Abstract: The specification describes an RNA vector. The vector may be derived from a plant virus or an umbravirus-like associated RNA such as Citrus yellow vein-associated virus (CYVaV). The vector contains a heterologous segment comprising a small interfering RNA (siRNA) that targets Xylella fastidiosa (Xf). In some examples, the heterologous segment may target the Xf PilG and/or TolC gene. The heterologous segment may be in the form of a hairpin structure inserted into a CYVaV-like molecule. A method of treating a plant against a disease caused by Xf includes introducing the vector into a plant before or after the plant is infected by Xf. The specification also describes a plant, or a portion of a plant, containing the vector and/or the heterologous segment. The plant may be a grapevine.