Quick Facts:

• Eurasian Watermilfoil (EWM) and Curly-leaf Pondweed (CLP) are invasive aquatic plant species found in many lakes and streams in Minnesota.
• The spread of EWM in Birch Lake was outlined in 2019 as part of a standard aquatic plant lake survey. This was conducted in partnership with Ramsey County Soil and Water Conservation Division (RCSWCD).
• As part of additional survey efforts in 2022 for EWM, a new infestation of Curly-leaf Pondweed (CLP) was detected and reported by RCSWCD and VLAWMO staff.
• Partnering with the Birch Lake Improvement District (BLID) and RCSWCD, VLAWMO coordinated this project to remove EWM and CLP.
• Dive Guys is a local company that specializes in hand-pulling for removal of aquatic plants. Dive Guys conducted the removal in 2022.

Funding:

This effort was funded in part through a 2-year (2022 and 2023) Aquatic Invasive Species Grant from the Minnesota Department of Natural Resources (MN DNR). BLID provided funding for the treatment portion of the project that is not covered by the grant. VLAWMO provided technical support in the form of funding for required surveys with RCSWCD. VLAWMO provided grant administration and project coordination.

Reasons for the Project:

• Birch Lake is one of a few high quality lakes in the Vadnais Lake Area Watershed. VLAWMO emphasizes protection for these high quality lakes.
• To work with partners in maintaining a healthy lake and removing invasive aquatic plant species. 
• Birch Lake is a priority area as part of VLAWMO's small, priority watershed program and designation. This program includes grant funding from the US Environmental Protection Agency (EPA) 319 funds, and is administered by the Minnesota Pollution Control Agency (MPCA).

Implementation: 

Hand-pulling is done by small teams of people using SCUBA gear. For target species in this project, hand-pulling occurs during the early summer months when both EWM and CLP are readily detectable and able to be harvested according to permit requirements/approval by the MN DNR.

Results:

The native aquatic plant community in Birch Lake is healthy, meaning diverse and abundant, and likely helps to prevent the spread of invasive species.

In 2022, EWM was found to be sparser and more widespread than what was found during the prior survey that was conducted in 2019. Incorporating updated information andand considering Birch Lake's healthy native plant community, a chemical treatment was deemed inappropriate because it would likely have an adverse effect on the native plant community in the lake. A switch in treatment techniques to hand-pulling was recommended and approved by the granting entity (MN DNR).

The contractor, Dive Guys, removed 125 lbs of EWM in 2022 and estimated the total number of stalks pulled at ~300. The follow-up survey showed very few remaining EWM plants. Dive Guys were unable to locate the few CLP plants that were detected during the pre-treatment survey. Removal of CLP will remain a priority for 2023. See survey maps below.

Both invasive plant species were removed in 2023, and a maintenance removal is underway for 2024. Early detection of CLP is important for this project because there is still a potential for eradication.

A follow-up survey by RCSWCD and VLAWMO staff did not detect CLP turions in the lake sediment. Turions are dormant winter buds produced by CLP that move with the water current, settle on lake sediment, and grow when conditions are optimal. This dispersal strategy allows the infestation to spread. The lack of turions detected supports the hypothesis that CLP is still localized and represented by only a few plants.

Early detection and removal are considered best practices for eradication of invasive species. 

Diverse and Important Underwater Forests: Aquatic Plants in Birch Lake

Birch Lake Eurasian Water Milfoil Hybrid Strain 2022

Project Image Gallery