Urban ash management and emerald ash borer (Coleoptera: Buprestidae): facts, myths, and an operational synthesis

Survival of North American species of ash (Oleaceae: Fraxinus spp. L.) is threatened by emerald ash borer (EAB), Agrilus planipennis (Fairmaire), a phloem-feeding beetle that destroys the vascular system of its host. In forested sites where ash is a dominant overstory species, mortality caused by EAB can substantially alter conditions, with potentially cascading effects on ecosystems. In urban forests, ash trees were often abundant and provided an array of ecosystem services because of their rapid growth, capacity to withstand stressful urban conditions and prior to EAB, low pest load. Annualized costs of managing EAB on urban ash trees over the next 30 yr in the United States has been estimated to approach $1.8 billion. Numerous cost-benefit analyses have demonstrated that it is more cost effective to retain mature ash trees with systemic insecticides than to replace these trees in urban areas. Effective protection of urban ash trees depends on deployment of systemic insecticides before EAB injury disrupts the vascular system that transports insecticide to the canopy. Given the ongoing spread of EAB, timely management is critical for protecting urban ash canopies. Over the last 2 decades, we have encountered persistent myths that have hindered the adoption of protective measures to preserve urban ash in communities recently infested by EAB. Here we review these myths and counter them with research-based evidence that supports and justifies an ash management program. Finally, we use the 5 basic tenets of IPM to outline an approach for managing EAB in urban forests.