Cross-protection is a phenomenon in which a plant prior infected with a mild viral strain can be protected from subsequent infection by severe strains of the same or closely related viruses. Since its discovery in the 1920s, this phenomenon has become an important strategy for controlling viral diseases in plants. Telosma mosaic virus (TelMV, a species of Potyvirus) is an emerging pathogen that threatens passion fruit production in subtropical and tropical regions. Here, we present a protocol for screening mild TelMV strains and their application in protecting passion fruit from severe TelMV infections. This provides an efficient TelMV management strategy and a framework for cross-protection implementation against other plant viruses.