Wisconsin Forums

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Posted June 25, 2006

Invasive species wreak havoc in county, state

By Kristopher Wenn
Herald Times Reporter

MANITOWOC

– Invasive species experts fear a small, green Asian beetle responsible for the destruction of 20 million ash trees in the Midwest will make its way to Wisconsin.


The emerald ash borer first appeared in the Detroit metropolitan area in 2002 and was spotted earlier this month in northern Illinois.


The proximity has local leaders watching.


From 5 to 10 percent of the 19,000 trees in the city of Manitowoc are ash, said Joe McLafferty, parks and recreation director.


"It's not a huge number, but any time we have the possibility of this coming here it is of concern," he said.


Two Rivers' latest tree inventory in 1990 doesn't specify the number of ash among the 10,000 trees in the city, according to Rick Manchester, parks and recreation director. About 10 percent of all trees in Wisconsin are ash, according to the DNR.


Emerald ash borer larvae enter the bark of ash trees, starve the trees and cause them to die after a few years. Until the beetle is sighted in Wisconsin, property owners don't need to apply pesticides, according to officials with the state Department of Agriculture, Trade and Consumer Protection officials said.


While the ash borer creeps north, other invasive species — terrestrial and aquatic — are having an immediate impact in Manitowoc County and elsewhere.


The cost of invasive species to the national economy has been estimated as high as $137 billion per year and increasing, due primarily to losses in agriculture, forests and fisheries, according to the Wisconsin Council on Invasive Species.


On Pages A6 and A7 is a look at what the DNR considers the 10 most potentially destructive invasive species in Manitowoc County.


:arrow: Plants and forest

Name: Emerald ash borer


Description: Emerald ash borer is a small, green beetle from Asia.


How they got here: The borer isn't here yet, but forestry officials believe it could make its way to the state soon. The pest has spread from Detroit to northern Illinois in about four years. It has been blamed for the destruction of 20 million ash trees in the Midwest. The insect has spread on nursery stock and firewood.


Local impact: Manitowoc County's southern hardwood tree area is especially susceptible to emerald ash borer.


Steps taken: The DNR has quarantined nursery stock from affected areas and bans the use of out-of-state firewood on any state property it manages. The DNR is encouraging private campgrounds to do the same. State agencies also are setting up bait ash trees in areas like Point Beach State Forest and studying whether the trees attract emerald ash borer.


Name: Purple loosestrife


Description: Purple loosestrife grows individual flowers with five to six pink-purple petals. The plant can reach 6 feet in height.


How they got here: Settlers introduced purple loosestrife, originally from Europe and Asia, in the 1800s as an ornamental plant for flower gardens. Seeds were found in ballast water of ships. The plant eventually made its way into local waterways and began growing in wetlands.


Local impact: Purple loosestrife competes with native plants in wetlands in Manitowoc County and, as a result, destroys native habitat where fish and wildlife feed, seek shelter, and reproduce. According to the DNR, about 40,000 acres of wetlands, marshes, pastures and meadows in Wisconsin are threatened by purple loosestrife.


Steps taken: Purple Loosestrife will stay in the county, but it is not spreading nearly as much as it used to due to the introduction of the Galerucella beetle, a loosestrife-eating insect. Property owners can manage plant populations by weeding and chemical controls.


Name: Garlic mustard


Description: Garlic mustard is a woodland plant that can grow from 1 to 4 feet tall. Its leaves and stems smell like onion or garlic when crushed.


How they got here: Garlic mustard, brought to Wisconsin by European settlers, has spread in the forested areas of Manitowoc County and northeastern Wisconsin. Seedlings are spread from people and the fur of animals.


Local impact: Garlic mustard grows and spreads over the underbrush of the forest. The plant competes with native species for nutrients and sunlight and can kill trees indirectly through destroying the fungus that trees depend on for absorbing water and nutrients.


Steps taken: Garlic mustard has been in Wisconsin for at least 100 years and there's little chance of getting rid of it. Property owners can choose to suppress it by weeding and using chemical controls.


Name: Gypsy moth


Description: Gypsy moth is an invasive insect native to Europe, Asia and North Africa.


How they got here: In 1869, gypsy moths were brought to the U.S. by a French naturalist seeking to establish a domestic silk industry. The moths traveled westward through natural spread and movement by humans. The moths were detected in Michigan in the 1950s and arrived in Wisconsin in the 1990s.


Local impact: Gypsy moths defoliate trees by feeding on tree leaves. The moths eat on oak, aspen, birch, crabapple, tamarack and willow tree leaves. The pest is present throughout the county, but it is a threat to birch and oak trees in urban areas.


Steps taken: In the early and mid-1990s, the state sprayed areas to eradicate gypsy moths, but it proved unsuccessful. In May, the DNR sprayed 300 acres on the north side of Manitowoc to reduce moth nuisance and minimize defoliation of trees. According to the DNR, the average costs for gypsy moth suppression spraying is $24 per acre.


