Bacterial hyperplastic canker of almond

The causal agent of bacterial hyperplastic canker is the phytopathogenic bacterium Pseudomonas amygdali. This is a destructive disease affecting stone fruit trees, with the almond being the primary and most severely impacted host. The disease is classified as hyperplastic because the pathogen triggers abnormal cell division, resulting in gall formation on the host's tissues.

Symptoms appear on twigs, branches, and occasionally on leaves and fruit. The diagnostic feature is the development of soft, white, or light-colored swellings on the bark, which eventually harden into woody, irregular galls or cankers. Over time, these cankers crack and may serve as entry points for secondary fungi and bacteria, further complicating the tree's health.

The development and spread of Pseudomonas amygdali are heavily dependent on environmental conditions, particularly high humidity and mild temperatures. Rain splash is a primary vector, spreading bacteria from cankers to healthy tissue. Additionally, contaminated pruning tools are a major transmission pathway within an orchard, while the pathogen survives between growing seasons in existing cankers and on infected plant debris.

The economic impact of this disease is significant, as it leads to reduced nut quality, decline in tree vigor, and eventual dieback of limbs. In severe outbreaks, the cumulative damage can result in the loss of entire trees, leading to major yield gaps in commercial almond production. Preventing the establishment of the pathogen is crucial for maintaining long-term orchard productivity.

• Regular inspection of trees to detect early signs of gall formation.
• Rigorous sterilization of all pruning equipment with disinfectants between trees.
• Removal and destruction of infected branches to reduce the bacterial inoculum in the orchard.
• Preventive spray programs using copper-based bactericides during dormancy.
• Management of orchard pests that cause bark wounds, as these facilitate bacterial entry.