The swan posing beside the dock. The beetles treating your roses like a salad bar. That stubborn green wall at the edge of the woods. Some of Wisconsin’s most familiar scenery has a surprisingly foreign backstory.
These 25 introduced species are already established somewhere in Wisconsin, but their footprints and damage vary widely. Here’s how they got here, what makes them troublesome, and which familiar neighbors deserve a second look on your next walk or lake trip.
Birds that made themselves at home
1. Mute Swan
It looks like the finishing touch on an expensive pond: white feathers, an elegant neck, and absolutely no interest in sharing. The mute swan’s ornamental appeal helped bring this Eurasian bird to North America in the late 1800s.
Escaped and released birds established wild populations. Wisconsin’s breeding birds are concentrated mainly in the southeast, with seasonal visitors also reaching northeastern waters from Michigan.
Mute swans pull up aquatic plants while feeding, sometimes disturbing more than they eat. Territorial pairs can also drive other waterbirds away from nesting and feeding areas, turning an attractive shoreline into a rather exclusive club.
Look for the orange bill and black knob at its base. Wisconsin’s native trumpeter and tundra swans have black bills; their comeback and migrations are very different stories.
2. European Starling
Watch a starling closely and the plain dark bird becomes a little show-off: purple-green shine, speckles, whistles, and borrowed bird calls.
People deliberately brought starlings to North America during the 1800s. Several introductions failed, but New York releases helped establish the population that spread across the continent. Their familiarity around Wisconsin farms and towns disguises that relatively recent arrival.
The trouble comes with numbers and competition. Starlings crowd feeders, occupy nesting cavities, and gather in large roosts that leave buildings and nearby surfaces thoroughly decorated. Wisconsin pest-management guidance treats them as a recurring nuisance around human structures.
Their seasonal wardrobe has a clever trick: pale feather tips wear away, exposing the darker, glossy color beneath. A spring starling and a speckled autumn starling can be wearing the same feathers.
3. House Sparrow
The little brown bird investigating the grocery-store entrance has had a long time to learn our habits. House sparrows thrive around people, nesting in building crevices and finding meals wherever we spill grain or leave scraps.
Introduced to Brooklyn in 1851, they spread across much of the continent with help from additional releases. Wisconsin’s barns, towns, and backyards supplied ample shelter and food.
A house sparrow may be small, but a coveted nest hole brings out its aggressive side. It can evict bluebirds, tree swallows, and purple martins. A nest box intended as a welcome sign for native birds can become disputed property.
The male’s black bib, gray crown, and chestnut neck help distinguish it from Wisconsin’s many native sparrows. “Sparrow” is a family resemblance, not a guilty verdict. Plenty of our brown backyard birds belong here.
Small insects, outsized appetites
4. Emerald Ash Borer
The beetle is jewel-green and small enough to overlook. The missing shade tree is harder to miss. Native to northeastern Asia, emerald ash borer probably reached America in shipping-crate wood.
Wisconsin confirmed its first infestation in Ozaukee County in 2008. In July 2024, a Burnett County detection completed an unwelcome map: the insect had been confirmed in all 72 counties. That doesn’t mean every ash was infested.
Larvae carve winding tunnels that interrupt the movement of water and nutrients. Upper branches decline, the canopy thins, and a seemingly ordinary ash can become a removal project. Woodpeckers peeling at the bark may reveal the infestation before anyone spots the beetle.
Firewood helps it travel farther than its wings would carry it. A load hauled to the cabin can deliver living insects along with next weekend’s campfire.
5. Spongy Moth
A leafy oak that suddenly looks ready for November may have hosted a spongy moth banquet. The caterpillars are the hungry stage; during outbreaks, their collective appetite can strip trees across conspicuous patches of woods.
This European moth was introduced in Massachusetts in 1869. Wisconsin had isolated finds decades before reproducing populations became established in the late 1980s, including Door and Kewaunee counties. Egg masses transported on outdoor belongings helped give the insect a lift.
Those tan, fuzzy-looking egg masses explain the name. They can cling to surfaces that later leave the yard, turning an ordinary move or trip into transportation for the next generation. The caterpillars feed on hundreds of tree and shrub species.
