Water soldier (Stratiotes aloides), a prohibited invasive aquatic plant, continues to be a growing concern in Cook’s Bay on Lake Simcoe.
First discovered in there in 2024, surveys from 2025 have confirmed the plant’s presence across more than 450 hectares, making it the largest known infestation in Ontario. Water soldier forms dense surface mats, displacing native vegetation, altering fish habitats, and creating hazards for boating, fishing, and swimming.
In response, the Lake Simcoe Water Soldier Working Group has been actively coordinating monitoring efforts and evaluating management options. Currently, water soldier remains concentrated in Cook’s Bay. Early detection is critical to preventing further spread.
Sightings outside of Cook’s Bay are considered a priority and should be immediately reported to the Invading Species Hotline: 1-800-563-7711
Originally published in the Ontario Out of Doors Fishing Annual 2026
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