Gene silencing as a potential novel tool in Ips calligraphus suppression

Global climate change and human disturbance have caused insects that were previously considered secondary pests to expand beyond this classification, becoming primary agents of damage in forest ecosystems. Ips calligraphus (Germar) (Coleoptera: Curculionidae) is a native North American bark beetle that, due to increasingly severe droughts and storms, and expansion into introduced ranges, has become a pest capable of substantial ecological and economic damage. Traditionally, silvicultural techniques that promote healthy forests kept I. calligraphus at innocuous levels, but due to environmental stressors impacting tree health this is no longer sufficient, and innovative new management techniques are required. RNA interference (RNAi) is an endogenous mechanism for viral defense and gene regulation present in most eukaryotes. Advances in molecular technologies have provided the ability to trigger this pathway with high specificity and efficacy, and it is now being utilized to induce mortality and suppress insect pest populations. I tested two candidate dsRNAs for efficacy in inducing mortality in I. calligraphus. One of the candidate dsRNAs caused significant beetle mortality (F_2,78=3.687, p=0.02), and gene expression analysis is underway to corroborate these results. This is the first study to trigger the RNAi pathway in an Ips species using exogenously administered dsRNA, a critical step in evaluating feasibility of this technology for pest suppression in a genus responsible for forest damage across the globe. My next steps include annotating chemosensory transcripts in the I. calligraphus head transcriptome for novel target genes that could potentially interrupt aggregation during outbreaks.