Public Info

Union County Plans for Emerald Ash Borer

County Agent, Madeline Flahive DiNardo training volunteers on how to measure the diameter of a tree.

A team of 25 carefully trained volunteers from Rutgers Cooperative Extension (RCE) of Union County have been inspecting hundreds of ash trees in several Union County Parks for signs of Emerald Ash Borer (EAB), a non-native insect pest that infests and kills all species of Ash trees. As of yet, EAB has not been detected in Union County although it is anticipated to be discovered soon.

“A huge thank you goes out to all of the volunteers who are helping to inventory and map Ash trees across Union County,” said Freeholder Chair Bette Jane Kowalski. “Creating an Ash tree inventory is the first step in developing an EAB response plan to ensure the county is ready for this new insect if it emerges.”

Infestations throughout the U.S. and Canada have killed tens of millions of ash trees since 2002. Currently it is known to be in 14 of 21 New Jersey counties.

Volunteers meet weekly at different parks throughout the county. The Ash tree inventory has been completed for 9 parks including Warinanco, Lenape, Echo Lake, Cedar Brook, Rahway River, Nomahegan, Meisel Ave., Green Brook, and Oak Ridge Parks.  Close to 800 Ash trees have been inventoried in these parks.

The information collected is being used to make recommendations on the value of treating and saving Ash trees, verses removing them. This process will help take action to develop long range budgets for Ash tree management.

Ash trees can be identified by their compound leaves meaning the leaf is divided into smaller leaflets. Another distinguishing characteristic includes the arrangement of branches and buds which are in pairs across from each other, known as opposite branching.

The first sign that an Ash tree has been infested by the EAB is usually damage to the bark. Woodpeckers flake off the bark with their beaks to get at the EAB larvae. The distinctive white stripes left from this flaking are called “blonding”. The adult female EAB creates characteristic D-shaped exit holes, 3-4mm in size, when they emerge in May or early June.  As the infestation worsens the crown will begin to die back starting at the top.

EAB infestations are fatal to trees not treated properly with insecticides.  Ash trees killed by EAB become brittle very quickly, making them a greater safety hazard to pedestrians and arborists removing trees. 

Homeowners looking for assistance protecting their Ash tree should contact a certified licensed tree expert. More information for homeowners and communities on EAB in New Jersey can be found at  For more information on this project contact RCE of Union County at 908-654-9854.

The Rutgers Master Gardener program in Union County is supported by the Union County Board of Chosen Freeholders and Rutgers, the NJ Agricultural Experiment Station with offices at the Union County Complex in Westfield, at 300 North Avenue East.

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