1. Bacterial wilt, scab and soft rot of potato
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2. Bacterial Wilt or brown spot (Ralstonia solanacearum)
Symptoms:
The disease affects both above and underground parts of the plant.
Infected plants show sudden wilting and complete collapse of plants.
Vascular browning is the characteristic symptom of the disease.
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3. Bacterial mass ooze out from the cut ends of the stem.
Infected tubers are the main source of infection from one place to another.
Bacteria spread from plant to plant by root contact or through water films.
Increase in the temperature enhances wilting and high soil moisture favours survival of pathogens in soil.
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4. Epidemiology
Infected tubers are the main source of infection from one place to another
Bacteria spread from plant to plant by root contact or through water films
Increase in the temperature enhances the wilting and high soil moisture favours survival in soil
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5. Management (Bacterial wilt)
Use of disease free tubers for planting.
Crop rotation with non host crop plants
(maize, sorghum, garlic, onion, cabbage etc)
Avoid injuries to the tubers during intercultural operation.
Seed tuber treatment with bio control agents
( Bacillus subtilis, Pseudomonas florescens)
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6. Potato scab (Streptomyces scabies)
It is caused by a soil borne pathogen. The same organism also attacks many other root crops like beet, radish, turnip and carrot.
Symptoms
Two phases of scab viz. shallow and deep scab are found.
Shallow scab consists of a superficial rough area on the skin of tubers.
Deep scab consists of lesions which are 1-3mm or more deep and darker than the shallow lesions.
The tissues of the pits are corky in both the phases.
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7. Epidemiology
Pathogen introduce into the soil through infected tubers and survives indefinitely once soil is contaminated
Survive on decaying plant debris
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8. Management Use disease free seeds
Green manuring before planting will reduce infection
Irrigate the land at regular intervals for keeping the soil moist from the time of tuberization. This will check the disease incidence
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9. Soft rot & black leg (Erwinia carotovora)
Symptoms
It occurs in two phases viz., black leg of shoots and soft rot of tubers. In black leg phase, black lesions appear at base of the stem followed by yellowing, rolling of top leaves
Tuber develops water soaked areas which rot and emit an offensive odor in the soft rot phase
Small sunken areas develop on tuber surface
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10. Epidemiology Moisture and temperature are factors affecting soft rots
Infection occurs at 94 – 100 % Relative Humidity and temperature of C
Immature tubers are more susceptible
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11. Management Cut and injured tubers should be discarded
Avoid prolonged wetting of tubers
Store and transport the tubers under well ventilated conditions.
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