Goldspotted Oak Borer
Goldspotted oak borer (Agrilus auroguttatus) is a small black beetle with six golden dots on its forewing. Native to southeastern Arizona, it is currently isolated to the western United States, however, it has resulted into complete oak death in some areas and is a serious threat to Eastern forests.
Goldspotted oak borer larvae feed beneath the bark of oaks in the red oak group, and damage the vital tissues of 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 thin. 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)