Emerald Ash Borer (EAB)
Emerald ash borer is an invasive insect that has killed millions of ash trees throughout the eastern half of the U.S. and southeastern Canada. Native to eastern Russia, northern China, Japan, and Korea, emerald ash borer infests and kills both weak and healthy ash trees. All ash species native to North America are vulnerable to attack. With nearly 1 billion ash trees in Minnesota, the spread of emerald ash borer will have a serious impact on our forests and communities.
Emerald ash borer is regulated by the Minnesota Department of Agriculture. For information on quarantined counties and more, please refer to Emerald Ash Borer Program - Minnesota Department of Agriculture.
Identification and life cycle
Most of the emerald ash borer life cycle takes place below the bark. Woodpeckers readily probe for larvae feeding beneath the bark, and often reveal infested trees during the winter months. These trees become covered in light-colored "flecking" as woodpeckers remove the outer bark.
As tunnels (called galleries) from feeding larvae accumulate and disrupt the flow of a tree's nutrients, trees begin to show signs and symptoms of the infestation. Once symptoms have started to show, trees generally die within one to three years.
Emerging adult beetles chew characteristic 1/8-inch-wide, D-shaped exit holes that can be useful in confirming infested ash trees. Because the holes are small and frequently high in the tree, they can be difficult to find. Below are photographic examples of an EAB infestation.
How to identify ash trees
The Minnesota Department of Natural Resources has a web page with information on how to identify the most common species of ash trees in the state.
Treatments for emerald ash borer
Ash trees can be protected with a chemical treatment. Treatment can be used as a preventative measure before trees are infested with EAB or therapeutically if the infestation is caught in the early stages. Trees that are 10” in diameter and in good physical condition are considered ideal for treatment. By the time ash trees show the signs and symptoms of EAB such as woodpecker activity, bark splits and crown dieback, treatment may not be an effective option. Trees showing more than 30% crown decline are no longer good candidates for treatment.
Treatments are injected at the base of the trunk and trees must be re-treated every other year. Cost of treatment is based on the size of the tree and the overall number of trees on the property. This is an ongoing cost, but it can be more cost-effective over the long term versus the cost of removing and replacing the tree. Recent research has indicated you can protect a tree for 20 years for the cost it would take to remove and replace an ash tree. Treatment has the added benefit of protecting and preserving ash trees that provide numerous benefits to homeowners and the community.
If you would like to a use a tree care company to help protect your ash trees, be sure they are a Minnesota licensed pesticide applicator. The Minnesota Department of Agriculture’s website can help you find the best tree care company for you.
Local options for tree treatment services
See where emerald ash borer has been found
The Minnesota Department of Agriculture hosts an interactive map that tracks where EAB has been found throughout the state. This map does not show a “tree-for-tree” designation, but a pin dropped in a neighborhood where EAB has been confirmed.