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The Wisconsin Department of Natural Resources has a wonderful field guide to use in identifying invasive plants. Hard copies are available to order by submitting an order form (http://dnr.wi.gov/topic/Invasives/documents/Orderform.pdf).
You can also view an online pdf of the guide for free by clicking on the picture to the left.
Autumn Olive (Elaeagnus Umbellata) *
Autumn Olive has alternate oval leaves that have pointed tips, and have no teeth. The underside of the leaves is silvery and has a scaly texture. The underside is the the easiest way to identify Autumn Olive. In addition,
Autumn Olive is a deciduous shrub or a small tree. It can grow up to 20 feet in height and 30 feet in diameter. Autumn Olive was brought from Asia to the US, and it was planted for wildlife food.
Why is it Invasive?
Autumn Olive grows
leaves early and retains its leaves in the fall, shading out native species. It
is also germinates in both the shade and in the sun. In addition to its leaves,
Autumn Olive has root nodules
The best control for Autumn Olive is prevention of the seeds from spreading. Aside from that, early identification is key. When seedlings, pulling and clipping both work for prevention. Additionally, grazing control with goats and sheep also helps control the spread of these plants. When established or on larger sites, chemical control may be used. Spraying in the spring and fall can minimize damage to native plants.
For More Information:
Common buckthorn is a deciduous shrub or small tree that is capable of invading forests, savannas, prairies, fields and roadsides. It was introduced and an ornamental shrub to North America to be used as fence rows and as wildlife habitat.
Common buckthorn can grow up to 20-25' in height often with many stems. When cut the inner bark is yellow and the heartwood is pink to orange. In spring, yellow-green flowers are in clusters of 2-6 near the base of the leaf stalks. Fruits are in abundant clusters of small black pea sized berries that ripen late in the summer. Leaves are mostly opposite and oval with 3-4 pairs of up-curved veins and small teeth. Twigs are oftem tipped with a spine. Similar species: Rhamnus frangula (Glossy buckthorn) does not have toothed leaves or spines on the end of twigs.
Once established common buckthorn tends to form dense, even-aged thickets that crowds and shades out native shrubs and herbs. Common buckthorn is also capable of altering soil nitrogen dynamics and is a host for the crown rust of oats. For more information, click above image. For more information about managing Common buckthorn populations check out this MI DNR publication or this UW-Extension publication.
Dame's Rocket (Hesperis matronalis) *
Dame’s Rocket is also known as mother-of-the-evening and dame’s violet. It is a part of the mustard family. It was introduced as an ornamental around the time of European settlement. It can be found throughout North America, and is still widely used as an ornamental.
Why is it Invasive?
The Dame’s Rocket lacks natural predators and diseases in North America and successfully competes with native species for water, nutrients, and light. The reason this flower is so successful is because of its seeds in the distribution of commercial “wildflower” seed mixes. These seeds easily escape gardens and travel by means of waterways, rainfall, footwear, animal fur, and vehicle tires.
Dame’s Rocket can range from 1.5 to over 3 feet tall. They have a shallow root system with numerous flower stalks. The leaves of this flower are oblong with toothed margins. These leaves are alternately arranged and decrease in size. The stems and leaves of Dame’s Rocket are covered in little hair-like fibers. The flower consists of four petals and develops in stages. This allows the plant to produce flowers and seeds at the same time. Large amounts of seeds are found in long pods and are their sole method of reproduction.
One of the main methods of control is pulling or cutting flower stalks to prevent seed dispersal. The stems often break when the mature plant is pulled and it may resprout if not removed. The site will need to be monitored for years to be sure that none grow back. The flower heads should be bagged, or dried and burned. Applying herbicides can also help to control the spread of Dame's Rocket. Herbicide should be applied to the rosettes in the late fall of early spring to avoid affecting other vegetation. When using herbicides, be sure to read the labels and follow the directions. Some native replacement flowers for the Dame’s Rocket are sidebells penstemon, palmer penstemon, bee balm, columbine, narrowleaf coneflower, and woods rose.
For more information:
While earthworms seem very commonplace, they are in fact not native to Wisconsin and Michigan and can have detrimental effects on our hardwood forest ecosystems. In gardens, compost piles, and agricultural fields, worms help by decomposing organic matter and aerating the soil. However, when these animals are let loose in northern forests, these same skills wreak havoc on the forest floor. By speeding up a normally slow decomposition of debris on the ground, earthworms alter the soil chemistry and throw a wrench into the system's natural processes. This can result in some dramatic changes in forest composition as new seedlings struggle to germinate and even adult trees are damaged when the protective duff layer over their roots is removed.
