On the contrary plants resulted as symptomatic in spring 2015 were not characterized by any signal of stress during the previous season and showed a growth vigor exceeding the average. In this case another predisposing factor for the pathogen has to be taken into consideration; this is the occurrence of frost events, mainly those occurring during spring and especially affecting vigorous plants for which tissue hardening and vegetative rest are delayed during autumn. As showed for other fruit crops (Scortichini, 2010;Ferrante and Scortichini, 2014), spring frosts are very conducive for P. syringae multiplication with in the plant