Emerald Ash Borer
Emerald Ash Borer (EAB) is an exotic beetle that was discovered in southeastern Michigan near Detroit in the summer of 2002. The adult beetles feed on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. EAB likely arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating from its native Asia. It has since then spread throughout the Midwest from southern Arkansas north into Canada. It is estimated that EAB has killed millions of ash tree and it is just getting started. Untreated ash trees will die leaving behind a great loss in our urban tree canopy.
Knowing what to look for can help you quickly verify that you have an EAB infestation and allow you time to decide on your next course of action.
- Ash Identification: Be sure the tree you’re concerned about is an ash tree. Visit Missouri Urban Trees or Distinguishing Ash from other Common Trees to correctly identify your tree.
- Description: EAB is a very small (1/2 inch long and 1/8 inch wide) bullet shaped borer with a flat head. The beetle is iridescent green in color and fits on the head of a penny. There are look-alike insects of about the same size and color, including other borers and a few beetles, making identification of the insect itself challenging.
- Life Cycle: The female beetle lays any where from 65-90 eggs on the bark of the branch/tree from May-July. The eggs hatch and begin to burrow into the trunk of the tree as larva. During the winter months, the larva feeds on the vascular tissue of the tree causing “S” shaped galleries. It will feed and pupate from October to April before emerging again as an adult.
- Symptoms: The signs of EAB infestation are difficult to diagnose, because decline of the tree’s health usually happens gradually. Early symptoms could include dead branches near the top of the tree or leafy shoots growing out from the lower trunk, but these symptoms alone are not absolute evidence of an EAB infestation. This die back is a direct result of the feeding that has taken place by the the larva. The “S” shaped galleries, cut off the flow of nutrients and water between the roots and the canopy ultimately strangling the tree. Also a marker to look for is the small “D” shaped holes left by the adult as they emerge from the tree. This also can be difficult to use for identification as infestation starts in the canopy making it difficult to see from the ground.
If you have an ash tree located within 12 feet of the street or between the sidewalk and the curb, you should contact the city forester or Parks Department. Many cities in the metro have an Emerald Ash Borer Action Plan outlining the treatment/removal/replacement of public trees. If your ash tree is located on private property (front or backyard) the decision will be yours to make whether you move forward with treatment.
Trees infected with EAB will die, typically within 5-7 years. Treatment can be costly and is required every 1-2 years for the life of the tree. A mature tree however provides a number of environmental benefits and cost savings that a small newly planted tree will not. The decision to treat vs remove and replace is yours but first have your tree evaluated by a certified arborist. If there are structural defects or other issues, your tree may not be a candidate for treatment.
- Treatment: There are many products on the market that can effectively kill EAB. Cost for treatment can very depending on the method of application. This could include a soil drench, trunk spray or trunk injection. There are products on the market that a homeowner can use to treat small ash trees. Once the tree is over 15 inches in diameter, a certified arborist should be contracted to apply treatment. With any chemical application, it is important to read the label carefully and be aware of effects on the environment. At the end of this article for further information about treatment options.
- Replant: It is estimated that the KC metro has 6.5 million ash trees. Whether you decide to treat your tree or cut it down, please start planting now! The devastating loss of benefits provided by those 6.5 million trees will be felt for generations to come. If we’ve leaned nothing else from other devastating diseases and pests such as Dutch Elm disease and Pine Wilt, diversity of species is vital. Most metro cities have an overwhelming number of ash trees second only to red maple. To prevent catastrophic loss in the future, diversify your plantings with many different species of trees.