Emerald Ash Borer (EAB)

This spring, the City will be treating all healthy parkway ash trees for the Emerald Ash Borer. Please water treated trees to improve the effectiveness of the treatment.

Any week with less than 1” of rainfall should be supplemented with 10 gallons of water at the base of the tree from April to September.

Want to know if your tree has been treated? Follow the City's treatment efforts using the Interactive EAB  Treatment Map

Latest News (Last Updated March 1, 2015)

In 2012, the City of Naperville implemented an aggressive, multi-year, comprehensive treatment plan for all healthy parkway ash trees in order to reduce the devastating effect of Emerald Ash Borer (EAB) in the community. Without treatment, all of the ash trees would be expected to die within 5 years.

After three years, the comprehensive treatment program is showing positive results. The 2014 inspection revealed over 90% of the parkway ash trees exhibit only minor or no EAB damage. Annual ash tree deaths have stabilized since the beginning of the comprehensive treatment program. At 700-800 trees annually, ash tree deaths on the parkway are much lower than the exponential increase being witnessed in untreated areas.

2014 Ash Tree Health Pie Chart

The best time to treat ash trees and control the spread of the EAB is early spring to early summer. By getting the treatments into the tree in early spring, the chemical is moved up throughout the tree and is then ingested by the EAB larvae, which kills them thereby helping protect the tree from serious damage.

In April 2015, the City will begin the fourth year of comprehensive treatment. Licensed contractors will utilize three types of treatments for the City's estimated 15,000 parkway ash trees.  

  • Xytect™ (imidacloprid)
    The City will be using this treatment for most trees that are less than 18 inches in diameter. This annual treatment is applied as a soil injection around the base of the tree.
  • TREE-äge® (emamectin benzoate) 
    Used for larger trees, this treatment consists of a chemical application that is injected directly into the tree and lasts for two years.
  • Safari® (dinotefuran)
    A limited number of trees will be treated with Safari. This product is reapplied every year.

Homeowners with trees that receive treatment for EAB will be notified with a door hanger indicating what treatment has been performed. To protect trees, this year treatments will be done in April through June. Parkway trees that are badly infested will be removed and replaced. Residents will be contacted if their tree needs removal. Please be sure the City has your current phone number on file. Update Contact Information Now

What is the Emerald Ash Borer?

Adult Emerald Ash Borer- Photo courtesy of The emerald ash borer (EAB) is a small (1/2 inch long, 1/8 inch wide) metallic green beetle that has killed millions of ash trees across the Midwest. Native to Asia, the beetle was first discovered in the summer of 2002 in southeastern Michigan and has since spread to a number of states, including Illinois.

The adult emerald ash borer emerges in mid to late May. Soon after they emerge, the adult females lay numerous eggs on the trunk and branches of the ash tree. The eggs hatch within 7-10 days and the larvae, which are creamy white in color, bore into the bark of the tree. The larvae begin to feed on the inner bark and create S-shaped galleries, which cut off the food and water supply to the tree, causing it to die.

Click here to read more about signs and symptoms of the emerald ash borer. Signs and Symptoms of EAB Brochure (PDF)

In June 2008, the City of Naperville received confirmation from the United States Department of Agriculture that the emerald ash borer was present in a portion of southwest Naperville, making this the first confirmed case of the emerald ash borer in Naperville and Will County. Since then most communities in the Chicagoland area have confirmed the presence of the beetle.

Visit the State of Illinois web site at or for more emerald ash borer information.

Ash Trees

Native to Illinois, ash trees are commonplace in Naperville. The ash genus (Fraxinus) is the second most abundant genus on Naperville’s parkways. Naperville’s 14,000 ash trees comprise more than 20 percent of all parkway trees. The green ash species (Fraxinus pennsylvanica) is the most abundant species in the parkway at 14 percent.

Characteristics of Ash Trees:

  • Ash trees feature compound leaves made up of small, glossy green leaflets
  • Leaves, twigs and branches grow in opposite pairs
  • Bark of mature ash trees is gray and furrowed, often appearing in a diamond pattern
  • Some ash trees will produce small canoe paddle-shaped seeds

Green Ash Leaf
Green Ash Leaf
[Photo courtesy of Dave Roberts, Michigan State University]

White Ash Leaf
White Ash Leaf
[Photo courtesy of Dave Roberts, Michigan State University]

What the City of Naperville is Doing to Prevent EAB Infestation

The City's Forestry section is working in cooperation with the Illinois Department of Agriculture, DuPage and Will Counties, the Naperville Park District and area townships to manage the EAB infestation. When the beetle was first discovered in 2008, the City of Naperville developed a containment strategy that included inspection and inventory of all trees in infested areas. Neighborhoods with known infestations received treatment to combat the spread of the beetle. Over the next four years, infested trees were found in new areas of the City.

