MINNESOTA DEPARTMENT OF NATURAL RESOURCES

DIVISION OF ECOLOGICAL RESOURCES

STAFF REPORT 45

Management of Rooted Aquatic Vegetation,

Algae, Leeches, Swimmer’s Itch, 2008

May 2009
A Summary of Permitted Management Work for Aquatic Vegetation,

Algae, Leeches, Swimmer’s Itch, 2008

By

Steve Enger

Aquatic Plant Management Program Coordinator

and

Steven Hanson

Aquatic Pesticide Enforcement

Minnesota Department of Natural Resources

Division of Ecological Resources

May 2009
Mn DNR, Ecological Resources 1 2008 APM Annual Report May 2009

Executive Summary 2008 Aquatic Plant Management Program

In Minnesota the state is the owner of wild rice and other aquatic vegetation growing in public 

waters (M.S. 84.091). The Minnesota Department of Natural Resources (DNR) regulates the 

harvest, transplanting, and destruction of aquatic plants in public waters through a permit 

program. The purpose of the Aquatic Plant Management (APM) permit program is to protect the 

beneficial functions of aquatic vegetation while allowing riparian property owners to obtain 

reasonable access to public waters. 

Permits/Properties/Fees

The number of public waters where aquatic plant management is permitted has increased 

gradually from 1953 until 2000. However, from 2003 through 2005 the numbers of lakes with 

permitted APM activity have remained essentially the same. During this period, there was an 

average of 898 public waters with permitted APM activity annually. In 2006 the number of 

public waters with permitted APM activity rose to 953 but fell to 927 in 2007. In 2008 there were 

925 public waters with permitted APM activity. 

The increase in the numbers of permits issued from 2003-2007 averaged approximately 360 per 

year. The numbers of permits issued decreased in all regions in 2008. In 2008 there were 237 

fewer permits issued than in 2007. The Central Region, which includes the seven county 

metropolitan area, typically issues more permits for more properties than any other DNR 

regional office. However, in 2008 the Central Region issued 49 fewer permits than they issued 

in 2007. The largest decreases in the numbers of permits issued were in Region 1 (down 126 

permits from 2007) and Region 2 (down 158 permits from 2007). 

The numbers of properties involved in the APM program statewide decreased for the second 

consecutive year. There were 712 fewer properties permitted in 2008 than in 2007. The 

number of properties with permitted aquatic plant management activities decreased in all 

regions with the exception of Region 4 which saw a small increase of 39 properties. The 

Central Region saw the largest decrease in the numbers of properties permitted, down 433 

properties from 2007. 

Permit revenue decreased from about $315,000 in 2007 to about $300,000 in 2008. The 

average fee per property was up $3.37, from $24.58 in 2007 to $27.95 in 2008. 

AUAPCD

The Department first began issuing permits for Automated Untended Aquatic Plant Control 

Device’s (AUAPCD’s) in 1997. Now, permits for AUAPCD make up nearly 40% of the active 

Aquatic Plant Management permits. The number of single season permits issued in 2008

increased by 11 statewide over 2007. The number of single year permits issued has increased 

annually since 1998. The 2005 total of 1081 is more than double the number of 1-year permits 

issued in 1998. After a decline in the number of three-year duration permits issued from 2003-

2005, the number of 3-year permits increased in both 2006 and 2007. However, in 2008 there 

were 132 fewer three-year AUAPCD permits issued than in 2007. The three-year permit option 

is allowed for persons who limit the size of the area of AUAPCD operation to 50 feet alongshore 

or one-half their frontage whichever is less and no more than 2,500 square feet. Persons who 

obtained a three-year permit in 2008 will not have to reapply again until the year 2011. Some 

people (177 of those reporting) obtained a permit but did not run their device in 2008. In 2008,

about 39% of the permits issued allowed the use of automated aquatic plant control devices like 

the Crary WeedRoller, the Colman Beach Groomer, the Lake Restoration Lake Sweeper and 

similar home made devices. The remaining 61% of the aquatic plant management permits 
Mn DNR, Ecological Resources 2 2008 APM Annual Report May 2009

issued in 2008 allowed chemical or other mechanical removal as the method of control. These 

percentages were similar in 2007. 

Most AUAPCD permits are issued to a single property owner. Although AUAPCD’s make up 

39% of the permits issued, they only accounted for about 16% of the total number of properties 

permitted in 2008, this was unchanged from 2007. The other 84% of properties were permitted 

to use other mechanical methods or herbicides for aquatic plant control. 

Summary of Aquatic Plant Management permits issued in 2008.

Region

Harvest

Chemical***

2008

Issued 

Channel*

<2008

Active 

Channel**

AUAPCD’s 

with 

chemical 

control

AUAPCD

All 

Active 

Permits

Issued 

Restoration 

Permits

Issued

2008

Issued 

2007

Issued 

2006

1 year 3 year 3 year 3 year

Reg 1 481 46 - 64 682 197 248 294 1,902 15

Reg 2A 146 14 - 0 0 7 7 4 164 9

Reg 2B 616 9 - 54 199 211 220 227 1,473 4

Reg 3A 801 9 - 8 93 21 18 35 968 15

Reg 3B 468 6 - 18 165 61 102 71 867 15

Reg 4 181 7 - 2 49 23 52 7 312 7

All 2,693 91 711 146 1,188 520 647 638 6,397 65

* Channel permits are of unlimited duration issued to the property owner to mechanically maintain a channel to more than 16 

shoreline feet wide of vegetation.

** All active permits as of 11/23/2008. Total by Region cannot be calculated because Region boundaries were changed in 2003.

All Active Permits = Permits issued in 2007 and all active AUAPCD and channel permits excluding restoration permits.

*** Excludes permits for AUAPCD’s

Summary of all APM permits issued, fees collected, numbers of lakes properties treated and harvested in 

2008.

Region

Permits

Issued in 

2008*

Lakes** Fees***

Properties

Permitted

in 2008

Ave. Fee/

Property

All Reporting ****

Harvest

Work

Chemical

Treatment Both

Reg 1 1,356 259 $ 51,245.00 1,356 $ 37.79 125 204 32

Reg 2A 153 52 206 10 75 8

Reg 2B 1,025 143 1,608 30 458 14

Reg 2 total $ 51,112.00 1,814 $ 28.18

Reg 3A 915 262 4,747 48 500 20

Reg 3B 694 131 2,035 10 347 13

Reg 3 total $ 183,151.00 6,782 $ 27.01

Reg 4 253 78 $ 14,663.00 786 $ 18.66 22 97 5

2008 TOTAL 4,396 925 $ 300,171.00 10,738 $ 27.95 245 1,681 92

2007 TOTAL 4,633 927 $ 315,417.74 11,450 $ 24.58 277 1,773 115

CHANGE -237 -2 $ 15,246.74 -712 $ 3.37 -32 -92 -23

* Permits issued for restoration work are excluded.

** Includes all lakes, ponds, ditches and streams listed on APM permits for 2008.

*** Fee totals provided by Karen Sokola on 12/16/08.

**** Data tabulated from 2,159 surveys and commercial applicator reports returned as of 2/4/09.
Mn DNR, Ecological Resources 3 2008 APM Annual Report May 2009

INTRODUCTION

Value of Aquatic Plants

Aquatic plants are essential components of most freshwater ecosystems. In many lakes, plants 

are the base of the aquatic food chain. The habitat aquatic plants provide in the shallow nearshore areas is important to both aquatic and terrestrial animals. They also serve important 

functional roles in lakes by stabilizing the lake bottom, cycling nutrients, and preventing 

shoreline erosion.

Many of Minnesota’s most sought-after fish species depend heavily on aquatic vegetation 

throughout their life histories. Yellow perch, northern pike, muskellunge, panfish, and bass all 

depend on aquatic vegetation to provide food, spawning habitat, and nursery areas. Juvenile 

fish of most species feed on small crustaceans and insects that are abundant in stands of 

aquatic vegetation. Even species that may not require vegetation for spawning depend on the 

cover and forage found in aquatic vegetation.

Many species of wildlife are dependent on aquatic plants for food and nesting sites. Ducks eat 

the seeds and tubers produced by various water plants. Other aquatic plants, which are not 

eaten directly by waterfowl, support many insects and other aquatic invertebrates that are 

important sources of food for migratory birds and their young. Ducks have been known to alter 

migration patterns in response to food availability. Emergent aquatic vegetation provides 

nesting cover for a variety of waterfowl, wading birds, shorebirds and songbirds. The 

reproductive success of ducks that nest near lakes is closely tied to available aquatic plants and 

the cover it provides to hide young birds from predators.

The muskrat, an important furbearer, is almost entirely dependent on aquatic vegetation for food 

and shelter. Minnesota’s largest mammal, the moose, also relies heavily on aquatic vegetation 

for food.

The distribution of many amphibians and reptiles is directly linked to the vegetation structure of 

aquatic habitats. Species preference of particular habitat types is related to food availability, 

types of escape cover, and specific microclimates. Emergent and submerged vegetation 

support invertebrate populations that are an important food source for amphibians and reptiles. 