You can help by learning about the threat posed by earthworms, educating others, and remembering to properly dispose of any worms used as bait. Always throw worms in the trash, never in the water or on the ground.
For more information about Earthworms check out the Great Lakes Worm Watch.
Exotic Bush Honeysuckles (Lonicera sp.)
There are several species of exotic honeysuckles, but they all share general identification characteristics. Exotic honeysuckles are upright, deciduous shrubs that have shaggy bark. Older stems and branches have a hollow center surrounded by a dark ring. The leaves are oval shaped and are arranged opposite of each other on the stem. Exotic honeysuckles have bright tubular flowers that are often pink, but can be white or red. The berries can be red, orange, or yellow. Berries are always arranged in clusters of two along the stem.
Exotic honeysuckles are one of the first plants to leaf out in the spring and the last to keep their leaves in the fall. This makes them relatively easy to spot during these times. Exotic honeysuckles often form dense thickets in the woods, which shades out native species and inhibits animal and human access. For more information about managing honeysuckle populations read this UW-Extension publication.
Like other invasive plants, this disruptive weed out-competes native life for sunlight, soil, water and nutrients. Each adult plant can produce hundreds of seeds which are spread easily by animals, people, and flowing water. Furthermore, the pungent odor of the plant defends it from native insects, which are deterred by the smell.
This plant is easy to identify: mainly due to its distinctive characteristic of smelling like onion or garlic when its leaves are crushed. Garlic mustard’s leaves are heart shaped, with deep veins and toothed edges. The plant itself reaches heights of 12-48 inches as an adult and is dark green in color. Older plants produce numerous clusters of tiny white flowers with four petals in a cross shape. Seeds lie dormant throughout the winter and germinate in spring and early summer. For more information on garlic mustard visit WDNR's website or watch this video. Check out this publication from UW-Extension for information about management of Garlic mustard populations.
Lately, the invasive plant Giant Hogweed has been making headlines. As a plant that grows twice as tall as an average human, and can cause some serious health problems from minor rashes to severe blisters and even possible blindness, this is understandable. However, despite the media buzz, Giant Hogweed has yet to be confirmed in the WRISC area (the closest confirmed siting being Ironwood, MI). Instead, people are much more likely to see the native cow parsnip, particularly in wet roadside ditches. The image below compares the two species, which also differ greatly in size (with every part of giant hogweed growing nearly twice as big as its native counterpart). For more comparisons, visit the NY Dept. of Environmental Conservation or the Ohio State University website.
Glossy buckthorn is a deciduous shrub or small tree that invades various types of wetland and upland habitat and can tolerate full sun to deep shade. A native to Eurasia glossy buckthorn was introduced to North America in the mid 1800's as a popular hedging material and as wildlife plantings.
Glossy buckthorn can grow to a height of 10-25ft often with multiple stems. Bark is brown-green with prominent lenticels, inner sapwood is yellow and the heartwood is pinkish-orange. Leaves are simple, alternate, oblong, untoothed, dark green and shiny. These leaves will often be slightly hairy on the underside. Fruits are round and pea-sized that ripen progessively from red to dark purple in the late summer to fall. Flowers are inconspicuous 5-petaled and greenish-yellow clusters from late May to September. Similar species: Rhamnus cathartica (Common buckthorn) will have toothed leaves, a spine on the end of twigs, and non glossy leaves.
Glossy buckthorn will form dense thickets that will reduce light availability for understory species and eventually prevent native tree regeneration. Buckthorn leaves stay green through late fall. For more information click the above image. For more information about managing Glossy buckthorn populations check out this MI DNR publication or this UW-Extension publication.
Meet the Knapweeds
Spotted knapweed (Centaurea biebersteinii, c. stoebe), is a common invasive in sunny open areas, particular disturbed locations such as roadsides. It came to North America accidentally mixed in with hay and has since spread, damaging everything from western rangelands to midwest prairies. Plants are easy to see in mid to late summer when their pink to purple thistle-like flowers cover roadsides. Knapweed plants release chemicals into the soil, inhibiting the growth of other plants, are unpalatable to most animals, and can also result in increased runoff and erosion when native grasses are replaced by knapweed's taproots.
