Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 2011
Publication Date: January 8, 2012
Citation: Dean, K.M., Vandenberg, J.D., Griggs, M., Bauer, L.S., Fierke, M.K. 2012. Susceptibility of two hymenopteran parasitoids of Agrilus planipennis (Coleoptera: Buprestidae) to the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales). Journal of Invertebrate Pathology. 109:303-306. Interpretive Summary: The emerald ash borer (EAB) is an invasive insect that has killed millions of ash trees and has spread to most northeastern states. In previous work we have shown the potential utility of a fungal pathogen, Beauveria bassiana, for killing adult EAB. Three wasp parasitoids of the emerald ash borer have been approved for release in the US. We tested the susceptibility of two wasp species, Spathius agrili and Tetrastichus planipennisi, to Beauveria bassiana. Adult EAB and wasps were exposed to ash twigs inoculated with B. bassiana and monitored daily for infection. All EAB adults exposed to B. bassiana were fatally infected while mean survival for control EAB was 77%. Average survival in the treatment groups for T. planipennisi and S. agrili were 99% and 83%, respectively, indicating these parasitoids are relatively unaffected by exposure to B. bassiana. This research elucidates interactions among natural enemies of EAB. It also provides data necessary for developing a successful integrated approach for EAB management.
Technical Abstract: Emerald ash borer (EAB), Agrilus planipennis Fairmaire, native to Asia, is killing ash trees (Fraxinus spp.) in eastern North America. Integrated pest management using biological control is the only viable long-term approach for controlling the spread of EAB outside of host resistance. Three hymenopteran parasitoids, Spathius agrili Yang, Tetrastichus planipennisi Yang, and Oobius agrili were discovered attacking EAB in China and were approved for release in the United States in 2007. The objective of this study was to assess susceptibility of the larval parasitoid species S. agrili and T. planipennisi, to Beauveria bassiana, an entomopathogenic fungus that infects and kills EAB adults when sprayed on ash bark or foliage. Adult EAB and parasitoids were exposed to B. bassiana inoculated ash twigs for two hours and then monitored daily for death and signs of infection for up to ten days. All EAB adults exposed to B. bassiana were fatally infected while mean survival for control EAB was 77%. Average survival in the treatment groups for T. planipennisi and S. agrili were 99% and 83%, respectively, indicating these parasitoids are relatively unaffected by exposure to B. bassiana. This research elucidates interactions between a fungal pathogen and two parasitoids of EAB, and provides data necessary to developing a successful multi-stage integrated management approach to control of EAB.