Lilac Ash Borer Identification and Life Cycle
This wasp-mimicking moth targets the lower trunk of ash and lilac trees, and it's easy to mistake for the far more destructive emerald ash borer.
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Not the same insect as the emerald ash borer
The adult lilac ash borer (also called the lilac borer) is a clear-winged, day-flying moth that closely resembles a wasp. It's a separate species from the emerald ash borer, though both attack ash trees and the names get confused constantly.
Life cycle
Adults emerge in August or September and deposit eggs on the bark of the lower trunk. Once the larvae hatch, they bore through the bark and feed within the branches and trunk, remaining there until the following fall, when they emerge as adults to start the cycle again.
Why lower-trunk borers matter for ash and lilac
Because feeding happens inside the trunk and branches over an extended period, damage from lilac ash borer can compound year over year, weakening the structure of the tree from the inside before any obvious external symptoms appear.