Now,other species of knapweed are also moving into the Midwest. For more information about this newest threat, look at the "Meet the Knapweeds" brochure to the right. Another useful knapweed guide can be found online, provided by the Washington State Noxious Weed Control Board at https://www.nwcb.wa.gov/weeds/spotted-knapweed
Leafy Spurge (Euphorbia esula)
Cypress Spurge (Euphorbia cyparissias)
Leafy Spurge (Euphorbia esula)
Cypress Spurge (Euphorbia cyparissias)
Leafy spurge is an herbaceous perennial plant with an extensive root system and vast energy stores that can allow it to recover from most control attempts. Where leafy spurge is widely present, it can reduce the livestock carrying capacity of rangeland and pastures by 50-75%. This decrease in carrying capacity is due to the milky sap present in leafy spurge. The sap is distasteful to some animals, which causes them to avoid it and eat native plants. In some cases the sap can cause blistering in their mouths. Cypress spurge is an erect, semi-woody perennial plant that reproduces primarily vegetatively through lateral root buds. Both plants have extensive root systems and milky sap. Both leafy and cypress spurge are native to Europe. Leafy spurge was introduced to the United States around 1825 probably as an ornamental or as a contaminant in imported grain. Cypress spurge was introduced in the 1860’s as an ornamental and was widely planted in graveyards. From there, it was able to escape cultivation and became established on open ground, particularly in pastures. Both plants and widely distributed, with the exception of several southern states.
Why is it Invasive?
Both leafy and cypress spurge invade oak savannas, prairies, fields, pastures, and roadsides and are most aggressive when soil moisture is limited. Their ability to tolerate drier conditions is likely a result of the milky sap they produce. This thicker sap will evaporate much slower than sap that is thinner, thereby providing this plant with moisture for longer. Additionally, the sap in this plant is potentially toxic to horses and cattle, and can irritate the eyes, mouth, gastrointestinal tract, and skin of these animals. The sap also has the ability to cause dermatitis in some humans upon contact. Both varieties of spurge are able to produce monospecific stands that effectively exclude native vegetation and reduce wildlife habitat value. Finally, both leafy and cypress spurge are able to reproduce vegetatively as well as by seed. This gives the plants an added reproductive advantage over native plants that may not be as prolific as the spurges.
Leafy spurge can be identified by alternate bluish green leaves, oblong to lance shaped, about 1-4 inches long. Cypress spurge on the other hand has leaves that are bright green and can be either oriented in an alternate or whorled pattern on the stem. With smaller, narrower leaves that look more like needles, it is easy to see how cypress spurge got its name. The flowers of leafy spurge are small with a yellow-green color, and are surrounded by cup shaped bracts. Flowers generally appear in seven to ten pairs clustered in umbels at the tops of the stem. Cypress spurge flowers look very similar to those of leafy spurge, but as they mature, they take on a purple-red color. Both plants bloom in the late spring to early summer and will produce milky sap when the stem is broken. Reproduction of these plants can occur vegetatively or by seed pods that explode, shooting seeds up to 20 feet from the parent plant. These seeds can remain viable in the soil for up to seven years. Finally, the roots of both plants are woody rhizomes that can grow as far down as 15 feet deep and spread laterally as far as 35 feet away from the plants. Sprouts that shoot off of the root buds enable these plats to spread into undisturbed areas. Root fragments as deep as nine feet deep in the soil can create new plants.
Hand pulling or digging these plants can be effective control methods in populations were the root system has not become well established, however; the entire root needs to be removed along with the plant. Another effective treatment for leafy and cypress spurge is prescribed burning in conjunction with repeated herbicide treatments. If burning is not an option, a foliar spray can be used with repeated follow-up treatments to catch any plants that were missed in the initial treatment. Finally, biological control has also been used with several insect biocontrols that have been released in some areas and goats that are able to graze on plants above ground.
Oriental Bittersweet (Celastrus orbiculatus)
Oriental Bittersweet was introduced into the United States in the 1860s as an ornamental plant and it is still widely sold for landscaping despite its invasive qualities. It is often associated with old home sites, and has spread into surrounding natural areas. Its native range includes Eastern Asia, Korea, China and Japan.
