Love your ash trees? Take steps to protect them from the Emerald Ash Borer

Emerald Ash Borer by USDA
May 26, 2017

All ash trees in Montgomery County are at risk of long term damage or death caused by the Emerald Ash Borer (EAB). This beetle was brought to the United States from Asia and has spread across all of Maryland and surrounding states.

As adults, EAB do not cause significant damage to trees. However, their larvae threaten all species of ash trees by feeding on the tissue between the bark and wood.

Unless we are proactive in protecting ash trees from damage caused by EAB, scientists predict that nearly all ash trees in Montgomery County will die within the next 10 years.

Treatment is effective and treating ash trees in the early stages of EAB infestation can minimize damage, allow for recovery, and prolong their life.


Emerald Ash Borer


Be Proactive in the Battle Against Emerald Ash Borers

Even if your ash trees do not have EAB now, you should expect EAB to infect your trees sometime over the next ten years.  To save your ash trees, you must act before EAB arrives.


Seek the Advice of a Tree Expert

Due to the nature of EAB, we recommend everyone with ash trees seek the help of a tree expert.


  • If your trees isn’t showing clear signs of EAB-related damage, advance treatment is the best way to protect the tree and prevent infection
  • If your trees have an early stage EAB infection, treatment is the best way to save your tree.
  • If your trees have an advance EAB infection or you have a dead tree, a tree expert will help you determine if your tree is hazardous and at risk of falling.  You also want to prevent the EAB from spreading to other trees.

Long story short – if you have ash trees, seek the guidance of a tree expert as soon as possible!



How do I identify ash trees?

Here are two fact sheets to help identify ash trees:


How can I identify if my ash trees already have EAB?

Ash trees infested with EAB rapidly become brittle and hazardous. These trees often become hazardous before they die. Watch this short video about how to identify ash trees and damage from EAB:



Note that you no longer need to report EAB to authorities because it’s now found everywhere in Maryland and surrounding states.


Remember: Don’t move firewood.

Buy your firewood locally. Moving wood products, especially firewood, increases the spread of invasive pests, like EAB and gypsy moths, that threaten the health and life of forests and trees. Learn more here.


How do EAB kill ash trees? Why are infested trees dangerous?

EAB larvae feed on the layers of cambium tissue between the bark and wood of ash trees. They bore tunnels while feeding on the cambium. This boring interrupts the flow of water and starch through each tree causing the leaves and branches to die.

The lack of water in the leaves and branches causes them to rapidly dry and become brittle. Once the crowns are dry, ash trees are hazardous and could fall or snap off at the base. Large dead branches could fall at any time, as well.

EAB typically feed from the top of ash trees down the branches to the stem. As such, visible signs of damage starts at the top of trees and spreads to the lower trunk. Therefore, if you can see the D-shaped exit holes made by EAB larvae at eye-level, then the tree is likely to be heavily infested.

It is important to contact a licensed tree expert as soon as ash trees are identified.


Signs and symptoms of emerald ash borer infestations


More information is available on the following websites:

6 comments on "Love your ash trees? Take steps to protect them from the Emerald Ash Borer"

  1. Sherry Marshall says:

    It is my understanding that treatment can delay the infestation by EAB, but not prevent it. In other words, unless some as yet unavailable remedy is found, we will lose all of our ash trees. If this information is incorrect, please let me know. Thank you.

    1. susan says:

      Thanks for your question, Sherry. You’re right, treatment delays the infestation. As long as ash trees are treated with the appropriate amounts of effective pesticides, infestation will not occur and treated trees will remain alive. Untreated trees and trees not adequately treated, will likely die. So, if your ash trees are valuable to you, plan to treat them for the next 10 to 15 years, maybe longer.

      At that time, scientists think the populations of EAB will decline due to natural causes, parasitoids, and other treatments currently being developed.

      If you need more information about treating your tree, or need the advice of an expert for any other tree issues, please visit this page and then click “Hiring a Tree Expert”: .

  2. RT Shea says:

    What is the County doing to address ash trees in the right-of-way areas? We have several streets in our community lined with ash trees and are concerned about losing so much tree canopy. Please advise.

    1. susan says:

      Thanks for the question. Ash trees are estimated to make up 3 to 5 percent of the street trees along rights-of-way maintained by Montgomery County. The County removes ash trees as they decline from EAB infestations, then the stump removals and a replacement plantings are scheduled. The County’s Street Tree Maintenance Section is working with communities to address EAB impacts, and recommends that you contact them as soon as possible. To report an ash tree or to request a new street tree, please call 311 or submit a request through the 311 website (

  3. Leslie Kofron says:

    I know this sounds crazy, childish but what about finding a way to heat living trees, temporarily to intense degrees (140) to kill the borer under the bark? Would this kill the tree? Could the tree be injected with a toxin that the borer would ingest (rather than spraying)? When in Sequoia I saw trees that were still alive after a forest fire so I have to think a tree can somehow endure some burn/ heating and recover. I was also reading that if you turn ash wood into lumber it should be heat treated in a kiln to kill off any larva.

  4. Nathaniel J Simon says:

    Thanks for your work on this. You should add tree of heaven (Ailanthus altissima) to your pdf of look-alikes.

Leave a Reply

Your email address will not be published. Required fields are marked *