Spraying plants with RNA molecules to exploit RNA-regulated cellular processes is a highly innovative approach in plant protection. Our research focuses on understanding how exogenous RNAs are processed and degraded in plants, with a particular emphasis on ribonuclease that determine RNA stability and the efficiency of RNA interference (RNAi). We investigate key enzymes of the RNAi pathway such as Dicer-like-proteins, argonauts proteins, and RNA-dependent RNA polymerases as well as other ribonucleases that degrade or clear exogenous RNAs. Using molecular, biochemical, and imaging approaches, we study RNA stability in vivo. This mechanistic insights allows us to design RNA sprays that are more stable, and effective.