Pine Bark Beetles

How do Pine Bark Beetles kill trees?

There are many species of bark beetles that infest not only pine, but other softwood tree species as well. Bark beetles kill their host trees when the adults bore holes through the tree’s outer bark into the inner bark, or the cambium-phloem layer of the tree. In addition, bark beetle adults excavate galleries where the female beetle lays eggs. When the eggs hatch, the grub stage (larvae) further damages the inner bark layer as they construct feeding galleries. Eventually, the combined excavation by adults and larvae will girdle (encircle) the tree’s inner bark and cause death.

Tree death is caused by:

• The downward movement of the plant’s food sugars is blocked and does not reach the roots and other parts of the tree. Therefore, the roots die.

• When the roots die, the tree’s upper portions cannot get enough moisture to generate the tree’s food. This also contributes to the tree’s death.

• Bark beetles may also infest a tree with blue stain fungus that grows in the xylem layer of the wood. This fungus also damages the tree by blocking moisture from being transferred to the leaves.