Name: Earthworms

Description: Earthworms are reddish, cylindrically shaped. They burrow, aerate and enrich soil.


How they got here: Common earthworms did not exist in the state following the Wisconsin Ice Age, which decimated the native earthworm population. European immigrants helped to transport them into the state.


Local impact: Earthworms are a hazard to sugar maple trees, the dominant tree in Manitowoc County forests. The worms quickly decompose leaves and organic matter on the forest floor into the soil below, leaving a dense layer of soil lacking nutrients trees need to grow.


Steps taken: Earthworms are so widespread that they are probably here to stay, but people can reduce the spread of worms by dumping unused fishing worms in the trash instead on in the water on the land.


:arrow: Aquatic pests

Name: Zebra and Quagga mussels


Description: Zebra mussels and Quagga mussels are closely related filter-feeding organisms, which hail from the Black and Caspian seas. Quagga mussels tend to be bigger than Zebra mussels. Both mussels feature striped shells.


How they got here: The mussels arrived in the Great Lakes from ballast water from ships traveling through the St. Lawrence Seaway.


Local impact: Zebra and Quagga mussels threaten native fish and organisms in Lake Michigan by filtering out plants and nutrients that native species need to survive. The successful adaptation of the mussels has been blamed for the cause of smaller game fish sizes and reduction of native forage organisms. Zebra mussels have been found in 70 Wisconsin inland lakes, including Cedar Lake in Manitowoc County. Quagga mussels have not been found in any inland lakes. The mussels could wreak havoc for municipalities by clogging intake pipes.


Steps taken: There are no means of controlling Zebra and Quagga mussels once they are established. Public outreach programs for anglers and boaters to prevent the spread of the mussels are believed to be the most feasible approach in controlling them.


Name: Sea lamprey

Description: Sea lampreys are parasitic fish with dark brown and black backs and yellow-brown stomachs. Sea lampreys can grow from 12 to 20 inches long.


How they got here: Sea lamprey was first detected in Lake Michigan in 1936. The lamprey arrived here from ballast water from ocean-faring ships traveling on the St. Lawrence Seaway.


Local impact: Sea lampreys use their round mouths to attach to fish gills and gradually suck out a fish's blood and body fluids. Sea lampreys, predators of game fish such as trout, salmon and white fish, contribute to the lowering of game fish populations.


Steps taken: The Great Lakes region spends $25 million to $26 million annually for chemical treatments to kill young sea lamprey and for barriers to prevent them from spawning. Efforts to eradicate sea lamprey have, at best, proved effective in keeping populations in check.


Name: Eurasian water milfoil


Description: Eurasian water milfoil is an underwater aquatic plant native to Europe, Asia and northern Africa. The plant features thin stems circled with groups of leaves. Stems can grow up to 10 feet.


How they got here: Eurasian water milfoil, first discovered in Wisconsin in the 1960s, spread into local water bodies from fishing equipment, ocean-going ships and boats.


Local impact: The plant is problematic in inland lakes where they grow on the water surface in a canopy and dominate native plants. Plant growth can interfere with boating and fishing activity and can alter native fish habitats.


Steps taken: Population controls for Eurasian water milfoil are expensive, reaching up to $1,000 per acre to rid water bodies of the plant. Property owners can control plant population numbers with physical removal and chemical applications.


Name: Round goby


Description: Round gobies are invasive fish that live at the bottom of water bodies. The have large, tadpole-like heads and can grow from 5- to 6-inches long.


How they got here: Round gobies made their way to Lake Michigan from ballast water from ships traveling the St. Lawrence Seaway. The fish are egg predators and dominate native species for food and habitat.


Local impact: A native from the Caspian Sea, round gobies are aggressive fish that fare well in the relatively shallow waters of Lake Michigan.


Steps taken: There's not much that can be done to rid local waterways of round gobies. In order to slow their spread, the DNR advises that anglers throw caught round gobies in the trash rather than letting them go in the water.


Name: Rusty crayfish


Description: Rusty crayfish, which can be up to 2 inches in length, feature rusty spots on both sides of their hard outer body covering. The crayfish has large grayish-green to reddish-brown claws.


How they got here: Rusty crayfish are native to the southern U.S. and were introduced in the state by anglers who used them as live bait.


Local impact: According to the DNR, most Manitowoc County inland waters have rusty crayfish. Rusty crayfish dominate native fish in inland lakes and streams and destroy vegetation that serves as fish habitat. Rusty crayfish are known to pinch swimmers' toes.


Steps taken: Efforts to eradicate rusty crayfish have proven unsuccessful. The DNR advises that people do not buy rusty crayfish as fishing bait.