Larvae feed in the cambial region, cutting winding S-shaped galleries packed with frass. Individually these are small, but repeated attacks over two or three seasons interrupt enough of the phloem to girdle the trunk. The canopy thins from the top, epicormic sprouts appear on the trunk, and the tree usually dies within a few years of infestation.
Detection is the practical problem. Adults leave a distinctive D-shaped exit hole about three to four millimetres wide, but by the time exit holes appear the tree has already carried larvae for at least a year. Woodpecker damage stripping bark in search of larvae is often the first visible sign.
Spread in North America has been driven substantially by human movement of firewood and nursery stock, which carries larvae far beyond the beetle's own flight range. That is why firewood movement restrictions, rather than insecticide, have been the central regulatory tool, alongside releases of parasitoid wasps from the beetle's native range.