The Real Christmas Tree Board

The entomopathogenic fungus Conoideocrella luteorostrata has recently been implicated in natural disease outbreaks among exotic elongate hemlock scale (EHS) insects in Christmas tree farms in the eastern U.S. Since 1913, C. luteorostrata has been reported from various plant feeding insects in the southeastern U.S. including whiteflies, soft scales and armored scale insects, but comprehensive morphological and molecular studies of U.S. populations are lacking. The recovery of multiple strains of C. luteorostrata from mycosed EHS in North Carolina provided an opportunity to both confirm pathogenicity and conduct morphological and molecular studies of this fungus and compare it with closely related, well-studied insect pathogens within the same fungal family, the Clavicipitaceae. Pathogenicity assays confirmed C. luteorostrata causes mortality of EHS crawlers, an essential first step in developing this fungus as a biocontrol. Morphological studies were consistent with historic observations, yet also revealed a previously unreported spore stage. Comprehensive molecular studies of our strains and other previously studied strains confirmed the identity and placement of North American strains of C. luteorostrata. Additional sampling across diverse Hemipteran hosts present in historic herbarium / museum specimens is currently underway in order to allow for direct comparisons between modern day strains and historically archived samples. At the same time, expanded pathogenicity testing is needed to clarify which hosts are susceptible and how effective this fungus is on EHS.