Bacterial bulb rot

The causative agent of this disease is the bacterium Pseudomonas salomonii, which is recognized as a significant threat to onion production worldwide. It acts as a phytopathogenic agent capable of infiltrating and breaking down plant tissues, primarily targeting the bulb structure. The disease is characterized by rapid degradation of the flesh, causing severe post-harvest losses.

The primary host for this pathogen is the onion (Allium cepa). The infection typically begins when the bacteria enter the bulb through wounds caused by harvest tools, soil-dwelling pests, or natural fissures in the bulb scale. Once inside, the pathogen secretes extracellular enzymes that degrade the pectin in cell walls, leading to the characteristic rot.

Typical symptoms include the softening and water-soaking of inner bulb scales. Affected areas often emit a pungent, unpleasant odor and can range in color from yellowish to translucent brown. In advanced stages, the internal tissue structure collapses completely, turning into a watery, mushy mass, eventually making the entire bulb unmarketable.

Environmental conditions play a critical role in the development of Pseudomonas salomonii. High relative humidity and warm temperatures create an ideal environment for the bacteria to multiply. In storage facilities, poor ventilation that leads to surface moisture on the bulbs is the primary catalyst for rapid disease transmission between stored onions.

Effective management requires a combination of cultural and preventive practices. Growers should focus on careful harvesting to minimize mechanical injury and ensure thorough curing of bulbs before long-term storage.

• Implement strict crop rotation
• Control thrips and other bulb-damaging insects
• Maintain low humidity and constant cool temperatures in storage
• Remove and destroy infected bulbs immediately upon detection