Eyes on the Lake
This feature will help us all with learning what plants are native and healthy for our lakes vs. the invasive plants. We hope you find this information helpful. Thanks for helping to keep our waters clean.
Slowing the Spread
Our AIS Efforts are Working
In 2014 Minnesota started allocating funds to Counties for efforts to control Aquatic Invasive Species (AIS). That funding has made a major contribution to reducing the spread of AIS across Minnesota. Since the County AIS funding came online the rate of new infestations in Minnesota has declined by almost 50%.
Looking at AIS of all types the peak of new infestations was 2012 through 2014 with an average of 93 lakes being listed as infested in each of those years. In the most recent three years of 2021 through 2023 we saw an average of only 56 lakes listed as newly infested in each of those years. There has been a trend of fewer infestations each year for the past five years and in 2023 only 42 lakes were listed down from the peak of 118 new infestations in 2012.
Looking specifically at zebra mussels the story is even better. The peak of zebra mussel infestations in Minnesota was 2014 with 67 lakes listed that year as newly infested. Since then the rate of new zebra mussel infestations has dramatically dropped with only 28 lakes being listed in 2023. In Cass County only 13 lakes with public accesses have been listed as zebra mussel infested out of the 103 lakes with public accesses. Only 12.6% of publicly accessible lakes in Cass County are infested with zebra mussels.
Through the efforts of local groups and individual water users we have made a dramatic change in the spread of AIS across Minnesota. We have shown that by working together to implement AIS inspections, education, and outreach we can reduce the spread of AIS across Minnesota. The rate of AIS spread across Minnesota is a function of the behavior of each of us individually. Let’s all commit to continue reducing the spread of AIS and redouble our efforts to preserve Minnesota’s lakes for future generations.
Steve Henry
AIS Lake Technician
PO Box 3000/303 Minnesota Ave W, Walker, MN 56484
steve.henry@casscountymn.gov
(218)-536-0584
AIS Explorer
How 10,000+ Lakes Are Protected with Limited Resources
After five years of development, researchers at the Minnesota Aquatic Invasive Species Research Center (MAISRC) released an online dashboard in 2021 that predicts the introduction risk of aquatic invasive species (AIS) and identifies the optimal placement of watercraft inspection locations for waterbodies across Minnesota – AIS Explorer. Based out of the University of Minnesota, an extensive network was created that explains how Minnesota boaters travel between waterbodies. This tool helps Minnesota’s resource managers prioritize their AIS prevention efforts, and maximize efforts with limited resources.
The prioritization for watercraft inspections is run at the county-level and considers the movement of boats into, within, and out of an individual county paired with “risky” boats—the predicted number of boats moving from an infested waterbody to an uninfected waterbody.
AIS Explorer is utilized by the Cass County AIS Program to assist with determining the number of AIS watercraft inspector hours to be scheduled for the various lakes. This tool helps to rank the lakes within the county that should be prioritized for watercraft inspections, as well as visualizes the point of diminishing returns from added inspections and provides a figure that displays the optimal balance of inspections to maximize the number of intercepted risky boats.
The AIS Explorer is easy to use and available for all. Users can focus on any lake in Minnesota. Not only will you see the overall risk score for potential future infestation, but it’s also possible to see the incoming and outgoing network of boater activity.
Summary data from our lakes: (Overall risk score: 1.0 indicates lake is infested)
Little Boy Wabedo
Risk Score: Overall: 0.3865 Risk Score: Overall: 0.3535
Boater Network: Boater Network:
Incoming infested: 25.5% Incoming infested: 27.4%
Incoming non-infested: 74.5% Incoming non-infested: 72.6%
Outgoing Infested: 13.1% Outgoing infested: 13.6%
Outgoing non-infested: 86.9% Outgoing non-infested: 86.4%
The AIS Explorer dashboard is free and open to the public at www.aisexplorer.umn.edu. Funding for AIS Explorer was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Minnesota Aquatic Invasive Species Research Center (MAISRC) and the Legislative-Citizen Commission on Minnesota Resources (LCCMR).
For more information: www.maisrc.umn.edu/aisexplorer
Is It Curly-leaf Pondweed or Clasping-leaf Pondweed?
Curly-leaf (non-native/invasive)
Keys to identify the 2 types of pondweed:
Thin, submerged leaves with distinct “teeth”/wavy edges.
