|JENNINGS, DAVID - UNIVERSITY OF MARYLAND|
|SHREWSBURY, PAULA - UNIVERSITY OF MARYLAND|
Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2018
Publication Date: 10/22/2018
Citation: Jennings, D.E., Duan, J.J., Shrewsbury, P.M. 2018. Comparing recovery methods for the emerald ash borer (Agrilus planipennis, Coleoptera: Buprestidae) egg parasitoid Oobius agrili (Hymenoptera: Encyrtidae) in Maryland, USA. Forests. 659(9): 1-9. https://doi.org/10.3390/f9100659.
Interpretive Summary: Emerald ash borer (EAB) is one of the most destructive invasive forest pests in North America and has caused widespread mortality of ash trees in the U.S. To date, four of its Asian natural enemies have been introduced to the U.S. for EAB biological control, including a tiny parasitic wasp that attacks EAB eggs. Monitoring the wasp’s effectiveness is challenging because female beetles lay eggs in bark crevices, and the eggs and those of the wasp are very small. Scientists from USDA ARS and the University of Maryland compared visual surveys and bark sifting to monitor the wasp’s establishment and impact in Maryland. The impact measured by the two methods was similar, but visual surveys of ash trees for EAB eggs were faster. Both methods confirmed that this introduced natural enemy has successfully established in Maryland.
Technical Abstract: Emerald ash borer, Agrilus planipennis (EAB), is an invasive beetle that has caused widespread mortality of ash trees in North America. To date, four parasitoids have been introduced in North America for EAB biological control, including the egg parasitoid Oobius agrili (Hymenoptera: Encyrtidae). Monitoring EAB egg parasitism is challenging because female beetles oviposit in bark crevices and EAB eggs and O. agrili are small (<1 mm in diameter). Consequently, multiple methods have been developed to recover this parasitoid. Here we compared two methods, visual surveys and bark sifting, used to monitor recovery of O. agrili in Maryland, USA. From 2009 to 2015, a total of 56,176 O. agrili were released at 32 sites across the state. In 2016, we surveyed nine of the study sites for O. agrili establishment using both methods. We found that visually surveying ash trees for EAB eggs was more efficient than bark sifting; the percent parasitism observed using the two methods was similar, but visually surveying trees was more time-efficient. Data from both methods indicated that O. agrili can successfully establish populations in Maryland. June may be the best month to release O. agrili in Maryland. Future research should investigate EAB phenology in the state to help optimize parasitoid release strategies.