An exotic killer attacks San Diego County oaks An invasive pest called the goldspotted oak borer is devouring enormous numbers of oak trees in San Diego County and could threaten oaks elsewhere in California. U.S. Forest Service / March 11, 2013 By Bettina Boxall March 12, 2013, 5:00 a.m. For a glimpse of the trail of destruction left by an invasive beetle in some of San Diego County's oak woodlands, take a look at the video prepared by UC Riverside researchers hunting for ways to stop the bug. The goldspotted oak borer, an Arizona native, has killed tens of thousands of oaks in the county. National forest campgrounds have been denuded and county parks and communities have lost graceful old oaks. Scientists believe the pest is spread by people hauling infested firewood from one location to another. Adult borers feed on oak leaves, and female boreres are thought to lay their eggs in bark crevices. After the eggs hatch, larvae burrow into the tree and feed under the bark. Signs of oak borer infestation include crown thinning, small D-shaped holes in the bark where adults have emerged and the presence of larvae. The video features Mark Hoddle, director of UC Riverside's Center for Invasive Species Research. For more on Hoddle's work, read Amina Khan's story: Hunting for good bugs to fight bad bugs.