The Emerald Ash Borer (EAB) is a new pest starting to affect trees in the Chicago area. The emerald ash borer came from northern China and Korea and parts of Russia, Japan, and Mongolia. Before June of 2002, the EAB had never been found in North America or anywhere outside of Asia. As it is not a major pest of ash trees in Asia, little was known about EAB biology or control methods.
While it is not known for certain, the EAB probably arrived in solid wood packing material that originated in China or another Asian country. This could include ash wood used for crating, pallets or stabilizing cargo in ships.
Since arriving in North America it has been mainly found in Michigan, Indiana, Ohio, Virginia, Maryland and Ontario, Canada, and only in ash trees. Many of these outbreaks have been caused from the transportation of infested ash nursery trees, ash logs or ash firewood into new areas. Quarantines are now in effect to limit artificial transport of EAB in ash trees or logs, although this has proven to be a difficult task, as recent Illinois outbreaks in St. Charles and Wilmette suggest. To date none have been found in the Village of Niles.
The EAB is dark metallic green in color, 1/2 inch-long and 1/8 inch wide. When adults flare their wings, you can see their violet abdomen.
Adult beetles begin emerging in mid to late May with peak emergence in late June and early to mid July and leave a characteristic "D"-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge.
Females usually begin laying eggs about two weeks after emergence. Eggs hatch in 1-2 weeks, and the tiny larvae bore through the bark of trees and into the cambium and phloem. This is the area between the bark and wood, where nutrients are transported within the tree. Larvae feed in the inner bark between the wood and the rough outer bark. They are flat, cream colored grubs with wide heads. Shown here are a picture of an EAB and larvae in different stages.
Tunnels excavated by feeding larvae destroy the water and nutrient conducting tissues under the bark. The canopy of heavily infested trees will begin to die, usually near the top of the tree and progressing down the trunk. Bark may crack over larval galleries.
Woodpeckers often attack larvae, especially during the winter. Woodpecker holes are larger and easier to see than the D-shaped exit holes left by EAB. Several infestations have been discovered because people noticed woodpecker damage on ash trees.
EAB adults can fly at least 1/2 mile from the tree where they emerge. Many infestations, however, were started when people moved infested ash nursery trees, logs, or firewood into uninfested areas. Shipments of ash nursery trees and ash logs with bark are now regulated.
Transporting firewood outside of quarantined areas is illegal, but many people are not aware of this restriction.
Closely related beetles that are native to North America such as two-lined chestnut borer and bronze birch borer only attack very stressed trees. Scientists have found that EAB adults are more attracted to stressed ash trees than healthy trees and larvae develop more rapidly in stressed trees. However they will attack and eventually kill healthy ash trees, including those under irrigation and fertilization. When EAB populations are high, small trees may die within 1-2 years after becoming infested and large trees can be killed in 3-4 years.
Several universities and agencies are now working together on the EAB situation, including the USDA Forest Service.
Scientists are working to learn more about the biology of EAB, its rate of spread, methods for EAB detection, predators and other natural enemies that may attack EAB, and how insecticides can be used to protect trees in infested areas. Unfortunately at this time there is no method for killing the EAB. The only control method available is removal of infected trees in the fall before the EAB is able to fly to other areas.
We will continue to receive updates from the State of Illinois and will be providing information on the EAB through the Village’s newsletter, flyers and web site. Should you have any questions or believe your ash tree is infected by the Emerald Ash Borer, please contact the Niles Public Services Department Forestry Section at 847-588-7900.
More information can be obtained from the following links: