Like any living thing, pines may die from a variety of causes. But how can you tell if they were killed by SPB? The best way is to remove sections of bark from trees with fading (yellow) foliage or from trees with bark just starting to loosen. Look for the winding, S-shaped tunnels or galleries made only by SPB adults (fig. 2). SPB galleries are filled with a sawdustlike material (frass) left behind by feeding adult beetles. In pines just coming under attack, galleries are not yet present. The first symptoms of SPB in this case will usually be pitch tubes in bark crevices. These glossy masses of resin mark where the adult beetles bore into the trunk of a tree. SPB pitch tubes are soft and pink when fresh, becoming hard and white or yellow with age.