Eurasian watermilfoil confirmed in Big Mantrap Lake

Featured photo by Rich Halvorsen, President of the Big Mantrap Lake Association

The Minnesota Department of Natural Resources confirmed the presence of Eurasian watermilfoil in Big Mantrap Lake near Emmaville.

The invasive aquatic plant was first confirmed in Hubbard County in 2017 at Bad Axe Lake, which is near Big Mantrap.

Eurasian watermilfoil (Myriophyllum spicatum L.), Minnesota DNR.

According to a release, a small piece of Eurasian watermilfoil was found near a public access last fall. Only a small piece was discovered and nothing further was found at the time.

After an extensive search last week, invasive species specialists found a small population of the invasive plant near the access.

The specialist removed all visible specimens by hand, and the local lake association is currently discussing potential follow-up treatments.

These treatments can include systemic herbicides, which the DNR says can minimize the watermilfoil’s impact and protect native aquatic plants. Treatment is unlikely to eradicate the invasive plant from the lake.

Rich Halvorsen, the Big Mantrap Lake Association’s President, briefly discussed the situation with Bemidji Now today. Halvorsen says the association is fiercely proud of their loon habitat efforts, and hopes the invasive plant can be contained.

Eurasian watermilfoil, according to the DNR’s release, can limit recreational activities on water bodies by forming mats on the water surface, and can alter aquatic ecosystems by displacing native plants. It is typically spread when plant fragments have not been properly cleaned from trailered boats, personal watercraft, docks, boat lifts, anchors or other water-related equipment.

With this new confirmation, the DNR reminds boaters and anglers to follow Minnesota laws to prevent the spread of aquatic invasive species:

  • Clean aquatic plants and animals from boats, trailers and equipment.
  • Drain all water by removing drain plugs, and keep drain plugs out while transporting watercraft.
  • Dispose of unwanted bait in the trash.

Some invasive species are small and difficult to see at the access. To remove or kill them, take one or more of the following precautions before moving to another waterbody, especially after leaving infested waters:

  • Spray with high-pressure water.
  • Rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds).
  • Dry for at least 5 days.

Photo by Rich Halvorsen, taken during recent storms over Big Mantrap Lake


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