First insights towards RNAi-based management of the pollen beetle Brassicogethes viridescens, with risk assessment against model non-target pollinator and biocontrol insects

The pollen beetle Brassicogethes viridescens has become an invasive pest to rapeseed crops in North America, especially Canada, the world's most prolific grower of rapeseed. The use of conventional insecticides to control Brassicogethes spp. can lead to substantial insecticide resistance development in target pest populations and detrimental effects on non-target organisms in and around rapeseed crops. Therefore, economically and ecologically sustainable alternatives to conventional insecticides must be explored. Given the continued increases in production efficacy- and the nucleotide sequence-specific mode of action of dsRNA pesticide products, RNA pesticides represent a potential tool for use within the management of B. viridescens. We examined the insecticidal efficacy of dsRNA against B. viridescens, using transcripts of its intragenus relative Brassicogethes aeneus as a template for dsRNA design. In B. viridescens, we observed similar sensitivities to dsRNA compared to B. aeneus. Furthermore, survival assays using three model non-target species suggest highly selective insecticidal activity of the dsRNAs. Finally, we generated the first transcriptome draft for B. viridescens, which provides valuable information for future management needs against this pest species. Given these first insights towards sustainable RNAi-based management of B. viridescens, further work (different exposure methods, semi-field larval studies) is needed to develop RNAi-based approaches to managing B. viridescens in both European and North American rapeseed systems.