Guest Post by Brian Bradley

Bark beetles cause more damage to pine trees than any other forest insect in Alabama. They generally attack less vigorous and stressed pines, e.g., trees weakened by drought, old age, tree competition, or other stressors.

Land Trust of North Alabama has identified a bark beetle infestation at our Green Mountain Nature Preserve and is currently taking measures to address it before the problem worsens. This requires removal of infected trees, primarily along Alum Hollow Trail. 

The first signs of attack are usually pine needles changing color, green to yellow to red and finally brown. The trunk will often have whitish pitch tubes, about the size of a wad of gum, which is sap that oozed out from the beetles entrance hole in the bark.  In severe drought conditions, pitch tubes may be absent and only reddish-brown boring dust can be seen at the base of the tree. Removal of the bark will show a distinctive winding “S”, “Y” or “H” shaped gallery patterns depending on the type of bark beetle.

The adult beetles bore through the bark and excavate winding galleries where eggs are laid in niches along the galleries. Upon hatching, the larvae feed in the cambium area under the bark until they are grown. Eating the cambium layer effectively cuts off the flow of nutrients resulting in the death of the tree. The larvae then excavate cells near the bark surface and after pupation the adult beetles chew through the bark and emerges. The complete life cycle of the attack, takes from 25 to 40 days to complete, depending on the temperature.

Cutting and removing infected trees which are then transported to a mill for processing is the ideal control method. Often that option is not possible so cutting and leaving trees on the ground is an alternative. Increased solar radiation and corresponding heat helps kill the beetles at all life stages when on the ground. In some cases, buffer zones of cut trees are needed to help prevent the spread of the beetle attack.

For more detailed information, visit aces.edu/blog/topics/forestry/managing-pine-bark-beetles-in-urban-forests.