Location: Beneficial Insects Introduction Research Unit
Project Number: 8010-30400-001-033-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. Native to Northeast Asia, this invasive beetle has now spread to 37 U.S. States and five Canadian provinces and killed hundreds of millions of ash trees since it was first detected in Southern Michigan in 2002. 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 Louisiana. Specific objectives are:
(1) Survey emerald ash borer eggs and determine parasitism along a gradient 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) and determine parasitism and predation from their common host trees (naturally infested or artificially girdled).
Approach:
The proposed work for objective 1 will be carried out across a north to south gradient starting in Webster parish Louisiana, where the introduced egg parasitoid (O. agrili) was released in 2015, 2016, and 2019. Initial release sites were between 1.0 – 5.6 ha, and contained an ash density of 12 – 25%, with green ash (Fraxinus pennsylvanica) being the most dominant species of ash, co-occurring with red maple (Acer rubrum), sweet gum (Liquidambar styraciflua), and hickory (Carya spp.). We will setup 3 – 5 study sites originating from the initial release sites along a gradient of emerald ash borer infestation (low to high to low) within the region. This gradient will allow us to assess the presence of O. agrili according to the infestation history of EAB within the state. We will perform the proposed work for objective 2 in Plaquemine, Louisiana, where we have an abundant population of A. macer on sugarberry (Celtis laevigata). Our focal trees exist within production stands of green ash, encompassing four rotation periods (6, 12, 18, 24 year old). To survey eggs of non-target Agrilus beetles and associated parasitoids, we will first artificially girdle five to 10 potential host trees such as oak (Quercus spp.), maple (Acer spp.), hackberry (Celtis spp.), or other relevant tree species and then deploy the burlap traps on those girdled trees the same way as for ash trees. However, we point out that burlap traps are not needed for A. macer as it lays eggs on smooth surface of sugarberry trees (Todd Johnson unpublished data). Observation of EAB eggs laid on the surface of ash trunks or branches covered by the spiraling wraps of each trap will be conducted every 2 weeks. All emerged adult parasitoids from parasitized EAB and other Agrilus eggs will be taxonomically curated for conventional taxonomy based on key morphological characters.l