Fungal wilt, wart, early blight, late blight, black scurf and leaf spot disease of potato - PowerPoint PPT Presentation

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Fungal wilt, wart, early blight, late blight, black scurf and leaf spot disease of potato

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Title: Fungal wilt, wart, early blight, late blight, black scurf and leaf spot disease of potato


1
Fungal wilt, wart, early blight, late blight,
black scurf and leaf spot disease of potato
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Fungal wilt of potato
  • Two Types

Sclerotial wilt Sclerotium spp
Fusarium wilt Fusarium spp
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Common in the plains of Maharastra and West
Bengal in Kharif Potato crop
Sclerotial wilt
  • 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
  • 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 _at_ 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.
  • 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 _at_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.
photo
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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 (gt90 ) 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 _at_0.2
    alternating with Metalaxyl _at_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 _at_ 2g/lit
    at 15 days interval

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