Post harvest diseasesPost harvest diseases
Bacterial soft rot - Erwinia carotovora subsp. carotovora
Anthracnose - Colletotrichum capsici
Fruit rot - Alternaria solani
Gray Mould - Botrytis cinerea
Late blight -Phytophthora capsici
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
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
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
Bacterium Gram –ve, rod shaped bacterium
1 to 6 peritrichous flagella
Epidemiology Warm, moist weather - highly favorable for infection
Temperature - 25° to 30°C, RH - 95%
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
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
Anthracnose- Anthracnose- ColletotrichumColletotrichum capsicicapsici
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
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
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
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
Gray Mould - Botrytis cinereaBotrytis cinerea
Brownish spots develop near the soil line or cotyledons
Water-soaked lesions on leaves & stems darken and collapse
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
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
Favourable conditions and spread
Fungus sporulation and infection, is favored by cool and wet weather
Temperatures of 17–23°C, 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
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
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
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
Spores of A. solani Alternaria solani conidia. Note the transverse and vertical septa and the long "beak" (arrow)
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
Late blight Late blight -Phytophthora-Phytophthora capsicicapsici 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
FungusProduces microscopic, asexual spores called sporangiaSporangia - spherical to pyriform, hyaline, papillate and have a long pedicel attached to the base of the sporePathogen grows well between 25 and 30oC
Mode of spreadSurvives in the soil in host debris Roots, stems, and mummified fruits left in the field after harvest, harbor the pathogen for monthsPhytophthora capsici is also seed borne
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