In 2012, an aggressive, multi-year, treatment program was implemented. This comprehensive treatment plan calls for the treatment of all healthy parkway ash trees and the strategic removal of infested trees. Small ash trees (less than 18 inches in diameter at breast height) receive Xytect™ treatments while larger ash trees are treated with TREE-äge®. A limited number of trees are treated with Safari®.

The City's Forestry section has eleven certified arborists that are trained to look for signs of the presence of the emerald ash borer and actively check ash trees everyday during their regularly scheduled work. The City also conducts an annual inspection of every parkway ash tree during the summer months. The City's Forestry section will continue to evaluate all parkway ash trees and remove any diseased or weakened trees in an effort to reduce the overall percentage of ash trees in the City's urban forest. Residents are encouraged to report sick or dead trees by calling (630) 420-6095.

What You Can Do

  • Water your treated tree:
    Treatment can take 4-6 weeks to circulate throughout the tree. Watering encourages this process and increases the effectiveness of the treatment. The City recommends homeowners water their treated trees with 10 gallons of water every week with less than 1” of rainfall from April to September. 
  • Inspect your ash trees for the EAB:
    Signs of infestation include noticeable woodpecker damage, dieback, splits in the bark, excessive sprouts, or small D-shaped holes in the bark. Spring is the time to treat your ash trees with insecticide though certain products can be applied later in the year.
  • Infested private ash trees:
    Private ash trees that have succumbed to the Emerald Ash Borer are required to be removed by Municipal Code. If you are not treating your ash trees, they will die and need removal.
  • Monitor the health of your ash trees:
    Look for dead and dying branches at the top of the tree's crown. If you suspect an ash tree located in the parkway seems sick or needs maintenance, call the City's Department of Public Works Forestry Section at (630) 420-6095.
  • Do not transport firewood:
    Emerald ash borer can easily be transported in ash logs and branches. Purchase firewood locally from a known source. Ash borer infested material may not be stored within the City of Naperville and should be disposed of properly.  

Treatment Options for Private Ash Trees

There are several treatments for EAB control (Insecticide Options for Protecting Ash Trees from Emerald Ash Borer.)

It is recommended residents get more than one estimate to help make an informed decision. Tree owners are encouraged to thoroughly research the various treatment options currently available and carefully weigh the costs associate with the required repeated treatments.

The City of Naperville is providing a Qualified EAB Treatment Vendor list as a resource to residents who would like to treat their private trees. The list is subject to change.

Use this tool to calculate the economic and ecological benefits of your tree.

Research has been ongoing since the borer first arrived in this country and many trees are being saved. The healthier the tree is when treatment begins seems to be a large factor in the survival of the tree. Treatment of an ash tree will not guarantee that a specific tree might not eventually need to be removed. Certified arborists can determine the health of an ash tree and whether treatment is viable.

Ash trees that are not treated will succumb to the EAB. To ensure the insecticide is in the trees by the time adults emerge to feed in early June, products are most effective when applied in April until mid June, or mid July with TREE-äge®. Trees over 15 inches in diameter should be treated professionally. The strength of the chemical in the home product is less than the product available by professional arborists. The applications of emamectin benzoate (TREE-äge®), imidacloprid (Xytect™), or dinotefuran (Safari®), which moves through the tree, are more likely to provide useful control. These options require a licensed professional to apply the insecticidal control to the tree.

See the document Insecticide Options for Protecting Ash Trees from Emerald Ash Borer (PDF) for the most up to date research on Emerald Ash borer control options and effectiveness.

Inform the City

While the City will treat all healthy parkway ash trees, it is beneficial and helpful to the City's Forestry Section to document the treatment of private ash trees so the future treatment and containment can be improved upon for the City as a whole.

If you decide to treat any ash trees, please print and complete the Emerald Ash Borer Treatment Form (PDF) and return it to the Department of Public Works each time the tree is treated so that it can be stored in a database. An electronic version of the treatment form is now available. Complete the Emerald Ash Borer Treatment Form - Electronic Version (PDF) online to submit by email. If an arborist identifies an emerald ash borer infested tree anywhere on your property, please notify the Department of Public Works at (630) 420-6095.