Seal of Dane County County of Dane
Dane County Tree Board

Emerald Ash Borer (EAB)

The emerald ash borer is a devastating non-native insect that has killed millions of ash trees in the Eastern U.S. It was first identified in Michigan in 2002, but had probably been in the state for up to 12 years prior to that. It attacks only ash trees. It probably arrived in ash wood materials used for packing and shipping, such as wooden pallets.

The adult insect is about one-half inch long and one-eighth inch wide on average. It is a bright metallic emerald green color, hence the name. The larval stage, called a borer, does the damage to the tree, chewing its way through the bark and into the cambial layer, feeding on wood as it grows and destroying the vascular system that allows the tree to pull up water from the ground. Limbs die as the tree is unable to supply them with water, and within two to three years the entire tree dies. Symptoms of EAB infestation include dead limbs, vertical cracks in the bark, tall leafy shoots growing out of the lower trunk, small D-shaped exit holes in the branches and trunks where the adults emerge, and excessive woodpecker damage called flecking. When bark is removed, the S-shaped larval tunnels etched in the wood from the larval feeding can be seen. On their own, the adult insects only spread about one-half mile per year, but they are easily spread much greater distances in infested firewood. Therefore, it is critical that ash firewood not be moved around. The Dane County Tree Board recommends you visit Wisconsin's Emerald Ash Borer Information Services for information on identifying EAB, learning about its life cycle, identifying ash trees, firewood regulations and treatments.

The Dane County Tree Board has created three factsheets that bring together many of the resources available online:

If you have ash trees, there are preventative insecticidal treatments available, but it is not recommended that these be applied until an insect find is confirmed within 15 miles of your tree. There are products that are available for homeowners to use to treat trees themselves.


In Dane County, the county government has created a response plan to help municipalities deal with the expected large quantities of dead trees and establish protocols for handling, transporting, storing and chipping or safely re-using infested wood at specially designed marshalling yards to prevent further spread of the insect.
Other organizations in Dane County such as the Urban Tree Alliance and Sustainable Atwood are also working on the wood stream issue and recycling wood resources in a safe, sustainable manner.

The video clip below featuring Jennifer Statz from the Wisconsin Department of Natural Resources gives further information on EAB and the national fight against this devastating forest pest.