Lilac/ash borer (Podosesia syringae1 ) is common wood borer associated with ash throughout Colorado and a species that is native to North America. Damage is caused by the larvae which tunnel into the trunks and lower branches of ash trees. These feeding injuries produce irregular gouging wounds under the bark and tunneling frequently extends deeply into the heartwood . Almost all larval feeding activity occurs in the lower trunk, particularly around the soil line. Lower scaffold limbs may also be attacked and infestations may extend about 10 feet up the trunk. Feeding damage can often be found in the mid and upper crown of trees above areas that were treated with contact insecticides. External evidence of lilac/ash borer activity in trees can include irregularly round exit holes of about 1/4-inch diameter on trunks. As larvae near full development some sawdust may be expelled from these holes and, when adults emerge, the pupal skin often remains extruded from the hole. Ash trees heavily damaged by lilac/ash borer often show some disfiguring of the trunk, with areas of irregular, gnarled growth, and often development of excessive branching. Extensive tunneling of the lower trunk may seriously weaken plants and cause them to break. Trees may be killed by this insect, although that is rare. Serious problems almost always involve ash grown in suboptimal locations (e.g., parking lots, street trees) or recently transplanted trees. Damage is usually insignificant to well established trees that receive adequate water and care. In Colorado, more problems have been associated with white ash (e.g. ‘Autumn Purple’) than green ash. Lilac (Syringa) and privet (Ligustrum) are other hosts for this insect but damage to these plants is much less frequently observed in Colorado. On lilac and privet, damage is confined to the base of the plant. On smaller diameter branches, such as is common with lilac and privet, larval injuries may girdle and kill stems. The larvae are creamy white grubs with a small dark head. Prolegs on the underside of the abdomen are highly reduced but elliptical rings of small hook-like crochets are readily visible at the tip of the prolegs. The presence of abdominal prolegs allows separation from lilac ash borer larvae from those of the various other wood borers found in ash, all of which are larvae of beetles. Adult lilac/ash borers are mimics of Polistes paper wasps, quite similar in both size and coloration. The wings are dull black with chestnut brown tones and wingspan typically ranges from 28-35 mm (ca 1-inch). The body is generally dark brown with reddish markings and narrow yellow bands occur on the abdomen. Long hind legs also reinforce the superficial similarity with paper wasps.