Nasonia vitripennis as a parasitoid wasp model for pest-specific dsRNA safety assessment

RNA interference (RNAi) is a promising mode of action for pest control. It can play an important role in inte-grated pest management (IPM), where it could be used alongside beneficial insects (such as predators and parasitoids) for pest control. However, despite the possibility of designing the active molecule double-stranded RNA (dsRNA) to be pest-specific, potential adverse effects to beneficial insects cannot be ruled out a priori, thus prompting the need for safety assessment studies. In this study, the jewel wasp Nasonia vitripennis is presented as a parasitoid wasp model for the evalua-tion of possible unintended effects that could arise from oral exposure of a parasitoid to exogenously delivered pest-specific dsRNA. First, the susceptibility of N. vitripennis to ingested dsRNA was tested through a worst-case exposure scenario, where they were exposed to a high concentration (1 mu g/mu l) of N. vitripennis-specific dsRNA (dsNv_alphaCOP). Ingestion of dsNv_alphaCOP resulted in 97% wasps mortality by day 16 post treatment when compared to the control. Once the risk of exposure was established, N. vitripennis were orally exposed to a pollen beetle pest (Brassicogethes aeneus)-specific dsRNA (dsBa_alphaCOP), after which both lethal and potential sub-lethal effects (development time, fecundity and sex ratio) were evaluated. In this worst-case scenario exposure setup, dsBa_alphaCOP did not cause any adverse effects to N. vitripennis. This study confirms that RNAi-based pest control, under laboratory conditions, can be compatible with bio- logical control based on parasitoid wasps. Furthermore, this study can contribute to guiding the development and safety assessment of future RNAi-based pest control products.