By Gary Allen Burns, consulting forester
Stressed pine trees are particularly susceptible to attack from Ips bark beetles. They attack weak branches, and in healthy trees, the attack is confined to the branch. The beetles usually don’t kill the trees, but merely push dying trees over the edge. The attack is commonly on one of a small group of trees, causing the needles to turn yellow, red, and then brown. Globs of sap, called pitch tubes, may be present on the dying tree. These pitch tubes, smaller than those of southern pine beetles, indicate where the beetle has tunneled into the tree. Sometimes the tubes emit so much sap, the beetle becomes stuck and dies in the pitch.