Tomato
Bacterial Wilt
Ralstonia solanacearum
Bacteria
In a Nutshell
- Wilting of plant.
- Leaves stay green and attached.
- Roots and lower stem become brownish.
- Rotting of roots and excreting of yellowish secretion.
Tomato
Symptoms
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 leak a white to yellowish, milky secretion.
Recommendations
Organic Control
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.
Chemical Control
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 non-viable, less effective or ineffective.
What caused it?
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.
Preventive Measures
- Plant resilient varieties.
- Ensure pathogen-free soil, irrigation water, seeds, and transplants.
- Use suggested planting space.
- Provide good drainage to the field.
- Crop rotation for periods of 5 years or more.
- Ensure a slightly acidic soil-pH of 6,0-6,5.
- Ensure a good nutrient supply.
- Remove infected plants to avoid spreading.
- Avoid transferring equipment from contaminated to uncontaminated soils.
- Disinfect tools with bleach before working on the next field.
- Destroy all infected plants as well as residues by burning.
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