Emerald Ash Borers

Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is a small exotic beetle (about 1/2 of your fingernail) that was discovered in southeastern Michigan near Detroit in the summer of 2002. The adult beetles nibble on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients. Emerald ash borer probably arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating in its native Asia. Emerald ash borer is also established in Windsor, Ontario, was found in Ohio in 2003, northern Indiana in 2004, northern Illinois and Maryland in 2006, western Pennsylvania and West Virginia in 2007, Wisconsin, Missouri and Virginia in the summer of 2008, Minnesota, New York, Kentucky in the spring of 2009, Iowa in the spring of 2010, Tennessee in the summer of 2010, Connecticut, Kansas, and Massachusetts in the summer of 2012, New Hampshire in the spring of 2013, North Carolina and Georgia in the summer of 2013, Colorado in the fall of 2013, New Jersey in the spring of 2014, and Arkansas in the summer of 2014. Since its discovery, EAB has:

Ash trees infected with Emerald Ash borer die from the top down. This is called canopy dieback. You might also note sprouts coming out from the base of the tree, in an effort to survive. Once a tree becomes infected, it takes approximately 5 years to die. It is the larval or caterpillar stage of the beetle's life cycle that  damages the trees. The worms live just under the bark and disrupt the food and water distribution system of the tree. Therefore, the tree starves to death.

Ash Trees

Ash trees are a sturdy hardwood and used to be favored for the production of wooden baseball bats (the Louisville Slugger bat is famous), furniture, flooring and tools.


Multiple species of ash trees are affected by the beetle including Northern White Ash (Fraxinus americana), Green Ash (Fraxinus pennsylvanica), and Blue Ash (Fraxinus quadrangulata).
You may recognize an ash tree by observing the following traits:

  • Branching pattern is opposite. The buds are opposite and rotate 90 degrees 
  • Leaves are compound

How EAB Kills an Ash Tree

Emerald ash borer is deadly to ash trees because the larvae feed right under the bark. This is where a tree conducts water and nutrients from its root system up to its leaves. As the number of larvae increases, more of the tissue is damaged which blocks the flow of water and nutrients, and the tree dies. After a tree is infested, these symptoms often take several years to show up, adding to the challenge of management.

EAB how it kills

Image from Rainbow Tree Care