Since the beginning of the twentieth century symptoms of apricot tree decline were observed in France and Italy: Morvan in 1977 named the disease associated with leptonecrosis (Goidanich, 1934) or with new sprouting in winter "apricot chlorotic leaf rolling" (ACLR). Only since the late 1970ies these symptoms were associated with phytoplasma infections, since electron or fluorescence microscopy (by DAPI-staining) allowed to detect phytoplasmas as single cells in sieve tubes (Fig. 1) and transmission experiments to other stone fruit and indicator plants were successfully carried out (Morvan, 1977; Goidanich et al., 1980; Giunchedi et al., 1982, Pastore et al., 1995). European stone fruit yellows (acronym: ESFY) has been proposed as the common name for phytoplasma-related diseases in European stone fruits (Kison et al., 1997). Among others it includes the French ECA or ACLR, which is a quarantine organism of EPPO (OEPP/EPPO, 1986), included in the EPPO certification scheme for virus tested fruit trees (OEPP/EPPO, 1991/1992).The presence of ESFY disease has been reported in France, Spain, Italy, Greece, and in Hungary, Romania, Switzerland, Germany, former Yugoslavia, the UK and Austria (Nemeth, 1986; Morvan, 1977, Davies and Adams 2000, Laimer da Câmara Machado et al. 2001a) causing decline and death to apricot, Japanese plum, more rarely to peach (Llacer and Medina, 1988) and to almond, flowering cherry and European plum (Seemüller et al. 1998) http://www.boku.ac.at/iam/pbiotech/phytopath/v_esfy.html). An increasing presence of phytoplasma associated diseases such as leptonecrosis on Japanese plum (Prunus salicina) and chlorotic leaf roll on apricot (Prunus armeniaca) has been observed in commercial orchards in several European regions in the last twenty-five years (Giunchedi et al., 1978; Desvignes and Cornaggia, 1982; Dosba et al., 1991; Bertaccini et al., 1993; Laimer et al., 2001; Torres et al., 2004). Prunus rootstocks are also affected by this disease (Dosba et al. 1991, Jarausch et al. 1998). ESFY phytoplasmas have also been detected in wild Prunus species, e.g. Prunus spinosa and P. cerasifera (Carraro et al. 2002) and cherry (Prunus avium) (Paltrinieri et al., 2001). In recent years ESFY phytoplasma has been detected in other wild plants such as Rosa canina, Celtis australis and Fraxinus excelsior (Jarausch et al., 2001) as well as in grapevine in Hungary (Varga et al., 2000) and in Serbia (Duduk et al., 2004).