Recovery and assessment of Spathius agrili (Hymenoptera: Braconidae), a parasitoid of emerald ash borer, in the southeastern U.S

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive species native to eastern Asia that has become a significant threat to Fraxinus species in North America. Spathius agrili Yang (Hymenoptera: Braconidae), a gregarious ectoparasitoid of EAB from its native range, was approved for release by USDA APHIS PPQ and is included in the EAB biological control program. All current knowledge about S. agrili was collected in northern climates. Thus, studies were initiated in Tennessee in 2012 to assess the overwintering ability, parasitism rates, and life history of S. agrili in southern climates. Adult S. agrili were released in 2012 and monitored using pan traps in 2013. Parasitoids released in screened cages containing EAB-infested ash were monitored to assess overwintering. Adult S. agrili were released into barrels containing EAB-infested ash limbs; limbs were removed at regular intervals, dissected, and examined for EAB larvae and signs of S. agrili to determine the parasitism at each time interval. S. agrili successfully overwintered in Tennessee, as adults were recovered from field releases and overwintering cages. Overall, 30% of EAB larvae collected after 12 days were infested with S. agrili. Further results of these studies will be presented and discussed.