Reference Gene Identification and RNAi-Induced Gene Silencing in the Redbay Ambrosia Beetle (Xyleborus glabratus), Vector of Laurel Wilt Disease

Management of invasive species is especially difficult when the organisms involved are endophagous and their interactions complex. 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). LWD has caused extensive mortality of coastal redbay, Persea borbonia, and is expanding to utilize additional lauraceous hosts, including sassafras, Sassafras albidum. Current management has not been successful in preventing its spread, warranting investigation into additional techniques. RNA interference (RNAi) is a highly specific gene-silencing mechanism used for integrated pest management of crop pests and currently being investigated for use in forests. When targeting essential genes, RNAi can cause rapid insect mortality. Here we focus on RAB, identifying for the first time species-specific reference genes for quantitative real-time PCR (qPCR) and assessing mortality and gene expression after oral ingestion of double-stranded RNAs (dsRNAs) targeting essential genes (hsp, shi, and iap). Our study validates reference genes for expression analyses and shows significant mortality and changes in gene expression for all three target genes. Our research aims to contribute to the development of innovative management strategies for this invasive pest complex.