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Ash Borer

Not to be confused with Emerald Ash Borer.

The Ash Borer (Podosesia syringae), aka Lilac Borer, is a clearwing moth in the family Sesiidae. It is found throughout the United States east of the Rocky Mountains. The ash borer is an example of Batesian mimicry, and is a serious pest of various trees of the olive family.



The black and yellow bands, prominent antennae and hind legs, and overall body shape of the Ash Borer resemble those of the paper wasp (Polistes fuscatus). When a potential predator encounters the Ash Borer, it may refrain from conflict mistakenly thinking that it may be stung. Thus the Ash Borer benefits from the similarity of its appearance to a more dangerous foe, making it a Batesian mimic of the wasp.

The Ash Borer is distinguished from the wasp in that it is somewhat larger, growing to a length of ¾ to 1½ inches, is amber-colored in addition to black and yellow, and lacks a stinger.


Ash Borer larvae feed on European Ash (Fraxinus excelsior), lilac, privet and mountain ash. The larvae destroy the tree's phloem, cutting off the supply of nutrients to the roots, weakening and possibly killing the tree. The tunnels dug by the larvae appear as dark wormholes in lumber harvested from infected trees, reducing its value.


Adult male approaching pheromone trap

About two weeks prior to reproducing, Ash Borers attract mates by releasing sex pheromones. This mating activity can be detected by the use of pheromone traps containing (Z,Z)-3,13-octadecadien-1-ol acetate (ODDA). Once Ash Borers are detected in the traps, insecticide can be placed on a tree to protect it from egg laying Ash Borers.


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