Ash: Ash borer

categories: Ash Ash Insects Ornamental trees Ornamentals

revision date: 2022-11-21 12:29

ash borer pupal 'skeleton' at emergence hole on tree trunk.
ash borer pupal 'skeleton'
Photo by: A.L. Antonelli


The ash borer, also known as the lilac borer, is a member of the clearwing moth family. The adults of many clearwing moths mimic yellowjackets or paper wasps. The larvae of this moth cause damage to ash, lilac, and privet. The larvae tunnel in the bark of stems (trunk) and branches causing a gradual weakening of the plant. Other than emergence holes, one can determine the pests’ presence by the pupal skeletons attached to the bark at the emergence sites. There is usually only one generation per year. However, a two-year cycle can occur in the northern part of its range. Adult numbers usually peak in May or June and females lay their eggs singly in bark crevices where they soon hatch and burrow their way into the phloem tissue and continue feeding. Emerging full-grown larvae produce a round hole about 1/16 inch in diameter. Urban, open grown trees are highly susceptible to infestation.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • Since eggs are almost always laid in or near wounds, avoid pruning when moths are present.
  • There is little that can be done after trees have been attacked.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • None recommended