Leaves don’t clasp around stem where they connect.
Generally, first pondweed to come up in the spring.
In waters up to 15 feet deep.
Dies back in the summer.
Turions look like small, greenish-brown pinecones.
Clasping-leaf (native)
Leaves are wide and wavy without "teeth"
Leaves clasp around stem
Leaves alternate along the stem
In waters up to 12 feet deep.
Curly-leaf pondweed impacts:
In spring, curly-leaf pondweed can interfere with recreational and other uses of lakes and rivers by producing dense mats at the water’s surface.
Matted curly-leaf pondweed can displace native aquatic plants.
When curly-leaf pondweed dies back in the summer, the dense mats decay and release nutrients into the water column which contribute to algal blooms. The decomposing plant material can also deplete oxygen levels in the water, causing anoxic conditions leading to possible fish kills.
Curly-leaf pondweed is native to Eurasia, Africa, and Australia. It was likely introduced when common carp were intentionally introduced into Midwest waters as a game fish in the 1880’s. The species was likely spread through the movement of watercraft and water-related equipment. It was first noted in Minnesota around 1910. It is known to be present in more than 750 lakes in 70 of the 87 counties in Minnesota.
Curly-leaf pondweed is classified as prohibited invasive species in Minnesota. It is illegal to possess, buy, sell, transport, and introduce a prohibited invasive species.
Neither Little Boy nor Wabedo lakes are known to have curly-leaf pondweed, however we do have the native clasping-leaf pondweed. Broad-leaf pondweeds, e.g., clasping-leaf pondweed, provide excellent habitat for panfish, largemouth bass, muskellunge, and northern pike; bluegills nest near these plants and eat insects and other small animals found on the leaves; walleyes use these pondweeds for cover.
Credits:
Aquatic Invasive Species Identification Guide for Minnesota, www.maisrcumn.edu.
MN DNR website
Siberian Pea shrub
Siberian Pea shrub has been identified growing along the shore of Wabedo Lake. Ideally, these shrubs should be removed, or at minimum, not allowed to spread. If you suspect you have Siberian pea shrub on your property, contact us at wlbcrlakes@gmail.com or Cass County or the Minnesota Department of Natural Resources for assistance in identification and management. Siberian Pea shrub is listed as a Restricted Noxious Weed – propagation, importation, transport and sale of the plant are prohibited in Minnesota.
Keys to identify:
Small or large shrub (woody stems) up to 18 feet tall
Alternate, compound leaves with an even number of leaflets, usually 8-12
Yellow flowers in May and June
Long seed pods that are green in summer, then turn brown, curl, open and release seed in the fall
Impacts:
Outcompetes native vegetation
As a legume, the plant fixes nitrogen in the soil, altering soil chemistry and making the soil less hospitable to native plants
Looks similar to:
Honey locust (native) – Honey locust is a tree with leaves that look similar to Siberian peashrub leaves. Honey locust leaves can be once or twice compound and have 18-28 leaflets per leaf on once compound leaves and up to 150 leaflets on twice compound leaves. Siberian peashrub has 8-12 leaflets per leaf. Honey locust flowers are white and Siberian peashrub flowers are yellow.
Bristly locust (invasive) – Bristly locust has pink flowers and has stems covered in red bristles.
Forsythia (non-native) – Forsythia have yellow flowers with four petals and simple, oval-shaped leaves, not compound leaves with multiple leaflets as Siberian peashrub has.
How to eradicate:
Pull up or dig up small or medium shrubs getting as many roots as possible
Cut down large shrubs, then paint the stump with herbicide
Plant these natives instead:
Red osier dogwood (Cornus sericea) or gray dogwood (Cornus racemosa)
Chokecherry (Prunus virginiana)
Bush honeysuckle (Diervilla lonicera)
Nannyberry (Viburnum lentago)
American hazelnut (Corylus americana)
Credits and for more information on eradication and control:
Photographs: Minnesota Department of Agriculture, MinnesotaWildflowers.info
http://extension.umn.edu/identify-invasive-species/siberian-peshrub
http://www.dnr.state.mn.us/invasives/terrestrialplants/woody/siberianpeashrub.html
http://extension.umn.edu/planting-and-growing-guides/woody-vegetation-control
Rusty Crayfish and Chinese Mystery Snail
Chinese mystery snails and rusty crawfish are both present in Little Boy and Wabedo. Although they are considered to be invasive species, a lake isn’t identified as “infested” when these species are present. According to the MN DNR they are regulated invasives.
