Emerald Ash Borer: Threat to Our Native Landscape

Emerald Ash Borer


If you haven’t heard about the Emerald Ash Borer, it is important to be aware of this invasive pest, especially if you own an Ash tree or are concerned with preserving our native natural Kentucky landscape and our Lexington streetscape.

Ash Trees in Our Landscape

Many varieties of ash trees are native to Kentucky and the Eastern US region as well. There are even some Ash trees native to the western US too. There are (and were) a lot of Ash trees throughout our Kentucky landscape. It’s not only used as a specimen tree in our designed landscape, but they are also native in our forests and woodlands. There are a few different types of Ash trees including Blue, Green, Black, and White. The Ash tree is in the genus of Fraxinus, which is the Olive family.

Old Ash Trees in Shillito Park, Lexington KY. All dead due to Emerald Ash Borer
Old Ash Trees in Shillito Park, Lexington KY. All dead due to Emerald Ash Borer

Shillito Park in Lexington, KY is somewhere I have visited all my life. This line of old Ash trees is a noted special spot here in the park, especially since they’re in the middle of the disc golf course. I’ve hit some discs on these trees! These trees are all dead due to the borer. As you can see in the background, they are now removing them, as they were likely to not have been treated by LFUCG. This is a huge asset now gone from this park, and it could have been prevented if they had been treated. This park is not the same without them, it is now merely a barren landscape (and now without out any disc golf obstacles).

Also in the Olive family is our native Fringe Tree. The borer has also been found in it. Also in the Olive family is forsythia and privet. These 2 shrubs actually actually non-native and invasive plants, why couldn’t the borer go to them!

A Little History

It is said that there are a lot of Ash trees around the Lexington, KY area because of our historical statesman, Henry Clay. He helped create the landscape around Lexington because of his penchant for trees and his noted love of the Kentucky landscape. His particular like of the Ash tree is why he named his estate ‘Ashland’. There are many Blue Ash in the area, including some that are noted to be 250 years old around his property. Read more about the Flora of Ashland, Henry Clay Estate.

Something has come to threaten our beautiful native landscape full of Ash trees, and it’s destroying the Ash population all over the US and even Canada.

Ash trees are an important tree in our Kentucky landscape. There are so many, and they have have beautiful fall color! They are also unique that they have opposite tree branching and compound leaves. Their fall color is a combination of oranges, reds, and even purples.

From www.nj.gov
From http://www.nj.gov

This is the compound leaf of the Ash. The whole piece is the leaf, with a multitude of ‘leaflets’ that have an opposite branching pattern.

The Invasive Pest: Emerald Ash Borer

The Emerald Ash Borer, an exotic beetle not native to the US. It was found in Detroit in 2002, most likely hiding out on a shipping pallet that was on a ship importing goods from Asia. It is now costing people in the US millions of dollars. Those people would be local municipalities, parks, private landowners, state and federal government, universities, and YOU, the homeowner.

It’s costing us millions of dollars in preventing the borer from killing all of the Ash trees. Those dollars are going to chemical treatments, removing the dead Ash trees, and in research to figure out how to control this invasive pest.

Emerald Ash Borer in Kentucky

I first heard about the Emerald Ash Borer when I was working at the LFUCG/UK Arboretum and Botanical Gardens. There was a painted purple wood triangle box hanging up in the tree that was supposed to do attract the beetle to trap it. This was about 6 years ago. There was much concern about the borer in the area, but I don’t think it had reached us yet at the time, or its findings were slim. Today in the US, I think it is largely affecting at least 25 states if not more, including parts of Canada.

There is a creepy feeling when you come upon a dead Ash tree that died because of the borer. They are merely a skeleton, all dried up and covered in lichen. Out in the woods where they aren’t taken care of, they slowly fall apart as their limbs become brittle.

Fast forward to today, and I see nearly Ash here in Lexington affected by the borer. The only trees not affected are those that have been treated. All around Lexington and Kentucky, I see even giant Ash trees that are completely dead or very close to it. The borer acts quickly. It can only take a two to a few short years for a giant Ash tree to be completely dead after becoming infested. There are many neighborhoods that are lined with Ash trees as their street tree. I see lines of Ash trees in parking lots, parks, down city streets, and many giant ash trees in private residential home’s landscapes and in natural woodland areas. In a line of trees, the borer just travels from one tree to the next. You can see how the borer is just going down through the line from the level of decline from one tree to the next. Oddly, sometimes, the borer can skip a tree, but it doesn’t mean it will eventually become infested.

