Goldspotted Oak Borer
Emerging Threat Note: This insect is not established in Tennessee, but we actively monitor for it and encourage residents to report potential sightings.
Goldspotted oak borer (GSOB; Agrilus auroguttatus) is a black beetle with six golden dots on its forewings. Native to southeastern Arizona, it is currently isolated to the western United States, however, it has resulted in complete oak death in some areas and could pose a serious threat to Eastern forests.
Goldspotted oak borer larvae feed beneath the bark of oaks in the red oak group, and damage the tissues that transport nutrients within the main stem and larger branches. Generally, a few years after initial infestation, trees decline and die from the damage caused by multiple generations of this aggressive beetle.
Crown thinning and dying branches are usually an initial indicator of moderate to severe infestation. A healthy Oak will exhibit full thick leaves at the top, but as infestation occurs and progresses, branches and leaves will begin to die and canopies will thin. The process of infesting oaks and eventually causing mortality typically takes 3-5 years.
Unlike some other wood-boring Agrilus species, GSOB does not attack the upper branches in the crown during the early stages of infestation. The GSOB adult emergence holes (approximately 0.15 inches in diameter) can appear before any other injury symptoms are observed, providing for early diagnosis. Evidence of insect attacks on oak trees can also be detected by:
- The presence of the insects under the bark
- D-shaped exit holes
- Woodpecker foraging (typically to eat GSOB located under the bark)
- Dark colored wet staining or red bleeding
- Crown color of tree from dark green (healthy) to grayish green (severely injured)
Goldspotted oak borer is not currently in Tennessee. Because of the high level of damage this beetle causes in the Western U.S., monitoring for this pest is ongoing.
What Can You Do?
While this beetle is not currently found in Tennessee, reporting suspected beetles or damage may help detect any introductions of the goldspotted oak borer.