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Experts warn insect could destroy up to 18 percent of trees

A pile wood infected with emerald ash borer larvae has been treated with variety pesticides varying concentrations. They are coded

A pile of wood infected with emerald ash borer larvae has been treated with a variety of pesticides at varying concentrations. They are coded on the ends so Morton Arboretum researchers can study the effectiveness of the products against the pest | Steven

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Updated: May 16, 2012 8:27AM

With spring having sprung, it will only be a matter of time before many area residents who have ash trees will find out if their trees will be added to the rapidly growing list of victims of the notorious emerald ash borer.

Scientists believe the insects first appeared in North America through wooden packing material shipped from China into the Detroit-Windsor area in 2002. Most likely carried in by people bringing firewood from Michigan, the insects were first noticed in Illinois four years later.

According to the Illinois Department Agriculture EAB website, “On June 9, 2006, two ash trees in ‘The Windings’ subdivision, near Lily Lake in Kane County, were positively identified as being infested with the Emerald Ash Borer.”

Experts estimate about 18 percent of all trees in the Chicago metro area are ash, and the borers could eventually destroy a vast majority of them. Professional arborists recommend that only 5 percent of all trees planted in any one place be of the same type.

Those on the front lines battling the borer say the infestation is at the management stage. That is, agencies are trying to keep the EAB from spreading past where it already is and attempting to minimize or make the most out of the situation in impacted areas.

To that end, we asked professionals directly involved in that fight for an update on the efforts taking place.

Fighting at the state level

The lead agency in Illinois in the battle against the emerald ash borer is the state’s Department of Agriculture. Juliann Heminghous is an EAB outreach coordinator for the IDA in Springfield, and she said the department will be setting up insect traps once again this year, starting in Southern Illinois and working north.

“Targeted trap locations are predetermined areas generated from U.S. Forest Service data and risk assessments intended to increase the likelihood of new EAB detections through a more scientific-based approach than in years past,” Heminghous said.

The borers are small and difficult to detect. The D-shaped holes they exit from are less that an eighth of an inch in diameter.

Females can lay 50 to 90 eggs per year, and often it can be two or three years before the impact is noticed, with large numbers of dead trees appearing in six or seven years. By then, big damage has been done.

“More than likely, it is the damage or the decline of the tree that reveals their presence,” Heminghous said. “Most of the time, EAB itself isn’t seen until the tree is cut down and the larvae are found within.”

The borers do their damage by the larvae choking out the tree, interfering with the process by which ash trees transport nutrients and water. This leaves the tree starved, dried-out and dead.

Unwitting humans are the chief way the borers are making rapid progress through much of North America. Firewood transported from one area to another remains one of the main ways in which the destruction spreads so far and so fast.

“An internal state quarantine affecting 39 counties — or nearly 40 percent of the state — is now in place, which strictly regulates the transportation of all hardwood firewood,” Heminghous said. “This is not only to help control the spread of EAB but help prevent the spread of other potentially troublesome pests such as walnut twig beetles, which is vectoring the spread of a fungus that affects walnut trees called thousand cankers disease.”

Another theory is that vehicles are unintentionally aiding the migration of the EAB, as the insects have also been found on the grills of trucks and other vehicles. So with the Illinois Department of Transportation, the IDA has set up kiosks at rest stops across the state containing EAB information. Those kiosks are made out of reclaimed ash from trees felled by the pests.

Insecticidal management through chemical treatments is viable and is showing some promise in prolonging and/or preserving the life of ash trees, Heminghous said. Still, it is probable that in the short term, many — if not most — of the ash will succumb to the EAB if left unprotected, “or it’s just too late to have the opportunity to protect them,” she noted.

“We are hopeful that this long-term work of determining the location of EAB, rearing/releasing natural predators, regulating movement of infested products and the collection of ash seeds — and hopefully the research of creating a hybrid ash that is EAB-resistant — may revive and help ash thrive once more,” Heminghous said.

A lesson to be learned from this invasion is that town planners, home builders and homeowners should work to make sure that neighborhoods are planted or replanted with diversity in mind. Heminghous noted that having a wider array of trees would lessen the impact of the inevitable presence of another invasive species and/or disease.

Area battle

Kris Bachtell is the vice president of collections at the Morton Arboretum in Lisle. Bachtell headed to China in 2005 and 2008 — a colleague went in 2011 — specifically to get seeds from a variety of ash that may have resistance to the EAB. The trees from such are being grown at Morton for experiments.

One test involves putting foliage in Petri dishes from these samples and from North American ashes and observing if the borers eat the leaves, and if they are able to complete their life cycles on such a diet.

A project that began this year involves trees that have been grown from the Chinese samples and from elsewhere that are 5 to 8 feet tall. These trees are being caged so that borers cannot escape the controlled environment, and scientists are observing the insects’ behaviors and whether they thrive or perish.

Bachtell said it is too early to tell if any of these ash trees will be able to serve as replacements for trees here that have been decimated. He knows that devastation firsthand, as his own neighborhood on the northwest side of Naperville near the McDowell Grove Forest Preserve has been battling the borers for at least two years.