During the breeding season some species of frogs call from emergent vegetation at the water’s 

edge and their egg masses are often attached to aquatic plants. Freshwater turtles often eat 

submerged vegetation, which is an important source of calcium.

Beyond providing food and shelter for fish and wildlife, aquatic vegetation is important in 

maintaining a stable lake environment. Aquatic vegetation helps maintain water clarity by 

limiting the availability of nutrients, and preventing suspension of bottom sediments. Aquatic 

plants limit erosion of shorelines by moderating the effects of wave and ice erosion. A healthy 

native plant community is also important in preventing the establishment of non-native invasive 

aquatic plants. In short, aquatic plants serve many important functions for lakes, fish, and 

wildlife. Many of the things that we enjoy most about lakes are directly linked to aquatic

vegetation.

The Aquatic Plant Management Program

Riparian property owners (lakeshore property owners) in Minnesota have a legal right to use 

and access the lake adjacent to their property. Aquatic vegetation may interfere with a 

lakeshore homeowner’s ability to exercise that right. The purpose of the DNR’s Aquatic Plant 
Mn DNR, Ecological Resources 4 2008 APM Annual Report May 2009

Management Program is to regulate how much aquatic vegetation lakeshore residents can 

control while preserving the beneficial functions of aquatic vegetation. 

Other aquatic organisms can also interfere with the lakeshore property owner’s enjoyment of the 

lake. Swimmer’s itch, caused by the immature life stage of a parasite common in waterfowl, can 

cause significant and sometimes severe discomfort in humans depending upon a person’s 

sensitivity to the organism. Algae (plankton and filamentous) can also create a nuisance and 

occasionally unhealthy conditions when they become overabundant. Relief from these 

nuisances may also be sought under an aquatic plant management permit.

Administrative Regions

In July of 2002 the number of DNR administrative regions was reduced. The previous sixregion structure was reduced to four administrative regions. The Brainerd Lakes Region, 

previously Region Three, was divided up between the Northeast Region (Region Two) and the 

Metro Region (Region Six), now the Central region. The southeastern part of the state, Region 

Five, was combined with the South Region or Region Four. Aquatic plant management permits 

were issued as they had been in the six-region structure through the remainder of the 2002 

open-water season. In 2003 APM permits were issued according to the new regional 

boundaries. The new regional structure makes historical comparisons between regions more 

difficult. However, it is still possible to identify statewide trends and make comparisons between 

years. 

DNR Administrative Regions DNR Administrative Regions as of

Pre-July 2002 October 2006

Lak e of the Woods

Kittson Ros eau

Kooc hic hing

Marshal l

St. Louis

Beltrami

Polk

Pennington

Cook

Lak e

Clearwater

Red Lak e

Itas ca

Nor man Mahnom en

Cas s

Hubbard

Clay Becker

Wadena Aitkin

Crow Wing

Carlton

W Otter Tai lilkin

Todd Pine

Morrison Mille Lacs

Kanabec

Grant Douglas

Travers e Benton

Stevens

Stearns

Pope

Isanti

Chisago

Big Stone

Sher bur ne

Swift

Kandiyohi Wright

Anok a

Meek er

Lac Qui Parle

Washington

Hennepin

Chippewa

Ram sey

McLeod Car ver

Yellow Medicine

Dak ota

Renville

Sibley Scott

Redwood

Lincoln Lyon Goodhue

Le Sueur Ric e

Brown

Nic ollet Wabasha

Pipestone Murray Blue Earth

Cottonwood

Winona

Waseca Steele Dodge Olmsted Watonwan

Roc k Nobles Jacks on Martin Faribault Freeborn M Fi llm ore Houston ower

1 2

3

4

# New Ulm

St. Paul

Grand Rapids

Bemidji

Little Falls

Brainerd

#

#

#

#

#

5

6
Mn DNR, Ecological Resources 5 2008 APM Annual Report May 2009

The number of staff reviewing APM permit applications increased concurrent with the reduction 

of DNR regions. The reorganization moved some regional headquarters farther away from the 

major centers of APM permit activity (Appendix Table G). The Brainerd DNR Office, now in the 

Northeast Region, retained an Aquatic Plant Management specialist because the Brainerd 

Lakes Area is a center of APM permit activity. The Brainerd (2B) area office is responsible for 

application review for Aitkin, Crow Wing, and southern Cass counties. Grand Rapids, (2A) the 

location of the Northeast Regional DNR Headquarters, is responsible for application review for 

Carlton, St. Louis, Lake, Cook, Koochiching, and Itasca counties. The Central Region added an 

APM position to the Little Falls Fisheries office to accommodate the large number of permits 

previously issued from the Brainerd office. The Little Falls office (3B) is responsible for 

application review for Benton, Isanti, Kanabec, Pine, Mille Lacs, Morrison, Sherburne, Stearns, 

Todd and Wright counties. The Central Region DNR Headquarters in St. Paul (3A) is 

responsible for application review for the metropolitan area, Anoka, Carver, Chisago, Dakota, 

Hennepin, Ramsey, Scott, and Washington counties. In October of 2006 the Central Region 

boundaries were expanded to include Goodhue, Wabasha, Olmsted, Winona, Fillmore, and 

Houston counties along the Mississippi River in Southeastern Minnesota. 

The DNR’s Division of Fish and Wildlife is responsible for the administration of the Aquatic Plant 

Management Permit Program. Riparian property owners apply for a permit to their Regional 

Fisheries Manager. The Northwest, Northeast, and Central DNR Regions have Aquatic Plant 

Management Specialists who make site inspections and review applications for permit. In 2006, 

an Aquatic Plant Management Specialist was hired for the South Region. This person works 

out of the New Ulm Regional Fisheries office. Prior to 2006, site inspections and application 

review in the South Region were the responsibility of the Area Fisheries Supervisors. 

The recommendation for the disposition of the permit application (approval, modification, or 

denial) is determined during the review process. This decision often involves a discussion with 

the lakeshore property owner. When applications for APM permits are received for shallow 

lakes where waterfowl management is the primary focus, the Aquatic Plant Management 

Specialist will seek the advice of the Area Wildlife Manager. When applications are modified or 

denied, the applicant may appeal to the Commissioner’s Office for review. The purpose of this 

review is to determine if the permit decision was based upon rule standards. Finally, permit 

decisions can be appealed to an Administrative Law Judge through the contested case hearing 

process. 

The coordinator of the Aquatic Plant Management Program is in the Division of Ecological 

Resources. This position is the department’s contact with commercial mechanical control 

businesses, commercial aquatic herbicide applicators, and the Minnesota Department of 

Agriculture (MDA). The coordinator provides technical expertise on aquatic plant control 

methods and permitting requirements to lakeshore property owners and Department staff. The 

coordinator works to insure consistent interpretation of the APM rules throughout the 

Department. This position administers exams and issues operating permits to commercial 

aquatic plant harvesters. This person also reviews appeals of permit decisions for the 

Commissioner. The Program Coordinator maintains current labeling for aquatic plant control 

products and provides that information to field personnel. The Program Coordinator also 

prepares an annual report on program activities (this document) and coordinates the 

development of informational materials and forms provided to riparian property owners 

interested in aquatic plant management.
Mn DNR, Ecological Resources 6 2008 APM Annual Report May 2009

The APM program coordinator supervises staff in the Division of Ecological Resources whose 

job responsibility includes enforcement of aquatic pesticide rules and pesticide label 

requirements. An Aquatic Pesticide Enforcement Specialist conducts inspections of herbicide 

applications in public waters to monitor compliance with state and federal pesticide law and 

respond to reports of pesticide misuse (Appendix Tables E and F). The U.S. Environmental 

Protection Agency (EPA) partially funds DNR’s aquatic pesticide enforcement activities through 

a grant administered by MDA.

Regulations

Authority for the DNR’s aquatic plant management program is found in Minnesota Statutes M.S. 

84.091 Subdivision 1, which designates ownership of wild rice and other aquatic vegetation in 

public waters to the State. M.S. 103G.615 authorizes the Commissioner of the DNR to issue 

permits to harvest or destroy aquatic plants, establish permit fees, and prescribe standards to 

issue or deny permits for aquatic plant control. The standards for the issuance of permits to 

control aquatic vegetation and the permit fee structure are found in MN Rules Chapter 6280. 

Minnesota Statutes and Rules can be reviewed at the Revisor of Statutes website 

http://www.leg.state.mn.us/leg/statutes.asp. 

A permit from the DNR is required to use pesticides in public waters (generally any body of 

water 2.5 acres or larger within an incorporated city limit, or 10 acres or larger in rural areas), to 

use an automated aquatic plant control device, to control emergent vegetation such as cattails, 

wild rice, or bulrush, and to control submerged or floating-leaf vegetation above specified limits. 

A riparian property owner may, without a permit, physically remove (cut, pull, or harvest) 

submerged vegetation along one half the individual’s lake frontage or 50 feet, whichever is less. 

The total area where submerged vegetation is removed may not exceed 2,500 square feet. In 

addition, a boat channel up to 15 feet wide, and as long as necessary to reach open water, may 

also be maintained by mechanical means without a permit. If floating-leaf vegetation is 

interfering with riparian owner’s access, a channel, not more than fifteen feet wide, extending to 

open water, may be mechanically maintained without a permit. The vegetation that is cut or 

pulled must be removed from the lake and the managed area must remain in the same location 

each year.

