Project Number: 8010-22000-031-060-A
Project Type: Cooperative Agreement
Start Date: Sep 15, 2022
End Date: Aug 31, 2023
The emerald ash borer (EAB), Agrilus planipennis, an Asiatic pest of ash trees, is the most destructive invasive forest insect in North America. EAB causes widespread ash mortality, resulting in severe economic losses to U.S. forestry and plant industries, as well as degradation of essential ecosystem services. The proposed work will focus on effectiveness of the current biocontrol programs in protecting North American ash resources through suppressing EAB populations at regional levels by releasing EAB egg and larval parasitoids. The overall goal of this project is to develop strategies that optimize long-term and sustained control of EAB in the aftermath of EAB invasion to protect and conserve ash trees of all sizes in natural and urban ecosystems by releasing introduced natural enemies (Oobius agrili, Tetrastichus planipennisi, and Spathius galinae). Our specific objectives are: (1) Monitor and evaluate the long-term impact of introduced EAB biocontrol agents on ash regeneration and growth from seedlings, saplings, basal sprouts, and surviving ash trees at our previous (long-term) biocontrol study sites in both Lower Michigan and several Northeast States (Connecticut, Massachusetts, and New York), where all three biocontrol agents (O. agrili, T. planipennisi, and S. galinae) were either sequentially or simultaneously released more than five years earlier. (2) Determine the establishment, spread, and impacts of more recently released parasitoids on EAB population densities and ash health at the new study sites in Lower Michigan and two selected Northeast States (Connecticut and Massachusetts), where releases of these introduced agents were completed between 2018 and 2021.
The proposed work will be carried out in two distinctive regions: (1) infested areas of lower Michigan, where EAB was first detected in 2002 and (2) the Northeast region (Connecticut, Massachusetts, and New York), where EAB was first detected between 2010 and 2013. In Michigan, six, secondary mixed-hardwood bottomland forests containing both green ash (Fraxinus pennsylvanica Marshall) and white ash (F. americana L.) received releases of O. agrili, T. planipennisi, and S. agrili from 2008 to 2010 (Duan et al. 2013), and S. galinae from 2015 to 2017 after confirmation of successful establishment of O. agrili and T. planipennisi (Duan et al., 2020). More recently, three additional forests from this region were also selected as new study sites (~60 km from the six earlier sites) with simultaneous releases of O. agrili, T. planipennisi and S. galinae from 2018 to 2021. While historical data on ash crown condition, EAB densities and associated mortality factors including the introduced biocontrol agents have been collected from the earlier (long-term) biocontrol study sites (along with the paired no-parasitoid release control plots), these newly established biocontrol release sites have not been sampled for establishment, spread and impacts of the newly released biocontrol agents on EAB infesting ash trees and/or saplings. In the Northeast region (CT/NY/MA), where, the six, long-term sites consisted of secondary mixed-hardwood forests containing green and white ash trees received O. agrili, T. planipennisi, and S. galinae were released simultaneously from 2015 to 2017. More recently, several new forest sites were also established with simultaneous releases of these three biocontrol agents from 2018 – 2020. Historical data on ash crown condition, EAB densities, and associated mortality factors including the introduced biocontrol agents have been collected from the earlier established (long-term) biocontrol forests in this region; however, no data have been collected there from the additional new sites that were established from 2018 to 2020.