Management of Aquatic Invasive Plants

Purple loosestrife plant

Application for Invasive Aquatic Plant Management (IAPM) permits in 2014.

If you wish to apply for an IAPM permit for 2014, please complete the permit application This link leads to an Word document.. Please read the instructions This link leads to an Word document. carefully and submit all the required information to the appropriate Regional Ecological and Water Resources Office (see page 6 of the instructions). Until all documents are submitted, applications will be considered incomplete.

Also, grants are available from the DNR to support control of Invasive Aquatic Plants This link leads to an Word document..
 

Introduction

Invasive species are a serious threat to lakes, rivers, wetlands, recreation, property values, and tourism in Minnesota. The purpose of this web page is to serve as a clearing house for information related to managing aquatic invasive plants in Minnesota. This includes the latest information on:

Invasive Aquatic Plants in Minnesota

Familiar invasive aquatic plants include curly-leaf pondweed, Eurasian watermilfoil, flowering rush, and purple loosestrife. Invasion of lakes or wetlands by these plants can result in interference with use of surface waters and displacement of native plants.

Identification of Invasive Aquatic Plants

Response to Invasive Aquatic Plants in Minnesota

The Minnesota Department of Natural Resources works with citizens to monitor the distribution of invasive aquatic plants in the state, prevent further spread, and manage problems caused by these plants.

Permits for Management of Invasive Aquatic Plants

In 2012, the greatest number of Invasive Aquatic Plant Management (IAPM) permits were issued to manage curly-leaf pondweed (Table 1), followed by permits to allow control of Eurasian watermilfoil. A small number of permits were issued to allow control of flowering rush and purple loosestrife. The primary method to control purple loosestrife is bicontrol by insects that were introduced into Minnesota twenty years ago; this activity does not require issuance of IAPM permits.

Table 1. Estimated numbers of Invasive Aquatic Plant Management (IAPM) permits issued in 2012 to allow control of various species.

Species

Estimated Number of Permits

Curly-leaf pondweed

110

Eurasian watermilfoil

70

Curly-leaf pondweed and Eurasian watermilfoil

20

Flowering rush

6

Purple loosestrife

2

Curly-leaf pondweed

Curly-leaf pondweed was first reported in Minnesota in 1910 and is known to be present in more than 750 lakes in the state. In spring, curly-leaf pondweed can form dense mats that may interfere with boating and other recreation on lakes. In late June or early July, curly-leaf plants usually die. So control of this plant usually is done in early spring. When applied early in the season, certain herbicides can control curly-leaf pondweed without reducing native plants. That is, these treatments can be selective. Maintaining or increasing native submersed aquatic plants is important because they provide habitat for fish and wildlife, as well as protect water clarity.

Selective control of curly-leaf pondweed usually is done by treatment with Aquathol ® herbicide, in which the active ingredient is endothall. Such applications of herbicide usually are done between mid-April and mid-May. This plant also can be managed with mechanical control.

This means that lake groups who want to control curly-leaf pondweed usually develop their plans and apply for permits or grants or both in later winter or early spring. In most cases, groups who want to control curly-leaf pondweed on a particular lake have documented the distribution of the plant in the lake in previous years and, based on experience, know where the plant is likely to produce mats at the surface and interfere with use of the lake.

Eurasian watermilfoil

Eurasian watermilfoil was discovered in Minnesota in 1987. At the end of the 2012 open-water season, this invasive plant was known to be present in 273 lakes, ponds, rivers and streams in the state. Like curly-leaf pondweed, Eurasian watermilfoil can form dense mats that may interfere with boating and other recreation on lakes. Unlike curly-leaf, Eurasian watermilfoil does not die by mid-summer, but usually grows all summer. In most cases, applications of herbicide to control Eurasian watermilfoil begin in mid to late May and are done before the beginning of July. This plant also can be managed with mechanical control.

Flowering rush

Flowering rush was first reported in Minnesota in 1968 and is known to be present in 27 bodies of water in the state. It grows along lake and river shores as an emergent plant with three-angled fleshy leaves and also may grow as a submersed plant with limp, ribbon-like leaves. Where flowering rush grows abundantly, it may displace native wetland vegetation and interfere with use of surface waters. This plant is managed on a small number of lakes in Minnesota.

Purple loosestrife

Purple loosestrife was introduced to the east coast of North America in the 1800s. Currently there are more than 2,400 infestations of this invasive plant recorded in 77 of Minnesota's 87 counties. Of those sites, the majority (70%) are lakes, rivers, or wetlands. Inventory totals indicate that Minnesota presently has over 63,000 acres infested with purple loosestrife. The principal focus of management is biocontrol; a limited amount of herbicide treatments are done each year.

