Gene silencing: A next gen approach to bark beetle management

Dendroctonus bark beetles pose a substantial threat to conifer forests and in North America the southern pine beetle, Dendroctonus frontalis (SPB), and mountain pine beetle (MPB), D. ponderosae, are responsible for catastrophic economic and ecological losses. Increasingly erratic abiotic conditions and a history of inconsistent silvicultural management practices have allowed for devastating and persistent outbreaks within their native ranges. Furthermore, the breakdown of geoclimatic barriers has led to geographic range expansion of both SPB and MPB into naïve forests well outside of their endemic ranges. Innovative management approaches are needed to mitigate the consequences of these invasions. Few forest insects have benefitted from genomic advances like bark beetles have, and the manipulation of the RNA interference (RNAi) pathway to induce mortality has proven effective in SPB and MPB. Ingestion of carefully designed exogenous dsRNAs can cause rapid mortality in both species. Demonstration of RNAi’s specificity through evaluations of model non-target organisms and pine associates has been demonstrated, as has the translocation and persistence of exogenous dsRNAs through tree tissue, paving the way for the use of RNAi for tree protection. Forest level protection, however, faces additional hurdles, including the role of genetic variation in primer design, and the creation of dsRNA vectors for landscape level delivery. Although additional work is needed, gene silencing using RNAi provides hope for managing these persistent and recalcitrant forest insects.