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Emerald Ash Borer in Southeast Minnesota

Emerald Ash Borer in Southeast Minnesota

By Katie Drewitz, University of Minnesota Extension 

PRESTON and CALEDONIA, Minn. (06/28/2022) — In my travels throughout Fillmore and Houston counties I have noticed numerous trees with potential and verified Emerald Ash Borer (EAB) damage. EAB was confirmed in Houston County in 2010 and in Fillmore County in 2015. While Emerald Ash Borer has been in the area for some time, I feel it is important to remind home and landowners of actions they can take to avoid spreading EAB, what to do with their Ash Trees, and next steps if EAB is suspected. 

Emerald Ash Borer (Agrilus planipennis) strictly impacts Ash trees in the Fraxinus family. Therefore, the first step to understanding if your tree is being impacted by EAB is correctly identifying your tree. Ash trees have opposite branches and buds and compound leaves with 5 or more leaflets. Mature Ash trees have distinct diamond-shaped ridges. Young ash trees have relatively smooth bark. Once you have correctly identified your tree as Ash, you can begin looking out for other symptoms of EAB. 

The amount of time it takes for EAB to kill an Ash tree depends on the insect load in the tree. This could take anywhere from two to seven years. EAB damage is likely to start at the top of the tree and work down. The larval stage of EAB creates distinct S shaped galleries behind the bark. In most infestations you will begin seeing bark cracking and dying limbs. Woodpecker damage can also be a sign of Emerald Ash Borer. The woodpeckers are looking for the insect food source and will often scrape the bark from your ash tree in their pursuit. It is important to remember that woodpeckers may be interested in your tree for reasons other than EAB. Finally you will notice D shaped exit holes from the emerging adults. 

As you look around at the ash trees on your property you may consider replacing your ash trees with another type of tree before EAB infests them. Fillmore and Houston County Extension offices have a list of recommended trees if you choose to replace your ash tree. Once an ash tree becomes infected with an EAB population it will die quickly. This can lead to an increased danger for you and your property as dead trees will break and fall more easily. It also becomes more expensive to remove trees once they are dead due to the increased danger to the worker. If you decide to keep your ash tree you should consider treating with an insecticide. When using an insecticide of any kind you must read and follow all label directions. The Minnesota Department of Agriculture (MDA), as well as, the University of Minnesota Extension has resources available to help you when choosing which insecticide to use and when to apply it. 


The best way to stop the continued spread of the Emerald Ash Borer is to stop moving firewood. It is always best to buy your firewood locally and burn it where you buy it or cut it. If you believe you have Emerald Ash Borer in your Ash tree you should submit information to the MDA Arrest the Pest line at 1-888-545-6684 or arrest.the.pest@state.mn.us. For more information about the Emerald Ash Borer please reach out to your local County Extension office. Residents in Fillmore and Houston counties can email wins0115@umn.edu or call 507-765-3896 or 507-725-5807 for assistance.


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