Detection and distribution of European stone fruit yellows in apricot cv. Bergeron and epidemiological studies in the province of Trento (Italy).

The aim was to investigate the field performance of “Bergeron” on “Wavit” in 4 experimental fields, in the province of Trento (Italy), where European Stone Fruit Yellows (ESFY), caused by “Candidatus Phytoplasma prunorum” has been constantly spreading since 2000. This included visual inspections for typical symptoms (early bud-break during dormancy and premature leaf-roll) and a highly sensitive real-time PCR assay; 25 % of the propagation material was checked with this method and found to be healthy, before planting in 2005. The epidemiology of the disease was also studied by focusing: the presence of the vector Cacopsylla pruni (Scopoli) on conifers, the detection of “Ca. Phytoplasma prunorum” in psyllid eggs and the transmission efficiency at different stages. This was done by exposing apricot trees in 2 locations, during 2 periods from January to July, to the overlapping presence in the orchards of the reimmigrants and the new generation of C. pruni. The results obtained demonstrated that “Bergeron” seems to be highly susceptible to ESFY: typical bud-break was rarely observed, but up to 20-30% of the plants showed premature leaf-roll, fruit deformation and dieback. As regards the vector: - C. pruni was caught only once on Picea abies during winter; - “Ca. Phytoplasma prunorum” was found in 4 egg samples from 2 locations; - the preliminary results on the exposed trees confirmed that the reimmigrants could be the most efficient vectors at least on apricot.