Following the EFSA opinion (2015) on the risks to plant health posed by Xylella fastidiosa in the EU territory and later on, its report in 2018 in a nursery of West Flanders, the threat of this pathogen for the Belgian flora needs to be assessed. Based on a first screening of the Xylella host plants, four model tree species were selected to be subject to susceptibility investigations: Prunus domestica cv. Opal, Quercus petraea, Salix alba and Populus tremula. The susceptibility to the bacterium of these plant species is investigated in different ways. Firstly, it is assessed through “Sentinel plantationâ€, which consists in the establishment of these plant species in areas contaminated by the bacteria to evaluate their susceptibility under natural conditions. The second complementary way consists in mechanically inoculating different strains of X. fastidiosa into the plant xylem under biosafety quarantine controlled glasshouses. The presence and the progression of the bacterium into the plants is monitored by PCR as well as by confocal microscopy with the use of a GFP-tagged strain kindly provided by S. Lindow (Newman et al., 2003). On the other hand, three potential insect vectors for Belgium were selected, the Hemiptera Cicadella viridis, Philaenus spumarius, and Aphrophora salicina. Their potential for bacterial acquisition through artificial diets and artificially infected plants is also studied using a set of X. fastidiosa strains. Furthermore, the bulk sampling of these potential vectors through Belgium is undertaken, with the aim of using an "insect spy" strategy for an early detection of the bacteria in the country.