Transcript Bacterial Wilt

Bacterial wilt, scab and soft rot
of potato
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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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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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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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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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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 13mm or more deep and darker than the
shallow lesions.
The tissues of the pits are corky in both the
phases.
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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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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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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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Epidemiology
Moisture and temperature are factors affecting
soft rots
Infection occurs at 94 – 100 % Relative Humidity
and temperature of 21-29 0C
Immature tubers are more susceptible
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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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