What does it mean if it is a regulated invasive species? In Minnesota, it means it is legal to possess, sell, buy, and transport, but it may not be introduced into a free-living state, such as being released or planted in public waters.
Rusty Crayfish
Rusty crawfish were likely introduced and spread through the improper use and disposal of live bait. The species is also commonly imported and sold by the aquarium trade, and to schools by biological supply houses, leading to the potential for illegal release into the wild. The first established population in Minnesota was in Lake Superior in the late 1990s.
Rusty crayfish are omnivores, consuming many food sources such as plants, animals, organic material, sediment, etc.
There is no known population control for rusty crayfish in natural water bodies at this time. Trapping may reduce numbers but would likely not have a significant impact on the population. Increasing fish predator numbers, either through regulation and/or stocking, has shown potential for reducing crayfish populations.
Keys to Identify:
All crayfish resemble miniature lobsters with long antennae, a pair of claws, and 8 legs.
Light to dark brown body.
Red spots on the sides of carapace.
Has larger, more robust claws than native crayfish species.
Claws have dark black bands on the tips.
Can grow up to 5” long.
Impacts:
Destruction of aquatic plant beds.
Aggressive displacement of native crayfish species.
Breeds with native crayfish, replacing native crayfish populations with hybrids.
Competes with fish for prey and consumes fish eggs.
Credits: AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu.
MN DNR website: https://www.dnr.state.mn.us/invasives/index.html
Chinese Mystery Snail
Chinese Mystery Snails:
The Chinese mystery snail grazes on lake and river bottom material. They are called “mystery” snails because females give birth to young, fully developed snails that suddenly and “mysteriously” appear.
They are spread primarily through movement of water-related equipment and illegal release of aquarium pets. It is illegal to release or dispose of unwanted aquatic plants or animals in or near public waters.
There is no known effective population control for Chinese mystery snails in natural water bodies at this time.
Keys to Identify:
Large, smooth, tan to brown shell that can grow 2-3” long.
Shell lacks banding and can have 6–7 whorls.
Snails have an operculum (structure that functions much like a lid or “trapdoor”) with distinct growth rings.
An operculum is not likely to be present in dead specimens.
Impacts:
Can die-off in large numbers, fouling beaches and shoreland.
Looks similar to:
Zebra mussels and quagga mussels
Native snails and mussels
Credits: AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu.
MN DNR website: https://www.dnr.state.mn.us/invasives/index.html
Purple Loosestrife (Lythrum salicaria)
What Is It?:
A prohibited invasive aquatic plant/terrestrial.
Is on the control noxious weed list meaning you must prevent the spread of this plant, and that it should be reported.
Where is it Found?
It can invade many wetland types including wet meadows, stream banks, pond or lake edges and ditches.
Keys to Identify:
Flowers are purple-pink bloom in tall spikes.
Blooms from early July through September, and then goes to seed.
Flowers typically have 6 petals. Multiple rings of flowers boom at once from the bottom of the spike to the top.
Can grow 3-7 feet tall with multiple stems growing from a single rootstock. Bushy appearance.
Stem is stiff, typically square shaped.
Leaves are opposite or whorled with smooth edges.
Roots are a large, woody taproot with rapidly extending fibrous rhizomes.
Impact of Purple Loosestrife and Why Does It Matter:
It is exceedingly aggressive and can overtake native plants very quickly.
Creates dense growth along shoreland areas making it difficult to access open water.
How It Grows and Spreads:
Spreads primarily by seeds which are tiny. Up to 300,000 seeds produced per stem each year and are viable for up to 20 years.
Through the movement of water-related equipment and uninformed release of garden plants.
Seeds can be hidden in mud and debris, and can stick to boots, waders, and other fishing and hunting gear. Roadside maintenance equipment can also spread this plant and its seeds.
How to Prevent:
Follow the “Play, Clean, Go” best management practices:
Remove plants, animals, and mud from your boots, gear, boat, and trailer
Clean your gear before entering and leaving a recreation site
Drain bilge, ballast, wells and buckets before leaving the area
Dry equipment before launching into another body of water
Dispose of unwanted bait in a sealed container
Use certified or local firewood and hay
Management can include chemical, mechanical, mowing/hand-cutting and biocontrol treatments.
