Aquatic Invasive Species

Aquatic invasive species are plants and animals not native to Minnesota. They may include plants such as curly-leaf pondweed and animals such as zebra mussels or spiny water flea.

Aquatic plants improve water quality and dissolved oxygen, and provide food & cover for fish and wildlife. However, when there are too many plants, they reduce the recreational suitability and navigability of the lake. The Lake Management Plan states that the proliferation of invasive curly-leaf pondweed, and overgrowth of nuisance native aquatic plants and algae are of concern.

Identification of Aquatic Plants

• DNR invasive aquatic plant identification
• DNR aquatic plant identification (includes favorable plants)

Inspect and Clean Equipment

To inspect and clean your dock and other water-related equipment, please see this handout:

If you find something suspicious, note the location, take a sample or photo and send an email to: oronolid@gmail.com

Clean In, Clean Out

When going to or from another lake with your boating, water sports or fishing equipment, protect our waters by following state aquatic invasive species laws:
https://www.dnr.state.mn.us/invasives/preventspread_watercraft.html

Zebra Mussels

A zebra mussel (approx. 4-5 mm in size) was found on a collection sampling plate in the spring of 2022 in the southeastern lobe of the lake near the dam along Main Street.

The samplers are provided by the Sherburne SWCD and SC COLA are a set of three connected plates for the zebra mussels to attach to. Six sampling plates around the lake are being monitored by volunteers.

Zebra mussels were confirmed in Lake Orono in 2020. The lake was tested for eDNA (environmental DNA) in 2021 and one of the results was positive. Volunteers have also increased their veliger (zebra mussel larvae) testing.

Eurasian Watermilfoil

On July 14, 2025 our aquatic plant contractor conducted a vegetation survey on Lake Orono and discovered a new infestation of Eurasian Watermilfoil (EWM). This is the only time it has occurred since it was first detected in July 2020 and a rapid response herbicide treatment was successfully done in August 2020.

The EWM was discovered in the four areas in the upper portion of Lake Orono.

The MN DNR issued a rapid response treatment permit and the Eurasian Watermilfoil was treated by Lake Management, Inc. on August 11th.  There are orange markers bordering the treatment areas. Although the treatment starts to work immediately, it can take up to two weeks for full remediation.

Please avoid boating in these areas and warn your neighbors as any fragment that a prop cuts loose can reproduce exponentially and spread to other areas.

Eurasian watermilfoil is a non-native plant that originates from Europe and Asia (see ID card). The invasive plant can have the ability to outcompete native lake vegetation. Surface mats and underwater growth of Eurasian Watermilfoil can interfere with recreational activities, and possibly decrease lakeshore property values.

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.

For more information, please see:
https://www.dnr.state.mn.us/invasives/aquaticplants/milfoil/index.html

EWM is rarely eradicated from a lake once introduced. Continued maintenance may be necessary in Lake Orono.

Curly-leaf Pondweed