Oriental Bittersweet is a vigorously growing vine that climbs over and smothers vegetation which may die from excessive shading or breakage. When bittersweet climbs high up on trees the increased weight can lead to uprooting and blow-over during high winds and heavy snowfalls. In addition, Oriental Bittersweet is displacing our native American Bittersweet (Celastrus scandens) through competition and hybridization.
Oriental Bittersweet is a deciduous woody perennial plant which grows as a climbing vine and a trailing shrub. Stems of older plants 4 inches in diameter have been reported. The leaves are alternate, glossy, nearly as wide as they are long (round), with finely toothed margins. There are separate female (fruiting) and male (non-fruiting) plants. Female plants produce clusters of small greenish flowers in axillary clusters (from most leaf axils), and each plant can produce large numbers of fruits and seeds.
Do not buy, plant, transplant Oriental Bittersweet or dispose
of live or dead seed-containing material. Manual, mechanical and chemical
methods can be employed to control it. Vines can be pulled out by the roots,
cut repeatedly or treated with systemic herbicides. No biological controls are
currently available for this plant. Oriental Bittersweet is sometimes
mistakenly labeled as American Bittersweet then sold and planted.
For more information:
is a herbaceous monocarpic perennial forming a rosette for the first
year growth. Most plants flower in the second, third or fourth season
after germination and after flowering, the entire plant will die. This
plant can invade open habitats such as prairies, savannas, pastures and
Wild parsnip leaves are pinnately compound with 5-15 oval, smooth, toothed leaflets. The stem can reach up to 5ft in height and is upright, unbranched, thick and hairy with grooves. The flowers are numerous, small and yellow with 5-petals that occur in flat terminal umbels that can be up to 6 inches wide. This plant will bloom in late spring or early summer .
Wild parsnip is threatening to humans. There are chemicals found in leaves, stems and flowers that can cause phyto-photodermatitis, meaning when skin becomes in contact with these chemicals severe rashes, blisters, and discoloration of the skin can occur.
This plant was likely introduced as a garden vegetable as the taproots are edible however, since escaped wild parsnip can densely infest open or disturbed areas like roadsides, right-of-ways and any type of open field.
For more information click the image. For more information about managing Wild parsnip populations read this UW-Extension publication.
Yellow and White Sweet Clover (Melilotus officinalis and Melilotus albus)*
Sweet clover is native to Europe and Asia. It was introduced to North America in the 17th century for cattle forage purposes and is now widespread throughout Canada and the United States, where it has become invasive and can outcompete native plant species. White sweet clover can grow up to 2 meters in height and can produce abundant amounts of seeds that readily float and disperse in water. This has allowed the plant to colonize natural habitat such as riparian areas all across much of North America.
Why is it invasive?
Sweet clover invades and degrades native grasslands by overtopping and shading native sun-loving plants thereby reducing diversity. It grows abundantly on disturbed lands, roadsides and abandoned fields.
It responds favorable to prescribed burns by scarifying seeds thereby stimulating germination. First year plants are hard to detect. Native to Europe it was brought to the U.S. in the late 1600s and still used today as a forage crop and soil enhancer predominantly in the Great Plains and Upper Midwest.
White and yellow sweet clover are biennial herbs that are somewhat easy to identify, especially when in flower. Flowers are crowded densely on the top 4 inches (10 cm) of an elongated stem, with younger flowers emerging nearest the tip, or apex. Each tiny flower is attached to the stem by a minute stalk. The small pea-like flowers are white or yellow and each produces one or two seeds during the second growing season. The compound leaves of sweet clover are alternate and have three leaflets per leaf. Leaflets are finely toothed and longer than broad. Mature plants (second-year) may appear bushy. These aromatic plants are members of the pea (legume) family, but they are not true clovers.
