Insecticide resistance management scenarios differ for RNA-based sprays and traits

RNA-based bioinsecticides that comprise a dsRNA active ingredient and function by RNA interference (RNAi) are being commercialised as insecticidal traits in transgenic crops and as sprayable biopesticides. These RNAi insecticidal technologies are valuable alternatives to conventional chemical insecticides due to their efficacy, high degree of specificity and favourable human and environmental safety profiles. As with all pesticides, appropriate insect resistance management (IRM) programmes are required to mitigate the selection for resistance in target insect populations and extend product durability in the field. IRM programmes for RNAi products follow the same guidelines that currently exist for insecticidal traits or conventional insecticidal sprays. These guidelines reflect the distinct exposure scenarios for traits versus sprays, that is, continuous exposure when dsRNA is expressed in the crop compared to intermittent exposure when sprayed on foliage. As such, IRM plans for dsRNA traits depend on pyramiding (stacking) non-cross-resistant traits along with a refuge of non-transgenic plants. On the other hand, IRM plans for dsRNA sprays rely on the timing of the application so that only a single generation of the pest is exposed, followed by the use of an insecticide from a different IRAC mode of action group.