Project Number: 8010-22000-031-04-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2019
End Date: Sep 30, 2021
The proposed research aims to develop and test a biocontrol-based Invasive Emerald Ash Borer (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 systemic insecticides. At research sites in Lower Michigan, where the EAB biocontrol agents were released (2007-2011) as the first EAB infestation wave peaked and most large overstory ash trees were dead or dying, we will focus on evaluating the impacts of EAB biocontrol agents on host population dynamics and on ash growth, regeneration, and conservation in the aftermath of EAB invasion. At research sites in the Northeastern U.S., where the biocontrol agents were released in conjunction with systemic insecticide treatments to control EAB in the large overstory ash trees, we will collect similar data, but include data on ash tree survival, growth, and reproduction before and/or during the outbreak phase of EAB invasion. The purpose of this work is to focus on reducing the frequency and amplitude of EAB outbreaks through suppressing EAB populations in natural forests at regional levels. In forests already damaged by the EAB invasion, widespread mortality of the overstory ash trees resulted in loss of the forest canopy, such as occurred in Lower Michigan. In this region, where EAB biocontrol was first implemented in 2007, we propose to monitor and evaluate the establishment, abundance, and long-term impacts of the EAB biocontrol agents introduced from China on ash tree regeneration and growth from seedlings, saplings, and basal sprouts in the aftermath of EAB invasion (Objective 1). In more recently infested regions such as the Northeastern U.S. (CT, MA, NY), where systemic insecticide treatments were applied to protect the large overstory trees from EAB-induced mortality, we propose to integrate selective systemic treatments with the introduction of EAB biocontrol agents before and/or during the outbreak phase of EAB invasion (Objective 2). In both regions, we will also release and monitor establishment, spread, and impacts of the recently approved parasitoid Spathius galinae, which is expected to survive in northern climates and protect large-diameter ash trees.
The proposed work will be carried out in two distinctive regions: the infested areas of Lower Michigan (the original epicenter of invasion in the 1990s) and the Northeast region (later invasion in CT/MA/NY in about 2010-2012). In both regions, data on ash inventory and demographics, EAB infestation rates, EAB mortality factors including parasitism by the introduced biocontrol agents, disease, host resistance, and abiotic factors will be collected and form the basis for developing an integrated EAB management program. The focus of EAB management strategies in Michigan will be on establishing and/or maintaining the low EAB density equilibrium so that existing ash can survive and grow to overstory trees, and ash sapling are regenerated in the aftermath of EAB invasion. Tactics to achieve this goal will include (1) additional releases of the newly introduced EAB parasitoid (S. galinae) across the region as well as previously introduced parasitoids (T. planipennisi and O. agrili) in non-established areas at relatively high temporal and spatial frequencies and (2) evaluating forested areas in Northeastern States (Connecticut/Massachusetts/New York), where limited trunk injections of emamectin benzoate were applied in 2016 and EAB densities are still relatively low. Combining systemic insecticide injections and parasitoid releases is expected to yield an additive or synergistic effect. Minimally, an additive effect will occur because the agents target different life stages of EAB.