You've Found Emerald Ash Borers Inside Your Tree—What Now?

Posted on: 20 February 2020


If you own ash trees and know that emerald ash borers are in your area, it's important to keep a close eye on the health of your trees. Thinning leaves, holes in the trunk and larval pathways behind the bark are all signs of an infestation. Once they're inside your tree, you can't get rid of them without treatment.

Thankfully, emerald ash borer treatment using pesticides is quite effective. However, the health of your tree plays a big role in making the correct determination on how to proceed — it's important to catch emerald ash borers early before they have the chance to cause substantial damage. If you've noticed that one of your ash trees has been infested, read on to find out how to continue.

How Do You Know if a Tree Is Worth Saving?

Whether or not a tree is worth treating depends on the amount of damage that the emerald ash borers have done to it. Their larvae tunnel around inside of the tree, which destroys its ability to carry vital nutrients up to the leaves in its canopy. As the damage inside the trunk worsens, more leaves will fall. This means that you can tell how damaged an ash tree is by the number of leaves growing on the tree.

If a tree has lost over half of its normal leaf growth, it's typically best to have an arborist remove it. While pesticides are normally an effective emerald ash borer treatment, they work poorly in trees that already have severe damage. It's difficult for pesticides to spread throughout trees with extensive damage, and it's also difficult for trees to recover from the damage itself.

Note that if your tree is damaged and needs to be removed, it's best to call an arborist to remove it before it deteriorates further. Damaged trees with decaying limbs are much riskier for arborists to remove, so you'll pay less to have it removed now instead of waiting until it's dead.

However, a tree that still has more than half of its leaves remaining should certainly be treated. Trees that aren't treated for their emerald ash borer infestation will inevitably die, and it's much more expensive to have a tree removed than it is to have it treated.

How Do You Treat a Tree That Has Emerald Ash Borers? 

Emerald ash borer treatment involves the use of pesticides that kill the insects while they're in their larval stage. Pesticides will eliminate the existing infestation and prevent it from being re-infested while they're still in the tree's system. 

The most effective method of applying pesticides to the tree is to inject them into the trunk. However, this requires boring a small hole into the trunk. Unfortunately, this opens your tree up to disease and infestation from other insect species — it's only suitable for healthy trees that can withstand the risk of further damage.

If your tree has already been damaged significantly by its emerald ash borer infestation, it's a better idea to inject pesticides into the soil surrounding the tree instead. This method is less reliable than injecting pesticides directly into the trunk, but it's less invasive. However, you'll need to call an arborist if your tree is over a foot in diameter — larger ash trees require stronger pesticides that only contractors have access to.

However, it's usually a good idea to call an arborist to examine your tree regardless of the situation. They will be able to determine if your tree is healthy enough to use a trunk injection for emerald ash borer treatment and they can carefully address the issues with minimal tree damage. In addition, they have access to pesticides that are effective for two years — consumer-grade pesticides need to be re-applied every year to remain circulating throughout the tree.