For this reason ash trees must be protected from early spring until autumn. Adult beetles emerge in late spring and early summer and feed on tender new shoots of young trees. They deposit eggs in openings chewed into the bark at the bases of trees below the soil line. The larvae burrow into the bases and roots of trees, pushing out frass, a sawdust-like excrement, at the entry points. Severely infested young trees may be badly damaged.
Larger trees tolerate light to moderate infestations without apparent serious effects.
They have a two-year life cycle. The adults are approximately 1 inch long and are dark grey with small orange spots on the wing covers. They emerge in summer and lay eggs in slits cut in bark, usually near the middle portion of trees. The larvae take three years to mature. Damage appears as swollen areas on trunks and larger branches.