Phytophthora root rot (PRR) of avocado, caused by Phytophthora cinnamomi, poses a significant threat to the avocado industry worldwide. While multifaceted approaches have been employed to manage PRR, chemical-based control remains the primary strategy for suppressing P. cinnamomi in the field. However, considering the long-term detrimental effects of this strategy, alternative methods to reduce reliance on chemical fungicides are imperative. RNA interference (RNAi), particularly through the application of double-stranded RNA (dsRNA) sprays, presents a promising alternative. Double-stranded RNA targeting essential P. cinnamomi genes have demonstrated efficacy in inhibiting the pathogen in in vitro, detached leaf, and lupin assays. This study aims to evaluate the effectiveness of dsRNA in suppressing P. cinnamomi infection in avocado plants. We have established a hydroponic system that allows direct inoculation of roots and observation of lesions across multiple timepoints without needing to dig plants out of soil. We will next test protective and curative effects of the dsRNA. This research serves as a proof-of-concept, enabling convenient observation of disease progression/suppression in avocado roots without causing physical damage. The findings from this study are expected to bridge the gap between laboratory-scale bioassay results and broader-scale applications at the nursery and field levels.