One bare summer doesn’t automatically mean a dead tree. Healthy trees can survive a defoliation, while repeated stripping and other stresses make the damage more serious.
6. Japanese Beetle
A rose can go from garden centerpiece to lacework with remarkable speed when Japanese beetles arrive. Their copper-colored wing covers and metallic green bodies look ornamental. Their dining habits are considerably less decorative.
Native to Japan and first found in the United States in New Jersey in 1916, the beetle spread into a major garden pest. In Wisconsin, adults commonly become conspicuous in July, right when flowers and foliage are supposed to look their best.
Adults chew the soft tissue between leaf veins on hundreds of kinds of plants. Underground, the white grubs feed on roots, including turfgrass.
Here’s the irritating catch: a beetle trap can attract more beetles than it catches. Hanging one beside a prized rose may bring additional hungry visitors into the neighborhood. A bag full of beetles doesn’t necessarily mean the nearby plants are better off.
7. Brown Marmorated Stink Bug
One shield-shaped bug on a windowsill is an annoyance. A collection gathering around the house in fall feels more like a meeting about your insulation. Brown marmorated stink bugs seek sheltered places to spend the winter.
This East Asian insect was confirmed in the United States in 2001, probably after arriving during the 1990s. Wisconsin finds began around 2010. It has since been reported from more than 50 counties, with especially strong footholds in the southern and eastern parts of the state.
The alternating light and dark markings along its abdomen and pale bands on its antennae are useful clues. Adults also hitchhike with people and belongings.
Wisconsin’s most familiar problem is the house invasion. Local home-garden damage has generally been relatively minor. Indoors, they don’t damage the structure, but crushing them supplies the smell that makes their name so memorable.
8. Multicolored Asian Lady Beetle
Those orange “ladybugs” crowding a sunny wall in October may have spent summer doing useful work. Multicolored Asian lady beetles eat aphids. The awkward part begins when their winter shelter of choice turns out to be your house.
Large numbers have been noticed in Wisconsin since 1994. The species is native to eastern Asia, and American release efforts stretched across much of the twentieth century. The successful population’s exact origins remain uncertain.
Fall gatherings can include thousands of beetles. They enter gaps in buildings and sometimes reappear indoors when conditions warm. Defensive fluid can smell unpleasant and leave stains, so their helpful reputation in the garden doesn’t always survive the move inside.
Their appearance varies enormously: some have many spots, others none, with colors ranging through yellow, orange, and red. Spot counting alone won’t settle the identification—and not every lady beetle in Wisconsin is this introduced species.
Uninvited guests above and below ground
9. Asian Jumping Worm
The first surprise is how vigorously it thrashes. The second is that finding more earthworms doesn’t always mean finding healthier soil. Asian jumping worms can consume the leafy layer that a woodland floor depends on.
Amynthas agrestis was documented near the UW–Madison Arboretum Visitor Center in fall 2013. It is one of several introduced jumping-worm species now found in Wisconsin. Native to parts of Asia, these worms spread with moved soil, plants, and other material.
Their feeding leaves a loose, granular surface often compared with coffee grounds. Removing leaf litter changes the conditions around roots, seedlings, and the small creatures that live beneath fallen leaves.
Winter doesn’t reset the problem. Adults die, but their cocoons can survive to start another generation. That makes a shared garden division with soil attached a more consequential gift than it appears.
10. Norway Rat
A hole beside a garage slab may look like an unremarkable patch of yard until something considerably bigger than a mouse disappears into it. Norway rats are burrowers, and human neighborhoods offer remarkably convenient real estate.
They reached North America unintentionally aboard ships from Europe. Now familiar enough to collect names such as brown rat, sewer rat, and barn rat, they follow our food supplies through cities, warehouses, and farms.
Milwaukee warns residents about burrows beneath garages and sheds, where shelter can sit a short commute from fallen birdseed, pet food, or unsecured garbage. The local problem is less mysterious than the rat’s globe-trotting history: we provide both the accommodation and the buffet.
Removing food and shelter matters as much as removing individual rats. A damaged garbage lid or an open feed sack keeps the invitation active. Look for a stocky body and coarse brownish fur.
11. House Mouse
The cereal bag with a suspicious little opening is often the first notice that someone else has moved in. House mice are so familiar that it’s easy to forget they are introduced animals, carried around the world alongside people.
