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Research Project: Biocontrol of Invasive Emerald Ash Borer to Protect Urban and Natural Forest Ecosystems

Location: Beneficial Insects Introduction Research Unit

Project Number: 8010-22000-031-051-A
Project Type: Cooperative Agreement

Start Date: Sep 15, 2021
End Date: Aug 15, 2023

The emerald ash borer (EAB), an Asian pest of ash trees, is considered the most destructive and costly invasive forest insect in North America. First detected in Michigan in 2002, EAB has spread to 35 U.S. states and five Canadian provinces. The proposed research aims to develop and test a biocontrol-based, area-wide EAB management approach that utilizes our understanding of the EAB invasion process, EAB population dynamics and new control tools, including releases of the more recently approved larval parasitoid Spathius galinae and limited trunk injections of large, mature ash trees (DBH>20 cm) with systemic insecticides. Specific objectives are: (1) Conserve ash as a component of natural forests in the aftermath of EAB invasion through releases and successful establishment of introduced biocontrol agents. To accomplish this objective, we will continue to monitor and evaluate the establishment, persistence, and long-term impacts of introduced EAB biocontrol agents on ash tree regeneration and growth including seedling, saplings, basal sprouts, and surviving ash trees at our previous and additional biocontrol study sites where S. galinae was recently released (Michigan). (2) Reduce the risk of EAB outbreaks through total population reduction by integrating selective treatments of large overstory ash trees with systemic insecticides combined with EAB biocontrol. To accomplish this objective, we will continue to monitor and evaluate the establishment, spread, and impacts of introduced biocontrol agents on EAB densities and ash health at all the study sites previously established in northeastern States (Connecticut, New York and Massachusetts), where systemic insecticide treatments (trunk injections) had also been integrated with releases of EAB biocontrol agents at some of the sites.

The proposed work will be carried out in two distinctive regions: (1) the infested areas of Lower Michigan near the original epicenter of the EAB invasion in the 1990s (discovered in 2002) and (2) the Northeast region where the EAB invasion in CT/MA/NY was detected in 2010 ' 2013. In both regions, we will continue to collect data on ash inventory and demographics and EAB infestation rates by walking 4 belt transects of 50 m long x 2 m wide at each study plot during the summer of 2021. Crown class scores (1 – 5), diameter at breast height (DBH), and any signs of EAB infestation will be recorded for each transect. We will debark 4 – 5 pole size trees and saplings (if available) from each study site between fall (October) and early spring (May) and observe stages of EAB larvae and associated mortality factors including parasitism by the introduced biocontrol agents, disease, putative host resistance, and abiotic factors from both treatment (parasitoid release or selective trunk injection with systemic insecticide) and control (no parasitoid release or no trunk injection) plots. To determine EAB egg parasitism by O. agrili, we will collect outer bark samples from the main trunk of ash trees with apparent EAB infestation symptoms and then examine these bark samples in the laboratory for EAB eggs and parasitism according to the procedure described in Abell et al. 2014. Recently, we have developed an improved larval sentinel log method to detect the parasitoid activity. This newly improved sentinel log method is easy to deploy and considerably more efficient than tree-debarking and yellow pan traps. We will deploy on a biweekly basis one freshly produced EAB larval sentinel logs at each selected location in both regions from June to August to detect parasitism by EAB larval parasitoids (S. galinae and/or T. planipennisi). Then, the distance and rate of spread of the newly released larval parasitoids will be determined using parasitism data collected from these sentinel logs.