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Lilac (Ash) Borer

Lilac (ash) borer larva
Lilac (ash) borer adult female

Lilac (ash) borer damage

About the Lilac (Ash) Borer

Mature larvae are about 25 mm long and creamy white with shining brown heads.  The wasp-like moths vary from black and yellow to orange and brown, have clear wings, and have a wingspan of 26 to 28 mm.

Mature lilac borer larvae overwinter and pupate in tunnels under th ebark.  Moths emerge and lay eggs on the bark during May, June and July.  Larvae of banded ash clearwings pupate in August, and moths fly in late August or early September.  Banded ash clearwings overwinter as young larvae in tunnels.

During the summer, larvae of both species mine the sapwood of young trees, causing leaves to turn reddish-brown and braches to die back and break.  Entire trees are often killed.  Entrances to the tunnels are frequently associated with sunken and cankered areas on stems and branches.  Dark moist sawdust clings to the tunnel entrances and to the bases of trees.  Empty pupal skins often protrude from exit holes.

To Control

Spray trunks and all branches below 3 m with chlorpyrifos.  Trees should be sprayed two to three times at 2- week intervals during moth flight.  Traps baited with a male attractant, (Z,Z)-3, 13-octadecadienyl acetate, can be used to monitor moth flight and determine the optimum times to spray.  Trees should be sprayed 10 to 14 days after the first moth is captured.  Cut and burn heavily infested trees and branches.