· Capsicum & Chili · Tomato · Potato
The youngest leaves start to wilt during the hottest part of the day and partly recover when temperatures are cooler. Under favorable conditions, the wilting may affect the whole plant and stay permanent. The wilted leaves maintain their green color and remain attached to the stem. The roots and lower part of the stem show a dark brown discoloration. The invaded roots may rot due to infection from secondary bacteria. When cut, stems can exude a white to yellowish, milky secretion.
The bacterium can live long in soils, it can survive in plant debris or on alternative hosts. It enters the plant through wounds in the root system during the emergence of lateral roots. Elevated temperatures (from 30°C to 35°C), high humidity and soil moisture, and alkaline soil pH favor disease development. Heavy soils that can retain soil moisture for long periods are particularly vulnerable. Main alternative hosts for Ralstonia solanacearum include tomato, tobacco, plantain and banana.
The incorporation of fresh plant mass (green manure) from the cruciferous family into the soil (biofumigation) can help to control the pathogen. The plant material can be macerated or chopped off before being dug into the soil, either mechanically or by hand. The plant-derived chemical Thymol has the same effect. Competitive bacteria that colonize the root systems of solanaceous plants are also effective.
Always consider an integrated approach with preventive measures together with biological treatments if available. Because of the soil-borne nature of the causing pathogen, the chemical treatment of the disease may be inviable, less effective or ineffective.