Recent investigation on molecular characterization of the "Candidatus Phytoplasma prunorum" (16 SrX-B subgroup), causal agent of the ESFY syndrome, on the non ribosomal tuf gene allowed to individuate 2 groups of isolates, named a and b, with a distinct geographical distribution in Italian stone fruit growing areas. Considering the role of Cacopsylla pruni in the epidemiological cycle of the disease, the presence of the 2 groups of isolates has been investigated also in infected individuals of the psyllid, sampled in different Italian areas. Both types has been identified in C. pruni specimens captured on apricot, plum and wild Prunus species.