Bacterial internal brown rot of bulbs

The causal agent of this disease is the bacterium Pseudomonas aeruginosa, which leads to the internal decay of bulbs. This type of bacteriosis is particularly insidious because it often remains hidden until the bulbs are cut or processed.

This pathogen primarily affects bulb crops such as onions and garlic. The infection causes significant damage both during the growing season under wet conditions and during post-harvest storage, leading to substantial losses for farmers.

Symptoms include the browning and softening of inner scales. In advanced stages, the internal tissue turns into a mushy, discolored mass that emits a foul odor. Notably, the outer skin of the bulb might appear perfectly healthy, making early detection difficult.

Development and spread of the disease are favored by high humidity, poor ventilation, and excessive irrigation. The bacteria typically gain entry into the bulb via mechanical injuries, pest damage, or through the basal plate from contaminated soil environments.

Effective protection and preventive measures include:

• Ensuring thorough curing of bulbs immediately after harvest.
• Practicing proper crop rotation to break the disease cycle.
• Maintaining optimal temperature and humidity levels in storage facilities.
• Implementing rigorous pest management programs to prevent tissue wounding.
• Selecting high-quality and disease-free planting stock.

The economic impact of bacterial internal brown rot is profound, as infected batches are often unsuitable for sale. Since there is no curative treatment for infected bulbs, integrated management strategies focused on prevention and hygiene are essential to safeguard the harvest.