Impacts of urban land cover on the distribution of emerald ash borer associated parasitoids

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Timothy D. Morris and Melissa K. Fierke, Environmental & Forest Biology, SUNY College of Environmental Science and Forestry, Syracuse, NY, Juli R. Gould, USDA APHIS

Background/Question/Methods
Urban land cover impacts relationships between parasitoid assemblages and host organisms. Trophic interactions may differ depending on both host and parasitoid ecology. Biocontrol agents Spathius galinae, and Tetrastichus planipennisi were released in Syracuse NY in 2015 as part of an ongoing integrated pest management study investigating the role of introduced parasitoids to suppress emerald ash borer (EAB) populations in urban forests. High value street trees were protected during peak EAB infestation with systemic insecticide injections. Here, we assess the role of parasitoids in protecting ash trees as use of systemic insecticides is ended, specifically focusing on determining if benefits of biocontrol are inequitably distributed within a city, i.e. ecosystem services associated with parasitoids are greater in areas with more green spaces. Yellow pan traps (YPTs) and sentinel logs containing EAB larvae were used to determine parasitoid distributions within the city and logistic models were utilized to assess whether parasitoid distributions were impacted by local land cover features quantified via a GIS raster dataset.
Results/Conclusions
Yellow pan trap results over the last 5 years indicate establishment of both biocontrol parasitoids. Deployment of sentinel logs infested with EAB larvae show frequent parasitism by T. planipennisi and less frequent parasitism by S. galinae. An analysis of land cover in Syracuse suggests the degree of urbanization (impermeable surface area) surrounding YPTs and sentinel logs significantly impacted presence of S. galinae (p = 0.0255), but not T. planipennisi or native EAB-associated parasitoids. These results suggests urban biocontrol programs should assess local land cover variation when considering management options. IPM practitioners can then apply additional control measures where biocontrol services may be diminished, thus ensuring more equitable management of pest species.