Taking action on emerald ash borer

Emerald ash borer has been found in the metro area. The city of Minnetonka recently received a $75,000 grant to begin planning and preparing for emerald ash borer. Here’s how you can help!

  • Emerald ash borer larva.
    EAB is a wood boring beetle that feeds under the bark in an ash tree’s living tissues. It starts out in larvae form and matures into the more familiar green metallic beetle.
  • Emerald ash borer adult, green, compared to the size of a nickel.
    Females lay their eggs in the upper branches first. Baby EAB are called larvae, and are a good source of food for woodpeckers.
  • The pathways made by EAB are winding and S-shaped.
  • Feeding in the living tissues damages the tree’s ability to transport water and nutrients throughout the tree, eventually killing it.
  • EAB only attacks ash trees. All types of ash are affected, even if they are healthy.
  • Branch blonding, where bark is stripped away, one of the few signs of emerald ash border.
    One sign of EAB is branch “blonding” where woodpeckers strip the ash bark of upper branches looking for larvae. This is one of the only obvious, outward signs that a tree is infested.
  • In areas where the EAB is feeding, all ash will eventually succumb to attack unless they are chemically treated.
  • Emerald ash borer adult, green, held in the palm of a hand.
    The adult emerald ash borer beetle is about one-half inch long
  • They leave D-shaped exit holes in bark when they leave the tree, but the holes are very hard to see unless you stare at the bark.
  • A dying ash tree, with suckers sprouting up from the still living roots.
    Look for adults in June and July, around the same time black locust trees flower
  • Symptoms of EAB are similar to construction damage or general decline. They are very subtle for several years.
  • Eventually, the tree will die on top but will continue to produce epicormic branches, often called “suckers,” because the roots are still alive.

Dos and don’ts of insecticide treatments:

  • Do consider hiring a certified arborist to evaluate the condition and health of your ash trees before treating.
  • Do be aware there are soil drenches, soil injections, trunk injections, and bark and foliage sprays to control EAB. Some have been found to be more effective than others. Timing and placement is crucial to properly apply insecticides.
  • Do prioritize and selectively treat your ash; only those that contribute significantly to your landscape should be treated.
  • Do remember most treatments must occur every one to two years.
  • Don’t forget that trees larger than 15 inches in diameter must be treated by a professional; the homeowner products are not formulated for larger trees.
  • Don’t apply soil drenches on top of turf or mulch. They must be applied to bare mineral soil.
  • Don’t apply soil drenches near storm drains, streams or other water bodies due to water contamination concerns.
  • Do get more tips on the Emerald Ash Borer page.

How to take action