Assessing susceptibility of two hymenopteran parasitoids of the emerald ash borer, Agrilus planipennis (Col: Buprestidae), to the entompathogenic fungus Beauveria bassiana.

Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is killing ash trees (Fraxinus spp.) across 15 states and southeastern Canada. Integrated pest management using biological control appears to be the only currently viable long-term approach for controlling the spread of EAB outside of host resistance. Two hymenopteran larval parasitoids, Spathius agrili Yang and Tetrastichus planipennisi Yang have been obtained from EAB in its native range and are now approved for release in the United States. The objective of this study was to assess susceptibility of these parasitoids, relative to that of EAB, to Beauveria bassiana, an entomopathogenic fungus that infects and kills EAB adults when applied to 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 A. planipennis 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.