How Emerald Ash Borers Damage Trees

Emerald Ash Borer Damage
In spring and summer, female emerald ash borer beetles lay eggs in ash trees. Larvae from these eggs hatch within a week or two, bore through the tree’s bark and eat nutrient and water-conducting material in the cambium layer beneath the bark.

The larval activity within the tree disrupts the vessels that move water and carbohydrates – essential to the ash tree’s health – within the tree. Over time, this disruption causes ash trees to decline and, eventually, die.  From initial infestation it takes three to four years for the tree to fully die.  If the presence of these ash borers is detected in years one or two and the proper action is taken, damaged ash trees might be able to be saved.

Damage from Emerald Ash Borer to Date

The emerald ash borer (EAB) has decimated tens of millions of ash trees in cities throughout Michigan, Ohio and Illinois. Photos from these states are potent reminders of the destructive power of EAB infestation.


  • Emerald ash borer was first discovered in the United States in Michigan in 2002. Since that time it has killed more than 30 million ash trees in southeastern Michigan alone.
  • In the Upper Huron River Watershed, ash tree mortality grew from roughly 10% in 2002 to 100% in 2010.
  • Michigan has enacted a quarantine to limit the movement of potentially infested wood throughout the state, and is working on a multi-year strategy to slow the spread of ash death and suppress further EAB infestation, if possible.


  • Ohio is home to an estimated 3.8 billion ash trees.
  • Unfortunately, since 2003, the emerald ash borer has infested so many counties across the state (including Wayne National Forest) that millions of ash trees have already fallen due to the pest, and it is anticipated that millions more will die.
  • The Ohio State Universityhas created an EAB Outreach Team to provide “non-biased, science-based information to home and woodland owners, communities and industry professionals” in hopes of educating citizens about the pest and what actions citizens can take to prevent further devastation.


  • Emerald ash borer’s presence was confirmed in the state of Illinois in June, 2006.
  • Illinois has already lost millions of ash trees due to the pest.
  • Many communities have been forced to undertake large-scale ash tree removals of dead and dying tree already infested by the borer.
  • Illinois is partnering with the USDA – Natural Resources Conservation Service to save and store native ash tree seeds before the species is completely wiped out.