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Emerald ash borer

This webpage contains information on Wisconsin's ash resource and the potential impact of emerald ash borer (EAB) in the state. The most current information on emerald ash borer in Wisconsin is available at the Wisconsin Emerald Ash Borer Information Source [exit DNR]. That website includes:

  • emerald ash borer and ash tree identification;
  • firewood and quarantine laws;
  • tips for managing EAB;
  • Wisconsin’s strategy to manage emerald ash borer; and
  • instructions for when and how to report a suspect emerald ash borer.

See the spread of emerald ash borer in Wisconsin by county from 2008–2018.

Wisconsin's ash

Ash in Wisconsin's forestlands

An estimated 834 million ash trees are in Wisconsin's forestlands as part of northern hardwood, oak-hickory and bottomland hardwood forests. Ash trees provide many ecological benefits: their seeds provide food for birds and small mammals, black ash twigs and leaves provide food for deer and moose and trunk cavities provide nesting areas for birds such as the wood duck. Ash is also valuable to Native Americans for its excellent basket-making quality and cultural importance.

Ash species make up 6.8 percent of Wisconsin's forests (counting all live trees one-inch in diameter or larger). Black ash is the most common species, at 3.8 percent of all tree species, while green ash is 1.6 percent and white ash is 1.4 percent. Blue ash is far less common with only a small amount in Wisconsin forests.

Graph showing precentage of ash

Ash species

Ash density on forested land in Wisconsin [PDF] (based on 2009 FIA data)

White ash

White ash (Fraxinus americana) grows throughout Wisconsin on a variety of sites but it's most frequently found on fertile, well-drained upland sites in both the northern and central hardwood forests. White ash typically grows as a part of other forest cover types and rarely is dominant. With its white, strong and straight-grained wood, it is the most commercially important ash species in Wisconsin. It is also valued commercially for its high elasticity, shock resistance and low shrinkage.

Green ash

Green ash (F. pennsylvanica var. lanceolata) is found throughout the state but is most common in southern Wisconsin. It may be in stands with only green ash or grow with black ash, red maple, silver maple, swamp white oak and elm. It grows as part of upland hardwood stands but is most common in and around stream banks, floodplains and swamps. Green ash wood is not as straight-grained as white ash and thus not as commercially desirable.

Black ash

Black ash (F. nigra) can be found in most of the state but is most common in northern Wisconsin. It is most common in wet sites such as riparian areas and swamps, and in forest cover types such as bottomland hardwoods, swamp hardwoods and swamp conifers. Currently, black ash is not very commercially important. However, it was historically valued by Native Americans due to its ability to split along growth rings, resulting in thin strips for making baskets, chair seats and barrels.

Blue ash

Blue ash (F. quadrangulata) is in southern Wisconsin (Waukesha County) but is not abundant. Blue ash is listed as a state threatened species in Wisconsin and is on the edge of its North American range here. It has inner bark that was used as a blue dye by Native Americans giving the species its common name. The species likes rich limestone hills but grows well on fertile bottomlands. Because of its small size and scattered distribution, blue ash is not commercially important.

Note: Mountain ash (Sorbus spp.) is not a true ash species. Therefore it is not susceptible to emerald ash borer infestation.

Potential impact

Impact of emerald ash borer in Wisconsin

Emerald ash borer (EAB) spreads slowly on its own, but its spread is greatly accelerated when people unintentionally move it in firewood and nursery stock. (See emerald ash borer detections in Wisconsin by county [PDF]) All types of Wisconsin’s native ash species – green, white, black and blue ash - are vulnerable to attack by EAB. Wisconsin's ash resource is vast; there are 834 million ash trees in our forests and 5.2 million ash trees in urban landscapes.

Emerald ash borer commonly kills ash in urban areas and along roadsides in infested areas, costing city governments millions of dollars for tree removal and replacement. The financial impact of EAB in Wisconsin forests is unknown, but believed to be substantial.

What to do as a forestland owner or manager to prepare ash resources

The Wisconsin Department of Natural Resources, along with other scientists, have written guidelines to help forest landowners minimize potential damages. It is important that landowners evaluate the potential impacts of emerald ash borer and take action if needed.

Preparing Wisconsin's Forests for the Emerald Ash Borer [PDF]

What you can do

Slow the spread of emerald ash borer. Get firewood where you will use it.

Slowing the spread of emerald ash borer (EAB) throughout Wisconsin is the best thing for the ash trees in our forests and urban areas. Please follow these suggestions:

  • although the entire state of Wisconsin is quarantined for EAB [exit DNR], it is still good practice to obtain firewood within 10 miles of where you will use it. Many parks offer aged or certified firewood [PDF exit DNR] for sale to campers at reasonable prices. Firewood is also often available from private sellers just outside the parks;
  • burn all firewood during your camping trip. Don't leave any unused wood behind and don't take it with you to another destination;
  • when obtaining firewood, choose pieces that are dry and have either no bark or loose bark (a sign that wood is very dry). This reduces the chance of spreading pests and diseases;
  • reduce your need for open fire by cooking over gas or charcoal. Instead of an evening campfire, explore new night-time activities like star-gazing or viewing wildlife by flashlight;
  • maintain the health of yard trees by watering during times of drought. Ash trees are sensitive to drought conditions and require plenty of moisture throughout the growing season. Please note, though, that the emerald ash borer infests healthy trees too, not just stressed trees;
  • be familiar with the signs and symptoms [exit DNR] ash trees exhibit when infested by EAB. Also, know how to distinguish emerald ash borers from look-alikes [PDF].
  • In counties where EAB has not yet been found [PDF], report any suspected findings to the Department of Agriculture, Trade and Consumer Protection by calling the Emerald Ash Borer Hotline at 1-800-462-2803.

Learn more by visiting Wisconsin's Emerald Ash Borer Information Source [exit DNR].

Last revised: Wednesday December 12 2018