Prescribed burning, a hot early complete first year burn followed by a hot late spring second year burn, (repeat after two years)
Hand pulling, effective on small infestations when the soil is moist
Cutting, before flowers emerge
Spray emergent seedlings with 2,4-D amine or mecamine after a fall burn, or after a spring burn before native vegetation emerges
For more informationhttp://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/whitesweetclover.html
Chinese Mystery Snail (Cipangopaludina chinensis)*
The shell of the Chinese mystery snail is smooth and strong. It is a uniform color throughout without banding and is usually a light to dark olive-green. The shell can have 6 to 7 whorls. The whorls are strongly convex and each suture is very indented. The outer lip is either round or oval and has a black color to it. The shell can grow to a couple of inches in length. In 1892, Chinese mystery snails were imported into live markets in San Francisco. In 1911, a thriving population was found in the San Francisco Bay. They were then found in Boston, Massachusetts in 1915 and in 1950 Florida reported finding a population. By 1965, Chinese mystery snails were established both on the west and east coast as well as some of the Gulf States like Texas. The great Lakes have been affected also; Lake Michigan and Lake Erie populations were reported in 1965.
Species of the genus Cipangopaludina can be identified by
their relatively large globose shells and concentrically marked opercula (Burch
1980). Cipangopaludina chinensis has
a width to height ratio of 0.74–0.82, the shell has 6.0–7.0 whorls, and the
inner coloration is white to pale blue (Clarke 1981, Jokinen 1992). This
species has a small and round umbilicus and the spire is produced at an angle
of 65–80º (Jokinen 1992). Cipangopaludina
chinensis exhibits light coloration as a juvenile and olive green, greenish
brown, brown or reddish brown pigmentation as an
Specific control methods for the Chinese mystery snail have yet to be developed but there are some general snail management techniques that could be applied. Biological control is a method that is supported because it usually causes the least amount of damage to other aquatic organisms. By introducing fish or turtles that eat snails you may be able to lower the population. There is also the option to use a chemical control method. There are copper compounds that are sold as snailicides but they are usually not selective in the snails they kill. With Chinese mystery snails possessing the ability to “close up”, more damage is likely to occur to native snails in the treatment area as compared to the target pest.
Curly-Leafed Pondweed (Potamogeton crispus)*
Curly-leaf pondweed spreads through burr-like winter buds (turions), which are moved among waterways. These plants can also reproduce by seed, but seeds play a relatively small role compared to vegetative reproduction through turions. New plants form under the ice in winter, making curly-leaf pondweed one of the first nuisance aquatic plants to emerge in the spring.
Why is it Invasive?Curly-leaf pondweed becomes invasive in some areas because of its tolerance for low light and low water temperatures.
These tolerances allow it to get a head start, out-competing native plants in the spring. In mid-summer, when most aquatic plants are growing, curly-leaf pondweed plants are dying off. Plant die-offs may result in a critical loss of dissolved oxygen. Furthermore, the decaying plants can increase nutrients, contributing to algal blooms, and this can create unpleasant pungent messes on beaches. Curly-leaf pondweed also forms surface mats that interfere with aquatic recreation.
Curly-leaf pondweed has leaves that are somewhat stiff and crinkled, approximately ½ inch wide and two to three inches long. Leaves are arranged alternately around the stem, and become denser toward the end of the branches. Curly-leaf pondweed produces winter buds; it can confused with clasping leaf pondweed. The leaves of curly-leaf pondweed are reddish-green, oblong, and about three inches long, with distinct wavy edges that are finely toothed. The stem of the plant is flat, reddish-brown and grows from one to three feet tall. The plant usually drops to the bottom of the lake by early July.
Turions and plants fragments can be carried on boats, trailers, motors and fishing gear from one water body to another; proper prevention techniques are essential to curb the spread of this aquatic invasive. An effective prevention and remediation program also addresses the overall health of a water body. Maintaining a healthy ecosystem with diverse native aquatic plants and animals, as well as minimizing nutrient and pollutant inputs will deter invasions. Once introduced, curly-leaf pondweed spreads rapidly. Long-term management requires the reduction or elimination of turions to interrupt the life cycle.
Chris Evans, River to River and Leslie J. Mehrhoff, University of Connecticut
For more information
European Frog-bit is an aquatic, floating, water-lily
plant. It's leaves are kidney shaped with a dark purple underside. The
flowers are white and have three petals. European Frog-bit resembles
our native waterlilies, but is much smaller (0.5-2.5 inches in
diameter.) The roots of the plant do not embed into the lake bed,
instead the entire plant free-floats in the water column. It is a
dioecious plant, meaning that male and female sexual parts occur on
separate plants. Many populations consist of only male plants, limiting
the plant's ability to reproduce sexually. European Frog-bit is
commonly found in shallow, slow-moving water on the edges of lakes,
rivers, streams, swamps, marshes and ditches. More information on Frog-bit can be found on the MDEQ website.
