Yersinia pseudotuberculosis

Pathogen and disease type. The causative agent is the gram-negative, rod-shaped bacterium Yersinia pseudotuberculosis. While widely recognized as a zoonotic pathogen, it is also a significant agricultural threat in post-harvest environments. The bacterium is highly psychrotrophic, meaning it thrives at low temperatures, which allows it to remain active and continue damaging fresh produce even under refrigerated conditions.

Affected crops. This bacterium primarily targets stored root vegetables and cruciferous crops. Susceptible commodities include carrots, beets, cabbage, onions, and various other leafy vegetables. Infection frequently spreads from the soil surface into the storage environment, where contaminated produce can lead to rapid decay of entire batches if not managed correctly.

Symptoms and signs. The characteristic sign of the disease is the development of soft or watery rot. Affected tissues soften and undergo discoloration, often turning brownish or black. As the bacteria metabolize the plant tissue, they may produce a slimy surface layer and a distinct odor indicative of rapid tissue degradation and the presence of secondary colonizers.

Conditions for development and spread. The development of the pathogen is favored by high relative humidity (above 90%) and cold to cool temperatures (0–10°C). Contaminated soil adhering to harvest produce is the primary vehicle for introduction into storage facilities. Lack of adequate airflow and poor sanitation within the storage area further accelerate the progression of the disease.

Harmfulness and protection measures. The economic impact is significant due to large-scale spoilage of harvest during winter months.

• Implementing strict sanitation protocols for storage facilities, including walls and pallets.
• Careful washing and drying of produce to minimize soil contact before storage.
• Maintaining optimal ventilation to prevent moisture accumulation and condensation.
• Frequent inspection of stored batches to remove infected units early.
• Strict adherence to temperature control to keep the environment less conducive to bacterial growth.