D3441: Little presents underneath the Christmas tree: a potential biocontrol fungus for elongate hemlock scale

Elongate hemlock scale (Fiorina externa; EHS) was first identified in New York in 1908 and has since spread throughout the eastern United States. This invasive insect is a pest of many important tree hosts across this range, including eastern hemlock, spruce, pine and firs. EHS has been especially problematic in Christmas tree farms, where infestations cause cosmetic damage and limit exportability of trees. This latter issue has made this scale the most concerning insect pest for Christmas tree growers. Due to the continuous emergence of EHS crawlers throughout the growing season, conventional management options do not provide adequate control. Here we report on our work isolating and identifying a fungal pathogen of EHS, Conoideocrella luteorostrata, which was observed to cause natural epizootics in Fraser fir farms across multiple sites in Ashe County North Carolina. We conducted laboratory bioassays to confirm pathogenicity of this fungus against EHS. We also generated multi-locus sequence data for several strains from North Carolina to resolve their phylogenetic placement among previously characterized strains from EHS and other insects around the globe. This pathogen has since been implicated in epizootics in multiple states, and we have sequenced the genome of one of our North Carolina isolates (ARSEF 14590). This genome will provide insight into the evolution of this fungus and will also serve as a benchmark for further investigation of this fungus as a biopesticide. Our work sets the stage for development of this biocontrol fungus as a management option for EHS in the United States.