Emerald Ash Borer (EAB) Signs, Symptoms, & Treatment
The Emerald Ash Borer (EAB) (*Agrilus planipennis*) remains the single most devastating invasive pest affecting trees in Michigan. Since its arrival, it has killed tens of millions of Ash trees. Knowing the subtle signs of infestation is vital because early intervention is often the only way to save your tree.
The Four Key Visual Signs of EAB Infestation
EAB larvae feed directly under the bark, cutting off the tree's water and nutrient supply. Look for these four critical indicators:
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Crown Thinning and Dieback
This is usually the first visible symptom. The tree’s leaves become sparse, especially in the upper canopy. The leaves may turn yellow or brown prematurely in the summer, followed by branches dying back from the top down.
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D-Shaped Exit Holes
When the adult EAB beetles emerge, they chew a small, distinctive D-shaped hole (about 1/8 inch wide) through the bark. These are the tell-tale sign of an active infestation.
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Epicormic Sprouting (Suckering)
In a desperate attempt to survive, the Ash tree will often grow dense clusters of new, fast-growing branches (suckers) lower on the trunk or near the roots. This reaction is a stress response to the damage in the main canopy.
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Serpentine Larval Galleries
Once the bark begins to crack or fall off (a process often accelerated by woodpeckers), you may see the feeding tunnels (galleries) etched into the wood underneath. These S-shaped tunnels, created by the larvae, effectively girdle the tree.
⚠️ Action Required: Immediate Consultation
If you suspect EAB, do not wait. Early diagnosis by a professional arborist is necessary to determine if the tree can be saved or if safe removal is required.
Treatment and Removal Options
The survival of your Ash tree depends on its current condition and the size of the infestation. We offer two main professional paths:
- Systemic Treatment: For Ash trees that are still relatively healthy (less than 30% crown dieback), we recommend preventative systemic insecticides. These are injected directly into the trunk and must be maintained every one to two years to remain effective.
- Removal: Trees that are heavily damaged (more than 50% canopy loss) are typically beyond saving. Furthermore, dead Ash trees become brittle and highly dangerous to remove, making professional tree removal a critical safety step.