Location: Beneficial Insects Introduction Research Unit
Project Number: 8010-22000-031-061-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2022
End Date: Sep 30, 2024
Objective:
Emerald ash borer (EAB) is the most destructive invasive forest pest in North America, causing widespread mortality of ash trees in urban landscapes and natural forests. First discovered in Michigan in 2002, EAB has now spread to 35 U.S. states, Washington D.C., and five Canadian provinces. Costs of treating or removing and replacing even half of the ash trees growing on municipal property in urban and suburban communities were projected to exceed $1.1 billion per year.
The proposed research aims to develop and test a sustainable EAB management approach that relies on releases of introduced biocontrol agents (parasitoids) to protect North American ash in both urban and natural hardwood forests. The proposed work will focus on evaluation of 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 (Oobius agrili, Tetrastichus planipennisi, and Spathius galinae).
Objectives: The proposed research has two specific objectives:
(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.
Approach:
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 (Duan et al., 2019). 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.
