Battle for control of Eurasian watermilfoil in the Cedar lakes

1. What is Eurasian watermilfoil?

Eurasian watermilfoil is an invasive aquatic plant originating in Europe and Asia. It arrived in North America during the 1950s and since then has continued to spread. It forms dense plant beds at depths ranging one to 10 metres.

Eurasian watermilfoil has no natural predators to curb its proliferation. As well, the plant has another advantage to speed its reproduction: one small part of a stem can take root to create a new plant. Plant fragments can be transported from one lake to another by boats, trailers, fishing gear and other nautical equipment.

To better understand and be able to identify Eurasian watermilfoil, consult the Canadian Invasive Species Centre


2. Problems caused by Eurasian watermilfoil

Experts agree that Eurasian watermilfoil is threatening the environment of our lakes. They recommend taking action against this plant not only because of its invasive character but also because it disturbs natural ecosystems and disrupts local biodiversity. It negatively impacts the reproduction of some fish and of indigenous aquatic plants. If it is allowed to spread freely, it can negatively impact activities like swimming and fishing. As well, its spread can lower lake property values, as seen in other regions in Quebec where Eurasian watermilfoil has spread uncontrolled. We know that, once established, it is very difficult to remove.


3. Situation on our two lakes

Every year, the APLC carries out inventories in the Cedar lakes to identify Eurasian watermilfoil weedbeds. Since 2015, watermilfoil has been spotted in Petit lac des Cèdres while, to date, the APLC has not yet detected its presence in Grand lac des Cèdres.

The results of the 2018 and 2019 inventories, which had been carried out by a team of volunteers supported by the ministry of forests, revealed that, in Petit lac des Cèdres, Eurasian watermilfoil covered a total area of ​​approximately 14,000 m2. On the other hand, the 2022 inventory, completed by the firm Fyto, shows that the total area is estimated at 32,000m2 of weedbed with a density of 25% and more of invasive plants.

Although the methodology followed by the Fyto team to complete the inventory is identical to that of our volunteers and the ministry of forests, we conclude that, by devoting a lot of time to the work and using more advanced technological tools, the Fyto team was able to obtain more precise results, more clearly delineate the weedbeds and improve the characterization of the sites. These results will allow us to more accurately and objectively measure our progress in future years.

Consult the complete results of the inventory in the 2022 OPERATION REPORT (French only) prepared by Fyto.


Summary of areas to treat in Petit lac des Cèdres

Type of weedbeds: A monospecific weedbed has a component of Eurasian watermilfoil in excess of 80%. The ministry allows the installation of tarps on these weedbeds only. For any other weedbed made up of native plants and less than 80% Eurasian watermilfoil, the ministry specifies the technique of uprooting.


2021: Total area of Eurasian watermilfoil

16,500 m2

Surface area treated with tarps placed by APLC volunteers

1,500 m2

2022: Total estimated area of Eurasian watermilfoil (density 25% and more)

** correction following Fyto inventory

39,000 m2

Surface area covered with tarps by Fyto

4,000 m2

Surface area uprooted by Fyto

3,000 m2

2023: Total estimation of Eurasian watermilfoil

(% invasion of the lake is estimated by Fyto at 1.67%)

32,000 m2

The surface area to be treated by tarping : 6 500 m2  and surface area to be treated by uprooting: 10 000 m2

16,500 m2

2024: Estimate of Eurasian watermilfoil

15,500 m2

The surface area to be treated by tarping and uprooting will be confirmed based on the results of the 2023 inventory.

minimum 8,000 m2

2025: Estimate of Eurasian watermilfoil

7,500 m2

4. Summary of the intervention strategies

The project to fight against Eurasian watermilfoil brings together several strategies aimed at curbing its growth in Petit lac des Cèdres and preventing its entry into Grand lac des Cèdres.

Consult financial plan 


Strategy 1 – The laying of reusable synthetic tarpaulins:

The technique consists of unrolling a tarpaulin on the entire weedbed and anchoring the tarp on the bottom of the lake with metal rods. The tarp prevents the growth of the plants while allowing the free flow of gasses through the tarp so that it remains wedged at the bottom of the lake.

The use of reusable tarps allows for rotation between weedbeds from year to year. The tarps are installed at the beginning of the season, removed after 8 to 10 weeks, then cleaned, and stored. The following year, divers do a check to make sure that the watermilfoil does not return to the treated weedbed, and they uproot any stems that may have survived. A synthetic tarp has a lifespan of eight to10 years. 


Strategy 2 – Removal of roots: 

One method, with encouraging results recently in the United States and Canada, is the removal of the plant and its roots by experienced divers. There is a protocol for this developed by the Réseau de surveillance volontaire des lacs (RSVL). This technique will only be used for weedbeds where watermilfoil is intermingled with native plants (mixed beds), where the use of tarps is prohibited by government. For beds with a Eurasian watermilfoil density greater than 80%, the tarps will be used.


Strategy 3 – Installation of buoys: 

At the same time, yellow buoys will be installed each spring for the summer season to mark the Eurasian watermilfoil sites in Petit lac des Cèdres. The objective is to make these sites easily identifiable so that people avoid entering these areas with their boats, fragmenting the plants and transporting pieces elsewhere, thus accelerating further growth.


Strategy 4 – Inventory and identification service for residents:

Plant inventory will occur each year at the end of the summer in accordance with the method prescribed by RSVL. The APLC will offer identification service to all residents who believe they have spotted plants outside of the previously identified areas.


