POST HARVEST DISEASES

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POST HARVEST DISEASES OF CHILLIES
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Post harvest diseases

• Bacterial soft rot - Erwinia carotovora subsp.
  carotovora
• Anthracnose - Colletotrichum capsici
• Fruit rot - Alternaria solani
• Gray Mould - Botrytis cinerea
• Late blight -Phytophthora capsici

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Bacterial Soft Rot- Erwinia carotovora subsp.
carotovora

• Symptoms
• Dark veinal tissue followed by leaf chlorosis and
  necrosis
• Internal dark brown discoloration
• Stem cankers develop - breakage of branches
• Wilting and drying
• Symptoms on fruits
• Fruit peduncle - highly susceptible is
  frequently the initial point of infection
• Both ripe and green fruit may be affected

Post-harvest softening of stem end of fruit
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• Initially, the lesions on the fruit are light to
  dark-colored, water-soaked, and somewhat sunken
• In later stages, bacterial ooze may develop from
  affected areas, and secondary organisms follow,
  often invading the rotted tissue
• Affected fruit hang from the plant like a
  water-filled bag

Collapsed fruit
Rotting fruit
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• Conditions for Disease Development
• Transmitted by irrigation water, but a wound is
  necessary for infection to occur
• High rate of nitrogen fertilization is associated
  with increased susceptibility to soft rot
• Post-harvest soft rot of pepper fruit arises
  when,
• infected fruit is harvested with healthy fruit
• harvest containers are contaminated with the
  bacteria
• fruit is subjected to contaminated wash water,
  contaminated surfaces or soil debris

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• Bacterium
• Gram ve, rod shaped bacterium
• 1 to 6 peritrichous flagella
• Epidemiology
• Warm, moist weather - highly favorable for
  infection
• Temperature - 25 to 30C, RH - 95

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• Disease management
• Disease incidence could be reduced by
• Early detection of symptoms
• Disinfection of pruning tools
• Avoidance of wounding plants
• Remove plant debris - fallen, diseased leaves
• Seed treatment 1 sodium hypochlorite for 30
  sec, then rinse with clean water
• Avoid planting pepper crops following crops of
  potato or cabbage
• Rotate instead with crops of bean, corn and
  soybean

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• Post-harvest disease management
• Use chlorinated water to reduce populations of
  soft rot bacteria and to reduce the risk of
  infection during washing
• Allow fruit to dry thoroughly
• During packing and storage, the fruit should be
  kept clean and maintained in a cool, dry place

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Anthracnose- Colletotrichum capsici

• Ripe fruits turning red are affected
• Small, black, circular spot appears on the fruit
  skin
• Badly diseased fruits turn straw colour or pale
  white colour, lose their pungency

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• Diseased cut open fruits - lower surface of the
  skin is covered with minute, elevated sclerotia
• Advanced stage - seeds covered by a mat of fungal
  hyphae, turn rusty in colour
• Causal Organism - Colletotrichum capsici
• Mycelium - septate and inter and intra cellular
• Acervuli and stroma on the stem are hemispherical
• Conidia - in mass appear pinkish

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• Epidemiology
• Temp - 28oC, RH - 95
• High humid conditions when rain occurs after the
  fruits have started to ripen
• Mode of spread survival
• Seed borne
• Secondary spread is by air borne conidia rain
• Flies and other insects responsible for
  dissemination of the spores from one fruit to
  another

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• Control measures
• Use disease free seeds
• seed treatment - thiram 2 kg/ha or zineb 2.5
  kg/ha
• Three sprayings with captan 0.2
• 1st spraying - just before flowering
• 2nd at the time of fruit formation
• 3rd - fortnight interval after second spraying
• Biocontrol
• P. fluorescens, Bacillus subtilis -effective
  (Rajavel, 2000)
• P. fluorescens and T. viride (Muthuraj, 1998)
• Saccharomyces cerevisiae P. fluorescens
  (Jayalakshmi et al., 1998)
• Essential oil - Nigella sativa - antimicrobial
  activity

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Gray Mould - Botrytis cinerea
Brownish spots develop near the soil line or
cotyledons
Water-soaked lesions on leaves stems darken
and collapse
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• Water-soaked spots that rapidly expand into large
  yellowish-green or grayish-brown, irregular
  lesions that are soft and spongy in texture
• Velvet-like fungus mycelium and spores are
  produced on the lesion surface under cool, humid
  conditions

Water-soaked spots collapse
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• Fungus
• Botrytis cinerea - abundant hyaline conidia
  (asexual spores) borne on grey, branching
  tree-like conidiophores
• It overwinters as sclerotia or intact mycelia,
  both of which germinate in spring to produce
  conidiophores
• The conidia are dispersed by wind and rain-water
  and cause new infections

Conidia and hyphae
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• Favourable conditions and spread
• Fungus sporulation and infection, is favored by
  cool and wet weather
• Temperatures of 1723C, RH - 90
• Excessive application of nitrogen makes plants
  such as young transplants more susceptible to
  gray mold
• High canopy density creates conditions for
  extended leaf wetness at night and subsequent
  increased gray mold severity

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• Control
• Field sanitation - remove and burn decaying
  infected plant parts
• Space seedlings and transplants to allow for free
  flow of air through the crop
• Treatment with hot air at 38oC for 48-72 h or hot
  water at 50oC to 53oC for 2 to 3 min

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Alternaria rot- Alternaria solani

• Brown lesions surrounded by a yellow halo develop
  on the fruit
• Lesions enlarge and result in the formation of
  irregular sunken patches with a dark brown margin
  and light grey centre

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• Fungus
• Hyphae - septate, branched, light brown becoming
  darker with age
• Conidia - single, muriform, beaked and dark in
  color
• Source of infection - infected seeds and plant
  debris

Alternaria solani conidia. Note the transverse
and vertical septa and the long "beak" (arrow)
Spores of A. solani
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• Control
• Fortnightly spraying of
• Bordeaux mixture 1.0
• Copperoxychloride 0.3
• Difolatan 0.3
• Mancozeb 0.2
• Reduction in the pathogenicity and development of
  these pathogens in inoculate peppers,
• Treatment with hot air at 38oC for 48-72 h
• Hot water at 50oC to 53oC for 2 to 3 min

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Late blight -Phytophthora capsici

• Infected leaf tissue - wilted, light green or
  gray-green, later becoming tan to white and
  scalded in appearance
• With moisture, leaf spots have a water soaked
  border
• Fruit rots - irregular in shape and olive green
  or light green with water soaked borders
• Rots expand rapidly and fruits can be completely
  diseased and desiccated, causing the formation of
  "mummified" fruits
• Infected seeds are brown and shriveled

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• Fungus
• Produces microscopic, asexual spores called
  sporangia
• Sporangia - spherical to pyriform, hyaline,
  papillate and have a long pedicel attached to the
  base of the spore
• Pathogen grows well between 25 and 30oC
• Mode of spread
• Survives in the soil in host debris
• Roots, stems, and mummified fruits left in the
  field after harvest, harbor the pathogen for
  months
• Phytophthora capsici is also seed borne

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• Control
• Rotation with non-susceptible crops will reduce
  the amount of Phytophthora capsici surviving in
  soil
• Fresh, clean seeds should be planted in new
  potting mix to establish healthy transplants
• Monitor seedlings as well as the field and remove
  diseased plants as soon as they occur