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Ash trees are beautiful deciduous trees with a strong native presence throughout Illinois. These towering giants reach incredible heights, so it’s no surprise that they continue to mature for decades before they’re fully grown. That’s part of what makes the tragic tale of these gentle giants so heartbreaking. Unfortunately, their population is dwindling after facing one of the worst documented plagues to any tree in North America — the Emerald Ash Borer.


What is the Emerald Ash Borer?

Emerald Ash Borers are invasive beetles native to Northeast Asia, and once nonexistent in North America. These nasty critters were first found in Michigan in 2002, but it’s likely that they’ve been creeping around for much longer than that. They likely arrived here sometime during the 1990s on shipments of untreated wood. Since their discovery, they have worked their way through many parts of North America, and have been found in 60 of our 102 counties in Illinois.

In the spring and early summer, adult Emerald Ash Borers lay eggs in the nooks and crannies of ash tree bark. After hatching, the larvae burrow through the bark and into the trunk of the tree. There, they set up camp for the remainder of the year while they mature into adult beetles. After they’ve finished maturing, they dig their way out of the tree to lay eggs and start the process over again.


The Effect of Emerald Ash Borers on Ash Trees

While living inside our precious ash trees, Emerald Ash Borers spend their time munching on the tree’s fibers and forming tunnels, disrupting the flow of important nutrients. While the tree’s roots might be getting everything they need, these insects prevent the energy and nutrients from being utilized, starving the tree from the inside.

Since they live within the wood for most of their lives, humans don’t often see them. Unfortunately, we usually can’t tell that a tree is infected until it’s already heavily infested and the damage starts to show. Symptomatic trees will start to thin out and dieback at the crown and their leaves will begin to lose their lush green color. As more and more tunnels are formed, the tree might start to develop sprouts in an effort to transport nutrients in new ways. Most trees will starve to death within 2-5 years.


emerald ash borer damage ash tree


Why Emerald Ash Borers are So Dangerous

Most gardeners are somewhat used to dealing with pests on their property. Although they’re bothersome, problem insects and animals are a natural presence and deserve to share this earth with us in harmony (for the most part). But Emerald Ash Borers can’t be compared to curious raccoons or annoying aphids, because they’re much more detrimental to our trees.

Emerald Ash Borers are especially dangerous here in North America because our trees have never had the chance to build up resistance to them. Asian ash trees have coexisted with these insects for thousands of years, evolving genes that are much better at resisting the beetle’s attack.

Another reason invasion comes so easily to Emerald Ash Borers is that they have no natural predators here. Their population is completely uncontrolled and continuously multiplying. Unlike fungus or disease which need certain conditions or physical contact to spread, beetles locomote on their own with impressive speed. With grasshopper-like legs that can help them travel up to 20 km in a single year, the continued infestation of Emerald Ash Borers is inevitable, especially in forests full of ash.

Although they can hop from tree to tree easily on their own, human movement plays an even bigger role in spreading these borer beetles. Since they live within the wood and aren’t usually seen, many people don’t know that they’re transporting such a harmful pest in their firewood and lumber. Even shavings as small as wood chips from an infected tree are likely to host the beetle and contribute to its spread.


How to Get Rid of Emerald Ash Borers

Recently, scientists have been researching Asian ash trees in an effort to identify genes associated with resistance. If successful, they’ll be able to breed more resistant trees here in North America and in other parts of the world. They’re also beginning to make advancements in biological control of the Emerald Ash Borer population. For our purposes, let’s focus on keeping the trees in our own backyard healthy and leave the forests to the experts.

The most important thing is identifying the problem early. But since they do their damage under the surface, you’ll have to be diligent if you want to spot them. Keep a close eye on your black and green ashes since they’re known to target those most often. They’ll also infest white and blue ashes, too.

Look for symptoms of an infestation, like thinning branches or paling leaves. Check dead branches and withered leaves for signs of the adult beetle, a metallic green, grasshopper-like insect. Look for cracks in the bark or the characteristic D-shaped hole that the adults leave behind. If you’re suspicious, peel back a small section of the bark and look for larvae and tunnels.


meyer CTA


If you’re unfortunate enough to find evidence of borers, don’t panic. At Meyer, we provide one of the most safe and effective treatments to eradicate emerald ash borers: the Arborjet Tree Injection Method. This method has a very minor environmental impact, because the insecticide is injected directly into the affected tree, instead of spraying it all over or drenching the soil. The results are astounding, and after treatments, trees are guaranteed to be protected from EAB infestations for two years!

For a little extra protection against these nasty critters, look for a neem seed-based insecticide to address the problem right away. This kind of insecticide is administered at the tree’s base and is distributed throughout the tree with the natural flow of water. It works to kill the larvae while also preventing adult females from laying more eggs.

Remember, human movement is the number one cause of spreading the infestation. Destroy any infested wood on-site immediately to avoid these nasty bugs from moving anywhere else in your area.


The Emerald Ash Borer poses a very real threat to one of our most beloved, beautiful trees. It’s important that we do our part in preventing the spread of this awful insect and protect the trees in our own backyards so we can continue to enjoy the majestic beauty of ash trees for years to come.


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