Emerald Ash Borer (EAB)

The emerald ash borer (EAB) is an invasive, wood-boring beetle. It was first discovered in the United States in southeastern Michigan in 2002. Experts believe the pest entered the country on solid wood packing material originating from Asia. Since its discovery, the emerald ash borer has killed millions of ash trees in North America.

EAB was first confirmed in Texas on May 6, 2016, in Harrison County. It has since spread across the state, with confirmed infestations in Dallas and Denton counties. As of 2024, EAB has moved south and was recently confirmed in 5 new Texas counties.

If you have an ash tree on your property, you MUST treat for emerald ash borer every 2 years. Otherwise, the tree should be removed and replaced with a regionally appropriate species.

What does EAB do to ash trees?

The larval stage of the borer feeds on the inner bark of ash trees, preventing the tree from transporting nutrients and water. Larvae actively feed from the early summer through the fall. Infested ash trees become stressed and decline quickly—most die within 2–3 years of initial infestation.

Ash trees killed by EAB are brittle and structurally compromised, making them much more susceptible to damage caused by high winds and storms. Additionally, they are extremely dangerous to remove through conventional methods and may require costly crane removal.

Signs and Symptoms of EAB

• Canopy dieback: Begins in the top third of the canopy, continues until the infested tree is bare.

• Epicormic shoots: New shoot growth proceeding from the bark of infested trees, usually found in the roots or on the trunk. The leaves from these shoots may be larger than usual.

• Bark splitting: Vertical ruptures in the outer bark, often exposing larval feeding galleries underneath; splitting caused by host tree forming woundwood in response to larval feeding activity.

• D-shaped exit wounds: Caused by adult beetles emerging from the bark of infested ash trees.

• Serpentine larval feeding galleries: Found in the inner bark of infested ash trees.

• Increased woodpecker activity and damage: Due to woodpeckers feeding on EAB larvae.

How is EAB transmitted?

Emerald ash borer, like other wood pests, may be spread when infested ash trees, logs, or firewood are moved from a quarantine zone. This may spread EAB to different regions or even between states. When the mature beetles emerge from the ash tree in June, they spread within the infested region by laying eggs inside nearby ash trees. Adult emerald ash beetles can fly at least 1/2 mile from their home tree.

Treating EAB

The most effective treatment for EAB is preventative. Treatment involves applying an insecticide to the ash tree via trunk injection. The best time to treat for EAB is in the spring while the larvae are still young and unestablished.

If EAB has been detected by the presence of symptoms, the infested tree has most likely sustained significant damage. At that point, it may not be feasible to treat the infestation. Instead, the infested ash tree should be removed and destroyed in accordance with state and federal guidelines.