The Emerald Ash Borer (EAB) is an invasive pest introduced from Asia which attacks and kills ash trees (Fraxinus spp.). This metallic wood boring beetle was first found in Detroit, Michigan and Ontario, Canada, in 2002. It is believed to have arrived in shipping crates. Since the initial discovery, it has also been identified in Ohio, Pennsylvania, Indiana, Illinois, Maryland, West Virginia, Wisconsin and on May 13, 2009, St. Paul, Minnesota.
Destructive Potential of the Disease
The destructive potential of EAB is enormous because there is currently no known cure. Minnesota has 900 million ash trees vulnerable to Emerald Ash Borer. It has already killed more than 20 million ash trees nationwide, most of which were in southeast Michigan.
EAB kills trees over a period of 1 to 4 years depending on the size of the tree. It is the larval stage that does the damage. The larvae live under the bark of the tree and feed in the tissue layer directly beneath the bark. This layer contains the vascular system of the tree which transports water from the roots to the crown. As the larvae develop they create tunnels throughout this tissue. This activity kills the tree by stopping the flow of water and nutrients.
Diebeck of the Tree Canopy
The most prominent symptom of EAB is dieback of the tree canopy. It is not unusual for as many as 1/2 of a tree’s branches to dieback during the first year of attack. The tree tries to compensate for this loss by sprouting new growth below the level of infestation. At this time the bark may begin to split. Eventually the adult beetles emerge from the bark. In the process of emerging as adults, they leave a “D” shaped exit hole that is about 1/8th inch wide.
Transporting EAB Pests
Adult EABs can fly at least a 1/2 mile from the tree where they emerge. However, the most likely way EAB is transported is by people moving ash logs, ash firewood, or infested ash trees from nurseries. This is one of the reasons the Coon Rapids Forestry Division has stopped planting ash trees. Learn about the city's efforts to Remove Ash Trees (PDF).