This plant is considered prohibited in both Wisconsin and Michigan, and is a priority watch-list species. If you find European Frog-bit in any of WRISC's five counties please contact us immediately at (906)774-1550x102 or firstname.lastname@example.org.
Flowering Rush (Butomus umbellatus) *
Flowering- Rush is native to Eurasia and was introduced to the eastern United States and Canada as an ornamental. Flowering-Rush is an aquatic plant that is typically found along slow-moving rivers, lake shores, and in water up to nine feet deep. This aquatic plant resembles a true rush, however flowering-rush is put in its own family and can be distinguished by its attractive pink flowers. It can grow between 1-4’ high on an erect stem, and can be difficult to identify when not in flower.
Why is it Invasive?
Flowering-Rush is said to be an actively expanding aquatic plant. It has spread from the Great Lakes and the St. Lawrence River to numerous other areas in the northern U.S. and southern Canada. The Flowering-Rush is considered invasive because it competes with native shoreline vegetation. This aquatic plant from Eurasia is sold commercially for the decoration in garden pools, however it is not illegal to buy, sell, or possess this aquatic plant.
Flowering-Rush is easiest to identify when it is flowering. The flowers grow in umbrella shaped clusters and with each individual flower there are three whitish pink petals on them. These flowers can only reproduce in very shallow water or on dry sites. Flowering-Rush has green stems that resemble bulrushes but are triangular in cross section. When Flowering-Rush is along shore, this plant erects leaves and it can grow to about three feet in height. The leaf tips may be spirally twisted, however under water, the leaves are limp. The extensive roots on this plant can produce new plants if disturbed.
To remove or control the flowering rush one should cut the aquatic place below the water surface. However, cutting will not kill the plant, but will decrease the abundance. Another method to control Flowering-Rush is by hand digging. This method can be used to remove isolated plants that are located downstream. When hand digging one must take extreme care because any disturbance may cause a small reproductive structures on the roots. Overall it is very difficult to kill this plant with herbicides, due to this plant being in water and the herbicides washing away. The best and easiest way to control Flowering Rush is to stop buying the plant altogether.
For more information:
Narrow-leaved Cattail (Typha angustifolia) *
The velvety, brown flower head and long, graceful, lanceolate leaves of the cattail are a common site throughout Wisconsin wetlands. The flower head, shaped like an elongate cylinder, is a compact spike at the terminal end of a stem 1-3 meters tall. The flower spike is divided into two readily distinguishable parts: pistillate flowers form the conspicuous brown club located below the yellow spire of staminate flowers. The leaves originate at the base of the stem and spread outward as they rise into the air. Below ground, starchy rhizomes anchor the plant to the soil. If the plants are growing in a colony, their rhizomes may become intertwined and form a dense mat.
Of the two species of cattail that exist in Wisconsin, common cattail is taller and generally more robust than the narrow-leaved variety. Observation of the flower spike also helps distinguish the two species. The pistillate and staminate flowers of the common cattail emerge in direct contact with one another, with no gap separating the male and female flower parts; on the flower spike of the narrow-leaved cattail, the pistillate and staminate flowers are separated by a gap 2-10 centimeters in length.
Distribution and Habitat
The common cattail is a native North American wetland species. The narrow-leaved cattail is either an exotic or hybrid. Cattails can be found in damp soil or shallow water where sufficient nutrients are available. It is a common site along expressways, in artificial ditches and shallow ponds, at the edges of calm waters, in consistently damp patches of rural and suburban yards, and in freshwater marshes. This prolific plant plays an important role as a source of food and shelter for different marsh-dwelling animals, especially when cattails form large stands on relatively open, wet soils abutted by water.
The acreage of narrow leafed cattail-dominated wetlands in the United States has increased dramatically since the early twentieth century due to changes in hydrology and land use. The optimal control technique for a given site will depend on the hydrologic state of the site, the size of the area to be managed, and if the manager is able to manipulate water levels.
New Zealand Mudsnail (Potamopyrgus antipodarum)*
The New Zealand Mudsnail is endemic to New Zealand rivers and streams but is now found throughout Europe, parts of Canada, and parts of the United States. 1859 was the earliest evidence of New Zealand Mudsnail in England and from there it has spread across Europe, finally crossing the Atlantic Ocean and reaching the Snake River in Idaho in 1987. Today the New Zealand Mudsnail is widely spread across the United States and heavily infests the Great Lakes region. As with most invasives, this snail has no natural predators or parasites in Europe, Canada, or the United States, allowing its spread to go unchecked.
