Project Number: 8010-22000-028-21-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 1, 2016
End Date: Sep 30, 2019
The proposed research will develop and evaluate an integrated EAB management strategy for protecting heritage ash trees in urban forests such as the USNA. This strategy will include use of tactics such as selective treatments of infested ash trees with a highly effective, systemic insecticide (emamectin benzoate, TREE-age®), girdled trap trees and classical biocontrol with parasitic wasps introduced from EAB’s native range. Specifically, we will: (1) determine whether application of a systemic insecticide and/or girdled trees alone, or in combination with introduced parasitic wasps, can suppress EAB populations and protect high value ash trees in the early phase of the invasion wave, and (2) assess interactions of these management tactics on EAB densities, and the associated persistence and condition of ash.
The study will be conducted in the USNA (446 acres) and surrounding areas (Anacostia and/or Kenilworth Parks, >500 acres) with abundant ash stands. We will work with Drs. Richard Olsen and Scott Aker (USNA) and Jil Swearingen and Mikaila Milton (National Park Service) to assess ash abundance, size and condition (dead, declining, healthy) prior to the application of management treatments (insecticide, parasitoid releases). While heritage trees (DBH > 20 cm) have been treated with trunk injection of emamectin benzoate) since 2015 at USNA and no control measures have been taken in the adjacent Anacostia and/or Kenilworth Parks). Considering this pre-study treatment conditions, we propose to release EAB biocontrol agents in this general area and use USNA as an area-wide integration of insecticides and EAB biocontrol agents and the adjacent area (Anacostia/or Kenilworth Parks) as biocontrol only treatment. Parasitoids will be released at periods corresponding to when EAB have developed to the susceptible life stages. A total of six study plots (three at USNA and three at Anacostia/or Kenilworth Parks) will be established for assessment of the treatment efficacy. Parameters to evaluate treatment efficacy include: • Establishment of introduced biocontrol agents (larval and egg parasitoids) and continuous sampling to recover the parasitoids at least for two years post-release using egg and larval sentinel logs or potted sentinel ash trees. • EAB density: Adult EAB presence and relative abundance will be monitored using two-tiered sticky panels (green or purple) baited with cis-3-hexanol (ash leaf volatile) in or adjacent to study plots. • EAB egg and larval densities: A fixed time of visual search of EAB eggs by examining loose bark of ash tree trunks (1.5 m above the ground) will be conducted twice a week during the EAB oviposition period (May to July). Larval densities will also be monitored via placement of EAB-infested sentinel ash trees during the growing season in each plot. Sentinel ash trees will be debarked each year (late fall or early the following spring) to document document EAB mortality (including parasitism and predation). Life table analysis will be used to assess effects of stage-specific mortality factors, including biocontrol agents, on EAB population growth (on sentinel trees) in all plots. • Ash survival and condition will be evaluated at the onset of the project, and again following treatments, ideally in mid- to late summer, using fixed-radius plots and linear transects. Variables to be recorded include tree DBH, canopy transparency and dieback, and evidence of current and past EAB infestation (e.g., epicormic sprouts, woodpecker attacks, EAB exit holes).