Assessing the Risks of Topically Applied dsRNA-Based Products to Non-target Arthropods

Abstract

RNA interference (RNAi) is a powerful technology that offers new opportunities for pest control through silencing of genes that are essential for the survival of arthropod pests. The approach relies on sequence-specificity of applied double-stranded (ds) RNA that can be designed to have a very narrow spectrum of both the target gene product (RNA) as well as the target organism, and thus allowing highly targeted pest control. Successful RNAi has been reported from a number of arthropod species belonging to various orders. Pest control may be achieved by applying dsRNA as foliar sprays. One of the main concerns related to the use of dsRNA is adverse environmental effects particularly on valued non-target species. Arthropods form an important part of the biodiversity in agricultural landscapes and contribute important ecosystem services. Consequently, environmental risk assessment (ERA) for potential impacts that plant protection products may have on valued non-target arthropods is legally required prior to their placement on the market. We describe how problem formulation can be used to set the context and to develop plausible pathways on how the application of dsRNA-based products could harm valued non-target arthropod species, such as those contributing to biological pest control. The current knowledge regarding the exposure to and the hazard posed by dsRNA in spray products for non-target arthropods is reviewed and suggestions are provided on how to select the most suitable test species and to conduct laboratorybased toxicity studies that provide robust, reliable and interpretable results to support the ERA.

RNAi-Mediated Suppression of Laccase2 Impairs Cuticle Tanning and Molting in the Cotton Boll Weevil (Anthonomus grandis)

“…Further studies should be performed to explore the feasibility of RNAi pest control approaches, such as transgenic cotton plants expressing ds AgraLac2 into the nuclear or the plastid genome as well as engineered fungi, bacteria, and virus expressing ds AgraLac2 or ds AgraLac2 complexed with nanoparticles as a dsRNA delivery method for foliar application on cotton leaves. Importantly, for field applications, the impact of RNAi-based pest control technologies to non-target organisms and environment needs to be cautiously assessed before they can be safely used on crops ( Arpaia et al, 2020 ; Bachman et al, 2020 ; Mezzetti et al, 2020 ; Romeis and Widmer, 2020 ). Consequently, future approaches relying on AgraLac2 dsRNA to control A. grandis will require a comprehensive risk assessment to ensure their biosafety.…”

Tyramine receptor drives olfactory response to (E)-2-decenal in the stink bugHalyomorpha halys

“…Although the dsRNA topically delivered results less efficient as gene silencer in H. halys, the administered amount of dsRNA is lower compared to the microinjection and the feeding applications. Reducing the dsRNA amount could be an effective strategy to prevent off target effects (Romeis & Widmer, 2020).…”

Environmental Fate and Dissipation of Applied dsRNA in Soil, Aquatic Systems, and Plants

“…As discussed in Romeis and Widmer (2019), problem formulation is a core component of the ERA framework offering a logical approach and roadmap to characterize risk. Key to this approach is defining assessment endpoints, developing a conceptual model of predicted environmental relationships, and drafting an analysis plan to collect relevant data in regard to exposure and effects to perform a risk characterization (Nickson, 2008).…”