Emerald Ash Borer
Emerald ash borer (Agrilus planipennis) is an invasive, wood-boring beetle that kills ash trees (Fraxinus spp.) by eating the tissues under the bark. Native to northeastern Asia, emerald ash borer (EAB) was first detected in the United States in 2002 and is thought to have been introduced from China via the wood from shipping crates.
True ash species are highly vulnerable to EAB regardless of ash or total tree density, ash or total stand basal area, tree size and tree health. Researchers in Michigan and Ohio observed that ash survival decreased 30-50% over three years in infested stands in southeastern Michigan. Models developed from field observations predict that a healthy forest will lose 98% of its ash trees in six years.
While the insect spreads slowly on its own, EAB impacts are greatly accelerated when people unintentionally move it in firewood and nursery stock. See the spread of EAB detections in Wisconsin by county [PDF] since it was first detected in 2008.
EAB commonly kills ash in urban areas and along roadsides in infested areas, costing municipal governments millions of dollars for tree removal and replacement. The financial impact of EAB in Wisconsin forests is unknown but is believed to be substantial.
Rays of hope for ash trees
Some progress has been made in managing EAB populations. A tiny, native wasp was discovered killing EAB larvae at two sites in Michigan. Between 24% and 56% of EAB larvae at these two sites in 2008 were parasitized by this native wasp. We may yet discover more native insects that attack EAB and help reduce their populations.
Parasitic insects from EAB’s native range in China show promise for biological control efforts. Wisconsin Department of Natural Resources forest health specialists have released a total of four species of parasitic wasps in efforts to control EAB populations, although only three species have proven cold-tolerant enough to survive Wisconsin winters. To date, one wasp species (Tetrastichus planipennisi) has been successfully recovered in seven southeastern Wisconsin counties, which indicates that wasp populations are sufficiently stable in these locations to reproduce and parasitize new generations of EAB larvae.
What you can do
While EAB is present in many Wisconsin counties, more of Wisconsin is still free of EAB than not. Many counties where it has been found have only small areas of infestation. That is why it is still critically important to limit the movement of ash wood and raw ash products. By taking these precautions, we all help slow the spread of EAB.
Insecticide treatments typically require repeated applications for the life of the tree. For more information, read this guide to insecticide options for protecting ash trees from EAB or visit the University of Wisconsin-Extension's EAB website. You may also wish to consult with a certified arborist, who can help determine whether trees are worth treating and what additional options may be available.
For woodlot owners and managers
The Wisconsin DNR has partnered with other scientists and land managers to create EAB silviculture guidelines [PDF] to help forest landowners manage their ash resources. It is important that landowners evaluate the potential impacts of EAB and take action.
For homeowners and communities
For ash trees in urban and residential settings, protecting them from EAB requires insecticidal treatment. Insecticides can be effective in preventing individual trees from becoming infested and for treating trees with low to moderate levels of infestation.
It is important to examine your ash trees for signs and symptoms of EAB and know how close you are to known infestations. If EAB has been found near you, you may want to treat your trees to avoid future infestation or prevent further damage if the trees are already lightly infested. See a map of known EAB infestations .
Insecticide treatments typically require repeated applications for the life of the tree. For more information, visit the University of Wisconsin-Extension's EAB website or consult with a certified arborist . A certified arborist can help determine whether trees are worth treating and what additional options may be available.
Homeowners and communities may also choose to remove ash trees and replace them with non-susceptible species to maintain the many benefits that urban trees provide. Removing ash trees should be done before EAB has killed the tree to avoid associated safety hazards of EAB-killed trees.
For all Wisconsin residents
To slow the spread of EAB into new, unaffected counties and townships, everyone in Wisconsin can follow the suggestions on this page. These recommendations also apply to other harmful pests and diseases, such as gypsy moth and oak wilt.
- Although Wisconsin is now under a statewide EAB quarantine [exit DNR], we still recommend that people buy and use firewood locally.
- Wisconsin’s statewide firewood rule prohibits bringing firewood onto any state property from more than 10 miles away or from areas within the gypsy moth quarantine. Due to the gypsy moth quarantine, movement of firewood is also prohibited from quarantined into non-quarantined counties. Visit the firewood page for more information.
- Buy certified firewood [PDF exit DNR] at state properties, retail locations or directly from firewood dealers.
- Burn all firewood during your camping trip. Do not take it with you when you leave or leave any unused wood behind.
- Look for firewood that is dry with either no bark or loose bark. EAB larvae live beneath the bark and can survive for up to two years on dead wood.
- Consider using gas or charcoal instead of firewood. Explore new nighttime activities like star-gazing or viewing wildlife by flashlight.
For more information on EAB management in urban and residential settings, visit the emerald ash borer community toolbox and the University of Wisconsin-Extension's EAB website [exit DNR]. You can also contact your regional DNR urban forestry coordinator or find a certified arborist [exit DNR].