Emerald Ash Borer

What is the emerald ash borer?

The emerald ash borer (EAB) is an insect that has found its way into the O’Fallon community in the spring of 2014 and will create an infestation that is fatal to all species of ash trees. The EAB will spread through the community and begin killing only ash trees during the next eight years.

There are possibly 37,000 ash trees in the O’Fallon community that are essentially doomed to die from the Emerald Ash Borer infestation by the year 2022. It is essentially unstoppable and it has devastated ash trees over much of the country, starting in the Northern states. Eventually, the EAB will hit communities all the way to the Gulf of Mexico. It is just beginning to reach the City of O'Fallon.


O’Fallon EAB:  Five Things to Know

  • Residents and businesses are responsible for tree removal on their property including trees between the sidewalk and the street.
  • O’Fallon staff will not diagnose EAB activity.
  • Remove ash trees when the tree reaches 50% dead or sooner if possible.
  • Residents can use O’Fallon’s yard waste program for disposing wood waste.
  • The City of O’Fallon encourages residents to plant trees where ever possible and as many as possible, even if you are not losing an ash tree.

Frequently Asked Questions about the EAB

Who is responsible for these ash trees as they deteriorate?


  • Residents and business owners are responsible for ash trees on their property. This includes trees growing between the sidewalk and the street. The City of O’Fallon recommends that property owners take this into account when assessing the upcoming EAB problem and make plans accordingly. This situation also lends itself as a topic of discussion for Home Owners Associations in which subdivision trustees may begin budgeting the removal of the ash trees and replacing the ash with another species, perhaps drafting and funding a five year plan for the subdivision.
  • Ash trees on municipal properties are the City of O’Fallon’s responsibility. 

Should I call the City if I think my ash tree has been infested?

No. The City of O’Fallon can not dispatch staff to diagnose EAB activity. Although this may sound abrupt, O’Fallon does not have the staffing capabilities to diagnose all of the potential requests to diagnose EAB activity. The fact of the matter is that EAB is in the area and every ash tree is vulnerable, therefore if an ash tree appears unhealthy it likely is infested with EAB and a diagnosis is unnecessary. 

Can ash trees be saved from this infestation?

A good deal has been learned about treatments to save ash trees since EAB was first discovered in 2002. There are do-it-yourself treatments and there are professional treatments, with one in particular, that is administered every two years.

What is not known is how long the commitment is for continuing treatments. Specialists have stated 6 years, 10 years, 15 years, and some state that treatments will need to be continued for the life of the tree. The one aspect that everyone can agree on is that there is no guarantee that the treated tree is 100% invulnerable to EAB.

What happens to a tree that is infested?


The tree will die a slow death as the EAB literally eats the tree just under the bark. Tree owners will first notice branches or tree sections dying over a year or two. After that, the tree will fight to survive by sprouting suckers on the largest branches and at the base of the trunk. This sucker growth is a sign that the tree is in the final stage.

Ash trees that have died from an EAB infestation are particularly brittle. If dying trees are left standing and subjected to high winds or an ice storm, the result could be a catastrophic drop of limbs and in some cases entire trees. Considerable damage has been suffered by houses and vehicles beside the dying ash trees, and neighborhood power outages become common from ash limbs dropping onto electric lines. The City of O’Fallon is recommending that residents have ash trees removed when the trees are showing 50% death of the tree structure. The 50% criteria coincides with research that demonstrates when an ash tree is subjected to this amount of decline, the tree’s fate is irreversible.

What is O'Fallon doing about the EAB?


O’Fallon has begun taking measures to proactively replace ash trees on city property. The decision was made to apply the city’s resources toward replacement of ash trees with other species and forego attempts to treat existing ash trees. Long term success with treatments to control EAB remains a gamble. Proactive tree planting in 2015 through 2019 will soften the transition of the expected ash tree loss.  Planting replacement trees began in January of 2015 with the intention of having a net gain in the total number of trees after the last ash tree is removed in 2021

The City of O’Fallon encourages every resident to plant trees in advance of the EAB devastation, even if the residents are not going to lose an ash tree.  Trees are good for our community and every effort should be made to add trees and buffer the impact of the EAB.

Can I dispose of the tree with the City?


The City of O’Fallon will continue to offer yard waste pickup for residents who sign up for it. This includes includes wood waste, from O’Fallon’s residents through the current program with O’Fallon’s Environmental Services Department. Please note:  Wood debris picked up through the program must meet all of the guidelines for yard waste pick up. 


Helpful Documents


Additional Resources

For additional information on the emerald ash borer, please check out these websites: