Succcessful RNA-based applications in agriculture require a deep understanding of how plants take u and transport exogenous RNAs. Our research identifies the factors that enable or limit RNA uptake in crop plants, providing the foundation for tailored RNA sprays for different plant species and pathosystems. We investigate why some plants respond to RNA sprays while other do not. For example, using advanced imaging techniques, we analyze leaf structures, such as stomata, their density, distribution, and architecture, and compare them across different crop species. Interestingly, barley is one of the few crop plants capable of efficiently taking up naked, unformulated RNAs, and it also shows systemic transport of RNAs after RNAi sprays (further information). This raises important questions: what makes barley particularly receptive to RNA uptake and systemic movement, and how can this knowledge be used to design more effective, systemically active RNA-based biopesticides? We also study pathogen-specific RNA uptake mechanisms, focusing on fungi (further information). Our results demonstrate that the lifestyle of the pathogen influences uptake and inter-species RNA transport. These mechanistic insights help us design RNA sprays optimized for specific pathogens, increasing their effectiveness and sustainability.