Native and introduced range surveys for egg parasitoids of Agrilus auroguttatus, an invasive pest of native oaks in California

Abstract

The invasive goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), has caused extensive mortality to indigenous oaks in southern California. This woodborer is native to southern Arizona where low population densities may, in part, be due to the presence of co-evolved natural enemies. Surveys were conducted in Arizona and California from June to August 2013 by deploying sentinel egg masses in an attempt to attract, collect and identify potential egg parasitoids of this beetle that could be used for a classical biological control programme in California. In total, 18,052 A. auroguttatus eggs were deployed throughout the native and introduced range. Parasitoids did not attack any eggs deployed in Arizona or California. The inability to detect egg parasitoids could be explained by the following: (1) host-specific egg parasitoids of A. auroguttatus do not exist, (2) surveying time did not coincide with peak activity of egg parasitoids or (3) surveying methods were insufficient at detecting egg parasitoids.