Borers are mostly the larvae of beetles or moths that feed just below the bark of trees and shrubs. They are usually cream-colored and grow from ¼ inch to 1½ inches in length.

Borer Damage

Adult Borers lay eggs on plant bark. Eggs hatch and larvae bore tunnels into and under the bark of the branches and trunk where they feed. When mature, adults emerge from the bark leaving behind exit holes and excrement that looks like sawdust. If you see this, you can confirm borers by looking for tunnels underneath the bark. The tunneling weakens tree structure and interrupts transport of water and nutrients to the canopy causing yellowing, wilting foliage and dying limbs. Borers are attracted to weak, wounded, stressed or newly-planted trees and shrubs. Many Borers, such as Emerald Ash Borer and Eucalyptus Longhorned Borer, are host specific and only infest specific types of trees. Other Borers attack a wide range of plants.

Where Borers are Found Geographically

Borers are common throughout the United States. Ash, elm, lilac and birch are just a few of many susceptible species.

Related or Similar Pests 

Asian Longhorned Borer. Emerald Ash Borer. Lilac Borer. 




Cultural Controls

  • Since weak and stressed tress are most susceptible, make sure to take proper care of your trees during all seasons.
  • Cut out and destroy infested limbs or branches as soon as they are noticed.
  • Protect tree trunks from damage from weed whips or lawn mowers. Borers are often attracted to wounded trees.
  • Some Borers are attracted to cut branches. Avoid pruning trees and shrubs prior to adult Borers laying eggs. Check with your local cooperative extension for proper timing for pruning susceptible species.
  • Plant only plant species that are well adapted to your area.
  • Inspect trees and plants frequently to catch early signs of Borer infestation.