Effects of parental diapause status and release time on field reproductive biology of the introduced egg parasitoid, Oobius agrili (Hymenoptera: Encyrtidae) in the Mid-Atlantic

Authors: GEORGE, DEVAN - University Of Delaware; Duan, Jian; TALLAMY, DOUGLAS - University Of Delaware; SLAGER, BENJAMIN - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2020
Publication Date: 6/12/2020
Publication URL: https://handle.nal.usda.gov/10113/6986289
Citation: George, D., Duan, J.J., Tallamy, D., Slager, B.H. 2020. Effects of parental diapause status and release time on field reproductive biology of the introduced egg parasitoid, Oobius agrili (Hymenoptera: Encyrtidae) in the Mid-Atlantic. Biological Control. 149. https://doi.org/10.1016/j.biocontrol.2020.104342.
DOI: https://doi.org/10.1016/j.biocontrol.2020.104342

Interpretive Summary: The Asian parasitic wasp Oobius agrili is an important natural enemy of the invasive emerald ash borer (EAB) that has killed tens of millions of North American ash trees since it was discovered in the U.S. in 2002. This wasp attacks ash borer eggs and survives winter in a state of dormancy inside the EAB eggs. It was introduced to the U.S. for biocontrol of EAB in 2007 and has since been released in many EAB-infested regions including the Mid-Atlantic states. To develop biocontrol strategies, ARS, APHIS and University of Delaware scientists examined the effects of dormancy and release time of adult wasps on their longevity, fecundity and dormancy of offspring under field conditions in the Mid-Atlantic states. Early season releases of dormant adult wasps promoted the establishment of non-dormant offspring in the release year, whereas later releases of non-dormant adult wasps helped establish dormant offspring populations for overwintering.

Technical Abstract: Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae), a solitary egg parasitoid native to China, was introduced to the United States for biocontrol of the invasive emerald ash borer (EAB) Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in 2007. To help develop effective biocontrol-release strategies, we evaluated the effect of parental diapause and release time of the adult parasitoids on their longevity, realized fecundity and progeny diapause rate under field conditions in the U.S. Mid-Atlantic states in 2016 and 2017. Results from two years of our study showed that both non-diapaused and diapaused O. agrili adults released in rearing containers exposed to field conditions in late spring to early summer (from May 26 to July 20th) in the Mid-Atlantic region successfully survived and reproduced on emerald ash borer eggs provided throughout the study period. The parasitoid diapause status and release time did not significantly affect the longevity and life-time fecundity of the released adult parasitoids except that both diapaused and non-diapaused parasitoids released on May 26th of 2017 produced significantly fewer progeny than those from later releases (June 14th and July 20th) of the same year. In both 2016 and 2017, non-diapaused parasitoids consistently produced a higher proportion of diapaused progeny than diapaused parasitoids, regardless of release times. These findings indicate that releases of O. agrili with different diapause status from late spring to early summer may cause variations in establishing overwintering parasitoid populations for biological control of emerald ash borer in the field.