Forest Service staff, working in cooperation with entomologists in the USDA Animal and Plant Health Inspection Service, and the University of California at Davis, developed an effective monitoring technique for the goldspotted oak borer. This invasive beetle, Agrilus auroguttatus, has been transported in infested firewood from southeastern Arizona into southern California where it is killing coast live oak and California black oak trees. A purple coroplast flight intercept trap coated with insect adhesive successfully trapped this beetle in flight during multiple field tests and during a range delimitation survey. The choice of trap color was based on a laboratory evaluation of the response of the retina of this insect to the color spectrum and a field screening procedure of many trap colors. The survey showed that the pest is limited to Riverside and San Diego counties.