Report new occurrences of purple loosestrife to the DNR immediately by contacting our regional DNR Invasive Species Specialist: Nicole Kovar, Park Rapids DNR, 218-616-8102, nicole.kovar@state.mn.us.
Look-alike Native Plants:
Blue Vervain
Fireweed
Credits:
MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticplants/purpleloosestrife/index.html
University of Minnesota Extension: www.extension.umn.edu
Photo Credit:
Minnesota Wildflowers: www.minnesotawildflowers.org
For more information:
Restore Your Shore – MN DNR: https://www.dnr.state.mn.us/rys/index.html
Score Your Shore – MN DNR: https://www.dnr.state.mn.us/scoreyourshore/index.html
Play-Clean-Go: https://www.playcleango.org/help-stop-invasive-species-with-playcleango
Spiny Waterflea (Invasive)
What Is It?:
Microscopic freshwater zooplankton that can decimate populations of other native zooplankton resulting in a decreased food source for native fish and an increase in algal blooms.
Keys to Identify:
Range in size from 1/4 to 5/8 of an inch.
Have a single long tail with 1-4 barbs, which helps them avoid predation.
Opaque in color.
Have distinctive black eyespots.
Most abundant during late summer & autumn.
Where to Look:
Most often found on fishing line.
When they are grouped together, as ensnared on fishing lines and cables, they collect and form gelatinous globs with a texture of wet cotton.
Nearby Lakes with Spiny Waterfleas:
First found in Lake Superior in 1987; and first discovered in inland Minnesota lakes in Island Lake Reservoir north of Duluth in 1990.
Lake Vermillion, Lake Milles Lacs, Lake of the Woods
MN DNR infested waters website for more info: https://www.dnr.state.mn.us/invasives/ais/infested.html
How to prevent Spiny Waterflea:
Because recreational boaters and anglers can inadvertently move them or their eggs on fishing line, bait buckets, live wells, or fishing nets, it’s so important to follow MN AIS laws:
o Clean watercraft of all aquatic plants and prohibited invasive species.
o Drain all water, including livewells and bait water. Remove boat drain plugs; keep them out during transport.
o Dispose of unwanted bait in the trash.
o Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.
Credits:
MN AIS Research Center (MAISRC): https://www.maisrc.umn.edu/about-spinywaterflea
AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu
MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticanimals/spinywaterflea/index.html
For More Information:
MAISRC spiny waterflea research: https://www.maisrc.umn.edu/spinywaterflea-research
Zebra Mussels
Keys to identify:
Stripes are generally in zigzag patterns
Pattern is variable; some may lack striping altogether and can be solid tan or brown
Have a flat edge and won’t topple over when set on its edge
Shells form straight light when closed
Range from 1/8 of an inch to 2 inches; adults are typically fingernail sized.
Looks similar to:
Other invasive invertebrates: Quagga mussels, Asian clams & Chinese mystery snails.
Native invertebrates: native snails and native mussels.
Where to look:
Often found attached to submerged objects (such as boats and docks, as well as plants and rocks)
Newly settled mussels are usually in shallow areas; adults are common in depths of 10-20 feet.
Zebra Mussel Impact:
Encrusts equipment, such as boat motors and hulls, which reduces performance and efficiency, and is costly to clean and repair
Swimmers and pets can cut their feet on zebra mussels attached to rocks, docks, swim rafts and ladders
Creates a costly problem for power plants, cities and residents when they clog water intakes.
Filters tiny food particles out of the water, which can reduce available food for larval fish and other animals, and can increase aquatic plant growth as a result of increased water clarity.
Attaches to and kill native mussels.
What we should know:
A single zebra mussel can filter one quart of water per day while feeding primarily on algae.
A female can produce 100,000 to 500,000 eggs per year. Fertilized eggs develop into microscopic, free-living larvae, called "veligers," that form shells. After two to three weeks, the veligers settle and attach to a firm surface using tiny fibers called byssal threads. Beds of zebra mussels can reach tens-of-thousands within a single square yard.
Microscopic larvae (veligers) can survive in water contained in bait buckets, live wells, bilge areas, ballast tanks, motors and other water containing devices.
Zebra mussels are unintentionally spread through the movement of water-related equipment, attaching to boats, docks, swim rafts and boat lifts, as well as aquatic plants.