The EAB situation is comparable to when Dutch elm disease wiped out most elm trees in the Chicago area, Bachtell said. A difference is that the elms at the time accounted for about 40 percent of all trees in this area. Bachtell noted that elms and ash are tough trees that can grow in less-than-ideal soil conditions. Replacing fallen ash might give towns a more diverse landscape in terms of what is planted, as well as in terms of the conditions which the replacements are planted. On other words, better soil and better drainage will allow a wider variety of trees to thrive.


University of Illinois Extension entomologist Phil Nixon in Champaign explained that in the parts of Asia where EAB come from, the insects have co-evolved with ash trees, each species trying to stay one step ahead of the other in surviving. In part, this means the trees there can hold off the effect of the borer until they are older and in poor health.

To stave off borers on trees here, Nixon said, three types of pesticides have been found to be effective. Tree-age and Safari must be applied by professionals. For a tree with a diameter of 18-20 inches, such treatments run $50-$75 annually or $150 for an injection that lasts two or three years.

Over-the-counter pesticides sold as Bayer Advanced Tree and Shrub Insect Control costs about $20 to apply annually. The same insecticide active ingredient is sold by Bayer as Merit for application by professionals, Nixon said.

According to Nixon, the cost of removing a tree of the same size can run $600-$1,000.

Nixon noted there are programs under way in Illinois using three types of tiny insects from Asia to try to control the spread of EAB. These three parasitoids lay eggs on the larvae or in the eggs of the ash borers, then feast or the borer larvae.

City of Chicago senior forester John Lough is overseeing experiments in about 15 heavily wooded areas throughout the city in a five-year project with the USDA Forest Service that began in 2009.

Similar projects are going on in Evanston and in Lake County forest preserves. But results have been mixed thus far, Lough noted. What makes it hard is that all three species are difficult to trap in the wild because they are smaller than fleas.

U of I’s Nixon said keeping invasive species under control is a never-ending battle. Though eradicated in Illinois, Asian longhorned beetles are feasting on hardwood trees in several other states. The aphid-like woolly hemlock adelgid is threatening coniferous trees in the Eastern United States. And thousand cankers disease, carried by the walnut twig beetle, is killing trees in several Western states, he said.

“Inspectors are keeping an eye out for a least 150 other bugs that could come into the country through shipping crates or luggage,” he added.

Action plan

Reinee Hildebrandt in Springfield is the urban conservation program administrator for the IDNR, an agency she describes as being a “concept provider.”

Still, she noted, the IDNR Illinois was the first to have an action plan: “Emerald Ash Borer Community Readiness Workbook — A Framework for Local EAB Preparedness and Community Action,” which was distributed June 2006.

“Information was provided to all Tree City USA communities, which include Elgin, Aurora and Naperville,” Hildebrandt said.

The IDNR also provided communities with a half-million door hangers distributed in potentially impacted areas to make residents aware of what to look for and what they might be able to do.

Hildebrandt said “wood utilization” was the topic of this year’s Tree City USA conference held in March in Springfield and Zion.

“The Tree City USA program has helped Illinois communities to be more ready than those is other states,” she said. “When a community has a local municipal forestry program in place, they can address exotic insect infestation, storm events and tree issues more efficiently.”

Continuing education

DeKalb’s Scott Schirmer is a plant and pesticide specialist supervisor and emerald ash borer program manager for the IDA who also has been involved with educating officials in towns throughout the state where the borers have yet to be found.

The EAB have been confirmed in 23 Illinois counties, and their path of destruction appears to follow the major interstates slicing through Illinois, Schirmer said.

At Morton Arboretum, Beth Corrigan is community trees project coordinator; and Andi Dierich is forest pest outreach and survey project coordinator, working with the Community Trees Program.

Corrigan does outreach to groups including residents, arborists and public works staff. With the EAB situation where it is, the effort is on municipal management plans that include tree inventories, treatment, removal and replanting. Many towns already have such plans in place, Corrigan said.

Corrigan said Morton Arboretum expects a flood of calls later this spring, after trees completely leaf out and it becomes apparent what has been damaged.

Even with all the information already published about EAB, Corrigan said many people still feel blind-sided when ash trees on their property or in their neighborhood are impacted.

Morton Arboretum has offered sessions on topics related to the infestation, including a training last November in St. Charles on municipal wood utilization. It covered ways in which towns can make use of the wood from felled ash for in-house projects, such as skids, wood chips for local parks or even donating boards to school wood shops.

Corrigan recommends that anyone interested in learning more should visit

Dierich’s work is funded through a USDA Animal Plant Health Inspection Service (APHIS) grant for community outreach regarding any invasive forest pest. In her role, she works with organizations, departments and agencies across the state.

She noted that EAB damage can manifest itself with fewer leaves on the tree and woodpecker damage, which is a sign the birds have found a supply of insects to eat off a particular tree.

If you’re worried about your own ash trees, “You should always try to contact your city forester or a certified arborist to evaluate all treatment options before settling on one,” Dierich said. “If you decide to use chemical treatment and it is not feasible to have a professional treat your ash tree, make sure to read all directions on insecticide labels to ensure the correct usage and application of chemical.”

For more information, call the Morton Arboretum Plant Clinic: 630-719-2424; or visit the website

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