Scientific Opinion on the pest categorisation of Pseudomonas syringae pv. persicae (Prunier et al.) Young et al.

The European Commission requested the EFSA Panel on Plant Health to perform the pest categorisation for Pseudomonas syringae pv. persicae (P. s. pv. persicae). The agent is responsible for bacterial die-back in peach, nectarine, Japanese plum and, possibly, myrobalan plum. The disease is caused by a genetic clade within genomic species 3 of P. syringae, but there is only limited knowledge of the diversity of the causative agent. The host plants are cultivated throughout Europe, although it is only in southern European countries that the production of peaches and/or nectarines is of economic importance, and the cultivation of Japanese plums is restricted to some parts of southern Europe. Outbreaks are rare and currently the disease occurs only sporadically in Portugal, France and Germany. P. s. pv. persicae causes symptoms on the bark, shoots, leaves and fruit. Detection is based on symptomatology and isolation; no DNA amplification (polymerase chain reaction) protocols are available. The pathogen can be identified on the basis of disease symptoms, including shoot die-back and leaf spots, and on the basis of distinct biochemical and genetic properties. No effective management strategies are available, although disease incidence and severity can be somewhat reduced by disinfection of tools, machines and materials, the use of planting material from disease-free areas, and the avoidance of conditions favouring disease expression. Initial infections may be due to the use of (latently) infected plant material, but infections may also occur from the environment. No effective biological or chemical control agents are registered for bacterial die-back in Europe. The outbreaks, although they occur sporadically, are usually severe and can result in the loss of entire orchards.