The mechanical control of purple loosestrife, a plant on the Minnesota Department of 

Agriculture’s noxious weed list, does not require a permit from the DNR. However, herbicide 

control of purple loosestrife below the ordinary high water level on public waters does require a 

permit. Because of the plant’s status as a noxious weed, these permits are issued free of 

charge.

Beyond the permit requirement, any pesticide used in surface waters must be labeled for 

aquatic use and registered with the United States Environmental Protection Agency. When 

using an aquatic herbicide all label instructions and precautions must be followed. The 

permittee must post areas treated with herbicides so that anyone entering the area is informed 

of the herbicide application. The notification signs contain the following information: the name 

of the applicator, the treatment date, the name of the product used, expiration dates of any 

water use restrictions on swimming, fishing, household, and other uses. The DNR provides 

these signs to permittees and commercial applicators at no cost. A list of herbicides most 

commonly used for aquatic plant control and the amount used under permit in Minnesota in 

1981-2008 is found in Appendix A and B.
Mn DNR, Ecological Resources 7 2008 APM Annual Report May 2009

Summary of Aquatic Plant Management Program Activities in 2008

The following summary of Aquatic Plant Management (APM) Program activities in 2008 comes

from four sources: permittee survey forms (Appendix Table C and D), commercial aquatic 

applicator and commercial mechanical control reports, and Aquatic Plant Management (APM) 

permits. 

Commercial applicators, harvesters, and riparian property owners who do control work in public 

waters are required to provide a yearly summary of their APM activity. With this information the 

past year’s activities can be summarized, the control of aquatic vegetation in public waters is 

monitored, and trends in aquatic plant management are identified. 

Survey forms are mailed to permit holders that did their own aquatic plant control work. Prior to 

2000, permit holders that hired commercial applicators to perform the control work for them 

were included in the survey. They were asked to answer only those few questions pertinent to 

their situation. This often caused confusion and permittees would either not respond or would 

send the form to the commercial service for completion. In addition, when commercial 

applicators do the control work there are usually many customers on a single permit. However, 

only one of those customers is listed as the permittee. Hence, this approach relied on one 

individual to provide accurate information for up to 100 or more other people. Since commercial 

pesticide applicators are required by law to keep detailed records and their reporting is generally 

more precise, permit holders who hire a commercial firm are no longer asked to complete a 

survey form.

Survey forms were sent to all permittees that did their own chemical or mechanical control work. 

Of the 1,287 surveys mailed 1064 (83%) were returned. A separate survey was sent to 1,708

AUAPCD permit recipients, 1,502 (88%) were returned.

Permit Issuance

In 2008, a total of 4,396 permits were issued statewide for APM activities (this includes 65

shoreline habitat restoration permits), 237 fewer than in 2007 (Appendix Table G provides the 

county by county distribution of permits and permitted properties). These permits were issued 

for properties on 925 public waters (i.e. lakes, ponds, and streams) in 2008 (Figures 1, 2, and 

3). In 2008, there were 1,708 permits issued for the operation of Automated Untended Aquatic 

Plant Control Devices (AUAPCD). The remaining 2,688 permits were issued to municipalities 

and lakeshore homeowners for pesticide use (includes algae and swimmer’s itch control), 

mechanical control (cutting, pulling, or harvesting) of aquatic vegetation, or shoreline habitat 

restoration.

Over the last 15 years, the number of public waters where permits are issued has almost 

doubled. Little increase occurred until 1999 when the number of public waters with permitted 

APM activity increased sharply (Figures 2 & 3). The number of public waters with permitted 

APM activity in 2008 was 925, 2 fewer lakes than in 2007.
Mn DNR, Ecological Resources 8 2008 APM Annual Report May 2009

0

200

400

600

800

1000

1200

1400

1600

1 2A 2B 3A 3B 4

Permit s and Lakes

Region

Figure 1. Permits issued, and the number of lakes with permitted aquatic plant 

control, by region, in 2008.

permits issued 

lakes with permits issued in 2008
Mn DNR, Ecological Resources 9 2008 APM Annual Report May 2009

0

500

1000

1500

2000

2500

3000

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 2. Numbers of permits issued for mechanical and chemical 

control (excluding AUAPCD) of aquatic vegetation, algae, and 

swimmer’s itch, and numbers of lakes where permits were issued 1992-

2008.

protected waters

permits issued (no 

AUAPCD's)
Mn DNR, Ecological Resources 10 2008 APM Annual Report May 2009

Aquatic plant management permit issuance increased annually from 1992 until about 1999. 

Then in the early 2000’s the numbers of permits issued decreased and there was a 

corresponding decrease in the numbers of participating properties. Permit numbers and 

properties began to increase again in 2003 through 2006. In 2008 the total number of 

properties declined for a second year in a row and the number of permits also declined. Spring 

of 2000 was the beginning of several years in a row that were cooler and wetter than normal in 

the Metro area. Cooler temperatures in the early part of the open water season may contribute 

to the decline in lakeshore property owners participating in the Aquatic Plant Management 

program.

Lakeshore homeowners may apply for an aquatic plant management permit as a group. Group 

permits are more popular in the Twin Cities metropolitan area than in greater Minnesota (Table 

1). Homeowner’s on large group permits can benefit from the $750 cap on permit fees. The 

individual permit fee ($35.00 per property) begins to decrease for groups larger than 21. Some 

permits have more than 100 properties listed on a single permit. In 2008 there were 10,738

properties covered by the 4,396 permits issued. 

The statewide average number of properties per permit in 2008 was 2.4, similar to 2007. The 

Central Region, which includes the Twin Cities metropolitan area, typically has larger group 

permits than other areas of the state. In 2008, the Central Region averaged 4.2 properties per 

permit issued down from 4.4 in 2007. The Northwest Region averaged one property per permit; 

the Northeast Region averaged nearly two properties per permit (1.5). The average number of 

properties per permit in the Southern Region in 2007 was 2.9, but increased to 3.1 properties 

per permit in 2008.

0

2000

4000

6000

8000

10000

12000

14000

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Properties

Figure 3. Numbers of properties permitted for APM statewide, 

1997-2008.
Mn DNR, Ecological Resources 11 2008 APM Annual Report May 2009

Table 1. Permits grouped by the number of properties listed (excluding AUAPCD) by Region, 2008.

Region 1 2A 2B 3A 3B 4

Properties/permits: >100

51-100

21-50

11-20

2-10

1

0

0

0

0

0

481

0

1

0

0

0

145

1

0

8

9

19

579

2

11

50

50

165

523

0

3

19

24

42

380

1

4

2

1

14

159

The rules regulating aquatic plant removal from public waters require an inspection of the 

treatment site the first time an application is received or when there are changes requested to 

previously issued permits. Aquatic plant management specialists and area fisheries staff visit 

these sites to determine if the permit application is consistent with the standards for permit 

issuance in APM rules. This is also an opportunity to determine what kinds of plants and habitat 

are present in the treatment area. During these inspections, the size of the area may be 

reduced to protect important habitat based on the observations and professional judgment of 

the specialist. The number of applications received for shoreline vegetation removal and the 

numbers of permits that are issued as requested is shown in Table 2. 

Table 2. Percent of permits requesting near-shore control that are issued as requested by region in 2008.

Region

1 2A 2B 3A 3B 4 Statewide

number of applications requesting near-shore control 1,315 149 988 796 568 200 4,016

permits issued as requested 1,099 97 635 613 411 158 3,013

% of permits issued as requested 83.6 65.1 64.3 77.0 72.4 79.0 75.0

Permit Fees

Permit fees were increased during the 2003 legislative session. People applying for APM 

permits after August 1, 2003 were required to pay the higher fee. The new fee increased many 

types of APM permits from $20.00 per property to $35.00 per property. The cap on large group 

permits to control submersed vegetation was increased from $200 to $750. 

Permit fee revenues in 2008 were $300,171 about $15,246 less than 2007. The average permit 

fee per property owner in 2007 was $24.58. In 2008 the average fee per property was $27.95. 

There is still an economy of scale for large group permits, hence the statewide average cost per 

property was a little above $27.00 in 2006, and $8.00 less than the cost of an individual permit 

under the new fee structure. The increase in the average permit fee in 2007 is likely due to a 

reduction in numbers and properties on multi-property permits and an increase in individual 

property permits.
Mn DNR, Ecological Resources 12 2008 APM Annual Report May 2009

Timing of Treatment

Permits are issued for the open water season, generally from May through September 1.

