The genetic diversity and structure of the Scaphoideus titanus leafhopper populations and of the "flavescence doree" phytoplasma (FDp) they carry, was studied in parallel in southern French vineyards. Seven polymorphic microsatellite loci were used to genotype S. titanus individuals sampled in 24 healthy or FDp-infected vineyards. For each insect, FDp detection and typing was performed by amplifying and sequencing the FDp map gene. A low level of population genetic differentiation (F-ST <= 0.114) was found in S. titanus French populations. It suggests that long-distance gene flows occur due to migration between populations. In addition, it can be hypothesized that passive transport of grapevine planting material carrying eggs could play a role in homogenizing S. titanus population genetic structure. No significant correlation was found between the genetic structure of the French S. titanus populations and the distribution of the different strain types they carry.