The Invasion and Impact of the Emerald Ash Borer

By Clare Matthias

Like the chestnut blight, Dutch elm disease, and Asian longhorn beetle before it, the Emerald Ash Borer (EAB) is the latest invasive scourge to take hold fast and carry with it the potential to kill billions of ash trees and do millions of dollars worth of damage across the continent. First discovered in Michigan in 2002, the EAB (native to East Asia) has already spread into Ohio as far south as Columbus, and has reached as far west as Indiana and north into the province of Ontario, Canada. This infestation has resulted in the death of approximately 8 to 10 million ash trees in just a few short years.

The EAB is not a pest in its native east Asia, where it is relatively uncommon and has natural biological controls. Adults, members of the metallic wood-boring beetle family, measure only a half inch in length by 1/8 inch wide and are a striking, bright metallic green color. The adult beetles, nibbling only on leaves, are relatively harmless to the trees. It’s their ravenously hungry larvae that are causing all the destruction.

The larvae, which measure 2 to 3 centimeters in length, burrow their way through the inner layer of the ash’s bark, impeding its ability to conduct water and nutrients throughout the tree. Once infested, an ash tree is certain to die within 1-5 years.

How do you know if your tree is infested with EAB?
The EAB attacks almost all species of ash trees (white, black, and green). Only the mountain ash seems able to have adequate defenses against this greedy pest. Typically, an ash tree stricken with EAB will show signs of withering brown leaves, first at the top of the tree, and then further down to about the top third of tree. Because the infestation starts at the top of a tree, where the female EAB lays her eggs, it is often very difficult to notice these signs from ground level as they begin to appear.

When the larvae finally emerge from the bark as adults, they typically leave a D-shaped exit hole in the bark, measuring an eighth of an inch wide. EAB larvae also leave a distinctive serpentine-shaped tunnel on the surface of the wood just under the bark. Additionally, if you see unusually high woodpecker activity in your area, there is a good chance that the emerald ash borer has arrived. Woodpeckers are known to feast on EAB larvae.

Origin of the pest
As with the chestnut blight and Asian longhorned beetle, the Emerald Ash Borer is a foreign import. The most conclusive evidence at this point suggests that the EAB arrived as a stow-away in wood crates and packing material, either on planes or ships that arrived from Asia. From there, the contamination has spread quickly, often as a result of imported goods that were transported to other parts of Michigan, Indiana, Ohio, and Ontario. Another key means of spread has been through the movement of firewood from infested to non-infested areas. The EAB was first discovered in Ohio in Lucas County in 2003. Since then, it has been found in 7 counties (Defiance, Franklin, Fulton, Hancock, Henry, Lucas, Wood). Recently in Franklin county, it has been successfully eradicated. As part of efforts to curtail the continued spread of the pest, the Ohio Department of Agriculture has eliminated close to 84,000 ash trees.

Economic Impact
As the EAB has taken hold, scientists and others fear that the overall impact on the economy and on the composition of forest communities could be worse in Ohio than Michigan. This is because Ohio has a higher number and greater variety of ash trees. Also, Ohio’s wood products industry is more supported by ash tree products, such as in flooring, cabinetry, baseball bats, and more, than Michigan’s. In an Ohio Nursery and Landscape Association survey in 2003, Ohio’s nursery growers estimated that ash trees contribute $20 million (wholesale value) to Ohio’s economy each year, not to mention revenue generated from retail garden centers and landscape contractors.

It isn’t yet known how well the EAB will adapt to climates in the United States beyond the upper Midwest, but should it continue to spread as quickly in other areas as here, costs to the greater United States economy could be staggering. The Nature Conservancy, in a report outlining funding needs for the United States Department of Since its arrival in Ohio a little under two years ago, the tiny Emerald Ash Borer has caused the death and destruction of over 38,000 ash trees and will cost the state millions in its efforts to save the remaining 3.8 billion ash trees in Ohio. It’s going to require a tough, relentless, and expensive fight to control this pest, and if not successful, the consequences for ash trees throughout the upper Midwest, and possibly the rest of North America, is dire. Agriculture (USDA) Forest Service Health Management program, cited a USDA study that asserts, “…if the EAB spreads from Michigan to the rest of the country, it could cause undiscounted losses of city trees worth $20 to $60 billion. Losses to the timber industry would be $25 billion in the Eastern states (alone).” Combined, all non-native insects and pests cause over $4 billion in damages to the nation’s forest every year.

