Identification
The adult beetle is approximately 1/8 inch long, brownish black with the posterior end rounded.
An infested tree’s needles will turn from green to yellow or brown as quickly as two weeks following initial attack.
Foresters spot the brown infested stands during aerial surveys and with GPS technology, check them on the ground. The foresters look for the telltale signs of a SPB infestation: pitch tubes, exit holes, and galleries.
Small yellowish-white pitch tubes found on the lower portion of a tree - approximately 15 feet from ground - indicates an infestation. Pitch tubes range from a nickel to a quarter in size. If you gently squeeze the tubes and they are soft, it can indicate that the SPB has recently infested the area. However, if the tubes are hardened, the SPB infestation may have occurred within the past year and the insects may or may not be present. Some pitch tubes may actually contain the insect that created them.
Another indication that the SPB has attacked a tree is the exit holes on the bark. These are approximately half the size of BB pellets and are usually clustered together. Exit holes indicate that the SPBs have matured and left the tree.
Another sign of an attack is reddish dust created during the boring of the tree. This dust can be found within the bark scales and on leaves at the base of infected trees.
If bark is removed from an infected tree, signature S-shaped egg galleries can be seen on the trunk surface and in the inner bark. S-shaped galleries distinguish SPB damage from other bark beetles.
Larval mines are generally perpendicular to the egg gallery (red arrow) located in the cambium-phloem or cambium-phloem-middle bark and are packed with fine boring dust Various galleries will contain adults (blue arrow) as well.
