Bacterial Canker of Plum Trees (Prunus domestica), Caused by Pseudomonas syringae Pathovars, in the Netherlands

In the Netherlands, bacterial canker in plum trees (Prunus domestica) is a serious and recent problem in plum production. Bacterial canker, caused by Pseudomonas syringae pv. syringae (Pss) and pv. morsprunorum (Psm), is a serious disease of stone fruit, and occurs in all major stone fruit producing areas of the world. The trunks of the affected plum trees are girdled by bacterial cankers resulting in sudden death of infected trees. Rapid tree death has been observed in several orchards 2-4 years after planting. Disease incidences can be very high, and sometimes complete orchards have to be removed. Recently, plum cultivation in the Netherlands has changed from a relatively extensive into an intensive cultivation. This was made possible by the use of a weak rootstock, Krymsk (R) 1 (VVA-1). The lack of chemicals to fight bacterial diseases in the orchards created a need for alternative methods of disease control. To achieve this, methods such as prevention, biological control and plant resistance must be explored and control strategies to manage plum decline have to be developed. In 2010 a project was started to study the epidemiology and possible control of plum decline.