Their ancestry traces to Asia, and human travel and trade brought them far beyond their original range. Our buildings shelter them from otherwise inhospitable climates.
Wisconsin’s rodent-management guidance emphasizes a humbling detail: a mouse can enter an opening barely more than a quarter-inch across. Around pipes, worn door edges, and basement gaps, the difference between “closed” and “mouse-proof” can be very small.
They nibble stored foods, contaminate cupboards, and gnaw property while often remaining unseen at night. The gray-brown house mouse is not every mouse in the woods. Wisconsin also has native mice, so a small furry shape alone doesn’t establish an identity.
Plants that escaped the invitation
12. Common Buckthorn
If the woods have dropped their leaves but a dense green understory is still hanging on, common buckthorn deserves a closer look. Its long growing season is one reason the shrub gets such an advantage over its neighbors.
Brought for ornamental planting, it spread into southern Wisconsin and beyond the tidy boundaries of yards. Birds and mammals carry its dark fruits, planting new patches without regard for fences, property lines, or anyone’s woodland restoration plans.
Buckthorn leafs out early and holds its leaves late. A thick stand throws enough shade to interfere with native understory plants and the next generation of trees.
Look for leaves with curved veins, clusters of black fruit on female plants, and twigs that often end in a thorn. A wall of shrubs isn’t automatically a healthy young forest. Sometimes it’s a bottleneck for the trees trying to replace the canopy.
13. Garlic Mustard
Garlic mustard arrived with a respectable résumé: a useful plant for people to eat. That history is less charming when its white flowers and triangular leaves spread through a Wisconsin woodland where spring wildflowers used to have more room.
It succeeds in shady places as well as disturbed ground. First-year plants form low rosettes; the next year, they send up flowering stems. That two-year schedule can make a small-looking patch turn into a much more obvious problem by the following spring.
The plant competes with native vegetation and releases chemicals that interfere with beneficial fungal relationships in the soil.
The seeds can remain viable for at least seven years. One satisfying afternoon of pulling doesn’t exhaust that reserve. The long, thin pods left on dry stalks are a reminder that the next round may already be waiting underground.
14. Purple Loosestrife
A marsh full of purple flower spikes makes an easy photograph and a complicated conservation story. Purple loosestrife’s beauty helped it spread through ornamental planting, adding deliberate garden introductions to its earlier accidental arrival in North America.
Once established beside water, it can form dense clumps that compete with native wetland plants. Its flowers keep opening up the stalk while seed capsules lower down are already maturing.
A large, many-stemmed plant can produce millions of tiny seeds. Cutting it carelessly creates another problem: pieces of stem can take root. Those impressive bouquets have more staying power than anyone wanted.
Wisconsin has also put specialist leaf-eating beetles to work against it. In some wetlands, chewed loosestrife leaves are welcome damage—a sign that biological control is helping other plants recover their place in the marsh.
15. Wild Parsnip
Those yellow flower clusters along a sunny roadside have a connection to the vegetable drawer. Wild parsnip is the same species grown for its edible root, introduced for food before escaping into a much less welcome career.
In Wisconsin it spreads through roadsides, old fields, prairies, and other open places. Tall, grooved stems carry flat-topped clusters of little yellow flowers. Its broad, toothed leaflets help distinguish it from plants that share a similar silhouette.
The unpleasant surprise comes from the sap. Sap on skin followed by sunlight can cause serious blistering. This isn’t a plant to gather casually into a bouquet or brush through while wearing shorts.
Its attractive flowers also resemble those of some native plants, including golden Alexanders. Identification matters before anyone decides a whole yellow roadside is an infestation.
16. Japanese Knotweed
The bamboo-looking thicket beside a stream probably isn’t bamboo. Japanese knotweed has hollow, jointed stems and can reach roughly ten feet tall, with broad leaves that turn a patch of bank into a dense green screen.
Its most effective travel arrangements are surprisingly ordinary: moved soil and floodwater. Soil containing underground stems can start a new colony elsewhere, while floods carry pieces downstream. A landscaping cleanup can accidentally become a planting project.
Small root fragments can resprout. A persistent underground system explains why knocking down the canes doesn’t settle the matter.
