The non-GMO delivery of genetic material in plants can provide an easy-to-use, environmentally friendly and flexible tool to improve plant performance and crop protection, which can be integrated into current pathogen management strategies. While spray-induced gene silencing with dsRNA/siRNA has been shown to offer protection against several pathogens, there is a high variability in the RNAi response related to differences in the dsRNA/siRNA uptake into cells and in the stability against e.g. nucleases. Increased RNAi efficacy can be achieved using dsRNA/siRNA carrier systems, such as dendrimers, which can overcome the barriers that the exogenous RNA needs to face. Preliminary results have shown the potential of dendrimers to improve dsRNA/siRNA uptake in plant cells and plant tissues. In this project, the full potential of the carrier technology will be exploited by developing novel and environmentally safe carriers and their use will be explored for the control of the oomycete pathogen Phytophtora infestans in tomato (Solanum lycopersicum). This project spans different levels of complexity: the cell, the organism and the system.