However, aquatic plant control can begin as early as January and extend through November. In 

2008 about 87% of the permitted work, reported statewide, was completed in June, July, and 

August (Figure 4). Because most aquatic plant control in Minnesota is recreationally motivated 

this pattern has been consistent over time. 
Mn DNR, Ecological Resources 13 2008 APM Annual Report May 2009

Acres of aquatic plant control permitted

The number of acres permitted for chemical control of submersed aquatic plants fluctuates 

annually and has increased sharply in recent years (Figure 5). This may mean that aquatic 

plant control is highly variable depending on the season. One contributing factor is the offshore 

control of aquatic vegetation focused primarily on non-native invasive species. A few large 

Eurasian watermilfoil and curly-leaf pondweed treatments can have a significant influence on 

the total number of acres permitted for treatment. This was evident in 2004 and 2005. In 2004,

several lake-wide treatments of curly-leaf pondweed in the Central Region were responsible for 

the increase in treated acres. These lakes in addition to Lake Benton, a 3000-acre lake in 

Lincoln County, (South Region), were treated again in 2006, 2007, and 2008 with an aquatic 

herbicide to manage curly-leaf pondweed. As the interest in managing invasive species 

increases this trend is likely to continue. 

Aquatic plant control methods

Again, in 2008, about 39% of all permits issued for aquatic plant control permitted the use of 

plant removal with AUAPCD’s. Aquatic plant control using herbicides, plant harvesting, and 

plant removal by hand, and aquatic plant restoration accounted for the remaining 61% of the 

permits issued for aquatic plant management (Figure 6). It is important to remember that a 

limited amount of mechanical control of submerged and floating leaf vegetation can be done 

without a permit and a permit is always required when herbicides or automated devices are 

used for aquatic plant control. The total area permitted statewide for the various methods of 

near shore aquatic plant removal and the average area permitted per property in 2008 are found 

in Table 3. Permit holders were asked if they performed the control over the entire area allowed 

in their permit. Nearly 24% of those responding indicated that control work done was less than 

the area permitted.

0

1000

2000

3000

4000

5000

6000

7000

8000

2001 2002 2003 2004 2005 2006 2007 2008

Acres

Year

Figure 5. Permitted offshore chemical control acreage of aquatic 

vegetation statewide from 2001-2008.

-

-
Mn DNR, Ecological Resources 14 2008 APM Annual Report May 2009

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 6. Numbers of permits issued for aquatic vegetation control including chemical, 

mechanical, chemical and mechanical, AUAPCD and algae and snail control, 1994-2008.

Chemical and Mechanical 

(both)

algae, snails and chara 

(only)

AUAPCD (issued year)

Chemical (macrophyte 

only)

Mechanical (no AUAPCD's 

and macrophyte only)

Table 3. Total near-shore area permitted, in acres, by region, for control of submerged vegetation, 

swimmer’s itch and AUAPCD use in 2008.

Control

Region Total number

of acres Props

Ave. 

1 2A 2B 3A 3B 4 Acres/Prop.

Herbicide control 

excluding off shore 

treatment

40.9 7.9 74.8 683.7 239.1 140.2 1,186.6 6,183 0.192

Mechanical control 

excluding off shore 

removal

19.2 1.2 19.6 28.0 0.9 7.3 74.2 406 0.183

Swimmer’s itch 

control *

31.7 7.1 102.0 865.3 191.8 75.4 1,273.3 5,587 0.228

AUAPCD 2008

issued

69.8 0.3 31.1 9.5 15.0 4.3 130.0 1,703 0.076

* includes all permits with swimmers itch control
Mn DNR, Ecological Resources 15 2008 APM Annual Report May 2009

Percent of Aquatic Plant Removal Permits Used

Each year some permits issued for aquatic plant management activities are not used (Figure 7). 

Statewide, 85% of permits issued were reported used by the permittees or commercial 

applicators/operators doing the work, this is down slightly from 2007. Permittees indicating that 

their permit was not used were asked to indicate why by responding to one or more choices 

provided on the survey. The results are summarized in Table 4, below. In 2008, the reason 

most frequently given (46%) for not using an APM permit was that the property owner was 

unable to do the permitted work; 4% reported not doing the work because of getting their permit 

too late, down from 20% in 2007.

Table 4. Response by permit holders to choices indicating that their APM permit was not used, 

expressed as a percent by region in 2008.

Region 1 2A 2B 3A 3B 4 Statewide

nuisance condition did not devel.

got permit too late

unable to do the work

other

total

20

4

48

28

100

4

22

44

30

100

18

2

49

31

100

39

0

57

4

100

25

19

36

19

100

33

22

28

17

100

21

8

46

25

100

2A = Grand Rapids, NE Region; 2B = Brainerd, NE Region; 3A = St. Paul, Central Region; 3B = Little Falls, Central Region

353

92

505

567 50

370

124

2011

85

28

97

54

24

338

0

500

1000

1500

2000

2500

1 2A 2B 3A 3B 4 statewide

Permit s

Region

Figure 7. Total reported number of permits used and not used by region 

(excluding AUAPCD permit holders), 2008

not used

used
Mn DNR, Ecological Resources 16 2008 APM Annual Report May 2009

Who does control

Lakeshore homeowners perform about 40% of the permitted mechanical and herbicide plant 

control. Commercial applicators and mechanical control companies performed about 60% of 

the control work statewide in 2008. This represents a slight increase over the percent of the 

work done by commercial applicator and aquatic plant harvesting companies in 2007. Permit 

holders in the Central Region hire commercial services more frequently than any other region 

(Figure 8). Commercial aquatic plant control companies perform about 74% of the control in the 

Central Region. In 2008, 60% of the control in the Northeast Region was performed by 

commercial service. However, most of the commercial treatment was done in the Brainerd 

Lakes Area (2B), most permitted control in the Grand Rapids area (2A) is still done by the 

homeowner. Permit holders perform about 78% of the control in the Northwest Region and 50%

in the South Region. Figure 8a shows the trend in the percent of permitted aquatic plant control 

performed by commercial service over the last eight years. 

Satisfaction

Permittees who personally undertook aquatic plant control activities were asked to indicate their 

satisfaction with the results of the aquatic plant control. Generally, permit holders were satisfied 

with the results of the control. About 72% of the respondents were satisfied with the results of 

the herbicide control. About 68% of those responding were satisfied with the results of 

treatments to control swimmer’s itch and 51% of respondents were satisfied with results of 

mechanical control. It is important to remember that permit holders hiring commercial services 

were not included in the survey.

Reapply for permit

Permit holders, excluding AUAPCD permittees, were asked if they would apply for a permit in

2008. Of the 1002 responses, 779 (78%) said they would reapply next year, a 6% increase 

from 2007. Approximately 19% (190) of the permit holders responding indicated that they were 

unsure if they would reapply for permit in 2008. The number of permittees reporting that they 

would not apply (33 or 3.3%) was slightly higher than in 2007. Regardless of their response, all 

2008 permit holders, whose permits expire, will receive permit application materials prior to the 

start of the 2009 open water season.
Mn DNR, Ecological Resources 17 2008 APM Annual Report May 2009

0

10

20

30

40

50

60

70

80

90

100

1 2A 2B 3A 3B 4 overall %

Figure 8. Percent of reported permitted APM work done by permittee and by 

commercial service for each region in 2008.

commercial 

service

permittee

0

10

20

30

40

50

60

70

80

90

100

2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 8a. Percent of reported permitted APM work done by permittee and 

by commercial service statewide from 2000-2008. -

commercial 

service

permittee
Mn DNR, Ecological Resources 18 2008 APM Annual Report May 2009

Automated Untended Aquatic Plant Control Devices (AUAPCD)

Before 1997 the operation of an automated mechanical aquatic plant control device did not 

automatically require an APM permit, and few AUAPCD permits were issued. The Aquatic Plant 

Management Rules were revised in 1997 to require a permit for the operation of these devices 

because of their potential to excavate bottom sediments, and impact spawning habitat. In 2008

there were 1,708 permits issued for these devices statewide. Of those permits 1,188 were 

issued for a one-year term and 520 were issued for a three-year permit term. Permits are 

issued for three years if the applicant agrees to a reduced area of operation and qualifies for a 

three-year permit based on the vegetation types present. More than 76 percent of the AUAPCD 

permits were issued in the Northwest and Northeast Regions; this is one percent higher than

2007. In addition to the permits issued in 2008, there are active three-year permits issued in 

2006 and 2007 (638 and 647 respectively). Of the 1,701 surveys mailed 1,610 (88%) of the 

AUAPCD permit holders statewide responded to the questionnaire. Three-year AUAPCD 

permit holders issued permits in 2006 and 2007 were not surveyed.

There are at least three different companies producing AUAPCD’s that are used in Minnesota, 

the Crary Company WeedRoller , the Colman Beach Groomer and the Lake Restoration 

Lake Maid . Thirteen permit holders that responded reported they used homemade devices in

2008. Based on survey results, two-thirds of AUAPCD owners in Minnesota have owned their 

device for more than three years. In contrast, 22% have owned their device from 1 to 3 years 

and 12% have responded that they have owned their device for less than one year. 

Most of the people responding to our questionnaire (83%) were the sole owner of an AUAPCD. 

Nine permit holders stated that they rented their device in 2008. This was a small decrease from 

those reporting renting in 2007. Some homeowners opt to purchase the device cooperatively 

and share it during the summer months. Approximately 17% of the people who used an 

AUAPCD in 2008 either, rented, borrowed, owned and shared, or jointly owned their AUAPCD, 

a 6% decrease from 2007.

