de la Forêt, Faune et Parcs (source MFFP, June 26, 2020).

In order to obtain this permit, an assessment of the proposed area must demonstrate that Eurasian watermilfoil constitutes more than 70% of the plants in the area. Blue Massawippi can update this inventory for you,contact us..

This permit is expensive. The solution is to join together with other residents interested in the same request, with the possible participation of the municipality. This is Blue Massawippi’s approach for the current Bacon’s Bay project.

Manual removal

This method is feasible on small areas. However, it requires the complete removal of the roots and the removal of the milfoil from the water body. Manual removal can be very effective and affordable when combined with another control strategy, such as targeting patchy, low-density beds. Large-scale projects requiring divers and a plant vacuuming system are very costly and involve delicate work.

Installing tarps made of burlap or Aquascreen©

These tarps suffocate all the plants underneath, allowing the space to be recolonized by native plants. Regular maintenance (ex: manual removal of plants from the tarps) is also necessary to avoid the re-establishment of milfoil. The effectiveness of the tarps decreases when they are installed in areas of high milfoil density, but this method still provides the most sustainable results for a given price.

Mowing

An aquatic plant mower cuts plants at a specific height (ex: 2 feet below the surface). This method, while providing rapid results, is rarely viable in the long term (Lavoie, 2019). It will not eliminate the milfoil; it will simply grow back like a lawn. Thus, mowing it several times annually is required to keep the plant in check. The fragments that inevitably escape collection will have a devastating contaminating effect This very expensive method is ecologically unsustainable for Blue Massawippi..

Lowering the lake level in winter

Although this method is considered effective (Lavoie, 2019), it would be impossible to implement in Lake Massawippi. The water level of the lake is regulated and it would take an exhaustive legislative effort, in addition to the support of all 5 municipalities, to even hope to make any changes to the established seasonal targets. In addition, due to the clarity of the lake water, Eurasian water milfoil is present at depths greater than 10 m. Therefore, it would be logistically impossible to lower the lake to a level that would allow eradication. Even if the lake was lowered a few meters, the milfoil would easily be able to recolonize the cleared areas.

Water aeration

This new technique is based on the joint effect of water aeration by microbubbles and the introduction of bacteria that require high levels of oxygen to proliferate. In theory, the bacterial population will reach extremely high densities in the presence of oxygenated water and will thus sequester all the nutrients necessary for the growth of milfoil. This technique is expensive and there is no evidence that it is effective in controlling Eurasian watermilfoil in a systematic manner (Lavoie, 2019). Certain projects report decent efficacy while others did not observe any difference.

Scientific reference: Lavoie, C., 2019.50 Plantes envahissantes : protéger la nature et l’agriculture. Les publications du Québec. Québec. p. 250-257., RAPPEL, Ministère des Forêts, Faunes et Parcs.