Why is it invasive?
The arrival of the New Zealand mudsnail was most likely from an ocean going ship dumping its ballast water in the Great Lakes, or it was transported with live game fish shipped from infected waters to western rivers in the United States. This species now resides in Lake Ontario, Lake Erie, Lake Michigan, and most likely Lake Superior. and is continuing to expand throughout the Great Lakes. This snail can reach densities as high as 5,600 per square meter in the Great Lakes. It is also established in all western states where it is found in the US.
The New Zealand Mudsnail. has an elongated
shell with 7-8 whorls separated by deep grooves. The shell has more
whorls (5-6) than the average hydrobiid snails indigenous to the United
States. Their shells
can vary from gray to dark brown to light brown. The operculum or thin membrane that covers its opening has an off center nucleus from which paucispiral markings radiate. New Zealand Mudsnails can exhibit spines for predator defence. It grows from 4-6 mm in the Great Lakes. An individual female may produce between 10- 90 embryos. These snails can occupy a wide variety of substrates including silt, sand, mud, concrete, vegetation, and gravel. The New Zealand Mudsnail is capable of withstanding a large range of temperatures.
The only known ways of preventing the spread of this invasive species is preventative action. The best things people can do is to clean their gear, whether it be waders, nets, fishing lines and boats thoroughly in areas where New Zealand Mudsnails are known to be present.
For More Information.
Phragmites, also known as common reed, is a perennial wetland grass that grows 3-20 feet tall with dull, rigid, hollow stems. It creates dense clones and canes persist throughout winter.
Phragmites leaves are smooth, narrow, and gray-green in color. The leaf is 6-24 inches
long and 0.4-2.4 inches wide. The leaf bases form overlapping, smooth
sheaths around the stem. Phragmites flowers are large and feathery;
measuring 5-16 inches in length. The flowers are initially purple-brown
and turn to a golden brown with age. Below ground, Phragmites forms a
dense network of rhizomes that can up to 6 feet deep. New plants can
grow from the nodes of rhizomes.
There is a
native subspecies of Phragmites. The native species can be identified
by its reddish-brown canes, its shinny black spots, and its flexible
canes. Native Phragmites has flower heads that are less dense and does
not form dense stands like the non-native.
The non-native Phragmites quickly forms dense monospecific stands and excludes native plants after it invades a site. These dense stands of Phragmites change the hydrology, alter the habitat for many species of wildlife, and the dead canes increase the potential for fire.
Click here for more information.
Purple Loosestrife is a perennial herb that is capable of infesting wetlands, river and streambanks, pond and lake edges, reservoirs and ditches.
Introduced in the early 1800's Purple Loosestrife has been widely sold as an ornamental plant throughout North America.
Purple Loosestrife has a square woody stem with alternate and whorled leaves. They can grow from 4'-10' in height, and produce bright flowers with 5-7 petals through July and September
Once established Purple Loosestrife can spread vegetatively through underground stems to form dense stands that outcompete and replace native wetland species as well as important wildlife habitat. For more information and look-a-likes, click above image. For more information about managing Purple loosestrife populations read this UW-Extension publication.
Rusty Crayfish (Orconectes rusticus)*
The rusty crayfish is native to the southern United States, but it is believed to have been brought to northern regions by fisherman. It looks very similar to a native crayfish but it it has patches of spots on its thorax that look like rusty spots. They are very aggressive and will push other crayfish out of their territory. They produce a lot of offspring with a female laying from 80-575 eggs that will hatch within 3-6 weeks.
Why is it Invasive?
The rusty crayfish is invasive is because it
is an aggressive animal that will consume plants and animals than native organisms would have otherwise eaten. They destroy the
plants that give the water good dissolved oxygen levels and by doing this they
can also cut down on plant diversity. They are aggressive enough to take
on and kill some fish that other animals would usually eat. Since normal
crayfish are sometimes eaten by fish, but fish will not eat the rusty crayfish
the food diversity for fish is also down. They also contribute to the spread of other invasive such as Curly-leaf Pondweed and Eurasian Milfoil as they slice these prolific plants up thus allowing new infestations to occur or exacerbating the current infestions.