Lakeshore homeowners have two AUAPCD permit options, provided the location is suitable for 

the operation of these devices. The annual renewal option is used when the lakeshore 

homeowner operates in an area greater than 2,500 square feet or more than 50 feet 

alongshore. The one-year permit option showed a moderate increase in 2008 (Figure 9). 

Applicants choosing the three-year permit option decreased significantly from 2007 (Figure 9). 

The manufacturer of the WeedRoller has stated that with time people will need to use the 

WeedRoller less frequently to achieve acceptable control. The company explained that once 

the plants were gone there would be little need to use the machine. We have asked the 

question, how often do you operate your AUAPCD? and sorted the responses by the length of 

time people had indicated they had owned the machine. Recent AUAPCD owners are more 

likely to operate the device longer than those people who have owned the device for several 

years (Figure 10). About 180 persons permitted to operate an AUAPCD stated that, for various 

reasons, they did not operate the device in 2008, similar to 2007. 

The AUAPCD had higher satisfaction ratings than other methods of aquatic plant control. When 

asked, were you satisfied with your AUAPCD, 96% of those responding indicated that they were 

satisfied with these devices. This percentage is 2% lower than 2007. 
Mn DNR, Ecological Resources 19 2008 APM Annual Report May 2009

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

permits issued

year

Figure 9. Numbers of permits issued allowing the use of AUAPCD's in

Minnesota public waters

1 yr. Issued current yr.

3 yr. Issued current yr.

Total 1 and 3 years issued current year

Lakes with active AUAPCD's
Mn DNR, Ecological Resources 20 2008 APM Annual Report May 2009

The DNR sends AUAPCD permit holders a sticker that must be displayed on or near the unit to 

help Conservation Officers and APM staff identify permitted units. Beginning in 2000 use of the 

sticker became a mandatory condition of the permit. For the last 5 years about 98% of the 

permit holders responding to this question had no difficulties displaying the sticker. For this 

reason 2008 permit holders were not asked if they had any difficulties displaying the sticker.

Filamentous algae control

The aquatic plant management rules allow the control of filamentous algae with copper sulfate. 

Filamentous algae can become a nuisance by interfering with swimming and wading. Permit 

issuance for filamentous algae control has increased at about the same rate as permits for 

submerged vegetation control (Figure 11). Filamentous algae control is commonly requested 

on applications for control performed by commercial services. 

Chara control

The aquatic plant management rules allow the control of chara with copper sulfate. Chara is a 

macro-algae that can interfere with recreation in some lakes. Since 1997 there have been 

approximately 300 hundred lakes each year where permits have been issued for chara control 

(Figure 12). 

0

5

10

15

20

25

30

35

40

>0-20 >20-50 >50-144 Continuous

Percent of AU APCD permittees reporting

Estimated Weekly Hours of Operation

Figure 10. AUAPCD use from May through August, 2008 catagorized by length of

ownership expressed as a percent of all AUAPCD permittees reporting.

AUAPCD owned less 

than 1 year

AUAPCD owned 1 -3 

years

AUAPCD owned more 

than 3 years
Mn DNR, Ecological Resources 21 2008 APM Annual Report May 2009

0

200

400

600

800

1000

1200

1400

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 11. Numbers of permits issued for filamentous algae control, 

and numbers of lakes where permits were issued 1997-2008.

permits

protected waters

0

100

200

300

400

500

600

700

800

900

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 12. Numbers of permits issued for chara control, and numbers of lakes 

where permits were issued 1997-2008.

permits

protected waters
Mn DNR, Ecological Resources 22 2008 APM Annual Report May 2009

Plankton algae control 

The aquatic plant management rules allow the control of plankton algae when there is an 

“excessive algae bloom.” The characteristics of an “excessive algae bloom” as defined by the 

rules are: an algae population dominated by blue green algae, a Secchi disc reading typically 2 

feet or less, floating mats or scums of algae have accumulated on the downwind shore, or 

decomposition of accumulated algae has occurred releasing a blue-green pigment and causing 

on offensive odor. 

The numbers of lakes treated with algaecides to control plankton algae has been decreasing 

over the last ten years (Figure 13). Copper sulfate treatments can cause an increase in water 

clarity when the turbidity is due to algae, but the increased water clarity is usually temporary and 

the treatment may need to be repeated. Due to the temporary nature of control, the possibility 

of a fish kill caused by a dissolved oxygen sag from decomposing algae, the buildup of copper 

in lake sediments, and the potential for algae to become resistant to copper, lake-wide plankton 

algae treatments are discouraged. 

Swimmer’s itch control in Minnesota lakes

A condition known as Swimmer’s itch (a.k.a. lake itch, wader’s itch) has garnered complaints 

from swimmers in Minnesota lakes since at least the 1800's and has likely been around for 

much longer. The cause of this irritating skin condition was discovered by W.W. Cort in 1928 at 

the University of Michigan Biological Station (Blankespoor and Reimink, 1991). Cort discovered 

that swimmer’s itch (cercarial schistosome dermatitis) is caused by the immature life stage of 

common non-human schistosome trematodes called the cercaria.

0

10

20

30

40

50

60

70

80

90

100

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 13. Numbers of permits issued for lake-wide plankton algae control, 

and numbers of lakes treated 1997-2008.

permits

protected waters
Mn DNR, Ecological Resources 23 2008 APM Annual Report May 2009

These parasites have a complex life history. The adult fluke lives in the blood vessels lining the 

intestine of its definitive host where it reproduces and releases eggs. The eggs enter the gut 

and leave the animal in the feces. The eggs hatch when they enter the water becoming a 

larvae called a miracidia. The miracidia then infects a snail where it develops into a life stage 

called the cercaria. The cercaria, upon release from the snail, seeks its definitive host, usually 

some sort of waterfowl. The cercaria does not feed and will only live for about 24 hours unless 

they find a proper host. When a proper host is located the cercaria penetrates the skin, finds its 

way to the blood vessels lining the gut, and becomes an adult completing its life history.

The problem for humans occurs when the cercaria mistakes us for its proper host. When a 

cercaria penetrates a human’s skin it is attacked and killed by the person’s immune system. 

Although the organism cannot complete its life history in humans, individuals sensitive to the 

infection can suffer from an allergic reaction. The symptoms will appear on areas of the body 

submersed in the lake and are typified by areas of redness and swelling, similar to a mosquito 

bite, and are accompanied by a severe itching sensation. These symptoms can last up to two 

weeks.

Not everyone is bothered by swimmer’s itch; about 30 to 40% of the population is sensitive to 

swimmer’s itch infection. This explains why some people swimming in a lake at the same time 

and place as a person severely affected experience no symptoms. Like other allergic reactions,

a person’s degree of sensitivity increases with each exposure. 

The numbers of permits issued for swimmer’s itch has increased steadily since 1997. The 

Brainerd Lakes Region, has had more lakes per year with permitted swimmer’s itch control than 

any other area. In 2008 there were nearly 370 lakes statewide with requests for permit to 

control swimmer’s itch (Figure 14, Appendix Table H). About 70% of those responding were 

satisfied with the results of treatments to control swimmer’s itch. 

0

200

400

600

800

1000

1200

1400

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 14. Numbers of permits issued for swimmer's itch control, and 

numbers of lakes where permits were issued 1997-2008.

permits

protected waters
Mn DNR, Ecological Resources 24 2008 APM Annual Report May 2009

Lakeshore property owners may get a permit from the DNR that allows the application of copper 

sulfate to the lake for the control of swimmer’s itch. The intent of the copper sulfate application 

is to kill snails that harbor the immature life stage of the fluke that causes swimmer’s itch. 

Individuals receiving a permit to control swimmer’s itch with copper sulfate are generally allowed 

to treat the permitted area 3 times per summer. 

Invasive species control

In addition to oversight (permitting) responsibilities for aquatic plant management efforts 

conducted by individuals to improve access or recreational use, the DNR has statewide control 

programs for three, non-native invasive aquatic plants: curly-leaf pondweed, purple loosestrife, 

and Eurasian watermilfoil. The DNR has recently initiated a pilot project to learn if ecological 

benefits can be attained from lake-wide control of curly-leaf pondweed or Eurasian watermilfoil 

or both. 

Curly-leaf pondweed

Curly-leaf pondweed (Potamogeton crispus) is a non-native invasive, submersed aquatic plant 

species introduced to Minnesota at the turn of the 20th Century. Curly-leaf pondweed is known 

to occur in 752 Minnesota lakes in 70 of the 87 counties in Minnesota. In many lakes this plant 

causes severe recreational nuisances. 

Curly-leaf pondweed’s life cycle is considerably different than native aquatic plants. When 

native aquatic plants are just beginning to grow (mid to late May) curly-leaf pondweed is forming 

dense mats on the lakes surface that can interfere with recreation and the growth of native 

aquatic plants. By mid-summer, (early to mid July) curly-leaf plants begin to die back, which 

results in rafts of dying plants piling up on shorelines. But before the plants die they form 

vegetative propagules called turions (hardened stem tips). New plants sprout from turions in the 

fall (Catling and Dobson, 1985). The die back is often followed by an increase in phosphorus 

(Bolduan et al., 1994) and undesirable algal blooms. These algae blooms interfere with light 

penetration and can also reduce native plant abundance. 

