Onion bacterial rot

Lonsdalea britannica is a plant pathogenic bacterium responsible for severe bacterial rot in onion and related Allium species. Previously associated with the Erwinia complex, this pathogen is now recognized as a distinct species that poses a major threat to the global onion industry, specifically causing internal bulb decay that is often undetectable from the outside.

The primary symptom of infection is the soft, watery rot of the bulb's fleshy scales. Infected tissues become translucent or yellowish and eventually break down into a foul-smelling mass. In many cases, the outer skin of the onion remains intact, masking the internal collapse until the bulb is cut or begins to leak fluid, which facilitates the spread of the bacteria.

Disease development is heavily influenced by environmental factors. High moisture levels, heavy rainfall near harvest, and warm temperatures promote the rapid growth and spread of the bacterium. The pathogen typically enters the bulb through natural openings or physical wounds, such as those caused by hail, heavy machinery, or insect damage during the growing season.

The economic impact of this disease is significant, particularly during post-harvest storage. Because Lonsdalea britannica can spread rapidly through contact or contaminated tools, it can quickly ruin entire batches of onions in storage facilities. This leads to substantial waste and financial loss for growers, wholesalers, and retailers alike.

Managing the disease requires a rigorous integrated approach to farm and warehouse hygiene. Key prevention strategies include:

• Planting high-quality, disease-free seed sets or transplants.
• Implementing effective pest control programs to reduce physical damage.
• Harvesting under dry conditions and curing onions thoroughly before storage.
• Maintaining proper ventilation and cool, dry conditions in storage rooms.
• Regular inspection of stored bulbs to identify and remove early signs of infection.