Issuing Invasive Aquatic Plant Management Permits (IAPMP)

DNR staff will use the following criteria to evaluate an application for an IAPMP during the 2013 season.

A successful application will receive a "yes" to questions 1-8, and a "yes" to questions 9-11 if these questions are relevant to the application.

  1. Has the application for an IAPMP 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 IAPMP 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 [see below], then stop here. If the proposed treatment results in control that exceeds the limits, then go to 8.
    • 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.
  8. If the proposed treatment exceeds the limits described above, is there an active Lake Vegetation Management Plan (LVMP) that authorizes a variance from the littoral zone limits described above?
  9. If yes to 8, is the proposed treatment consistent with the active LVMP?
  10. If no to 8 - there is no active LVMP - what is the justification for the proposed treatment?
    • Review of the proposed treatment usually requires that results of a recent Point-Intercept survey be available to the DNR so that the distribution and composition of the plant community can be considered. Also, the DNR will consider water clarity as indicated by Secchi disk depth and other water quality data, which usually are available through LakeFinder. Below are additional factors to be considered.

Eurasian watermilfoil - Proposed applications of herbicide to more than 15% of the littoral area

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:

  • In lakes where clarity as indicated by Secchi depth is greater than 2m:
    • Proposal will be considered further
    • Consideration will also be given to the distribution and composition of the plant community.
    • Justification-lake-wide reduction in Eurasian watermilfoil has been shown to be followed by an increase in native plants.
  • In lakes where clarity as indicated by Secchi depth is 2m or less:
    • Consideration will also be given to the distribution and composition of the plant community.
    • Proposer likely will be directed to develop an approach to management that involves application of herbicide to no more than 15% of the littoral area.
    • Justification - there is significant risk that lake-wide reduction in Eurasian watermilfoil may not be followed by an increase in native plants and water quality maybe reduced.

Curly-leaf pondweed - Proposed applications of herbicide to more than 15% of the littoral area

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.

  • Proposed applications of herbicide to more than 15% of the littoral area may be supported if the proposals include:
    • evaluation including monitoring by applicant or third party (other than the commercial herbicide applicator for the project) of
    • unique control treatments (e.g. alum, carp removal, or drawdowns)
  • Justification - There has been a focus over the last ten years on research and monitoring of herbicide treatment to control curly-leaf pondweed. These projects indicate that this method has been less effective especially on low clarity lakes. Specifically, treatments did not lead to an increase in water clarity. Although lake-wide reductions in curly-leaf were obtained, matching increases in native plants were not observed. Lake-wide control of curly-leaf pondweed in most cases appears to move in the direction of reducing the amount of vegetation in low clarity or eutrophic lakes.
    • Nevertheless, there is little information available on control of curly-leaf pondweed in combination with other management actions, such as drawdown, application of alum, removal of common carp, etc. Applicants who propose to explore these techniques further and who are able to monitor outcomes will provide needed information to lake managers.

Awarding grants to support costs of managing infestations of invasive aquatic plants

DNR staff will use the following criteria to evaluate applications and award grants. A successful application will receive a "yes" to all the questions below.

  1. Has the application for grant support been received and completed properly?
  2. Has the DNR approved an estimated acreage to be permitted in 2013 or issued an IAPMP to the applicant seeking grant support?
  3. Is there grant money available to support the control?

Grant Programs

References on management of aquatic plants

The document linked below contains links to a few selected references on management of aquatic plants, with an emphasis on invasive aquatic plants. The references listed tend to be somewhat technical and perhaps present more information than some readers will want. For others, these documents may be a starting point for more reading and research.

Past Stakeholder Engagement

The DNR is engaging stakeholders to help us improve management of invasive aquatic plants. This effort includes two distinct phases to date. Phase I, which took place early in 2011, gave citizens opportunities to express their concerns and suggest actions to the DNR related to aquatic invasive plant management. The goal of Phase II is to work with stakeholders to develop recommendations for possible revisions to Minnesota's approach to management of invasive aquatic plants. Phase II began with a meeting on September 22, 2011 (see Phase II - Results and Feedback below). This was followed in October by DNR Responses to Stakeholders. On November 2, 2011 a second meeting took place. Related documents are available below:

Phase I

Phase II


Contact Information

Chip Welling, Aquatic Invasive Species Management Coordinator
chip.welling@state.mn.us
500 Lafayette Rd, Box 25
St Paul, MN 55155-4025
tel. 651-259-5149

MN DNR Invasive Species Program Contacts