Standard control methods provide relief to lakeshore property owners from the recreational 

nuisances caused by surface mats of curly-leaf pondweed, but have no long-term effect on the 

abundance of the plant. Recent research conducted by the U.S. Army Corps of Engineers 

(ACE) has revealed promising control strategies that may help to reduce the abundance of this 

plant. The key to the new strategies for the control of curly-leaf pondweed is treating the plant 

early in the season (when water temperatures are between 50 and 60 degrees F). If this early 

season treatment strategy is repeated in successive years the turion bank should become 

depleted, resulting in the reduction of overall abundance of the plant, the severity of algae 

blooms, and give native vegetation a competitive advantage. 

Figure 15 shows how interest, reflected by the numbers of permits issued, in curly-leaf 

pondweed control has increased since the completion of the Army Corp of Engineers research 

on early season cold-water control. 

The Department of Natural Resources is conducting early season curly-leaf pondweed 

treatments in cooperation with several lake associations on a trial basis to determine the 

effectiveness of this strategy. In 2008, one lake was treated with the aquatic herbicide fluridone 

and 13 others were treated with Aquathol K. These lakes will be treated and monitored for at 

least three successive years to determine if it is possible to produce ecological benefits such as: 
Mn DNR, Ecological Resources 25 2008 APM Annual Report May 2009

1. Reduce peaks in concentrations of phosphorous and associated algal blooms.

2. Reduce the abundance of curly-leaf pondweed for long periods of time.

3. Increase the abundance of native, submersed aquatic plants.

4. Reduce the interference with use of the lake caused by curly-leaf pondweed.

Figure 16 shows how the development of the pilot project program has influenced the numbers 

of acres of curly-leaf pondweed and Eurasian watermilfoil treated since the programs beginning 

in 2005. 

See the 2008 Invasive Species Program Annual report for more detailed information on this 

project (http://files.dnr.state.mn.us/ecological_services/invasives/annualreport.pdf).

0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 15. Numbers of permits issued for curly-leaf pondweed and 

Eurasian watermilfoil control 1998-2008.

CLP

EWM
Mn DNR, Ecological Resources 26 2008 APM Annual Report May 2009

Purple Loosestrife

Purple loosestrife, a non-native invasive plant that can out compete native wetland vegetation, 

was introduced to North America from Europe in the 1800’s and until 1987 was a common 

ornamental sold by nurseries and landscape companies. Natural resource managers became 

aware of the plant’s invasive nature and disruptive effects on native wetland vegetation in the 

early 1980’s. The DNR, concerned about the plants impact on native species and wildlife 

habitat, conducted preliminary surveys to determine the status of the plant in Minnesota. The 

survey revealed that 77 of Minnesota’s 87 counties had populations of purple loosestrife in 

wetlands, lakeshore, stream banks and ditches. In 1987 Minnesota became one of the first 

states in the nation to develop a program to control this invasive plant. Minnesota has 

designated purple loosestrife as a noxious weed, which makes it illegal to import, buy, sell, 

propagate and transport. 

The main components of the purple loosestrife program are:

An inventory of purple loosestrife sites is maintained and used to prioritize control efforts.

To carry out management activities including chemical and biological control.

To support research to evaluate and expand control efforts.

To monitor and evaluate the success of biological control and other management efforts.

Public education/awareness efforts to involve the public in the management of this plant.

0

1000

2000

3000

4000

5000

6000

7000

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 16. Acres of off-shore curly-leaf pondweed and Eurasian

watermilfoil control 1998-2008.

CLP

EWM
Mn DNR, Ecological Resources 27 2008 APM Annual Report May 2009

Large stands of purple loosestrife are extremely difficult to control because of their enormous 

seed bank; therefore, it is necessary to prioritize purple loosestrife control efforts. The highest 

priority stands for herbicide treatment are small, recently established stands, located near the 

top of the watershed. Because of their small size these newly established sites are poor 

candidates for biocontrol. Rodeo, a broad-spectrum glyphosate herbicide, is used to spot treat 

high priority purple loosestrife sites with a backpack sprayer.

Minnesota’s herbicide control effort has been reduced dramatically since the introduction of biocontrol agents began in 1992. In 2008, DNR staff treated a total of 47 purple loosestrife sites 

with 0.2 gallons of Rodeo herbicide. Most of these sites were very small with the majority 

having fewer than 100 plants. For more detailed information on Minnesota’s purple loosestrife 

program, see the 2008 Invasive Species Annual Program report. 

(http://files.dnr.state.mn.us/ecological_services/invasives/annualreport.pdf)

Eurasian Watermilfoil

Eurasian watermilfoil, hereafter called milfoil, is an exotic aquatic plant introduced to North 

America in the mid-1900’s. It was first identified in Minnesota in 1987 in Lake Minnetonka. 

Milfoil is a submerged aquatic plant that can displace native vegetation. The plant reproduces 

by fragmentation, establishes itself readily in disturbed areas, and has the potential to become a 

nuisance in Minnesota lakes. The main strategies of the Eurasian watermilfoil program are:

Slow the spread of the plant through public education and awareness activities.

Support management by lake associations and local units of government of problems 

caused by milfoil.

Maintain an accurate inventory of populations.

Investigate new control methods and the biology of the plant.

Eurasian watermilfoil was discovered in 12 additional water bodies in 2008. There are now 215

Minnesota lakes known to have populations of this invasive submersed aquatic plant. 

The most commonly used herbicide for control of milfoil is a granular 2,4-D ester product 

labeled for aquatic use. In 2001, a liquid dimethylamine salt 2,4-D product was registered for 

aquatic use and has been applied to milfoil in Minnesota. Late in 2002, a liquid trimethylamine 

salt, triclopyr product, was registered for aquatic use and is available for control of milfoil in 

Minnesota. These systematic herbicides are preferred because they are the most selective 

products available.

The total reported 2,4-D use in 2008 for milfoil was 56,000 pounds. The total reported annual 

use of 2,4-D ester products since 1987 is provided in Figure 17. For more detailed information 

on the management of invasive species see the 2008 Invasive Species Program Annual Report. 

The report may be reviewed on line at 

http://www.dnr.state.mn.us/ecological_services/invasives/index.html.

In 2008, the DNR provided $105,000 in state funds to cooperators on 22 lakes for management 

of milfoil. The DNR spent an additional $17,000 on control work at public water accesses to 

control Eurasian watermilfoil to help minimize its spread between lakes. 
Mn DNR, Ecological Resources 28 2008 APM Annual Report May 2009

References Cited

Blankespoor, H.D., and R.L. Reimink. 1991. The Control of Swimmer’s Itch in Michigan: Past, 

Present, and Future. Michigan Academician XXIV, 7-23.

Bolduan, B.R., G.C. Van Eeckhout, H.W. Quade, and J.E. Gannon. 1994. Potamogeton 

crispus - the other invader. Lake and Reservoir Management 10(2):113-125.

Catling, P.M. and I. Dobson. 1985. The biology of Canadian weeds. 69. Potamogeton crispus 

L. Canadian Journal of Plant Science 65:655-668.

0

20000

40000

60000

80000

100000

120000

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 17. Permitted 2,4-D Ester (lbs.) use in Minnesota after identification of 

Eurasian watermilfoil in Minnesota, 1987-2008
Mn DNR, Ecological Resources 29 2008 APM Annual Report May 2009

APPENDIX

Table: Page_

A A list of commonly used herbicides registered by the EPA for 30

aquatic use and approved by the MN DNR.

B Reported various aquatic herbicide use statewide, 1981-2008. 31

C Aquatic Plant Management Report Survey, Chemical-Mechanical, 32

2008.

D Aquatic Plant Management Report Survey, AUAPCD, 2008. 33

E Aquatic Pesticide Enforcement Citizen Complaint Investigation, 34

2008.

F Aquatic Pesticide Enforcement Use Inspections, 2008. 34

G Statewide numbers of permits and properties by county, 2008. 36

H Lakes with nine or more total permits issued for swimmer’s itch 38

from 1997 through 2008.
Mn DNR, Ecological Resources 30 2008 APM Annual Report May 2009

Table A. A list of commonly used herbicides registered by the EPA for aquatic use and 

approved by the MN DNR.

Product Name Selective

Broad 

Spectrum Active Ingredient (Formulation)

Part 1. Aquatically labeled systemic herbicides.

Aquacide (Pellet)

Navigate (Granular)

Riverdaletm (Granular)

SEE 2,4-D (Liquid)

Weedtrine II (Granular)

Sonar (Liquid or Granular)

Rodeo (Liquid)

Pondmaster (Liquid)

Garlon-3A

X

X

X

X

X

X

X

X

X

2,4 Dichlorophenoxyacetic Acid (Sodium Salt)

2,4 Dichlorophenoxyacetic (Butoxyethyl Ester)

2,4 Dichlorophenoxyacetic (Isooctyl Ester)

2,4 Dichlorophenoxyacetic (Isooctyl Ester)

2,4 Dichlorophenoxyacetic (Isooctyl Ester)

Fluridone

Isopropylamine salt of Glyphosate

Isopropylamine salt of Glyphosate

Triclopyr (Experimental use permit, full aquatic 

label pending)

Part 2. Contact Herbicides.

