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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.

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.


How can I identify an ash tree?

There are five variations of ash trees generally found throughout Chicago; they are all members of the genus Fraxinus. Four are separate species - white ash (Fraxinus Americana), green ash (Fraxinus pennsylvanica), black ash (Fraxinus nigra),and blue ash (Fraxinus quadrangulata). The fifth is a hybrid variation of the white ash called autumn purple that was first introduced in 1956 and has become a favorite for parkway planting because of its brilliant red-purple fall color.

Two major things are common to all species of ash trees: opposite branching and compound leaf structure. Opposite branching simply means that each branch grows opposite of another branch. There are a few different kinds of trees that have opposite branching including maples but they don't have compound leaves.

A compound leaf is technically one leaf made up of leaflets that grow out of one bud. This bud is found at the base of the stem. A single leaf, on the other hand, is one leaf that has a bud at the base of the stem.

An easy way to recognize an ash is to take a close look at its compound leaf. The ash leaf is made up of 5-11 leaflets. There are equal numbers opposite each side of the stem, an additional one at the top of the stem, and one bud at the bottom of the stem.


What about the European Mountain Ash?

The European Mountain Ash (Sorbus aucuparia) is not affected by the EAB infestation. A native of Europe and northern Asia, the European Mountain Ash is not related to the true ash tree although the leaves are similar in structure. It is a popular ornamental tree that blossoms with white flowers in mid-to-late spring. In late summer the fruit ripens to a deep orange-red color and is a favorite of migrating birds.

We have received reports of unscrupulous tree-service companies misinforming homeowners and stating that these trees have to be treated or removed to prevent EAB infestation. This is completely untrue; Mountain Ash DO NOT have to be treated.


How can I identify an infected tree?



Early infestations of emerald ash borer are nearly impossible to detect as the tree does not immediately show outward symptoms; however, as the infestation grows,the tree will decline and ultimately die.

An EAB infestation is generally first detected by the yellowing and dropping of leaves in the upper canopy of the tree. And as the infestation progresses, more branches will die and the tree will sprout new shoots from the lower trunk to replace them.

After the first year of infestation, small D-shaped exit holes (approximately 1/8 inch in diameter) will appear on the trunk as the mature beetles exit the tree to begin the next egg-laying cycle. Splits in the bark may then develop revealing the damaged phloem layer beneath. Woodpecker holes are also common in an infected tree as the birds search for the larvae.

Arborists and other tree management officials generally use the percentage and location of canopy damage and branch dieback to determine whether an infected ash tree is treatable and worth saving. A homeowner would be wise to assume that if there are diseased ash trees nearby, his tree is also probably infested even if it is not yet showing the symptoms.


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 can the trees be saved?

The trees can be saved with chemical treatment. The Environmental Protection Agency has approved several insecticides to combat the infestation. If you elect to treat your ash trees, there are several options available and research has shown that treatments can be effective. Keep in mind, however, that controlling insects that feed under the bark with insecticides is not easy. This is especially true with EAB because our native North American ash trees appear to have no natural resistance to this pest. The various treatment options are outlined in the "Solutions" section.

Why should the ash trees be saved?


There are aesthetic, environmental, economic and moral reasons to do so.

Long valued for their shade and beauty, ash trees represent anywhere from 10 percent to 40 percent of all trees in urban areas. They provide substantial environmental and economic benefits to communities and homeowners, including increased property values, lower energy demands, storm water mitigation and storage of greenhouse gases. And if we were to just let them die, it would take generations to replace them.

Prior to the EAB infestation, Chicago's had 494,000 ash trees that made up 19% of its entire urban forest or about one out of every five trees. There were 94,000 on public parkways alone with the balance on private property, railroad right-of-ways, cemeteries, forest preserves, and parks. Each of these half-million ash trees absorbed almost 22,000 gallons of water each summer. Where do we think that water will go with the loss of so many trees? In addition, the death of these trees are a travesty for the outlying neighborhoods known for their stately ash. These trees offered more than beauty. They provided an economic benefit that we are just beginning to realize how to leverage.

The Sustainable Cities Institute cites a 2004 study which revealed that patrons overwhelmingly prefer business areas with well-planted canopy-covered streets. Shoppers have indicated that they will travel greater distances and drive for a longer time to visit a district having high quality trees and that they spend more time there once they arrive. Further, shoppers claim that they will spend 9-12% more for goods and services in central business districts having high quality tree canopy.

Green Cities: Good Health organization advises that the presence of larger trees in yards and parkways can add 3-15% to home values. One of its studies showed a 7% higher rental rate for commercial offices having high quality landscapes.

