Hybrid Eurasian/Northern Watermilfoil
Invasive SpeciesFound in 145 lakes
Hybrid Eurasian/Northern Watermilfoil appears on state infested-waters lists for 145 surface waters. Boaters and anglers moving gear in or out of those lakes carry a clean-drain-dry obligation under state law. With 145 documented lakes, Hybrid Eurasian/Northern Watermilfoil sits in the middle of the invasion curve — established enough that prevention requires real coordination, not so widespread that containment is hopeless.
The presence of Hybrid Eurasian/Northern Watermilfoil does not directly change a lake's LakeGrade rubric score — the grade measures the water itself, not the species inhabiting it. But invasive presence is a meaningful adjacent signal worth reading alongside the grade.
Lakes with Hybrid Eurasian/Northern Watermilfoil
| Lake | County | State | Grade | Depth |
|---|---|---|---|---|
| Deep Lake | Adams | WI | A | 49 ft |
| Bass Lake | Oconto | WI | A | 40 ft |
| Round Lake | Sawyer | WI | A | 74 ft |
| Round Lake | Waupaca | WI | A | 67 ft |
| Round Lake | Oconto | WI | A | 31 ft |
| Crystal Lake | Marquette | WI | A | 60 ft |
| Sea Lion Lake | Florence | WI | A | 82 ft |
| Pearl Lake | Waushara | WI | A | 45 ft |
| Pine Lake | Waukesha | WI | A | 85 ft |
| Pine Lake | Waushara | WI | A | 21 ft |
| Blue Lake | Oneida | WI | A | 49 ft |
| Dutch Hollow Lake | Sauk | WI | A | 38 ft |
| Parker Lake | Adams | WI | A | 36 ft |
| Arbutus Lake | Forest | WI | A | 28 ft |
| Little Muskego Lake | Waukesha | WI | A | 65 ft |
| Trego Lake | Washburn | WI | A | 36 ft |
| Brekke Lake | Waupaca | WI | A | 25 ft |
| Napowan Lake | Waushara | WI | A | 18 ft |
| Lake Beulah | Walworth | WI | A | 58 ft |
| Okauchee Lake | Waukesha | WI | A | 90 ft |
| Powers Lake | Kenosha | WI | A | 33 ft |
| Silver Lake | Waukesha | WI | A | 40 ft |
| Silver Lake | Waushara | WI | A | 50 ft |
| Plum Lake | Vilas | WI | A | 57 ft |
| Bass Lake | Florence | WI | A | 16 ft |
| Kusel Lake | Waushara | WI | A | 29 ft |
| Marl Lake | Waushara | WI | A | 35 ft |
| Round Lake | Shawano | WI | A | 39 ft |
| Rock Lake | Jefferson | WI | A | 60 ft |
| Pleasant Lake | Waushara | WI | A | 24 ft |
| Pleasant Lake | Walworth | WI | A | 29 ft |
| Lake Morris | Waushara | WI | A | 40 ft |
| Kelly Lake | Oconto | WI | A | 41 ft |
| Lilly Lake | Kenosha | WI | A | 22 ft |
| Lake Emily | Portage | WI | A | 35 ft |
| Jordan Lake | Adams | WI | A | 92 ft |
| Gilbert Lake | Waushara | WI | A | 65 ft |
| Little Hills Lake | Waushara | WI | A | 20 ft |
| Oconomowoc Lake | Waukesha | WI | A | 60 ft |
| Oconomowoc Lake Site | Waukesha | WI | A | 60 ft |
| Forest Lake | Fond du Lac | WI | A | 32 ft |
| Turtle Lake | Walworth | WI | A | 30 ft |
| Korth Lake | Shawano | WI | A | 48 ft |
| Little Horn Lake | Oconto | WI | A | 25 ft |
| Lower Nemahbin Lake | Waukesha | WI | A | 36 ft |
| Ellwood Lake | Florence | WI | A | 25 ft |
| Pine Lake | Shawano | WI | A | 35 ft |
| Roberts Lake | Forest | WI | A | 31 ft |
| Lake Five | Washington | WI | A | 23 ft |
| Elkhart Lake | Sheboygan | WI | A | 119 ft |
Showing 50 of 145 infested lakes.
Frequently Asked Questions
How many lakes have hybrid eurasian/northern watermilfoil?
Hybrid Eurasian/Northern Watermilfoil has been documented in 145 graded lakes: 145 in Wisconsin.
Does hybrid eurasian/northern watermilfoil affect water quality?
Invasive species can significantly affect lake ecosystems. They may alter nutrient cycling, displace native species, and change water clarity. Lakes with hybrid eurasian/northern watermilfoil should be monitored for changes in water quality over time.
Invasives Found With Hybrid Eurasian/Northern Watermilfoil
Co-occurs in 109 lakes · 432 total
Co-occurs in 86 lakes · 363 total
Co-occurs in 74 lakes · 688 total
Co-occurs in 59 lakes · 278 total
Co-occurs in 53 lakes · 493 total
Co-occurs in 29 lakes · 244 total
Source: EPA National Aquatic Resource Surveys, 2026.