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Emerald Ash Borer FAQ

Johnston Parks Director John Schmitz answers some of the most-frequently asked questions about EAB.

1.  What is Emerald Ash Borer and why are you so concerned?

Emerald Ash Borer is an insect native to China that arrived in the United States sometime in the late 1990’s.  Signs of its destructive force began showing up in the Detroit area in 2002.  Being a non-native, there are no natural predators (although some insects and birds are beginning to prey on them).  The EAB larvae lives in and eats the soft growing tissue of all varieties of ash trees (especially green and white) and will eventually cut off the flow of nutrients to the tree.  Their speed of “natural spread” is very slow (typically less than 15 miles in a year), but that is sped up through the transport of firewood.

Johnston has a very high percentage of ash trees (approximately 18% in public spaces).  The density in several neighborhoods is even higher and the loss of all of these trees will have both a physical and financial impact on the neighborhood.

2.  What does the borer do to the tree exactly?

The larvae of the borer lives in and eats the soft growing tissue under the bark of ash trees.  It will continue eating the soft tissue until it cuts the nutrient flow off for the tree and it slowly dies.

Metro Waste Authority Information on EAB

Check out this video for helpful information

3.  How many ash trees does Johnston have?

The City of Johnston has approximately 2,000 ash trees that are found in public spaces (parks, green spaces and street right-of-ways).

4.  Does EAB only target ash trees?


5.  What should I do as a homeowner right now if I have an ash tree in my yard?

The first thing that all homeowners should do is to assess the health of their ash tree(s).  If you have multiple ash trees and want to ensure that you have a diversity of trees in your yard (both species and age), you may want to create a plan for some removals of unhealthy ash trees.  If you have any trees that are stressed or unhealthy, now is the time to consider the possibility of removal.  These trees will be more susceptible to the EAB when it does arrive.  It also gives a little more time for new trees to grow.  The key to any plan that you develop is do diversify your tree selection.  Multiple species and ages are essential to a healthy environment. 

Residents interested in preserving street or city trees in the right of way adjacent to their home, may treat these trees at their own expense.  Residents wishing to treat ash trees for EAB need to follow the procedures established in this application.

6.  Why doesn't the city of Johnston just treat all its ash trees instead of removing some of them?

We look at all factors when deciding whether to remove an unhealthy tree or treat a healthy tree.  We have already removed more than 200 unhealthy ash trees susceptible to EAB.  In 2015 we treated 60 healthy ash trees in the hope that the borer will not attack the treated trees.  This method has been successful in other cities, but it can be costly.

7.  What would happen if the city did nothing?    

The City could wait until the EAB was discovered in Johnston.  The positive of that plan is that these trees would not be removed.  The negative is that a far higher percentage of trees would all need to be removed at the same time.  This would be very costly and would create a mass removal program.  We are slowly removing unhealthy trees at a rate of 50-75 per year and to replant a variety of trees in their place.  This will create a far more diverse urban forest and will give us a head start on the borer before its eventual arrival to Johnston.