|Jennings, David - University Of Maryland|
|Larson, Kristi - University Of Delaware|
|Lelito, Jon - Animal And Plant Health Inspection Service (APHIS)|
|Shrewsbury, Paula - University Of Maryland|
Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2014
Publication Date: 9/1/2014
Citation: Jennings, D.E., Duan, J.J., Larson, K.M., Lelito, J.P., Shrewsbury, P.M. 2014. Evaluating a new method for monitoring the field establishment and parasitism of Oobius agrili, an egg parasitoid of the emerald ash borer. Florida Entomologist. 97:1263-1265.
Interpretive Summary: Oobius agrili is a parasitic wasp that attacks eggs of the invasive emerald ash borer (EAB), and can be responsible for over half of EAB egg mortality in its native range of northeastern Asia. This parasitic wasp has been released as a biological control agent for EAB in the US for several years, but the methods currently used to monitor its establishment and parasitism in the field require considerable time and effort and are not able to prevent high predation of EAB eggs by other predators such as ants (which reduces our ability to detect parasitism). In the present study, our objectives were to develop a new method for monitoring the establishment and parasitism of this beneficial wasp that would be simple to replicate, and that would reduce predation on EAB eggs without interfering with parasitism by the wasp. Toward that end, we created egg-sentinel mesh envelopes (ESEs) containing EAB eggs on filter paper, and tested how different mesh sizes affected parasitism of EAB eggs in the lab, and how they affected parasitism and predation of EAB eggs in the field. In the lab, we found that a smaller mesh only slightly reduced egg parasitism relative to a larger mesh. Parasitism for all treatments was much lower in the field compared to the lab, but the smaller mesh did significantly reduce predation of eggs by other predators in comparison to the larger mesh. To reduce EAB egg predation by other predators while enabling detectable levels of parasitism by the parasitic wasp, we therefore recommend using the smaller mesh screen to protect EAB eggs for the field deployment to monitor the establishment and parasitism of this parasitic wasp.
Technical Abstract: Oobius agrili is a solitary egg parasitoid of emerald ash borer (EAB), Agrilus planipennis, and can be responsible for 50-60% of EAB egg mortality in its native range. O. agrili has been released for biological control of EAB in the US since 2007; however, current methods to monitor its establishment and parasitism are labour intensive and unable to prevent interference from high predation of eggs by other predators (e.g., ants). In the present study, we created 10 cm x 10 cm mesh egg-sentinel envelopes (ESEs) containing EAB eggs on filter paper, and tested how two different mesh sizes (0.5 mm and 1 mm) affected parasitism in the lab, and parasitism and predation in the field. Mesh size significantly affected parasitism in the lab, with the 0.5 mm mesh reducing parasitism by approximately 20% relative to the 1 mm mesh. Parasitism was much lower in the field with no significant difference among treatments, but the 0.5 mm mesh did significantly reduce predation by almost 50% in comparison to the 1 mm mesh. To reduce egg predation while enabling detectable levels of parasitism by O. agrili, we therefore recommend using mesh screen 0.5 mm wide to create ESEs for field deployment.