Invasive Pest Alert for Homeowners – the Emerald Ash Borer

Emerald Ash Borer – Agrilus planipennis

eab_howard_russellThe Emerald Ash Borer (EAB) is an invasive Asian pest that was accidentally imported into the US in 2002. It was first discovered in Michigan and has since spread to over 25 states. It was found in Somerset County in 2014. A Rutgers University study (EAB Rapid Ash Survey Report and Management Options, prepared for the Township of Ewing, Mercer County , NJ, By The Rapid Ash Survey Team (RAST) October 2015) confirmed its presence in Ewing in 2015.

Appearance and Damage

The iridescent green beetle with its copper red abdomen is about 1/2 inch long and 1/8” wide. The larvae are white or cream colored, measure approximately 1 to 1 ¼” long and have 10 abdominal segments that are bell shaped. The EAB has a 1-year lifecycle.

EAB adults emerge in May or early June creating D-shaped exit holes, 3-4 mm in size on the branches and trunks of infested trees. The female adult EAB feeds on the margins of the ash leaf. After feeding, the female EAB deposits eggs in bark crevices or under bark flaps on the trunk or bark. The adult beetle stays active until August. After the egg matures, the larvae feed on the inner bark and block the movement of water and nutrients, essentially girdling the tree. The larvae become adult beetles in April or May.

The EAB are strong fliers and readily find and kill ash trees. They have spread rapidly throughout North America and parts of Canada since their introduction. Their progress was observed in Maryland and the infested area expanded about 1/2 mile each year.

All Ash species, with the exception of mountain ash, are vulnerable and white fringetrees also have been found to be susceptible. The EAB works its way down from the upper branches of the tree which may make it difficult to spot early on. It may affect branches as small as 1″ in diameter. It may take as long as 2 – 4 years for infested trees to die, but without treatment mortality is imminent.

What to look for in infested trees

Early detection is difficult as the exit holes are tiny and the infestation starts from the crown of the tree. However, since trees only live an average of 3 -4 years after infestation, it is important that you contact a qualified arborist as soon as possible to determine if the tree can be saved.

  • woodpecker damage is often the first sign- the outer bark is scraped off, leaving smooth light colored patches
  • crown dieback – thinning starts at the top of the tree and becomes progressively worse as more nutrients are cut off
  • bark splits – these are vertical and result from the callous tissue that grows around the EAB feeding galleries (see S-shaped galleries following)
  • epicormic branching – sprouts or suckers at the base of the tree grow when a tree is stressed
  • S-shaped galleries weaving back and forth on the surface of the wood will be seen under the bark
  • small D-shaped exit holes (in contrast to the round or oval exit holes from other insects)
  • You may see the beetle itself from May thru August


As noted above, the EAB is quite proficient at getting around on its own, but its spread has also been unintentionally aided thru the movement of firewood from an infested area to a new location. Additionally, they have been known to hitch a ride on nursery tree stock.


Over the next few years, 99% of NJ ash trees will die due to emerald ash borer infestations. This is a signification portion of our tree canopy. According to the NJ State Forestry Services Forest Health:

  • our forests contain 24.7 million ash trees
  • 24% of all forested land contains ash
  • Ash is a common planted street and landscape tree in the state

What You Should Do

Go to Save Your Ash Trees from the EAB