Population genetics and biological control of goldspotted oak borer, an invasive pest of California oaks

Abstract

California’s oak woodlands are threatened by the recent introduction of goldspotted oak borer (Agrilus auroguttatus). This invasive wood-borer is indigenous to mountain ranges in southern Arizona where its low population densities may be due to the presence of co-evolved, host-specific natural enemies. Reuniting A. auroguttatus with these natural enemies can potentially provide permanent control of this pest. To initiate a classical biological control program, our research focused on investigating the genetic variation within and between populations in the native and introduced ranges in attempt to identify the geographic origin of the invasive California population. The area of origin for the invasive population was not determined conclusively, although molecular data suggests the Dragoon Mountains in Cochise County, Arizona as a potential source of this beetle, and its host-specific natural enemies. Native and introduced range surveys for natural enemies were conducted in 2012 and 2013 by deploying more than 30,000 A. auroguttatus sentinel. In 2012, the first known egg parasitoid was collected in Arizona and identified as a generalist Trichogramma sp., but in 2013, no egg parasitoids of A. auroguttatus were found. Despite the lack of success in explorations for host-specific egg parasitoids, classical biological control may still be the most viable long-term management option. However, additional research on the biology, life history, and potential natural enemies of this beetle is needed in order to advance its management in southern California.

Parent Publication

• Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world

Citation

Lopez, Vanessa; Rugman-Jones, Paul F.; Coleman, Tom W.; Stouthamer, Richard; Hoddle, Mark. 2015. Population genetics and biological control of goldspotted oak borer, an invasive pest of California oaks. In: Standiford, Richard B.; Purcell, Kathryn L., tech. cords. Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world. Gen. Tech. Rep. PSW-GTR-251. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 331-338.