Strategy 5 – Information and awareness campaign: 

This campaign will provide information on problems resulting from invasive species, using several communication methods aimed at informing residents:

  • Reminder of the importance of boat washing before launching (in partnership with the Municipality of Messines)
  • Warning to avoid zones encircled by yellow buoys
  • Awareness meetings for owners who have properties near Eurasian watermilfoil


5. Activities

The pilot project, the fight against Eurasian watermilfoil, requires significant financial and human resources.


Activities scheduled for 2023

  • Placement of buoys marking the Eurasian watermilfoil beds
  • Following the inventory, which indicates a greater presence of the plant in Petit lac des Cèdres, a new request for financial assistance has been submitted to the Fondation de la faune du Québec
  • Request for financial assistance of $8,500 from the Municipality of Messines
  • Fundraising campaign
  • Contractual agreement for a second year with Fyto, a company specializing in the management of invasive alien species
  •  Installation of tarps (# of weedbeds to be confirmed)
  • Uprooting treatment (# of weedbeds to be confirmed)
  • Survey of Petit lac des Cèdres by the Fyto team planned for fall 2023
  • Survey of Grand lac des Cèdres by the Fyto team planned for fall 2023


Activities taken in 2022

  • Placement of buoys marking the Eurasian watermilfoil beds
  • Submission for financial aid to the program for the fight against invasive exotic plants, offered by the Fondation de la faune du Québec and decision of Fondation de la faune du Québec to provide grant of $64,900 for the project
  • Fundraising campaign with residents: The APLC collected $11,295.25, which is in addition to the $20,276 collected in 2021
  • Contract agreement with Fyto, a firm specializing in the management of invasive exotic plants
  • Installation of tarps on weedbeds 3, 4, 5, 8, 9, 10, 12, 18 for a total area of ​​4,085 m2 by Fyto divers
  • Uprooting of Eurasion milfoil on weedbeds 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 18. In total, 1,313 kg of fresh biomass were uprooted from an area approximately 3,000 m2. Work done by Fyto divers
  • Removal of tarps in August 2022
  • Survey of the Cedar lakes at the end of the summer by Fyto team. Adjustment of the total area by more than 25% of watermilfoil from 16,000 to 32,000 m2—a 50% increase
  • Update of the FINANCIAL PLAN  for the project
  • Submitting of 2022 OPERATIONAL RAPPORT (FRENCH ONLY)  prepared by the Fyto team


Actions taken in 2021

  • Placement of buoys marking the Eurasian watermilfoil beds
  • Request for permit for the placement of tarps
  • Initial purchase of 1,500 square metres of reusable synthetic tarps
  • Assembly of 50 rolls of tarp, and the construction of a motorized barge with a pulley and reinforcing metal bars to handle the unrolling of the tarps.
  • Laying of the tarps on June 8 and 9, 2021, with three divers and a dozen volunteers to validate our methodology.
  • Treatment of two weedbeds upstream on the lake, in line with the strategic action plan developed in cooperation with the provincial government.
  • Removal of synthetic tarps on August 16th and 17th. After a visual inspection of the two target weedbeds, it seems that all the stems of watermilfoil are dead.
  • Survey of the Cedar lakes at the end of the summer by trained volunteers from the APLC and an employee of the MFFP
  • No uprooting activity scheduled this year due to COVID-19


Actions taken in 2020

  • Placement of buoys to mark Eurasian watermilfoil areas
  • Installation of movable sandwich boards to inform residents of the placement of the yellow buoys
  • Removal of Eurasian watermilfoil roots (activity delayed until 2021 due to COVID-19)
  • Inventory, at the end of the summer, of both lakes by volunteers trained by APLC
  • Consultation and training with experts from Université Laval on tarp deployment techniques and other logistical considerations


Actions taken in 2019

  • Placing buoys to identify Eurasian watermilfoil areas
  • First root pulling activity in June with experienced divers and APLC volunteers.
  • Meeting with residents who live near Eurasian watermilfoil plants to encourage them to avoid boating there
  • Distribution of a flyer to inform residents of the presence of Eurasian watermilfoil and the reason for the yellow buoys
  • Inventory of both lakes by APLC volunteers—two new plant areas spotted in Petit lac des Cèdres—a total of seven. No Eurasian watermilfoil plants found in Grand lac des Cèdres (section outside Kitigan Zibi reserve)
  • Participation in a conference offered by the Lac des Plages association, innovator of the root removal technique
  • Publication of an educational resource on the APLC website, explaining problems linked to exotic invasive species
  • Installation of movable sandwich boards to inform residents of the placement of yellow buoys
  • Information session about the pilot project at the APLC annual meeting


Actions taken in 2018

  • Inventory of the two lakes by APLC volunteers—two new plants were seen in Petit lac des Cèdres, for a total of seven plants. No plants were found in Grand lac des Cèdres outside Kitigan Zibi reserve)
  • Participation of APLC board members at a Eurasian watermilfoil conference offered by l’Université Laval à Québec
  • Information workshop on invasive species for residents
  • Approval by the APLC board of a pilot project to fight Eurasian watermilfoil
  • Negotiation to obtain permission from the Municipality of Messines for root removal
  • Installation at the boat launches of a sign informing visitors of the requirement to wash boats before launching


Actions taken in 2015

  • First inventory of Eurasian watermilfoil in Grand lac des Cèdres and Petit lac des Cèdres by ABV des 7
  • ABV des 7 report