Aquathol (Liquid or Granular)

Hydrothol 191 (Liquid or Granular)

Reward (Liquid)

X

X

X

Dipotassium salt of endothall

Mono-amine salt of endothall

(liquid by licensed applicator only)

Diquat dibromide

(licensed applicator only)

Part 3. Copper Compounds (Algaecides and Herbicides).

Cutrine Plus (Liquid or Granular)

Komeen (Liquid)

K-Tea

X (A)

X (H)

X (A)

Copper-Ethonalamine complex

Copper-Ethylenediamine complex

Copper-Triethanolamine complex

Part 4. Other.

Copper sulfate

Aquashade (Liquid)

X (A) X CuSO4 (wide variety of registered brands)

Acid Blue 9 / Acid Yellow 23

(Filters light in wavelengths required for plant 

growth)
Mn DNR, Ecological Resources 31 2008 APM Annual Report May 2009

Table B. Reported aquatic herbicide use under DNR permit, 1981-2008.

Year

2,4-D

ester 

lbs.

2,4-D

salt

lbs.

2,4-D 

amine/acid 

gal.

Aquathol

lbs.

Aquathol

gal.

Diquat

(Reward)

gal.

Hydrothol

191

lbs.

Hydrothol

191

gal.

Copper 

sulfate 

lbs.

1981 150 370 0 1,900 1,300 730 3,200 390 *

1982 120 320 0 1,700 1,500 550 4,200 44 *

1983 - 350 0 1,400 1,500 560 11,900 31 *

1984 110 130 0 730 980 780 7,300 80 *

1985 25 270 0 740 1,200 870 14,000 100 *

1986 25 370 0 1,100 1,400 1,200 6,900 170 *

1987 100 1,400 0 1,100 1,400 1,400 13,000 62 *

1988 3.700 600 0 950 1,300 1,300 11,000 100 *

1989 13,000 470 0 910 1,300 1,700 12,000 200 *

1990 23,000 290 0 680 1,100 1,500 9,500 130 *

1991 48,000 1,300 0 1,400 850 1,400 9,600 210 55,400

1992 81,000 320 0 870 1,600 1,700 9,000 67 64,000

1993 96,000 40 0 830 1,000 1,600 5,000 240 34,600

1994 45,000 70 0 710 940 1,800 10,000 510 59,800

1995 80,000 87 0 930 700 2,300 8,300 420 55,000

1996 39,000 400 0 1,000 730 1,900 8,900 830 32,500

1997 46,000 290 0 1,200 700 2,400 7,800 820 39,700

1998 47,000 440 0 790 1,280 2,580 4,460 670 50,800

1999 39,800 650 0 1,050 740 2,280 4,190 740 31,600

2000 41,500 700 0 1,380 1,850 2,970 5,820 530 41,900

2001 49,300 1,000 0 700 2,600 2,700 3,900 950 58,200

2002 49,400 700 20 540 2,660 2,530 4,220 760 42,200

2003 71,100 634 336 339 2,515 2,370 7,610 429 47,100

2004 64,100 1,068 216 366 5,200 2,856 8,040 643 53,700

2005 48,800 1,154 533 1,077 7,054 2,773 6,744 715 63,500

2006 53,400 805 215 1,530 8,757 2,953 11,653 126 47,000

2007 57,700 971 85 1,320 9,838 3,685 10,105 782 46,000

2008 56,000 655 7.4 2,462 13,208 2,643 10,693 550 32,290

* Data not available
Mn DNR, Ecological Resources 32 2008 APM Annual Report May 2009
Mn DNR, Ecological Resources 33 2008 APM Annual Report May 2009
Mn DNR, Ecological Resources 34 2008 APM Annual Report May 2009

Table E. Aquatic Pesticide Enforcement Citizen Complaint Investigations, 2008.

Date Complaint Lake Name County Observation Action Result

June 10 Fish die off. Prior Lake Scott Not observed Small sunfishcrappie die off 

reported several 

days after the 

fact.

Fish 

decomposition 

too far 

advanced for 

analysis.

June 8 No posting 

following 

herbicide 

treatment.

Jennings Bay, 

Mtka.

Hennepin Inspected 

6/9/2008. One 

sign posted near 

access to marina. 

Posting was

inadequate.

Referred to area 

APM Specialist.

Pending

July 9 Unauthorized 

herbicide 

treatment.

Forest Lake Washington Aquatic Pesticide 

Enforcement staff.

Observation 

reported to 

conversation 

Jason Jenson.

Jason Jenson 

was unable to 

determine the 

person’s 

involved.

August 20 Unauthorized

herbicide 

treatment.

Blue Lake Isanti Aquatic Pesticide

Enforcement staff.

Referred to area 

APM Specialist.

Over treatment 

of a permitted 

area. Referred 

to area CO.

Table F. Aquatic Pesticide Enforcement Use Inspections, 2008.

Treatment

Date County Lake Applicator

Number of 

Treatments 

Inspected

23-Apr Ramsey Kohlman Lake Restoration 1

5-May Ramsey Bald Eagle Lake Restoration 1

8-May Crow Wing Lower Mission Professional Lake Management 1

8-May Isanti Long Lake Restoration 2

13-May Chisago Green Green Lake Association 2

14-May Hennepin Sarah Lake Restoration 2

14-May Sherburne Rush Lake Management 1

15-May Morrison Crookneck Professional Lake Management 1

16-May Ramsey Silver (nsp) Aquatic Engineering, Inc. 2

19-May Douglas Smith Professional Lake Management 1

19-May Stearns Grand Lake Management 1

21-May Cass Margaret Professional Lake Management 1

22-May Morrison Long Professional Lake Management 1

23-May Stearns Kings Professional Lake Management 1

28-May Cass Norway Professional Lake Management 1

28-May Crow Wing Sibley Professional Lake Management 1

30-May Hennepin Bass Lake Management 2
Mn DNR, Ecological Resources 35 2008 APM Annual Report May 2009

Table F. Continued

Treatment

Date County Lake Applicator

Number of 

Treatments 

Inspected

2-Jun Chisago Rush (west) Lake Restoration 2

4-Jun Washington White Bear Professional Lake Management 1

10-Jun Ramsey Gervais Lake Improvement Consulting 2

16-Jun Todd Little Birch Professional Lake Management 2

17-Jun Wright Clearwater Clearwater Lake Property Owners 2

18-Jun Hennepin Mtka Priest Lake Management 2

19-Jun Wright Augusta Lake Augusta Property Owners 2

20-Jun Morrison Alexander Professional Lake Management 1

23-Jun Sherburne Long Professional Lake Management 2

24-Jun Todd Mound Minnesota Shoreline Restoration 2

26-Jun Carver Mound Midwest Aquacare 2

9-Jul Washington Forest Lake Management 2

10-Jul Dakota Crystal Lake Restoration 2

17-Jul Anoka Coon Lake Restoration 2

21-Jul Hennepin Mtka Gideons Lake Management 2

23-Jul Carver Lotus Midwest Aquacare 2

30-Jul Crow Wing Upper Mission Professional Lake Management 1

31-Jul Mille Lacs Mille Lacs Midwest Aquacare 1
Mn DNR, Ecological Resources 36 2008 APM Annual Report May 2009

Table G. Statewide numbers of permits and properties by county, 2008.

County Properties Permits

Aitkin 197 156

Anoka 156 56

Becker 255 255

Beltrami 23 23

Benton 24 4

Big Stone 1 1

Blue Earth 3 3

Carlton 52 52

Carver 329 80

Cass 368 261

Chisago 380 86

Clay 8 8

Clearwater 3 3

Cottonwood 2 2

Crow Wing 1,086 678

Dakota 329 59

Douglas 228 228

Faribault 55 2

Freeborn 6 6

Grant 11 11

Hennepin 1,860 375

Hubbard 55 55

Isanti 134 40

Itasca 47 47

Jackson 6 6

Kanabec 34 8

Kandiyohi 100 86

Koochiching 1 1

Lake of the Woods 1 1

LeSueur 197 42

Lincoln 2 2

McLeod 40 4

Mahnomen 5 5

Martin 8 8

Meeker 159 29

Mille Lacs 60 21
Mn DNR, Ecological Resources 37 2008 APM Annual Report May 2009

Table G. (Continued)

County Properties Permits

Morrison 209 101

Murray 2 2

Nicollet 1 1

Nobles 1 1

Olmsted 2 2

Ottertail 571 571

Pennington 1 1

Pine 214 54

Pipestone 1 1

Polk 8 8

Pope 59 59

Ramsey 807 78

Rice 156 24

Rock 2 2

St. Louis 106 53

Scott 400 65

Sherburne 210 52

Stearns 254 120

Steele 2 2

Todd 175 131

Wadena 10 10

Waseca 13 6

Washington 485 115

Watonwan 1 1

Wright 826 235
Mn DNR, Ecological Resources 38 2008 APM Annual Report May 2009

Table H. Lakes with nine or more total permits issued for swimmer’s itch from 1997 through

2008.

