The objective of the present research was to identify the causal agent of soft rot disease in the stems of pitahaya plants (Hylocereus undatus (Haw.) Britton & Rose), also known as dragon fruit, in two production areas of Peru. Typical symptoms observed include rotting and soft consistency in stems, as well as yellowish colourations, which usually begin at the tips and outer edges of the stems and extend until they are completely decomposed. Symptomatic samples of pitahaya stalks were collected from two commercial fields, the first from the district of Independencia, Pisco, Ica, and the second from the district of Naranjos, Rioja, San Martin. The collected samples were transferred to the phytopathology laboratory of the National Agrarian University – La Molina where 19 bacterial colonies isolated from symptomatic stem tissue were processed. Nine bacterial colonies were selected fro...