The trigger for RNA interference to silence essential genes in southern pine beetle, Dendroctonus frontalis, demonstrates no lethal effects on pine-associated nontarget insects

Abstract

Environmental conditions associated with climate change are exacerbating pine mortality caused by the southern pine beetle (SPB) (Dendroctonus frontalis), prompting investigations into innovative management strategies. Triggering the RNA interference (RNAi) pathway using species-specific double-stranded RNA (dsRNA) to silence genes and cause mortality is effective in SPB and is an emerging technology for pest management, but specificity and safety must be demonstrated. We evaluated three pine-associates (the scolytine six-spined ips, Ips calligraphus, a foliage feeding pine sawfly, Neodiprion lecontei, and the detritivorous eastern subterranean termite, Reticulitermes flavipes), for transcriptome sequence overlap with the SPB dsRNA and performed bioassays to evaluate lethal and sublethal effects after dsRNA ingestion. Genetic analyses revealed little overlap between dsRNA sequences and target gene orthologs, with only two matches found in I. calligraphus, the most closely related phylogenetically. No lethal or sublethal effects were observed in any of the nontarget organisms evaluated, and changes in gene expression occurred only in I. calligraphus, but with no discernible effects on adult survival. Our findings build on previous nontarget evaluations for SPB-specific dsRNA in model insects and demonstrate that the use of RNAi as a component of an IPM strategy would not directly compromise commonly occurring non-congeneric pine associates.