Emerald Ash Borer Infestation

Emerald ash borer adult. Photo credit: David Cappaert, Michigan State University, Bugwood.org.
Emerald ash borer adult. Photo credit: David Cappaert, Michigan State University, Bugwood.org

The Forest Preserves of Cook County has been removing ash trees in response to the emerald ash borer (EAB) infestation since 2009. The EAB is a beetle from Asia that feeds on ash trees and was discovered as the cause of extensive ash mortality in southeast Michigan and adjacent areas of Canada in 2002. It is thought that this destructive pest was introduced in the early 1990s in infested solid wood packing material originating in Asia.

Frequently Asked Questions

What’s the Timeline?

EAB was first discovered in June 2002 in Detroit. It is believed that the EAB arrived in the Chicagoland region in 2006. The first confirmed EAB infestation was found on Forest Preserve District properties in 2008. As of June 2010, the EAB has been found in the following areas: Illinois, Indiana, Kentucky, Maryland, Michigan, Missouri, New York, Ohio, Pennsylvania, West Virginia and Wisconsin, as well as Ontario and Quebec in Canada. The District is in the beginning stages of addressing the infestation and anticipates the process of tree removal and replanting will continue over the next several years.

How did the Forest Preserves First Respond?

The Forest Preserves has been actively engaged in research and monitoring programs that were set up to help combat EAB through a coordinated strategy with regional, state, and federal agencies including: the Illinois Department of Agriculture (IDA), Illinois Department of Natural Resources (lDNR), United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), United States Forest Service (USFS), Morton Arboretum, City of Chicago’s Bureau of Forestry, Regional Forest Preserve Districts, local municipalities and Michigan State University. Forest Preserves staff participated in all 13 Illinois EAB readiness subcommittee meetings hosted by the Morton Arboretum from September 2003 to August 2008. Participating members created the EAB Readiness Plan and subcommittees of this team were formed once EAB was detected. The Forest Preserves director of resource management, John McCabe, is an ongoing member of the Municipal Committee. Internal training classes have been conducted with all Forest Preserves resource management staff on tree care and removal. The training sessions covered strategies to detect and address EAB, Asian Longhorn Beetle and Gypsy Moth. Additional training and updates have been administered as needed.

What is the Forest Preserves Strategy?

The Forest Preserves presented its EAB Management Plan to the Board of Commissioners in September 2008:

Once an infestation is detected, trees will be monitored and a hazard assessment will be done. Any tree, dead or alive, which has the potential to entirely or partially fail and impact a target, can be considered a hazard. A target can be a vehicle, building or any place with pedestrian traffic. Dead and dying ash trees, weakened or killed by EAB, pose a risk to public safety and therefore are a potential liability to the District if left standing along streets, parking lots, bike trails, horse trails or other public spaces. Trees that are deemed hazardous will be removed, while those that are not a threat to lives or property will be left with-in the Preserve…

Forest Preserves Emerald Ash Borer Management Plan – August 2008

The Forest Preserves’ number one priority is the safety of the general public and the users of the preserves.

Where Are the Trees Being Removed?

Trees have been removed throughout the Forest Preserves since 2009. For current locations undergoing EAB marking and removal, check the Closures & Alerts page.

The Forest Preserves is only removing trees that may compromise the safety of the general public or the users of the Preserve—NOT trees “in the woods.” The vast majority of the Forest Preserves’ ash tree removals will take place from the edges of the forested community, along roads, bike trails, mowed areas, groves, and public and private interfaces. The removal of ash trees in these areas will open canopy space that will be filled by younger trees.

What Are the Experts Saying?

While some communities have tried to fight the EAB infestation by applying chemicals, cutting down ash trees and even releasing the beetle’s nemesis parasite, the measures haven’t stopped the problem.

“EAB can infest a tree and be there for six or seven years before anyone has the slightest inkling it is there. It devastates the entire canopy of the tree… There is no silver bullet, no magic potion that will save a tree once it is affected.”

Juliann Heminghous, the EAB outreach coordinator for the Illinois Department of Agriculture quoted in “Signs of progress sought as emerald ash borer plague keeps spreading” – Chicago Tribune (June 20, 2011)

What is the Impact on Picnic Groves?

Unfortunately, the reduction of the ash tree canopy in certain picnic groves that have large populations of ash and mature ash trees could be significant. The Forest Preserves intention is to reduce the impact to the tree canopy as little as possible. Based on the level of infestation in areas where removals are taking place and surrounding areas, the Forest Preserves’ analysis is that most of the Ash trees in these areas have been infested with EAB and will eventually die. These dead and dying trees pose a risk and danger to residents and users of the preserves.

Is Removing Ash Trees the Only Strategy?

Thousands of trees are showing signs of advanced infestation and may pose a risk to the safety of the general public. The Forest Preserves’ strategic removal of ash trees is in the best interest and safety of the County’s residents and taxpayers. The Forest Preserves firmly believes that we should act now to prevent a problem or major crisis in the future as has been experienced in other states impacted by the EAB.

What About Monitoring the Infected Trees Before Removing Them?

The Forest Preserves will monitor some infested trees in picnic grove areas if they do not pose an immediate public safety hazard. The Forest Preserves’ analysis is that ash trees that are infested by EAB will inevitably have to be addressed and likely cut down. The Forest Preserves extensive land holdings make it impossible to monitor individual trees along roadways, bike trails, horse trails, parking lots, public facilities, picnic groves and the public/private interface.

Will the Forest Preserves Replace and Replant Trees That Are Removed?

It is a priority for the Forest Preserves to replant trees that have been removed from picnic groves and public facilities. The replanting began in the spring of 2012 and is ongoing as funding allows.

Why Hasn’t the Forest Preserves Looked at Other Measures Besides Removing Trees?

To be clear, ash trees infested with EAB will eventually die. The Forest Preserves’ objective is to responsibly remove infected ash trees that could pose a risk to the general public and the users of the preserves. Since 2003, the Forest Preserves has worked cooperatively with major agencies from all levels of government to manage the EAB crisis in the hope that a solution could be found and to save as many ash trees as possible. Unfortunately, no viable solutions have been found.