This presentation is a mere compilation of citrus post harvest diseases solely for education purpose. Most of the photographs and literature is from the post harvest book "Post harvest diseases and disorders of fruits and vegetables, Vol.I" authored by Anna L. Snowdon. The presentation is intended for PG students of plant pathology.
1. Post harvest diseases of citrus
Dr. P. Kishore Varma
Assistant professor
PJTSAU, Hyderabad
2. Green and blue mold – Penicillium spp.
Green mold
• Penicillium digitatum
(green mould)
• P. italicum (blue mould)
• Softening of damaged
tissue.
• White fungal growth,
which progressively turns
blue or green as spores
develop.
3. • Infections develop
from damaged areas.
• The growth of mould
increases with storage
• Optimum temperatures
(20-270
C).
• Late season fruit more
susceptible.
• Damaged rind is more
susceptible.
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Blue mold
Green and blue mold – Penicillium spp.
5. Sour rot - Geotrichum candidum / G. citri-aurantii
• Very soft, watery decay.
• Distinct margin between
decayed and healthy tissue.
• Lesions covered with slimy
off-white spores
• Sour odour detectable.
6. • Prevalent after warm
wet areas
• Pathogenic on ‘weak’,
wounded, bruised, and
split fruit
• Lemons, limes and
grape fruits stored for
extended periods
• Ripe fruit is more
susceptible
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8. 8
Stem end rot - Lasiodiplodia theobromae
• Softening of tissue
around button
• Brown rind with dark
flesh beneath
• Rapid decay down the
axis of the fruit
reaching stylar end
9. • Abundant rainfall during
crops eason
• Ethylene degreening
treatments predispose fruit to
Botryodiplodia infection
• Quiesecent in floral remnants
under the sepals of fruit
• Botryodiplodia – 300
C
• Phomopsis, Dothiorella -
230
C
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13. 13
Brown rot - Phytophthora citrophthora
• Greyish brown firm and
leathery spot
• Pungent odour
• Fine white spore bearing
mould on peel
• Develops rapidly at - 250
C
18. Trichoderma rot - Trichoderma viride
• Peel turns dark brown
• Veins on the interior
surface of the peel turn
brown
• Odour of coconuts
• Yellow green to dark
green sporulation on
surface
20. Management
• Careful handling
• Sanitation
• Sodium-ortho phenyl phenate, sodium carbonate
• Benzimidazole and imazalil
• Curing citrus fruits at 360
C for 3 days
• Yeast, eg. Debaryomyces, Pichia
• Candida famata, Pseudomonas syringae,
Aureobasidium pullulans
• Aspire – Candida oleophila
• Biosave – P. syringae
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21. Management
• Stem end rots – TBZ, Benomyl, Imazalil,
prochloraz
• Brown rot – Fixed copper fungicides, Metalaxyl,
Fosetyl-Al
• Hot water dip treatments at 46-490
C for 3 min
• Stem-end rots – Refrigeration between 4-70
C
• Anthracnose- <100
C
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22. Citrus disorders
Chilling injury
• Critical temperature – 10-150
C for grapefruit,
lemons and lime
• 1 and 50
C – Oranges, mandarins
• Brown pitting of rind
• Watery breakdown
• Brown staining of peel or peel tissue collapse
• Oil gland darkening – grapefruits
• Albedo browning, membranous stain - lemons
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24. Chilling injury
• Abnormal biochemical changes
• Moisture loss from peel
• Growth regulators and fungicides
• Varies from season to season
Chilling injury vs. Pitting
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Peel tissue collapse
Develops in 4-6 weeks in storage
Reduced by waxing
Oil gland targeted
Develops in 3-4 days
Caused by wax application
25. Chilling injury-Management
• Reduction of moisture loss by applying oil, wax
(shellac) or film
• Maintain high humidity
• Sealing in polyethylene film
• Pre-conditioning of fruits to chilling temperatures
• Intermittent heating
• Fungicide application (eg. TBZ)
• Low oxygen and high CO2
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Optimal temperature with proper wax is the best means for
controlling chilling injury
26. Freezing injury
• Temperature below -1.50
C
• Browning of peel
• Water soaked membranes between the
segments
• Mandarins- crystals in pulp
• Grapefruit – milky appearance of pulp
• Cavities in flesh
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28. Oleocellosis or rind-oil spotting
• Common on lemons and limes
• Injured areas firm, irregular in shape
• Yellow, green or brown discolouration
• Oil glands appear prominent
Reasons
• Compression of fruits
• Sudden spell of cold weather
• Physical injury to the peel
• Fruits harvested in cool, wet periods
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