Location: Beneficial Insects Introduction Research Unit
Project Number: 8010-30400-001-040-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 10, 2026
End Date: Sep 29, 2027
Objective:
The goal of this project is to delineate the host associations of the introduced egg parasitoid O. agrili and quantify its impact on the target pest EAB and possibly on other nontarget (native) Agrilus pests. Specific objectives are to:
(1) determine the host association of O. agrili with EAB and other Agrilus pests infesting their common host trees such as ash, birch, oak, and/or sugarberry in the EAB biocontrol release areas across a gradient of latitudes.
(2) quantify the impacts of O. agrili on EAB population densities in the long-term EAB biocontrol study sites established in Michigan (2008-2010) and the Northeastern states (2015-2017) including Connecticut and Massachusetts.
Approach:
The work for objective 1 will be carried out in several states across four different EAB-invaded regions in US, where the introduced egg parasitoid (O. agrili) was released at least two years prior to the study. These will include Connecticut and Massachusetts in the Northeast region, Delaware and Maryland in the Mid-Atlantic region, Michigan in the Midwestern region, and Georgia and Louisiana in Southeastern US (work in the latter two states will be performed under separate cooperative agreements). In each region, we have three to six study sites based on the release and recovery history of O. agrili from the USDA APHIS EAB biocontrol database from MapBioControl.org (also see progress reports). Each study site selected for this objective bears the following attributes: (1) two continuous releases of O. agrili (~total 1000 wasps per site) were completed prior to 2023, (2) there are enough live ash trees (DBH >5 cm) remaining to allow for sampling EAB eggs and associated parasitism (N= 5 – 10 for each site), and (3) there are birch, oak sugarberry, and/or other trees present to allow for sampling eggs of nontarget Agrilus beetles and associated egg parasitism (N = 5 to 10 for each tree species). Observation of EAB eggs laid on the surface of ash trunks or branches covered by the spiraling wraps of each trap were conducted every 2 – 3 weeks. At each observation time, all EAB and other nontarget Agrilus eggs will be collected and placed in the ventilated plastic vials (5 ml), and the fate or hatching of each egg was determined after approximately four weeks of incubation in a growth chamber under normal rearing conditions (25oC, long-day photoperiod L:D 16:8 h, and 65% RH). All emerged adult parasitoids from parasitized EAB and other Agrilus eggs will be taxonomically curated for conventional taxonomy based on key morphological characters. Host associations of the recovered egg parasitoids including O. agrili will then be determined with the parasitoid identification and host egg parasitism data.
The work for objective 2 will be conducted in our long-term EAB biocontrol study sites established 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). In both regions, we will use the same procedure described previously in Objective 1 to deploy 20 EAB oviposition traps (burlap bands) at each study site on ash trees (3 traps per tree) with 40 – 60% crown declines and/or fresh woodpecker feeding signs (holes) at various distances (with the radius of 15 -30 km) to the original egg parasitoid release point at each study site in late May or early June when EAB adults start emerging. The same procedures described in Objective 1 will be followed for observation and collections of EAB eggs laid on the surface of ash trunks or branches covered by the spiraling wraps of each trap.