On streambanks, thick colonies can suppress replacement trees and other vegetation, contributing to erosion problems. Look for broadly spade-shaped leaves and late-season sprays of small pale flowers. Related knotweeds and their hybrids complicate identification, so a hollow stem by itself isn’t the final answer.
17. Curly-leaf Pondweed
Most gardeners expect plants to get going as the weather warms. Curly-leaf pondweed starts early enough to survive beneath ice, then may be checking out for the summer just as Wisconsin boaters are getting enthusiastic.
Native to parts of the Old World, it was verified in North America during the 1840s and spread through the Great Lakes region. Its wavy, finely toothed leaves make the name unusually helpful, though several native pondweeds deserve a careful comparison.
It reproduces mainly through tough little buds called turions. Dense growth can tangle boating, fishing, and swimming in affected waters. When the plants die back, decomposition releases nutrients; the effect on water quality varies considerably from lake to lake.
Its calendar is part of its competitive advantage. But it isn’t equally harmful everywhere: in degraded, murky waters where other plants struggle, it can still provide habitat.
18. Eurasian Watermilfoil
The feathery green strand caught on a trailer can look too flimsy to matter. Eurasian watermilfoil makes that assumption expensive: a stem fragment carried to another waterbody can take root and establish a new population.
First reported in Wisconsin in the 1960s, it is now present in almost every county. That sounds overwhelming until the second half of the story: it has been verified in fewer than one in ten Wisconsin waterbodies.
Dense stands can form surface mats, interfere with navigation, and shade native plants. Yet recent Wisconsin research has found that most affected lakes have relatively sparse populations, with very dense growth limited to a smaller number.
Presence doesn’t automatically mean a lake is being smothered. Its featherlike leaves usually have many fine leaflet pairs, but native milfoils and hybrids make identification tricky. Avoid transporting plant fragments between lakes.
Trouble beneath the surface
19. Rusty Crayfish
Not every Wisconsin invader crossed an ocean. The rusty crayfish came from the Ohio River basin, and the likely vehicle for its northward expansion was something as humble as an angler’s bait bucket.
That short trip created a large problem. In some northern Wisconsin lakes, rusty crayfish have eaten much of the aquatic vegetation. Plants that once sheltered young fish and supported small animals disappear as the crayfish feed.
They also push native crayfish out of good hiding places, leaving those displaced neighbors more exposed to predators. Fish eggs are on the menu, too.
Rust-colored side patches and large claws with dark bands near their tips are helpful clues, though the patches aren’t equally obvious on every individual. A crayfish being native somewhere in America doesn’t mean it belongs in every American lake.
20. Zebra Mussel
Pull something solid out of an infested lake and zebra mussels may have turned it into waterfront housing. These small shellfish attach in dense clusters to docks, equipment, and even other living mussels.
They arrived in the Great Lakes as larvae in ships’ ballast water from Eurasia. Waterway connections and boat traffic helped them spread. By 1991 they had reached the Mississippi River’s Pool 8, bringing the invasion to Wisconsin’s western doorstep.
The familiar striped shells hide a surprisingly disruptive lifestyle. Colonies clog water intakes and encrust native mussels, interfering with animals that already had perfectly good shells of their own.
Clearer water can conceal a changed food web. Filtering particles out of the water also removes food other organisms need. And a clean-looking boat isn’t proof that its retained water contains no tiny larvae—a reason inspection and draining work together.
21. Quagga Mussel
The zebra mussel has the better-known name. Its relative, the quagga mussel, has helped transform vast areas of Lake Michigan out of sight of anyone standing on shore.
Quaggas followed a similar suspected arrival route in the ballast water of ocean-going ships. Found in Lake Erie in 1989, they spread throughout Lake Michigan. Their ability to occupy deep water expands the invasion well beyond the docks and shallow rocks people regularly inspect.
They filter plankton, shifting food away from the open-water community and changing how nutrients move through the lake. Colonies also clog underwater infrastructure. Lake Michigan’s historic shipwrecks have become another surface for invasive mussels to cover.
The quagga’s rounded underside contrasts with the zebra mussel’s flatter base, though shell markings alone can be confusing. This is why two small, striped shellfish deserve separate entries: their appetites reach different parts of the lake.
