Emerald Ash Borer

Brief History

  •  The Emerald Ash Borer arrived in the Detroit area in packaging material from Asia. 
  • First identified in Detroit 2002.
  • They are good flyers and have now been seen in 35 states and Canada. 
  • Expected to kill the ~8.7 billion Ash trees in America (~10% of our canopy of trees)
  • They have killed hundreds of millions of ash trees in North America and have cost many hundreds of millions of dollars.
  • First seen in NJ in 2014 in Bridgewater, by late 2018 they have been found in Bergen, Burlington, Camden, Essex, Hudson, Hunterdon, Mercer, Middlesex, Monmouth, Morris, Somerset, Sussex and Warren counties.
  • NEARLY ALL UNPROTECTED ASH TREES WILL PERISH. “Over the next few years, 99% of NJ ash trees will die due to emerald ash borer infestations.” Mountain Ash trees are not susceptible at this time. 


  • While there are a number of treatment regiment, one of the most effective is to inject the tree with a treatment that travels up through the trees vascular system and kills the borer. Its important to treat the trees while they are strong. 

Tree Removal

  • Trees not treated should be removed if near property or people. Trees that are infected and die become brittle and dangerous.

How do the borers kill trees?

  • The larvae feed on the inner bark. The web of paths that they cut as they feed disrupts the movement of water and nutrients up through the trees vascular system, which starves the tree.
  • The borers tend to start at the top of the tree and work their way down. By the time they exit the tree leaving their signature “D” shaped exit hole it is likely too late to save the tree.

How to identify an Ash tree?

  • Ash species have opposite branches and leaves and a compound leaf with 5-11 leaflets. The bark has a unique diamond-shaped ridge bark on older trees, but younger trees may have smoother bark. 


Emerald Ash Borer Fact Sheet from the New Jersey 


Rutgers articles (0lder)



Larvae feeding creates a web of paths that disrupts the movement of water and nutrients

Larvae feeding creates a web of paths that disrupts the movement of water and nutrients