Emerald Ash Borer Infestation: Signs, Symptoms, and Treatment Options

Spotting the Signs and Stopping the Spread

Ash trees are a quintessential part of many landscapes worldwide. Known for their hardwood used in furniture, tools, and sports equipment, these trees also bring charm and leafy shade to parks, streets, and yards. Ash trees play a vital role in the ecosystem, contributing to the natural beauty and ecological balance of the country and throughout the world.

Unfortunately, the emerald ash borer infestation represents a severe threat to these iconic trees. This invasive pest has devastated countless ash populations across the US, attacking species of green, white, black, and blue ash, and leaving homeowners, businesses, and municipalities grappling with its costly impact. US ash trees are in peril, and it is imperative to understand what exactly the emerald ash borer is, and how we can identify and combat its effects. This guide will cover everything you need to know, including how to recognize ash trees and the signs of an infestation, the dangers posed by infested trees, and the steps that can be taken to save an infested ash tree.

What Is An Emerald Ash Borer?

The emerald ash borer (EAB), Agrilus planipennis, is a small, metallic green beetle native to East Asia. Measuring about half an inch long, it has a slender, bullet-shaped body with a bright, iridescent green shell that catches the light. Its underbelly is a contrasting coppery red, and its large, dark eyes give it a distinctive look. Though small, its vibrant coloring makes it visually striking. The beetle’s wings cover its body entirely when closed, giving it a sleek, smooth appearance.

Though it was first detected in the US in Michigan over two decades ago, it has since spread to more than 35 states and poses a grave threat to all native species of ash trees. This shimmering green beetle goes through four life stages (egg, larva, pupa, and adult), but it is the larval stage that causes the most damage. An emerald ash borer infestation begins when larvae begin to feed on the tree’s vascular tissues beneath the bark. Shockingly, a single adult female can lay over 100 eggs, quickly multiplying the infestation in an area.

How to Identify an Ash Tree

Before you can start protecting your trees, it’s crucial to verify whether they are ash trees. Here’s how you can identify them:

• Leaves: Ash trees have compound leaves with 5–9 leaflets arranged opposite one another. The leaves are deciduous, turning bright yellow or purplish-red in the fall.
• Branches and Buds: These often grow in pairs directly opposite each other.
• Bark: Mature ash trees have distinctive diamond-shaped ridges on their bark, while younger trees have smoother bark.
• Height: Ash trees can range from medium height to towering specimens, with some exceeding 100 feet. Their seeds are wing-shaped and resemble a canoe paddle, known as samaras.

Knowing these characteristics will help you confirm if your trees are at risk from the emerald ash borers. Still unsure whether your trees are ash trees? An experienced arborist can help you identify whether you have ash trees on your property and assess their condition. Stephenson Tree Care also offers expert consulting services to guide you through species identification and tailored treatment options.

How to Spot an Infested Ash Tree

Recognizing the early signs of an emerald ash borer infestation could be the difference between saving a tree and losing it entirely. It’s also a good reminder of why consistent tree care matters, especially when facing aggressive pests and unpredictable damage.

1. Blonding: This is caused by woodpeckers drilling into the bark to feed on larval forms of the EAB, leaving pale patches on the surface.
2. Canopy Dieback: Infested trees often experience thinning at the top, resulting in large sections of dead branches.
3. D-Shaped Exit Holes: Adult emerald ash borers chew through the bark to emerge, leaving tiny D-shaped holes approximately 1/8 inch in diameter.
4. Bark Splitting and Galleries: Cracks in the bark may reveal winding tunnels or galleries left by feeding larvae.
5. Epicormic Shoots: Trees in distress often produce shoots or sprouts along the trunk as a last-ditch survival effort.

Small trees can succumb to an infestation in as little as two years, while larger trees may take up to four years to die if left untreated.

What Risks Do Infested Ash Trees Pose?

Infested ash trees quickly become brittle, increasing the likelihood of dangerous limb breakage or complete collapse. They pose a serious threat to property and public safety if located near homes, streets, or parks. Furthermore, deteriorated trees are more hazardous and costly to remove, as their weakened structure makes them unpredictable to handle.

Emerald ash borer infestations are particularly destructive, often killing ash trees within 2 to 5 years. The larvae tunnel under the bark, damaging the tree’s ability to transport water and nutrients, which leads to its decline and eventual death. If you suspect an infestation, immediate action is critical. The sooner preventative measures are taken, the better the chances of saving the tree once the infestation has begun. Delaying treatment or removal not only exacerbates the risks but can also increase the overall costs.

How to Stop an Emerald Ash Borer Infestation  

Stopping an infestation is possible, but only if action is taken quickly. Early detection is key, and a certified arborist can assess the tree’s condition and recommend the best course of action. Here are the most effective ways to stop an infestation:

• Preventative Treatment: For ash trees not yet infested, systemic insecticides can be applied to protect them from future emerald ash borer attacks. This is a proactive measure to safeguard healthy trees.  
• Tree Injection: For trees with a mild infestation, injecting specialized insecticides directly into the trunk can kill larvae and adult beetles as they feed, halting further damage.  
• Soil Drenching: In some cases, treating the soil around the tree with systemic insecticides can provide added protection by delivering chemicals through the roots.  
• Removal: Severely infested trees that cannot be saved should be removed promptly by professionals to prevent the infestation from spreading to nearby trees or becoming a safety hazard.  
• Wood Disposal: Properly disposing of infected wood is crucial to ensure the beetles don’t spread further. Chipping or burning the wood is often recommended.

It’s essential to work with certified arborists, like those at Stephenson Tree Care, to help spot and save ash trees while preventing the spread of emerald ash borers. Experienced arborists have the knowledge, tools, and treatment options to stop infestations safely and effectively while helping protect the surrounding landscape.

Protecting Your Ash Trees

Taking action for your ash trees from the emerald ash borer infestation starts with awareness and professional care. If you’re in Madison, WI, or nearby areas, Stephenson Tree Care offers comprehensive tree services to assess and protect your landscape.

Save Your Dying Ash Trees with Stephenson Tree Care

For over 20 years, Stephenson Tree Care has earned a reputation for exceptional tree care services, serving residential, commercial, and municipal clients. Our certified arborists specialize in low-impact pruning and removal, expert plant health care with custom pest treatments, advanced diagnostic tools for tree health, and outstanding customer service for a stress-free experience. We also offer specialized Emerald Ash Borer services to help identify, treat, and prevent infestation in vulnerable trees.

Schedule Your Free Tree Assessment Today

Don’t wait until it’s too late. Stephenson Tree Care’s arborists are experts in handling emerald ash borer infestation and are here to help preserve your trees, protect your property, and help keep Madison’s natural beauty thriving. Contact us today to schedule your free tree assessment!