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What is the Emerald Ash Borer?


The Emerald Ash Borer (Agrilus planipennis) is an invasive wood boring beetle from Asia that is predicted to infest all unprotected ash trees in the United States and Canada. It was first found to be attacking and killing ash trees in Michigan in 2002.

Bright green in color and about a half inch in length, the Emerald Ash Borer (EAB) only attacks ash trees and is a devastating and destructive pest that greatly affects the urban forest. EAB is easily spread through the movement of firewood, logs and nursery stock.

Since its detection, EAB has killed over 70 million ash trees and has spread throughout the upper Midwest into Indiana, Ohio, Illinois, Wisconsin, Iowa and beyond. Infestations have now been confirmed in 25 states. Discovered in Illinois in 2006, EAB has since spread throughout northeast Illinois into Chicago and all of the suburbs. All fifty wards in Chicago have some degree of infestation.


What is killing the ash trees?


All of the native North American ash trees are highly susceptible to a new invasive species of beetle, the Emerald Ash Borer or EAB. Emerald ash borers destroy an ash tree's ability to store water and nutrients, killing the tree from the top down. Evidence that may indicate the presence of emerald ash borers include dying branches at the top of a tree, vertical bark splitting, new branches sprouting from the base of the tree, D-shaped exit holes and increased woodpecker damage.

How bad is the infestation?


The grey areas on the map above depict the counties with EAB infestations by 2011. The red areas show the counties added in 2012. First discovered in the southeastern Michigan area in 2002, by June 2015 the EAB infestation has now spread to over 25 states from Colorado to Connecticut and from Minnesota to Georgia. Around the Great Lakes and in addition to Michigan and Indiana, most of Illinois is now infested and almost half of Wisconsin.


As of last year, the Emerald Ash Borer infestation had killed over 70 million ash trees across the eastern United States and Canada. The map above shows the range of the native North American ash susceptible to the EAB. All 8.7 billion ash trees in North America will eventually be attacked over the next 20 years. Any untreated tree will die.


The map above shows the Federal EAB Quarantine Area in the US as of June 19, 2015.


Why is the EAB infestation different?

The Emerald Ash Borer infestation is by far the worst natural disaster to affect the entire eastern hardwood forest of the United States in the last century. Its devastation makes the Dutch Elm disease and the recent Longhorn Beetle infestation look like child's play. The EAB's spread can not be stopped and any of the 8.7 billion ash trees in North America that remain untreated will die within the next 20 years.

How fast do infected trees die?

Depending on the health of the tree and the degree of infestation, an untreated ash tree will die within two to five years of being infected with the EAB. Studies have shown that communities will generally have all of their untreated ash trees die within ten years of the first signs of infestation -- slowly at first but with a dramatic increase in annual tree loss after year five. This is known as the ash tree death curve. Chicago has just entered it's fifth year of EAB infestation.

When should ash trees be cut down?

Once an ash tree loses over 50% of its canopy, it is not treatable, according to scientific consensus. The City of Chicago's criteria for treatment is far more stringent at 40% leaf loss. Once an ash tree dies, it does not maintain its structural integrity compared to other tree species like oaks or the American elms that were killed from Dutch elm disease. With thousands of trees dying all at once, a city's resources will be overwhelmed, creating major safety and liability issues.

Homeowners should have dead ash trees removed as soon as possible. A dead ash can drop large limbs and may fail in wind or ice storms. Property damage, power outages, human injuries and possible death may occur.