(1st Place) Investigating RNA interference (RNAi) in the exotic redbay ambrosia beetle (Xyleborus glabratus), vector of laurel wilt disease

Management challenges are exacerbated when invaders involve endophagous insect-pathogen complexes. Such is the case with laurel wilt disease (LWD), a lethal vascular condition caused by Harringtonia lauricola, the fungal symbiont of the non-native redbay ambrosia beetle (RAB), Xyleborus glabratus Eichoff (Coleoptera: Curculionidae). Initially discovered causing mortality of redbay, LWD is spreading northward and westward on additional lauraceous hosts, including sassafras and spicebush. Managers have not been successful in preventing its spread, warranting investigation into additional techniques. RNA interference (RNAi) is a natural cellular mechanism that, when manipulated, can result in gene silencing and mortality. Highly effective against coleopterans, RNAi is emerging as an insect suppression tool in agricultural settings and is being investigated for its utility in tree pests. In this study, I investigated mortality and changes in gene expression in RAB after oral ingestion of double-stranded RNAs (dsRNAs) targeting genes essential for survival (hsp, shi, and iap). After exposure to dsRNAs (N=7), mortality was recorded daily. To investigate changes in gene expression a separate group of beetles (N=7) were exposed to dsRNAs. After 72h, total RNA was extracted followed by cDNA synthesis, and quantitative PCR was performed. Significant changes in gene expression occurred in all three target genes (p<0.05) and significant mortality (F_4,124=28.6, p<0.001) was observed in beetles exposed to all three target genes. This research is important because invasive species are devastating our forests, and developing innovative management approaches is essential to forest sustainability.