Xylella fastidiosa is a quarantine bacterium transmitted by some xylem-feeding vectors and it is the causal agent of several diseases on economically important plants. The multiplication of the bacterium in a plant depends upon environmental factors, bacterial strains and the host plant species or cultivars. The EPPO Diagnostic Protocol PM 7/24 (5) gives some recommendations for sampling according to host plants, seasons and locations. In general, sampling should preferably be performed during the period of active growth of the plant to maximize the likelihood of detection (Hopkins, 1981). Plant analyses are required for trade prior to planting. For deciduous plant species, analysis is often required in autumn and winter, during the dormant phase. Recent experiments conducted in the framework of EU projects (POnTE, XF-ACTORS) have shown that in Mediterranean countries, Xylella fastidiosa can be detected in deciduous plants (such as almond and cherry trees) all year round and including the asymptomatic phases or the dormancy, the period with the lowest bacterial concentration. Although detecting Xylella fastidiosa in dormant plants was shown possible in some cases, the performance of the tests is dependent on the plant species and the geographical locations. The current EPPO Diagnostic Protocol PM 7/24 (5) mentions: “Experience in temperate areas shows that in grapevine or deciduous trees, e.g. cherry and almond, that have been infected for some time, the bacterium is not detected into the new season's growth until the middle of summer, when symptoms may also become visible. For example, the most suitable time for searching for symptoms in grapevine is late summer to early autumn when weather conditions are predominantly hot and dry or when grape plants are exposed to drought stress (Galvez et al., 2010).” In this context, this Euphresco project aimed at evaluating the detection methods of Xylella fastidiosa and identification methods of subspecies of Xylella fastidiosa within dormant Mediterranean plants that are commercially important throughout the year and during dormancy on woody stems.