Examining Resistance of Asian, European, and North American Ash and Elm Species to the Emerald Ash Borer (Agrilus planipennis) (Coleoptera: Buprestidae)

Abstract

The emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Bupresti-dae), native to East Asia and discovered in Michigan in 2002, has been a devastating pest of North American ash trees (Fraxinus spp.). Along with native ecosystems in Eastern North America, a large percentage of urban canopies in many North American cities consist of ash trees, and many of these areas have lost or risk losing these valuable trees. As part of a multi-faceted management strategy, it is important to develop and plant cultivars of ash with resistance to this damaging insect. Given that EAB is not considered a pest in its native range of East Asia, we suspect that Asian ash taxa may have some resistance based on their co-evolutionary relationship to the beetle. To test for possible resistance in a range of Fraxinus and Ulmus taxa, a series of no-choice adult EAB maturation laboratory feeding bioassays and larval phloem utilization and suitability bolt studies were performed with 19 different Asian, European, and North American Fraxinus and 16 different Ulmus taxa. Adult leaf-feeding susceptibility was variable among the Asian ash taxa. Fraxinus chinensis, F. chinensis subsp. rhynchophylla, and F. mandshurica were found to be the least susceptible. Larval phloem utilization studies revealed that F. chinensis and F. chinensis subsp. rhynchophylla were less suitable compared with F. mandshurica, F. angustifolia subsp. angustifolia, and the highly suitable F. pennsylvanica. None of the Ulmus taxa tested were susceptible to adult feeding or suitable for larval development. This study has revealed potential Fraxinus species to be used in future breeding programs and plantings.