Transcript All fungal1_0_1

Fungal wilt, wart, early blight, late
blight, black scurf and leaf spot
disease of potato
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Fungal wilt of potato
Sclerotial wilt
Sclerotium spp
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Two Types
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Fusarium wilt
Fusarium spp
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Common in the plains of
Maharastra and West
Bengal in Kharif Potato
crop
Symptoms:
Initial symptom is the presence of wilted plants
within a canopy of healthy looking plants.
Water soaked lesions develop on the stem
Thick white moulds appear on the collar region of
the stem.
Later fruiting bodies developed which look like
mustard seeds.
Causal organism : Sclerotinia sclerotiorum
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Fusarium wilt:
Symptoms:
Infection starts on the seed tubers and
progresses to underground parts of the
stem and roots
Affected plants show yellowing of margins
of the lower leaves later progressing to
the entire plant
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Finally the plant wilts completely
Causal organism : Fusarium oxysporum
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Epidemiology
Alternate period of wet and dry soil
condition is favourable for disease
Severity is more in sandy acidic soil
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Management
Crop rotation with non host crops.
Seed treatment with mancozeb, carbendazim @
0.25%
Use organic amendment mixed with
Trichoderma harzianum
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Wart of potato,(Synchytrium endobioticum)
Wart is widely distributed in
temperate and high altitude
tropical regions with cold and
rainy climate. In India, it is
most prevalent in Sikkim and
West Bengal.
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Symptoms:
White to brown tumour like outgrowth
develop on stem , stolon and tubers.
Symptoms usually develop below ground,
but under wet conditions may appear on
stem and foliage.
Tumours blacken with age and may rot
due to secondary organisms.
Above ground warts are green, reddish
and purple depending on the variety.
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Causal organism: Synchitrium endobioticum
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Epidemiology
Intensity of disease is affected by soil moisture, soil
temperature and soil pH
Management of wart disease
• Wart infected tubers should not be plnated
• Restrict the movement of potato tubers from infected to
non infected region through quarantine regulation.
• Grow immune variety such as Kufri Jyoti, Kufri Jeevan
and Kufri mathu.
• Quarantine legislation should be strictly followed.
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Early blight of potato
Alternaria solani
World wide distribution and one of the most
important diseases under favourable weather
conditions.
Starts appearing on potato just before the
initiation of tuberization.
Symptoms:
Older leaves show brown angular necrotic spots
marked by concentric rings
Distinguished from the late blight by the absence
of white cottony growth on the under surface of
spots.
Causal organism: Alternaria solani
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The spots enlarge and coalesce to form
large necrotic areas and the whole leaf
dries up and hangs along the stem
Brown, dry and brittle spots of limited
size and a well marked outline helps in
differentiations of the early blight from
other foliage diseases of potato
In tubers, lesions are dark brown,
sunken and surrounded by a raised
margin
The internal tissues of the tuber become
reddish brown and leathery to corky in
texture
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Epidemiology
Disease is severe in high temperature25-30 0C
alternating with moist period and poor vigour of
the plant
Poorly manured crop show severe attack
Continuous drought period checks the disease
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Management
• Spray the crop with Antracol, Mancozeb
@0.25% at 7-10 days interval.
• Crop debris should be destroyed after harvest
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Late blight of potato (Phytophthora infestans)
Most destructive
disease of potato. Any
part of the foliage may
be infected under cool
and moist conditions.
Complete destruction of
the plants in the field
takes place within few
days under congenial
weather conditions.
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Symptoms
Circular to irregular water soaked faded
green spots develop initially at the tip of
the margin of the lower leaves which
turn into brownish black lesions.
On the undersurface of the leaves the
lesions are covered with superficial
whitish (cottony) fungal growth.
The lesions on the petiole and stems are
black coloured of indefinite length.
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• During moist weather, the blighted areas rapidly enlarge, quickly
spread to tender and older plant parts.
• Under dry conditions enlargement of the lesions get restricted and
the blighted areas turn black and dry up.
• Stem infection occurs at nodes and plant topples over.
• In tubers purplish brown spot appear which spread to the entire
surface.
• On cuttings, affected tubers show brown necrosis spreading from
surface to center.
• Tubers rot in soil before harvest or during storage.
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Epidemiology :
Excessive humidity (>90 %) coupled with suitable
temperature (15-20 0C) and optimum soil moisture
(15-20 %) are most favourable for disease
development.
Continuous rain or light drizzle for 2-3 days followed
by low temperature is suitable for disease
development.
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Management
• Use tolerant varieties like Kufri Badsha, Kufri Jyoti, Kufri Ashoka and
resistant varieties like Kufri megha, Kufri Pukhraj
• Select healthy, disease free seed tubers
• Infected plant parts are to be removed and destroyed
• Harvest the fully matured tubers in dry weather
• Apply protective spray with Mancozeb @0.2% alternating with Metalaxyl
@0.25% at 8-10 days interval. In rainy days sticker like Triton AE (0.02%)
should be mixed with the spray solution.
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Black scurf of Potato
Rhizoctonia solani
Symptom
Hard, superficial, dark brown or black bodies known as sclerotia
are seen on the surface of the tubers.
When the infected tubers are planted emerging shoots are killed.
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Young sprouts are very susceptible to
infection.
In older plants, brownish black sunken
lesions develop on underground stems
and stolon.
Surface of the tubers have black bodies
known as scurf which are not easily
removed.
The growth of the fungus on the surface
of the tuber causes rusting of the skin.
The tuber shows hard dry rot with
browning of internal tissues.
During storage the entire tuber is reduced
to a spongy mass.
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Management
Crop rotation preferably for 3years with cereals.
Shallow planting followed by gradual filling up
reduces damage.
Avail seed tuber lots that does not contain scelotia.
Sundry the tubers before planting.
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Leaf spot of potato (Septoria sp)
Symptoms:
Small, water-soaked circular spots
1.6-3.2mm in diameter first appear
on the undersides of older leaves.
The centers of the spots are gray or
tan and spots have a dark brown
margin.
Spots may also appear on stems.
Heavily infected leaves will turn
yellow, dry up, and drop off.
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Management (Septoria)
Infected plant materials should be destroyed by
burning
Haulms of diseased crops are to be removed and
burnt before harvest of the crop
Fungicidal spray preferably with Zineb @ 2g/lit
at 15 days interval
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