Invasive species

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Management of Aquatic Invasive Plants

Purple loosestrife plant

Management of invasive aquatic plants that involves the application of herbicides to public waters in Minnesota requires a permit from the DNR.

The cumulative amount of area in a lake where aquatic plants may be controlled with herbicides may not exceed 15% of the littoral area. The littoral area is the part of the lake where rooted aquatic plants will grow and is limited to a depth of 15 feet or less.

Treatment of more than 15% of the littoral zone may be allowed under a variance. Before this treatment is allowed, consultation between the DNR and the proposer is necessary.

Invasive Aquatic Plant Management Permits

New for 2017

In February 2017, Invasive Aquatic Plant Management permit applications will be submitted through the online Minnesota DNR Permitting and Reporting System (MPARS). MPARS is designed to benefit permit holders and applicants with a simple, convenient and easy-to-use system.

Starting in February 2017, applicants are encouraged to use the online system to submit permit applications. Contact your local Invasive Species Specialist if a paper application is needed.

Permit Criteria

The following criteria will be used to evaluate applications for invasive aquatic plant management permits. A successful application will receive a "yes" to questions #1 - #7.

  1. Has the application for an invasive aquatic plant management permit been completed and submitted properly?
    1. Has a waiver from the requirement to provide signatures been requested?
  2. Is the target invasive aquatic plant(s) found in the proposed treatment area?
  3. Is the proposed treatment technique selective for the target invasive plant(s)?
  4. Is the purpose of the proposed treatment to significantly reduce the lakewide or baywide abundance of the target invasive plant(s)?
    • Treatments that work at a scale to cause a significant reduction of the lakewide or baywide abundance can range from a small set of scattered patches to a few large concentrations of the target invasive plant. Treatments can reduce interference with recreation by focusing on large concentrations of target invasives that mat on the surface or smaller patches that impede surface water use in strategic locations. Also, treatments can reduce the risk of spread by focusing on public access sites or heavily used travel routes.
  5. Does the proposed treatment minimize potential negative impacts to aquatic habitat, including water quality?
  6. If the proposed treatment includes near shore areas (within 150 feet of shore), are these near shore areas included in the application for an invasive aquatic plant management permit for reasons described in #4 above and not just to provide a landowner access to the lake?
  7. If the proposed treatment of invasive aquatic plants, when combined with all other treatment on the lake, does not exceed the limits on the littoral area allowed for treatment, then stop here. If the proposed treatment results in control that exceeds the limits, see the 'Special Permits' information below.
    • The limit on littoral area allowed for treatment with herbicide is 15% and the limit for mechanical treatment is 50%. The limit on the littoral area allowed for both herbicide and mechanical treatment combined is 50%. These limits are cumulative and include all permitted aquatic plant management activities on the lake.

Permits issued with a variance

To treat more than 15% of the littoral area with herbicide or harvest more than 50%, consultation between the DNR and the proposer is necessary.

Before meeting with the DNR, please assemble the necessary information in a Lake Vegetation and Water Quality Assessment. Contact an Invasive Species Specialist for your area to discuss the current conditions and possible approaches to management.

If a proposal is approved, the DNR will write a Lake Vegetation Management Plan.

Eurasian watermilfoil

In review of such proposals, the principle determining factors that the DNR will consider are:

  1. water clarity and
  2. distribution and composition of the plant community.

Water clarity is a major determining factor:

Curly-leaf pondweed

Research and monitoring over the past ten years has shown that the most successful (meeting project goals and costs) projects done to control curly-leaf pondweed are those that involve application of herbicide to less than 15% of the littoral area.

Grant Programs

Grant money may be available to support aquatic invasive plant management.

Aquatic Plant Management References

The document below contains links to a few selected references on management of aquatic plants, with an emphasis on invasive aquatic plants.

Past Stakeholder Engagement

The DNR has engaged with stakeholders to improve management of invasive aquatic plants. Phase I focused on suggested actions and Phase II developed recommendations for possible revisions to Minnesota's approach to management of invasive aquatic plants.

Phase I

Phase II


Chip Welling, Aquatic Invasive Species Management Coordinator
500 Lafayette Rd, Box 25
St Paul, MN 55155-4025