To elucidate the relationships between Xylella fastidiosa and its main European insect vector, the spittlebug Philaenus spumarius, experiments were conducted for two consecutive years to assess the kinetics, multiplication and persistence of the bacterium in the spittlebug. To this end, insects were first caged on infected source plants and then isolated, in groups of five, on olive or periwinkle plants at different times post-acquisition (3,7,14, 28, 56, and 72 days). Insects and recipient plants have been individually tested for X. fastidiosa by quantitative PCR. The bacterial load estimated in the infected insects at different times post-acquisition varied from few thousands to tens of thousands cells per insect’s head. The second experiment was carried out to assess the influence of environmental factors (temperature, season) and insect age on simulated epidemics progression on olive plants. Adults of P. spumarius, fed on infected olive branches, were then released in cages containing 16 olive plants and collected after 3-7-14-21 days. Although , most of the diagnostic tests will be carried out only in the upcoming months, preliminary results indicate a higher acquisition efficiency in September as compared to July, and a lower acquisition efficiency from periwinkle compared to olive as source plants, but higher transmission efficiency to periwinkle compared to olive as recipient plants.