Phenology and Voltinism of Emerald Ash Borer (Coleoptera: Buprestidae) in Central North Carolina.

The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), has killed millions of ash (Fraxinus spp.) trees across North America. Classical biological control using introductions of parasitoid wasps may provide a sustainable approach to managing this invasive insect. However, the establishment of parasitoids in the southern United States has been difficult. The phenology of emerald ash borer was studied in central North Carolina to inform biological control efforts that better align with the seasonal availability of susceptible emerald ash borer life stages in the warm climate of this region. Biweekly emerald ash borer life stage assessments were conducted in stands of infested green ash (Fraxinus pennsylvanica Marshall, Lamiales: Oleaceae) over 26 consecutive months (June 2019 through August 2021). Adult trapping was also conducted in these stands in the spring and summer of 2019, 2020, and 2021. Based on these collections, emerald ash borer exhibits a univoltine (1-yr) life cycle. Parasitoid-susceptible larvae (third and fourth instars in galleries) are present from late June through October (~1,100-3,000 degree days base 10ºC) and are mostly absent during the remainder of the year. Parasitoid release timings and the life history of selected parasitoid species should be aligned with this window of host availability to be effective. This characterization of emerald ash borer phenology and voltinism will help improve the timing and effectiveness of management efforts as this forest pest continues to spread in southern North America.