There are also moral reasons why we must make every effort to limit the ecological damage of this man-made, natural disaster. It was human error that caused the introduction of this invasive species to the American hardwood forest. Shouldn't we make every effort to undo the catastrophic results just as we would for an off-shore oil-spill, or acid-rain or industrial water pollution?

If 8.7 billion additional trees in the Amazon rain forest were suddenly threatened with extinction, there would be world out-cry and a call for action. Do we owe our native ash trees anything less?


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 seventh 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.


What is the government doing?

Each local community is responsible for dealing with the EAB infestation by itself. At this point, there is no unified national plan of action nor federal assistance available. Some communities are aggressively treating their ash tree population to stave off the disaster while others are cutting down their ash in a misguided attempt to stop the infestation. Some communities aren't doing anything and are finding themselves overwhelmed with thousands of standing dead trees.

Luckily, Chicago's Bureau of Forestry has chosen the treatment path and treated over 50,000 ash trees with "Tree-age" between 2010 and 2014. While no injections are scheduled for 2015, a second phase of treatment to save the remaining ash will begin in 2016. Of the 94,000 ash trees originally gracing the city's parkways, less than 50% will ultimately survive. Click HERE to see a map of the city neighborhoods and the treatment schedule.

For some undisclosed reason, the Chicago Park District chose not to treat any of the 30,000 ash trees originally located within the city's parks. Almost all of these ash are now too far gone to save. In 2013 and 2014, several local park councils on the northwest side of the city secured private donations to treat approximately 150 ash trees in six local parks including Horner, Peterson and Gompers. While these ash are faring well after treatment, they will soon be the sole remaining ash specimens in the entire park system. These local park councils are now proposing an "Adopt A Tree" program to support future treatment and save any other healthy ash trees that might have survived elsewhere.


What about ash trees on private property?

Homeowners are responsible for any ash trees on their own property. This includes the cost of treatment but also the much greater cost of cutting down and removing the ash tree if it were left to die. Certain suburbs have initiated programs to reimburse homeowners for the cost of treating trees so it is wise to check with your municipality. The Coalition is actively working with federal officials to see about homeowner relief.

What treatment options are there?

Insecticides that can effectively control EAB fall into four categories: (1) systemic insecticides that are applied as soil injections or drenches; (2) systemic insecticides applied as trunk injections; (3) systemic insecticides applied as lower trunk sprays; and (4) protective cover sprays that are applied to the trunk, main branches, and (depending on the label) foliage.

For more details on treatment options, visit the "Solutions" section from the main menu.


Who pays for ash tree treatment?

The local government pays for treatment of the ash trees on public property through tax dollars. Homeowners are responsible for treating any trees on their own property.




Is the treatment cost effective?

The economics of treating ash trees with insecticides for EAB protection are complicated. Factors that can be considered include the cost of the insecticide and expense of application, the size of the trees, the likelihood of success, and potential costs of removing and replacing the trees. Until recently, insecticide products had to be applied every year. A new product TreeAgethat is effective for two years or even longer (emamectin benzoate) has altered the economics of treating ash trees. As research progresses, costs and methods of treating trees will continue to change and it will be important to stay up to date on treatment options.

Benefits of treating trees can be more difficult to quantify than costs. Landscape trees typically increase property values, provide shade and cooling, and contribute to the quality of life in a neighborhood. Many people are sentimental about their trees. These intangible qualities are important and should be part of any decision to invest in an EAB management program.

It is also worth noting that the size of EAB populations in a specific area will change over time. Populations initially build very slowly, but later increase rapidly as more trees become infested. As EAB populations reach their peak, many trees will decline and die within one or two years. As untreated ash trees in the area succumb, however, the local EAB population will decrease substantially. Scientists do not yet have enough experience with EAB to know what will happen over time to trees that survive the initial wave of EAB. Ash seedlings and saplings are common in forests, woodlots, and right-ofways, however, and it is unlikely that EAB will ever completely disappear from an area. That means that ash trees may always be at some risk of being attacked by EAB, but it seems reasonable to expect that treatment costs could eventually decrease as pest pressure declines after the EAB wave has passed.


How can I find a good tree service?

The Coalition has interviewed and identified multiple private tree service providers that service this area and have posted their names in the Resources section. We are negotiating special rates and bulk pricing programs for area residents. More details will be coming shortly.

How can I help save the ash trees?

Get involved and spread the word to your neighbors. If your neighbor has an ash tree in their yard, knock on their door and warn them about the cost of inaction. Call your public officials and voice your concerns if they don't have a treatment program in the works. Join our email list for updates on the infestation, treatment schedules for your area and special pricing programs for home owners. Most residents are not aware of the devastating impact of the EAB until it is too late and they have already lost the ash trees around their home.