22. Round Goby
A small fish sitting on the bottom can seem like a minor addition to a huge lake. Round gobies proved otherwise, combining aggressive feeding, rapid reproduction, and a tolerance for conditions that challenge some native fish.
Probably introduced through ballast water, they were discovered in the Great Lakes region in 1990. In Wisconsin they are established in Lake Michigan and connected waters, including the Lower Fox River and Little Lake Butte des Morts.
Their movement has had consequences above the waterline: after gobies were found in Little Lake Butte des Morts in 2015, the Menasha lock was closed to help protect Lake Winnebago. Individual gobies later appeared in Winnebago, but the DNR’s June 2026 update still distinguished those captures from an established population.
Look for the dark spot on the first dorsal fin and fused, suction-cup-like pelvic fin. Native sculpins can look similar at a glance, so that underside detail matters.
23. Sea Lamprey
The mouth is the part people remember: a round suction disc lined with hard, toothlike structures. A sea lamprey attaches to a larger fish, rasps through its skin, and feeds on body fluids. Lake trout were among its costly victims.
Native to Atlantic waters, sea lampreys gained access through human-made canals and spread into the upper Great Lakes. Spawning was documented in Lake Michigan in 1937; Spawning runs reached Lake Superior tributaries by 1948.
Their life story includes a less cinematic beginning. Larvae spend years buried in stream sediment, filtering food from the water before transforming into the parasitic stage. Wisconsin’s Brule River is one place where this hidden life has been studied closely.
The damage helped drive a long-running international control effort. But lampreys aren’t all villains: native species also live in the region.
24. Spiny Waterflea
In 2009, a UW–Madison class sampling Lake Mendota pulled up an unwelcome surprise in its plankton nets. Spiny waterfleas were there in conspicuous numbers, despite being creatures most lakeside visitors would never notice individually.
These tiny crustaceans reached the Great Lakes region through ballast water and spread inland with recreational boating. Their exceptionally long tail spine makes them awkward prey for small fish, while they happily consume smaller zooplankton themselves.
That matters because some of their prey are Daphnia, the little grazers that eat algae. Remove enough of the grazers and the water can become murkier. Mendota researchers documented major losses of Daphnia and reduced clarity following the invasion.
They eat the animals that help keep algae in check. A lake can look unchanged from the parking lot while a nearly invisible newcomer is reorganizing the menu beneath the surface.
25. Common Carp
Common carp were once an improvement project. People deliberately introduced this Eurasian fish as an inexpensive food source, and Wisconsin imported carp in the late 1800s. The plan worked rather too well for many shallow waters.
Rooting along the bottom, carp disturb sediment and recycle nutrients into the water. That can encourage algae and reduce the light available to aquatic plants.
Wisconsin lake managers sometimes remove carp to help improve water quality and habitat. The effort can require years of follow-through, especially where reproduction and suitable habitat keep rebuilding the population.
This is the familiar common carp, not the silver carp famous for leaping around boats. Its long local history makes it easy to mistake for an original resident. On this list, familiarity is often the best disguise of all.
The most useful response starts with an accurate name. Photograph an unfamiliar plant or animal, note where you saw it, and keep soil, firewood, bait, and wet equipment from carrying it somewhere new. A native lookalike deserves to stay—and an introduced hitchhiker doesn’t need a ride to the next lake or backyard.
Photo credits
1. Mute Swan: Geni, Mute Swan Emsworth2.JPG. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
2. European Starling: Charles J. Sharp, Common Starling (Sturnus vulgaris) Leek Wootton.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
_Leek_Wootton.jpg){kind=link}
3. House Sparrow: Hobbyfotowiki, House sparrow (Passer domesticus), Amrum.jpg. CC0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
,_Amrum.jpg){kind=link}
4. Emerald Ash Borer: Benjamin Smith from United States, Emerald Ash Borer (Agrilus Planipennis) (12127981265).jpg. CC BY 2.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
_(12127981265).jpg){kind=link}
4. Emerald Ash Borer tunnels (supporting photo): ImagePerson, Trackways of Emerald Ash Borer Agrilus planipennis 1164.jpg. CC BY 4.0. Resized by Wikimedia thumbnail service; otherwise unchanged.