A rusty crayfish can be identified by its robust claws and
by the dark rusty spots on the back of its shell. These spots can be large or
small depending on the age of the crayfish. If you are unsure of whether it is a rusty
crayfish contact your local DNR or fishery so that they can assist you in accurate identification.
The largest problem of killing rusty crayfish is that any
chemical that kills them also kills native crayfish. The only sure way to kill
them is to trap them and select which are rusty and kill those while letting
the natives go free.
GreatLakes.net and netnewsledger
Spiny Water Flea
Spiny Water Flea is an aquatic invasive that is devastating our lakes and rivers. The water flea was introduced from ship ballast water and possibly as resting eggs from mud. These little critters range from ¼ to 5/8 inch long, and have a long needle like tail with little spines along it. The fleas thrive in deep, cold lakes which can be found across the Midwest. Populations are most abundant in late summer into autumn.
Why is it Invasive?
Spiny Water Fleas eat small zooplankton, including Daphnia, which is part of a diet for many young native fish. They may even cause the small decline or elimination of some species of native zooplankton, which in turn competes directly with small baitfish and may increase algal blooms as zooplankton that feed on algae are eliminated. Small fish have difficulties eating Spiny Water Fleas due to the large spiny tail, although larger fish can eat them, the spiny tails often stick in their digestive tract, eventually killing the fish. Anglers also have had troubles with Spiny Water Fleas getting on their tackle, clogging eyelets on fishing poles and attaching themselves to fish gill slits and ultimately choking the fish.
education about spiny waterflea is probably one of the most important roles of
control, not only for the flea but also for every invasive aquatic or
terrestrial. By education, we mean how to properly inspect equipment and then
effectively cleaning the equipment to help prevent the spread from lake to
lake. As of now, there are no known chemical control methods at this time. However,
a high tech method is out there using electron beam irradiation that has
For more information:
Yellow floating heart was introduced as an ornamental
plant for water gardens from eastern Asia. It is capable of prolific
reproduction through seeds, stems, or broken off leaves with part of a
stem attached, making control of the plant difficult. A single plant is
capable of producing over 100 new plants in 12 weeks. Yellow floating
heart can displace native species, decrease lake biodiversity, decrease
water quality, inhibit recreational activities, and reduce aesthetic
Yellow floating heart has small,
circular, heart-shaped leaves that float at the water’s surface. The
leaf edges are wavy and scalloped. The flowers grow on a stalk that
“floats” above the water’s surface and the five petals are distinctly
fringed. Yellow floating heart grows in lakes, slow moving rivers,
reservoirs, ponds, and in damp mud or wetlands. It grows in depths less than 10 feet.
Yellow floating heart is listed as Prohibited in the state of Wisconsin under NR 40 Invasive Species Rule banning the transport, possession, transfer and introduction. Similar native species include spatterdock and watershield. Spatterdock has larger leaves and cup-shaped flowers. Watershield has football-shaped leaves that often have a slimy underside and small purple flowers.
If you find yellow floating heart in any of WRISC’s counties please contact us at (906)774-1550x102 or email@example.com. Yellow floating heart has been found in lakes and ponds in Forest and Marinette counties. For more information about yellow floating heart click here.
Zebra Mussel (Dreissena polymorpha)*
Zebra Mussels are native to Eastern Europe and Western Russia. They were brought over to North America by attaching themselves to the ballasts of freighters. By 1980 zebra mussels were found in all of the Great Lakes. Then they found their way into the Mississippi River. This lead to the spread of the mussels throughout the midwest and southern states.
Why is it invasive?
It is invasive because they attach themselves to hard surfaces and produce millions of offspring annually. The mussels are hazardous to people because the clump together to cause mechanical issues. They are also a problem because they are sharp and cut the feet of people who step on them. The zebra mussels cloud over rocks on the bottom of the lake and can prevent any other life from happening.
They have a D shaped shell and usually have dark and light colored stripes. They look like tiny clams. They can be up to two inches long but are usually under one inch.
They can be found on the bottom of an algae filled lake. They grow in clusters next to each other. They can also be found of docks or boat hulls. What you can do to prevent the spread is to clean of your boat of any plants or other things. You can also report any sightings to the DNR.
For more information:
Minnesota DNR and SeaGrant Minnesota