The aim of the study was to assess the role of blackthorn (Prunus spinosa) in the epidemiological cycle of ESFY and to search if an epidemiological cycle may exist independently of stone fruit orchards. A typical blackthorn hedge was chosen in an area free of fruit orchards. A sample of 58 plants was tested for ESFY and 2 plants were detected infected. Samples of the population of Cacopsylla pruni (vector of ESFY) found on the hedge were taken at regular intervals from February to June and were tested for the presence of ESFY. The proportion of reimmigrants (C. pruni arriving after overwintering to reproduce on Prunus) infected remained stable during their 3 months of presence. Infected individuals were also detected in the new generation. On overwintering sites (conifers in a montainous area several km apart on the North-West), 2 C. pruni were detected infected by ESFY. From these results it is suggested that an epidemiological cycle of ESFY can be achieved in wild reservoirs of the phytoplasma even in the absence of Prunus orchards. On the other hand, the blackthorn hedge do not seem to be a very efficient reservoir of ESFY.