5. Spongy Moth: Ryan Hodnett, Gypsy Moth (Lymantria dispar) Caterpillar – Kitchener, Ontario.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
_Caterpillar_-_Kitchener,_Ontario.jpg){kind=link}
6. Japanese Beetle: Paul Harrison, Popillia japonica Japanese Beetle 05.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
7. Brown Marmorated Stink Bug: David R. Lance, USDA APHIS PPQ, Brown marmorated stink bug adult.jpg. CC BY 3.0 us. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
8. Multicolored Asian Lady Beetle: Romzig, Marienkäfer (Juni 2025).jpg. CC0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
.jpg){kind=link}
8. Multicolored Asian Lady Beetle (supporting photo): Jürgen Howaldt, Asian Lady Beetle (Harmonia axyridis) Larva & Macrosiphum rosae (jh04).jpg. CC BY-SA 4.0. Uncropped photograph reproduced at web resolution. This image adaptation is shared under the same license.
_Larva_%26_Macrosiphum_rosae_(jh04).jpg){kind=link}
9. Asian Jumping Worm: Njh5880, Amynthas agrestis (cropped).jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
.jpg){kind=link}
10. Norway Rat: Chuck Homler d/b/a Focus On Wildlife, Brown Rat (Rattus norvegicus) also called Norway Rat or Common Rat -with food container – Mathias Baldwin Park, Philadelphia, Pennsylvania, USA.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
_also_called_Norway_Rat_or_Common_Rat_-with_food_container_-_Mathias_Baldwin_Park,_Philadelphia,_Pennsylvania,_USA.jpg){kind=link}
11. House Mouse: Андрей Перцев 1967 at Russian Wikipedia, Mus musculus 2011.jpg. CC0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
12. Common Buckthorn: Krzysztof Ziarnek, Kenraiz, Rhamnus cathartica kz01.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
13. Garlic Mustard: Robert Flogaus-Faust, Alliaria petiolata 5 RF.jpg. CC BY 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
14. Purple Loosestrife: Robert Flogaus-Faust, Lythrum salicaria 3 RF.jpg. CC BY 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
15. Wild Parsnip: Krzysztof Ziarnek, Kenraiz, Pastinaca sativa kz10.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
15. Wild Parsnip (supporting photo): MurielBendel, Pastinaca sativa plant.jpg. CC BY-SA 4.0. Uncropped photograph reproduced at web resolution. This image adaptation is shared under the same license.
16. Japanese Knotweed: Tulipasylvestris, Parkslide – Reynoutria japonica – 2024 02.jpg. CC0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
17. Curly-leaf Pondweed: , PotamogetonCrispus.jpg. CC BY-SA 3.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
18. Eurasian Watermilfoil: Krzysztof Ziarnek, Kenraiz, Myriophyllum spicatum kz01.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
19. Rusty Crayfish: Ryan Hodnett, Rusty Crayfish (Faxonius rusticus) – Guelph, Ontario 2020-04-08 (03).jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
_-_Guelph,_Ontario_2020-04-08_(03).jpg){kind=link}
20. Zebra Mussel: H. Zell, Dreissena polymorpha 01.jpg. CC BY-SA 3.0. Full photograph fitted within a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. Original signature retained where present. This image adaptation is shared under the same license.
21. Quagga Mussel: NOAA Great Lakes Environmental Research Laboratory, Quagga mussel (8740859295).jpg. CC BY-SA 2.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
.jpg){kind=link}
22. Round Goby: Eric Engbretson, U.S. Fish and Wildlife Service, Neogobius melanostomus1.jpg. Public domain. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
23. Sea Lamprey: Photo Credit: Great Lakes Fishery Commission, Sea Lamprey fish.jpg. Public domain. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added.
24. Spiny Waterflea: Dmitry Kulakov, Bythotrephes longimanus 53114751.jpg. CC BY 4.0. Full photograph fitted within a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. Original signature retained where present.
25. Common Carp: George Chernilevsky, Cyprinus carpio 2021 G2.jpg. CC BY-SA 4.0. Cropped and placed in a 4:5 identification card; title, impact text and authentic Gardening Wins logo added. This image adaptation is shared under the same license.