Stopping the EAB
So what can and is being done to control and hopefully stop the spread of the Emerald Ash Borer? In September 2003, Governor Bob Taft signed an order to establish a quarantine in several northern Ohio areas, prohibiting the movement of ash materials from those points, and banning import of all ash materials from Michigan into Ohio. Eradication is another important step and occurs in the quarantine area, where all infested trees are destroyed and removed. This occurs during the months of October through May, after the adult flying season has stopped and before the next generation of adults emerges from the bark, in an effort to disrupt the EAB’s life cycle.

Control of future EAB spread is further managed through suppression cuts, in which any ash tree within 200 yards of an infested tree will be destroyed and removed. In the 200 yards beyond that area, a select number of ash trees will have a layer of bark removed to make them vulnerable to EAB. These girdled trees, and all other remaining ash trees, will be cut down and destroyed soon after.

Insecticides and other chemical agents have not proved effective in destroying or controlling the EAB and are not recommended methods for treatment, either at the individual tree level or on a large scale.

The responsibility and authority for undertaking these controls falls within the jurisdiction of local and state governments. Funding and oversight is administered on a national level largely by the Animal Plant Health Inspection Service (APHIS), a division of the USDA. In Ohio, the Ohio Department of Agriculture (ODA) is heading up the efforts in partnership with the EAB Task Force, a group made up of several organization including the USDA, the Ohio Department of Natural Resources (ODNR), and The Ohio State University. Together they are conducting studies and research to learn more about the EAB, implementing detection methods, quarantine, eradication, and suppression cuts, and are spearheading public education and awareness campaigns.

All of this is done on an as-funds-allow basis, however, making funding an extremely critical issue. In particular, the extremely important and time critical eradication efforts undertaken by the ODA are dependent, and contingent, on the continuation of federally provided funds. In 2005, the state of Ohio has asked the Federal Government for 11.5 million to continue the fight.

To help secure desperately needed future funding, Senator Mike DeWine of Ohio, in partnership with Senator Joe Liebermann of Connecticut, is teaming up to support a Dear Colleague letter that will circulate through Congress. This initiative is seeking support from other senators for increased funding (approximately $40 million) to fight the EAB and other forest pests and pathogens that greatly threaten the health of forests in many states and that pose grave economic consequences if not properly controlled.

The Nature Conservancy and the EAB
Up to this point, the EAB has not affected any Conservancy lands in Ohio. According to Carlen Emanuel, Forest Ecologist with the Ohio Chapter, the Kitty Todd preserve in northwestern Ohio (which is in the quarantine area) has been free of EAB so far. Primarily an oak savanna, Kitty Todd is not a native home to ash trees. While there are some growing there, they are often removed anyway as part of controlled restoration efforts to preserve the naturally occurring predominance of oak in the area. Should EAB be observed on any Ohio TNC preserve in the future, all efforts to control the infestation would be in accordance with methods established by the ODA.

On a national level, The Nature Conservancy is doing what it can to be a responsible partner in the crisis and is taking on a role of advocate for the cause of increased federal funding for eradication programs. The Conservancy is asking Congress and the Bush administration to greatly increase the funds provided to APHIS for the efforts to control the EAB problem in all states afflicted. “APHIS, along with state partners, are the ones with the power and responsibility to tackle this problem,” says FAITH CAMPBELL, Senior Policy Representative of The Nature Conservancy at their worldwide office in Washington, D.C. “EAB is APHIS’ highest priority right now. They think they’re on the edge of finding the spread point and could work backwards to contain the spread, but they don’t currently have enough money to do it.”

The Nature Conservancy is also strongly urging APHIS to carefully implement and monitor the new upcoming standard for wood packing and materials that will go into effect in the fall of 2005, as an important means of preventing future import and export of invasive foreign pests.

EAB adult and exit hole: EAB adults emerge in mid-May after boring D-shaped holes through the bark.

EAB larvae: EAB larvae are flat, legless, heavily fragmented, creamy white, and reach 1 inch in length when fully mature.

Serpentine, or S-shaped, galleries are made by EAB larvae as they feed on the phloem tissue or inner bark layer of the tree.
©The Ohio State University