Bacterial canker of stone fruits

Bacterial canker is a serious disease caused by the pathogen Pseudomonas cerasi (often identified as Pseudomonas syringae pv. morsprunorum). It affects the vascular system and bark of various stone fruit trees, leading to severe canopy loss and tree mortality.

The primary hosts of this pathogen are trees belonging to the Prunus genus, such as cherries, plums, peaches, and apricots. The bacteria enter the plant through pruning wounds, leaf scars, frost cracks, or natural openings like stomata during periods of environmental stress.

Typical symptoms include "shot-hole" lesions on leaves, dark brown spots on buds, and extensive cankers on stems and branches. In wet conditions, the cankers often ooze a sticky bacterial exudate, while the underlying wood tissue turns dark and begins to decay, often emitting a distinct fermented smell.

Disease development is highly dependent on climate. Mild, damp, and cool weather conditions in spring favor the rapid spread of the bacteria. Frost events are particularly dangerous as they create micro-cracks in the bark, allowing the pathogen to penetrate deeper into the tree's vascular system.

Effective prevention and control require a comprehensive strategy: planting disease-free stock, pruning in dry weather, and disinfecting all gardening tools.

• Use copper-based bactericides during dormancy
• Apply protective wound sealants to large cuts
• Maintain balanced tree nutrition to improve resistance