Region County Lake Total permits issued

1 Becker Detroit 22

1 Becker Height of Land 11

1 Becker Sallie 10

1 Beltrami Julia 10

1 Clay Blue Eagle 12

1 Douglas Carlos 20

1 Douglas Darling 24

1 Douglas Geneva 13

1 Douglas Ida 44

1 Douglas Irene 69

1 Douglas Le Homme Dieu 50

1 Douglas Miltona 43

1 Grant Pelican 15

1 Grant Pomme De Terre 11

1 Hubbard Alice 10

1 Hubbard Big Sand 21

1 Hubbard Fishhook 11

1 Otter Tail East Battle 19

1 Otter Tail Rush 20

1 Otter Tail Stalker 10

1 Otter Tail Wall 24

1 Pope Amelia 24

1 Pope Linka 46

1 Pope Minnewaska 22

1 Pope Scandinavian 12

2a Carlton Eagle 39

2a Carlton Tamarack 11

2a Itasca Bowstring 10

2a Itasca Jessie 12

2a Itasca Sand 14

2a Itasca Swan 91

2a St. Louis Big Sturgeon 13

2a St. Louis Long 16

2b Aitkin Big Sandy 27

2b Aitkin Cedar 11

2b Aitkin Farm Island 94

2b Aitkin Gun 35

2b Aitkin Hanging Kettle 10

2b Aitkin Minnewawa 27
Mn DNR, Ecological Resources 39 2008 APM Annual Report May 2009

Table H. Continued.

Region County Lake Total permits issued

2b Aitkin Pine 15

2b Aitkin Pine 18

2b Aitkin Round 20

2b Aitkin Spirit 22

2b Cass Birch 13

2b Cass Gull 280

2b Cass Margaret 12

2b Cass Roosevelt 50

2b Crow Wing Clark 13

2b Crow Wing Crooked 15

2b Crow Wing Cross 76

2b Crow Wing Crow Wing 67

2b Crow Wing Daggett 46

2b Crow Wing Edward 14

2b Crow Wing Gilbert 71

2b Crow Wing Gladstone 15

2b Crow Wing Hubert 19

2b Crow Wing Island 17

2b Crow Wing Little Hubert 19

2b Crow Wing Little Pine 35

2b Crow Wing Love 18

2b Crow Wing Lower Cullen 35

2b Crow Wing Lower Hay 26

2b Crow Wing Lower Mission 28

2b Crow Wing Middle Cullen 11

2b Crow Wing Nisswa 27

2b Crow Wing North Long 92

2b Crow Wing O’Brien 39

2b Crow Wing Ossawinnamakee 34

2b Crow Wing Pelican 36

2b Crow Wing Perch 49

2b Crow Wing Pig 17

2b Crow Wing Pine 19

2b Crow Wing Portage 16

2b Crow Wing Red Sand 18

2b Crow Wing Rice 27

2b Crow Wing Round 129

2b Crow Wing Roy 52

2b Crow Wing Rush 68
Mn DNR, Ecological Resources 40 2008 APM Annual Report May 2009

Table H. Continued.

Region County Lake Total permits issued

2b Crow Wing Serpent 104

2b Crow Wing Sibley 18

2b Crow Wing South Long 89

2b Crow Wing Upper Cullen 14

2b Crow Wing Upper Hay 65

2b Crow Wing Upper Mission 25

2b Crow Wing Upper South Long 51

2b Crow Wing West Fox 15

2b Crow Wing White Sand 41

2b Crow Wing Whitefish 130

2b Mille Lacs Mille Lacs 32

3a Anoka Centerville 11

3a Anoka Coon 66

3a Carver Minnewashta 73

3a Carver Pierson 47

3a Carver Riley 38

3a Carver Virginia 30

3a Carver Waconia 31

3a Carver Wassermann 10

3a Carver Zumbra 15

3a Chisago Chisago 35

3a Chisago Fish 18

3a Chisago Goose 16

3a Chisago Green 64

3a Chisago Horseshoe 10

3a Chisago Kroon 16

3a Chisago Little Comfort 12

3a Chisago North Lindstrom 12

3a Chisago Rush 64

3a Chisago South Center 75

3a Chisago South Lindstrom 33

3a Dakota Marion 28

3a Dakota Orchard 23

3a Dakota Salem 13

3a Hennepin Bass 11

3a Hennepin Bryant 31

3a Hennepin Bush 12

3a Hennepin Castle Ridge 11

3a Hennepin Christmas 29
Mn DNR, Ecological Resources 41 2008 APM Annual Report May 2009

Table H. Continued.

Region County Lake Total permits issued

3a Hennepin Duck 21

3a Hennepin Dutch 14

3a Hennepin Eagle 47

3a Hennepin Fish 36

3a Hennepin Forest 20

3a Hennepin Gleason 28

3a Hennepin Greentree Pond 11

3a Hennepin Hadley 13

3a Hennepin Independence 52

3a Hennepin Long 17

3a Hennepin Lower Twin 14

3a Hennepin Medicine 68

3a Hennepin Melody 12

3a Hennepin Minnetonka Cooks 65

3a Hennepin Mtka Jennings 43

3a Hennepin Mtka Lafayette 69

3a Hennepin Mtka Lower Lake N 27

3a Hennepin Mtka Lower Lake S 44

3a Hennepin Mtka Maxwell 46

3a Hennepin Mtka North Arm 68

3a Hennepin Mtka Phelps 59

3a Hennepin Mtka Priests 55

3a Hennepin Mtka Robinsons 26

3a Hennepin Mtka Upper Lake 56

3a Hennepin Mtka Seton 17

3a Hennepin Mtka Smiths 14

3a Hennepin Mtka Smithtown 48

3a Hennepin Mtka Spring Park 35

3a Hennepin Mtka St. Albans 59

3a Hennepin Mtka St. Louis 19

3a Hennepin Mtka Stubbs 28

3a Hennepin Mtka Wayzata 44

3a Hennepin Mtka West Arm 44

3a Hennepin Parkers 27

3a Hennepin Rebecca 12

3a Hennepin Red Rock 45

3a Hennepin Round 10

3a Hennepin Sarah 62

3a Hennepin Schmidt (Smith) 18
Mn DNR, Ecological Resources 42 2008 APM Annual Report May 2009

Table H. Continued.

Region County Lake Total permits issued

3a Hennepin Shady Oak 11

3a Hennepin Weaver 22

3a Hennepin Wrestling (Unnamed) 12

3a Ramsey Bald Eagle 58

3a Ramsey Gervais 29

3a Ramsey Gilfillan 19

3a Ramsey Island 12

3a Ramsey Johanna 25

3a Ramsey Josephine 28

3a Ramsey Keller 11

3a Ramsey Kerry Pond 12

3a Scott Fish 16

3a Scott O’Dowd 31

3a Scott Prior 128

3a Scott Spring 29

3a Scott Thole 28

3a Scott Upper Prior 65

3a Washington Big Carnelian 51

3a Washington Big Marine 34

3a Washington Demontreville 12

3a Washington Forest 161

3a Washington Jane 17

3a Washington Lily 12

3a Washington Mary 11

3a Washington Olson 12

3a Washington Pine Tree 10

3a Washington Tanners 17

3a Washington White Bear 94

3b Isanti Blue 30

3b Isanti Fannie 25

3b Isanti Long 16

3b Isanti Paul 21

3b Isanti Spectacle 13

3b Kanabec Fish 22

3b Kanabec Mud 14

3b LeSueur Tetonka 24

3b LeSueur Washington 45

3b Morrison Alexander 64

3b Morrison Crookneck 51
Mn DNR, Ecological Resources 43 2008 APM Annual Report May 2009

Table H. Continued.

Region County Lake Total permits issued

3b Morrison Fish Trap 33

3b Morrison Platte 122

3b Morrison Shamineau 17

3b Morrison Sullivan 17

3b Pine Cross 34

3b Pine Sand 10

3b Pine Upper Pine 13

3b Pine/Aitkin Big Pine 49

3b Sherburne Big 34

3b Sherburne Briggs 15

3b Sherburne Fremont 18

3b Sherburne Julia 14

3b Wright Charlotte 25

3b Wright Clearwater 114

3b Wright Crawford 11

3b Wright Deer 16

3b Wright French 24

3b Wright Maple 45

3b Wright Mink 10

3b Wright North Center 48

3b Wright Pleasant 35

3b Wright Pulaski 39

3b Wright Rock 19

3b Wright Somers 12

3b Wright Sugar 71

3b Wright Sylvia 49

3b Wright Waverly 31

4 Benton Little Rock 12

4 Faribault Bass 15

4 Kandiyohi Elkhorn 11

4 LeSueur Tetonka 24

4 LeSueur Washington 45

4 Rice Mazaska 11

4 Rice Roberds 16

4 Stearns Big Fish 15

4 Stearns Big Spunk 23

4 Stearns Grand 22

4 Stearns Koronis 19

4 Stearns North Browns 14
Mn DNR, Ecological Resources 44 2008 APM Annual Report May 2009

Table H. Continued.

Region County Lake Total permits issued

4 Stearns Pearl 24

4 Stearns Pelican 30

4 Stearns Rice 37

4 Waseca Clear 14
Mn DNR, Ecological Resources 45 2008 APM Annual Report May 2009

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