Factors affecting distribution of emerald ash borer parasitoids in an urban environment

Abstract

Invasive woodboring insects such as emerald ash borer (EAB), Agrilus planipennis, cause significant economic and environmental harm to both traditional and urban forests. Hymenopteran biological control agents were introduced to North America for protection of non-insecticide treated ash trees. Urbanization is known to impact arthropod abundance, richness, and services, and yet few studies specifically examine biocontrol agent distribution or services within urban environments. While EAB biocontrol agents are successfully establishing in traditional forests, it is not known whether urban forests are sufficiently hospitable for their establishment and persistence. In this study, we investigate how urban land cover impacted both the establishment and distribution of introduced biocontrol agents and the presence of EAB-associated endemic native parasitoids. Over the three year study period we detected a persistent negative impact of urbanization on presence of two parasitoids, the introduced Spathius galinae and native Atanycolus spp, while another native, Phasgonophora sulcata, was only negatively impacted by urbanization in the first sampling year. Presence of the introduced Tetrastichus planipennisi was negatively correlated with tree size, but not urbanization. Presence of all parasitoids was greater on trees with declining canopy health. This study indicates that while some parasitoids appeared to be negatively affected by urbanization, biological control agents of EAB successfully established and are generally widely distributed in Syracuse, NY.