Adult mussels can survive out of water – less than 5 days in dry conditions, but up to 21 days in very wet conditions (such as, inside dock/lift pipes).
It is a prohibited invasive species and it is unlawful (a misdemeanor) to possess, import, purchase, transport, or introduce this species except under a permit for disposal, control, research, or education.
How to prevent zebra mussels:
Clean watercraft of all aquatic plants and prohibited invasive species.
Drain all water, including live wells and bait water. Remove boat drain plugs; keep them out during transport.
Dispose of unwanted bait in the trash.
Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.
Credits:
AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu
MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticanimals/zebramussel/index.html
Eurasian Milfoil
Is It Eurasian Milfoil or Northern Milfoil?
Eurasian watermilfoil looks similar to many native, beneficial watermilfoils found in Minnesota lakes and rivers. Its common native look-alike is northern watermilfoil. It’s spread primarily through the movement of water-related equipment. Plant fragments can get tangled on boats, trailers, motors, anchors and other water-related equipment. All it takes is a single plant fragment to start a new population. It is a prohibited invasive species in Minnesota, which means it is unlawful (a misdemeanor) to possess, import, purchase, transport or introduce these species except under a permit for disposal, control, research or education.
Eurasian watermilfoil impacts:
Dense mats at the water’s surface inhibit water recreationists.
Overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity.
Provides unsuitable shelter, food, and nesting habitat for native animals.
Keys to Identifying the 2 Types of Milfoil
EURASIAN NORTHERN
Featherly looking with 4 leaves per whorl
Leaves have central axis with 12-20 leaflet pairs
Can grow up to 10 feet long
Produces pink & white flowers on spike above surface
Flowers 2x/year; usually mid-June & late-July
Leaves become limp when taken out of water
Grows best in 3-15 feet
4 leaves per whorl
Leaves have central axis
Each leaf has 4-11 leaflet pairs
Forms winter bud in late fall and winter
Leaves are rigid when taken out of water
Grows underwater in depths of up to 20 feet
Credits:
AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu
MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticplants/milfoil/index.html
Starry Stonewort
Keys to Identify:
Bushy, bright green macro-algae. It produces a characteristic star-shaped bulbil.
Small, white star-shaped bulbils form on clear threads at base of plant (asexual reproductive structure). May be found above or below the sediment surface – bulbils are the size of a grain of rice.
Small, orange spheres may be visible near the tips of the structure (male reproductive structures called antheridia).
Long, smooth branchlets are attached in whorls of 5-8 and branch asymmetrically at tips.
Stems are smooth.
Branchlets typically form several inches long – longer than Chara or Nitella (native aquatic grasses).
Can fill water column and form surface mats.
Looks similar to the follow native species:
Other native stoneworts and muskgrasses that are beneficial grass-like algae, and are found in Minnesota lakes and rivers.
Look-alike natives: Chara; Nitella; Sago pondweed; Water stargrass.
Where to look:
In shallow, still water and near accesses.
Starry Stonewort Impacts:
Dense mats at the water’s surface inhibit waterways and clog boat propellers, as well as water recreation.
Overtakes habitat and out-competes native aquatic plants, potentially lowering diversity.
Provides unsuitable shelter, food, and nesting habitat for native fish and wildlife.
No known herbicides will kill it. Mechanical harvesting is used to remove it and stop it from spreading.
What we should know:
Believed to be spread from one body of water to another by the unintentional transfer of bulbils, the star-like structures produced by the plant. These fragments are most likely attached to trailered boats, personal watercraft, docks, boat lifts, anchors or any other water-related equipment that was not properly cleaned.
First discovered in Minnesota in August 2015 on Lake Koronis near Paynesville in Stearns County.
13 Minnesota counties have infested lakes, including Cass and Itasca (Lake WInnibigoshish, 2016) and Beltrami County (Lake Beltrami, 2019; Wolf, 2018; Upper Red Lake, 2016; Cass, 2016)
How to prevent starry stonewort:
Clean watercraft of all aquatic plants and prohibited invasive species.
Drain all water, including livewells and bait water. Remove boat drain plugs; keep them out during transport.
Dispose of unwanted bait in the trash.
Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.
Credits:
AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu.
MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticanimals/zebramussel/index.html.
MN DNR infested waters: https://www.dnr.state.mn.us/invasives/ais/infested.html.