Brown rot

The disease is caused by the soil-borne bacterium Ralstonia solanacearum. It is a highly destructive pathogen responsible for bacterial wilt, a systemic infection that colonizes the plant's vascular system. By invading the xylem vessels, the bacteria multiply rapidly, creating a biofilm that blocks the transport of water and nutrients, leading to rapid wilting.

This pathogen has a remarkably broad host range, infecting hundreds of plant species worldwide. Primary hosts include solanaceous crops like potatoes, tomatoes, eggplants, and peppers. Beyond these, the bacteria also threaten economically significant crops such as tobacco, bananas, and ginger, making it a major concern for global plant health and quarantine services.

Symptoms typically manifest as wilting of the younger leaves at the top of the plant or one side of the foliage during the warmest part of the day. As the infection progresses, the entire plant collapses. A cross-section of the stem or tuber reveals a distinct browning of the vascular tissue, and in advanced cases, a sticky, whitish bacterial ooze is visible, which is a definitive indicator of the disease.

The development of the disease is favored by warm soil temperatures, generally between +20°C and +35°C, and high moisture levels. The bacterium can survive for extended periods in soil, in root debris, and within infected tubers or weeds. It is spread primarily through contaminated soil, irrigation water, infected planting material, and contaminated agricultural tools.

Management of Ralstonia solanacearum is challenging because no curative chemical treatments exist. Prevention is the only reliable strategy. Key practices include utilizing certified pathogen-free seeds and tubers, maintaining strict crop rotation to reduce soil inoculum, implementing rigorous sanitation of equipment, and ensuring effective drainage to prevent the spread of bacteria through water movement.