Pseudomonas amygdali

Pseudomonas amygdali is a Gram-negative, rod-shaped bacterium within the genus Pseudomonas, recognized as a significant phytopathogen. It is scientifically classified as the causal agent of bacterial canker and blast in various Prunus species. This bacterium is known for its ability to cause severe economic losses in orchards globally by damaging the vascular tissues and bark of stone fruit trees.

The primary hosts of this pathogen include almond, apricot, peach, and cherry trees. The disease manifests through various symptoms, including deep cankers on limbs, necrosis of floral buds, leaf spotting, and shoot dieback. If left unchecked, the infection disrupts the flow of nutrients and water, eventually leading to the decline or death of the entire tree.

The biology of Pseudomonas amygdali is strictly dependent on environmental moisture and plant wounds. The pathogen overwinters in infected bark tissues and dormant buds. During the spring, with rising temperatures and humidity, bacteria move to the surface of the plant and enter through wounds caused by pruning, frost cracking, or natural openings like stomata.

Environmental conditions favoring the development and spread of the pathogen are mild, wet, and cool weather. Rain splashes and wind-blown mist are the primary vectors for transmission within an orchard. Furthermore, contaminated pruning tools are a critical factor in the rapid spread of the disease between healthy and symptomatic trees, making farm hygiene essential.

Controlling this pathogen requires an integrated approach to orchard management to mitigate its impact. Key strategies include:

• Strict orchard sanitation by removing and burning symptomatic branches.
• Sterilization of pruning equipment using alcohol or bleach solutions between trees.
• Applying protective copper-based sprays before and after the dormant season.
• Maintaining tree vigor through balanced fertilization and proper irrigation.