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Invasive Beetle Alert: Emerald Ash Borer

The small invasive beetle known as the Emerald Ash Borer is devastating Ash tree species across Middlesex, Essex and 9 other Massachusetts counties this spring. Homeowners should be aware of the potential pest and know their options when it comes to treatment or ways to help prevent the spread of this beetle. 


What Is the Emerald Ash Borer? 

The Emerald Ash Borer (EAB) is a small, metallic green beetle that was initially identified in the United States in the area surrounding Detroit, Michigan in the summer of 2002. Since that time it has spread violently across the nation and can be found in 35 states as well as five provinces in Canada. 

Since its discovery, the EAB has killed hundreds and millions of Ash trees across the country. In response, the USDA enforced a quarantine on Ash tree firewood and mulch. The goal of this quarantine (which has been lifted in Massachusetts as of January 2021,) is to slow the spread of this pest and give the Ash trees a fighting chance. 

What’s the Danger of the Emerald Ash Borer? 

How dangerous can a small beetle be, you ask? 

Extremely dangerous, according to the Massachuestts state site dedicated to the identification, prevention, and treatment of the EAB. 

In the course of just a few years (between 3-5 years) an Ash tree can go from showing small signs of an infestation in the form of dieback on the upper canopy of leaves to full mortality with the disruption of the tree’s nutrient movement. 

Invasive species experts explain that the adult beetles do little damage to the Ash foliage, that the real problem occurs during the larvae or immature stage of development. The larvae feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients. (Source: US Dept of Agriculture

emerald-ash-borer-1447682_1920-jpgSigns of Damage 

The Emerald Ash Borer is hard to spot with an untrained eye. Sadly, most infestations are several years old by the time they are noticed by homeowners. At that point the life of the tree is in jeopardy. 

However, most entomologists know the signs to be aware of to treat and stop the spread of this highly invasive pest. These include: 


  • Defoliation in the upper canopy
  • Branch death in the upper canopy
  • Growth of new branches where they can get nutrients such as at the base of the tree (epicormic sprouting) 
  • Signs of woodpecker damage since woodpeckers seek out EAB larvae
  • D-shaped exit holes in the bark may indicate adult EAB 
  • S-shaped galleries in the areas beneath the bark (indicates larvae feeding) 
  • Vertically split bark which can indicate galleries of larvae underneath

What Can Be Done About EAB? 

Homeowners should have regular inspections of the trees in their yard. Most Emerald Ash Borers will not be recognizable without keeping a close eye on the growth of the problem. Often if the problem has gone on too long the tree may be unsalvageable.

Professional arborists are able to use spray and injectable treatments to keep your trees safe but need to do so before the infestation has gotten too far. Once detected, often the goal is to stop the spread to other trees in the area. 

Environmental methods such as using natural enemies of the EAB could help. For instance, woodpeckers and wasps could help along with professional treatments by trained arborists. 

The state of Massachusetts in partnership with the Forest Health Program has implemented a trapping program to continue emerald ash borer detections in the state. The trapping program allows state foresters to find new infestations, map the progression and spread of known populations, and determine sites suitable for biocontrol releases.

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