Maybe you’ve heard farmers who have suffered allot of losses due to bacterial wilt.This loss is felt in almost every country in Africa. Actually,only seventeen countries that haven’t exhibited the presence of bacterial wilt.The economic effect is estimated in millions of dollars across Africa.
The effect is worsened by presence of root nematodes.Experiments in India showed that the combined pathogenic effects of R. solanacearum and root-knot nematodes were greater than the independent effects of either (CABI, 2005)
Worst thing with bacterial wilt is that, it is worsened by its wide range if hosts.According to infonet biovision,bacterial wilt has three hosts;
- Primary hosts which include tomato,tobacco,aubergine,potato,banana,plantain and heliconia
- Secondary hosts which include castor bean,ginger,groundnut,bell pepper,taro,cotton,sweet potato and cassava
- Wild hosts which include black night shade,gallant soldier, pussley and stinging nettle
Bacterial wilt of tomatoes
First stage
Wilting of the terminal leaves, which after 2 to 3 days becomes permanent when the whole plant wilts due to the active development of the disease.
Stage two
The plant wilts and dies suddenly.Plants often wilt while green.This often happens during the heat of the day but may partially recover in the morning.
Bacterial wilt often tend to affect the crop at vegetative stage with most affected crops being Leaves, roots, seeds, fruits, stems, vegetative organs and whole plant.
Symptoms by affected plant part
- Growing points: wilting.
- Leaves: wilting.
- Roots: rot.
- Stems: internal discoloration; creamy exudates; wilt.
- Vegetative organs: internal discoloration.
- Whole plant: plant death; dwarfing.
Source of infection and spread
According to infonet biovision,the bacterium is soil-borne and can survive in soil for long periods.However, some soils are conducive to bacterial wilt and other suppressive.Important soil factors affecting the occurrence and persistence of the pathogen are soil moisture and antagonistic microorganisms. Soil type influences soil moisture and population of antagonistic microorganisms, which in turn affect the survival of R. solanacearum in soil.
Infestation by root-knot nematodes aggravates the disease.The bacterium is especially destructive in moist soils at temperatures above 24 degree Celsius.It is sensitive to high pH (alkaline soils), low soil temperature, low soil moisture and low fertility levels.Spread is effected by running water, movement of infested soil and also diseased seedlings.
Bacterial wilt can also be spread on vegetative propagating material. Therefore, plant quarantine of potentially infested plant material is very important to avoid long-range dispersal.(Hayward 1991)
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Conditions that favour disease development
- Crop residues infected with Ralstonia solanacearum left in the field .
- Injured roots caused by farm tools or by soil pests
- Warm temperature and high soil moisture
- Slightly acidic soils
- Poor and unfertile soil
- Infestation by root-knot nematodes
Cultural practices
- Crop rotation is not effective as the pathogen can survive for a long period (several years) in the soil and also attack a wide range of crops and solanaceous weeds
- Use plant varieties that are tolerant / resistant to bacterial wilt.
- Do not grow crops in soil where bacterial wilt has occurred.
- Rogue out wilted plants from the field to reduce spread of the disease from plant to plant
- Control root-knot nematodes since they could facilitate infection and spread of bacterial wilt
- Where feasible, extended flooding (for at least 6 months) of the infested fields can reduce disease levels in the soil
- Soil amendments (organic manures) can suppress bacterial wilt pathogen in the soil
Inter-cropping
In some developing countries intercropping has been used as a means of reducing pathogen populations in the soil and root-to-root transmission.
In Burundi, growing potato with bean showed a lower incidence of bacterial wilt, indicating that a bean intercrop, which has a dense root system and grows quickly, was better than a crop such as maize, which develops slower and has a more dispersed root system.(Hayward 1991)
Home experiment-Water test experiment
Water test:Bacterial wilt of tomato To distinguish this wilt from others, take a thin slice or sliver of the brown stem tissue and place it on the inside of a glass of water at the water level. If bacterial wilt is present, a milky bacterial stream (strands) flows from the lower cut surface of the sliver within seconds.
Bacterial wilt of potato: The infested leaves wilt during the (sunny) day and sometimes recover during cool hours. The wilting is similar to the result of lack of water. During the rapid development of the disease, the entire plant wilts quickly without yellowing. Othersymptoms could be wilting of only a part of the stem, or one side of the leaf/stem.
The stem wilts or dries up completely and the remainder of the plant remains healthy. When the diseased tuber is cut, it shows a browning of the vascular ring and the immediate surrounding tissues On the cut surface, a creamy fluid usually appears on the vascular ring.
Read Also:Cost-Profit Analysis, Farming Tomato In One Acre
Reference:
- Bacterial wilt :Infonet biovision https://infonet-biovision.org/PlantHealth/Pests/Bacterial-wilt
- Hayward, A.C. (1991). Biology and Epidemiology of Bacterial Wilt caused by Pseudomonas Solanacearum. Annual Reviews Phytopathol. 29: 65-87
- CAB International (2005). Crop Protection Compendium, 2005 edition. Wallingford, UK www.cabi.org
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