Location: Beneficial Insects Introduction Research Unit
Project Number: 8010-30400-001-026-A
Project Type: Cooperative Agreement
Start Date: Jul 30, 2025
End Date: Jun 30, 2026
Objective:
EAB is one of the most destructive invasive pests of North American ash (Fraxinus spp.) in United States. The egg parasitoid, Oobius agrili, is one of the four EAB natural enemies introduced from Northeast Asia for biological control of this invasive pest. The primary purpose of this cooperative agreement work plan is to delineate the host associations of the introduced egg parasitoid O. agrili with its target host, the emerald ash borer (EAB), Agrilus planipennis, and other nontarget Agrilus pests such as sugarberry borer (A. macer) in Geogia. Specific objectives are:
(1) Survey emerald ash borer eggs and determine parasitism from infested ash stands or forests where O. agrili were previously released at least two years ago.
(2) Survey eggs of other Agrilus beetles (such as A. macer, A. anxus, or A. subrobustus) from their common host trees (naturally infested or artificially girdled) in or near the O. agrili release areas.
Approach:
The proposed work for this objective will be carried out in five sites in northeastern Georgia, where the introduced egg parasitoid (O. agrili) was also released in 2022 and 2023. These sites have >25% ash density in each site, a variety of ash size and age classes, low to moderate levels of EAB and ash dieback, and are relatively easier to access. Currently, we have located an abundant population of A. macer in Louisiana and also likely in Georgia as well. To survey EAB eggs and associated parasitoids, we will deploy burlap traps in selected study sites on five to 10 ash trees (DBH > 5 cm; 2 traps per tree) with fresh woodpecker holes at various distances (within the radius of 15 – 30 km) to the original egg parasitoid release point at each study site in the spring (April to May) when adult EAB and nontarget Agrilus beetles begin to emerge. To survey eggs of non-target Agrilus beetles and associated parasitoids, we will first artificially girdle five to 10 potential host trees such as birch, oak, poplar, sugarberry, and other relevant tree species and then deploy the burlap traps on those girdled trees the same way as for ash trees.
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. All emerged adult parasitoids from parasitized EAB and other Agrilus eggs will be taxonomically curated for conventional taxonomy based on key morphological characters. Some emerged adult parasitoids along with host egg remains will also be curated in molecular alcohol for molecular identification based on known primers