What is emerald ash borer?

  • Agrilus planipennis, or emerald ash borer (EAB), is an invasive tree pest that has killed tens of millions of ash trees in the Midwestern and Eastern United States since it was first spotted in Michigan in June 2002.
  • EAB is native to eastern Russia, northern China, Japan and the Korean peninsula. It was likely transported to North America in ash wood packing crates on container ships.
  • A wood-boring insect, EAB attacks ash trees in both forests and landscape settings. Unlike native borers, which attack weak trees, EAB also attacks healthy trees. All types of North American ash trees are susceptible to EAB.
  • Adult beetles are dark metallic green in color, 1/2-inch long and 1/8-inch wide.
How far has EAB spread?
  • EAB has already been identified in at least 15 states—Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and Wisconsin—plus Washington, D.C., and parts of Canad.a
  • Most infestations are not new. Experts have become more adept at spotting them as they become more familiar with the EAB's habits.
  • Movement of infested firewood is believed to be the primary source of the long-distance spread of EAB within the US. Therefore, to slow the further spread of EAB, the public should NOT move firewood out of EAB quarantine areas.
How does EAB kill ash trees?
  • Larvae are the damaging life stage for EAB. Larvae feed on a tree's phloem and xylem tissue, which are located just under the bark. Adults feed on ash foliage, but cause little damage.
  • Larval feeding starves the tree of carbohydrates and water between the canopy and roots, which results in thinning foliage, branch dieback and, eventually, the tree's death.
  • Unless treated, an ash tree will usually die within 2-4 years after initial EAB infestation.
How do you treat trees affected by EAB?
  • EAB does not have to be a death sentence for ash trees. Systemic insecticides are effective at protecting ash trees from EAB infestation and can also be used to help save trees already showing early signs of infestation. However, treatment is more effective if begun before damage becomes apparent, and experts recommend removal of ash trees with more than 40 percent canopy dieback due to EAB injury. The results of numerous university research trials indicate that insecticides containing the active ingredients dinotefuran, emamectin benzoate or imidacloprid can help protect trees from EAB infestation and/or control existing infestations if trees are not exhibiting significant canopy dieback.
  • A soil drench or soil injection at the base of the trunk is the most common method of EAB treatment, and both imidacloprid and dinotefuran are labeled for this type of application. However, dinotefuran (Safari® Insecticide) is also labeled as a non-invasive basal trunk spray. With this method, dinotefuran is sprayed on the lower 5 feet of trunk, penetrates through the bark into the tree's vascular system and is transported upward to where EAB feed. The basal trunk spray can be applied quickly, and calibration is simple.
  • Finally, emamectin benzoate and imidacloprid are labeled for trunk injection. While effective, trunk injection is expensive, labor intensive and requires a trained applicator.
  • Removal of ash trees is often much more expensive than insecticide treatment. Some have estimated that it can cost as much as $5,000 to remove a large ash tree located near a building, and the loss of a large tree can significantly reduce property value. By treating trees rather than having them removed, municipalities and homeowners can save a great deal of money and retain aesthetic value, property value and/or privacy.