Eurasian watermilfoil (EWM) is a highly problematic invasive aquatic plant that forms dense, tangled mats on the water surface, choking out native plants, harming fish habitats, and blocking recreational activities like boating, fishing, and swimming. It spreads easily via fragments attached to boats or equipment, reproduces rapidly, and is difficult to control, impacting water quality and property values. Prevention through "Clean, Drain, Dry" practices and nutrient reduction is key, alongside management methods like hand-pulling, mechanical harvesting, bottom barriers, herbicides, and biological controls.
What it is & Why it's a problem
Dense Mats: Forms thick surface mats that block sunlight, killing native plants, reducing biodiversity, and creating mosquito breeding grounds.
Recreation Killer: Hinders boating, fishing, and swimming, decreasing lake enjoyment and property values.
Ecological Damage: Lowers oxygen levels when decaying, harms fish/wildlife, and alters water chemistry.
Spreads Easily: Fragments easily from stems, spreading rapidly to new water bodies.
How to Identify It
Feathery Leaves: Soft, olive-green leaves in whorls of four (sometimes 3-6) around reddish stems.
Blunt Tips: Leaves look like they've been trimmed by scissors.
Flower Spikes: Pinkish flowers on spikes emerging above water in summer.
How to Prevent Spread (Clean, Drain, Dry)
Clean: Inspect and remove plant fragments from boats, trailers, and gear.
Drain: Remove drain plugs and let all water out of boats and equipment.
Dry: Allow boats and gear to dry for several days before moving to another lake.
Boaters: Avoid shallow, weedy areas to prevent propeller damage.
Management & Control
Manual/Mechanical: Hand-pulling, raking, or harvesting clears access but needs repeated effort.
Benthic Barriers: Mats placed on the lake bottom to block sunlight.
Chemical: Herbicides can be effective but costly and often temporary.
Biological: Introducing weevils or other organisms (consult local experts).
Nutrient Reduction: Keeping phosphorus/nutrients out of lakes reduces EWM growth
