Plant-Insect Ecosystems
10-Minute Paper
Stokes A. Aker
Graduate Assistant
Penn State Entomology
State College, Pennsylvania
Dan S. Gruner
Associate Professor
University of Maryland
Silver Spring, Maryland
Rafael B. de Andrade
Assistant Research Scientist
University of Maryland
College Park, Maryland
Jian Duan
Research Entomologist
USDA-ARS
Newark, Delaware
Emerald ash borer (EAB; Agrilus planipennis Fairmare (Coleoptera: Buprestidae)), an invasive phloem-feeding beetle native to Asia, has devastated North American ash forests since its discovery in Michigan USA in 2002. As the EAB has continued to spread, the potential for successful management hinges upon the release, establishment, and spread of introduced larval and egg parasitoids for biological control. Here, we focus on the establishment and evidence for spatial spread of introduced larval parasitoid, Spathius agrili Yang and S. galinae Belokobylskij & Strazanac (Hymenoptera: Braconidae) in the state of Maryland. To assess each species, we analyzed historical release and recovery data and resampled previous release sites and non-release sites for establishment. We found little evidence of establishment or spread for S. agrili, despite a comparatively large number of release locations, events, and individuals. By contrast, despite much lower propagule pressure and shorter history of releases, we detected multiple established populations of S. galinae at release sites and at sites up to 45 kilometers from the nearest release point approximately 3 years after its last field releases. Our findings show that S. galinae is both established and spreading rapidly following field releases whereas its congener, S. agrili is not. Although it may still be too early to evaluate the level of population control and ash protection afforded by S. galinae, these findings indicate the need for continued investment in S. galinae for EAB classical biological control efforts.