Project Number: 8010-22000-031-16-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2020
End Date: Sep 30, 2021
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. Costs of treating or removing even half of the ash trees growing on municipal property in urban forests are projected to exceed $1 billion a year. Besides economic losses, EAB causes widespread ash mortality that degrades essential ecosystem services. The primary purpose of this agreement is to develop and test biocontrol approaches for protection of ash-dominated urban and forest ecosystems against the invasive emerald ash borer (Agrilus planipennis). The project has two specific objectives: (1) conserve ash as a component of natural forests in the aftermath of EAB invasion through releases and successful establishment of introduced biocontrol agents (Michigan), and (2) reduce the risk of new EAB outbreaks through total population reduction by integrating selective treatments of large overstory ash trees with systemic insecticides combined with EAB biocontrol as early as possible after EAB is detected.
Research activities for Objective 1 will be conducted in Lower Michigan, where ash-dominated forests have already been severely damaged by the EAB invasion and widespread mortality of the mature overstory ash trees resulted in loss of the forest canopy. In this region, EAB biocontrol was first implemented with releases of the egg and larval parasitoids Oobius agrili and Tetrastichus planipennisi from 2007 to 2011, and later augmented with releases of Spathius galinae from 2015 to 2017. In the aftermath of the EAB invasion in Lower Michigan, we will monitor and evaluate the establishment, abundance, and long-term impacts of these introduced EAB biocontrol agents on ash tree regeneration and growth from seedling, saplings, basal sprouts, and surviving ash trees at our previous and additional biocontrol study sites where S. galinae was recently released. Work for Objective 2 will be conducted in more recently infested regions of the Northeastern U.S. (Connecticut, Massachusetts, and New York), where EAB biocontrol was first implemented with releases of O. agrili, T. planipennisi, and S. galinae from 2015 to 2019, and systemic insecticide treatments were also applied to protect the large overstorytrees from EAB-induced mortality. In this region, we will integrate selective systemic insecticide treatments with the introduction of EAB biocontrol agents before and/or during the outbreak phase of EAB invasion. Following parasitoid releases and insecticide treatments in this region, we will continue to monitor and evaluate the establishment, spread, and impacts of the released parasitoids on EAB densities and ash health (as described above) at our previous study sites.