If you see any Ash trees that you think are affected by the borer, you can and should report them to the city/county government. It is their duty to asses the trees, either treating or removing them.

Here in Lexington that can be the LFUCG Urban Forestry Program

How the EA Borer Works

The adult beetle itself isn’t as destructive as its larvae. The adult beetles will nibble on its leaves, but doesn’t seem to do much damage. You usually don’t even see the beetles. What kills the tree is its larvae. The beetle lays its eggs underneath the bark, as the larvae grows, it eats away underneath the bark, cutting off the vascular system of the tree. If you were to look underneath the bark, you can see squiggle shapes where the larvae was eating. There are many borers, including native ones in our landscape. However, our native borers have native natural predators that keep them in check. The Emerald Ash Borer does not have any predators since it’s exotic, and our native landscape does not recognize it.


You can tell if your tree is effected in a  couple of ways.

The first sign is that the tips of the branches will be barren.

The next sign is that the tree looks like its having a hard time leafing out. This is because larvae of the borer is cutting of its vascular system, so water or nutrients can’t flow. It’s kind of like how our fingers and feet will go numb if we’re sitting in a bad way; our circular system isn’t able to flow like it normally should. The other way to know if the borer is present is to look for perfect ‘D’ shaped holes going through the bark. This is the shape the exit holes the adult beetle makes as it’s going through the bark.



Underneath the bark of the ash. The pattern of the larvae eating away.

Treating Ash’s for the Borer

If you have an Ash tree in Kentucky, it needs to be treated ASAP. You can treat the trees yourself with over-the-counter pesticides, or you may call a tree expert who has proper equipment and high quality pesticide to do so. While you can treat a younger Ash tree yourself, there is a chance it may not work. Calling a professional to treat the tree is a good investment. The trees must be treated every few years to remain effective. The cost to treat the tree will depend on the trunk’s size in diameter. Holes are drilled into the base of the tree, and tubes are connected to its vascular system to transport the chemical all throughout the tree. Effectiveness and time to treat the tree depends on the time of year, time of day, weather, and condition of the tree. You can tell if an Ash tree has be treated if you see drilled holes all around the tree with plastic plugs inside.


Prevent the Borer From Spreading

One big way the borer has traveled to one area from another is by the transporting of fire wood. The beetle has been transported by wood being distributed and sold at gas stations and the like, and also shipping pallets. It has also been transported by people moving around firewood, even those from dead ash trees, selling it or taking it elsewhere. This is one way it has spread from county to county throughout states.

Do not transport firewood from one location to another. Do not take firewood in forested land.

The next way to prevent the borer from moving is by treating your ash trees. If the tree is too far gone, you should have it removed as soon as possible if it is in an area highly trafficked by humans so falling limbs aren’t an issue. If it’s in a natural area, you can leave it standing, since it is still highly valuable to wildlife.

We need to save our Ash tree population, so if you are able to treat the tree, please take this option into consideration. Consider the cost of treatment vs removing the tree. It can cost hundreds if not into the thousands to remove a tree depending on its size. Treating the tree can be more cost effective. Remember, a tree is a very valuable asset to your property and a landscape in general. It can be worth several to several hundred thousand dollars in its value as a living tree. It is estimated that 20 million Ash trees have been killed so far. Most likely much more because we don’t know how many have been killed in naturalized areas.

If you do have an ash tree removed, it is important to take care of the wood properly. You could either have it chopped to use as firewood or if it is a large enough tree, you can have it sawmilled into boards to use for a project. Many sawmills have portable machines where they can come and mill the wood on your property.

If neither of these are an option for you, consider giving it to someone close by who can use it as firewood, or give or sell it to a sawmill/other industry who will then turn it into boards or make furniture out of it. Do not however, take the firewood into an area that has not been affected by the borer. The borer can still live in the dead tree for a few years.




EAB in Kentucky (http://pest.ca.uky.edu/EXT/EAB/welcomeeab.html)


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s