post harvest poathology

1. POSTHARVEST PATHOLOGY
Prepared by: Hamid Salari
Assistant professor
Department of Horticulture

2. Postharvest pathology
• Severe infection by fungus and bacteria
• Fruits are acidic thereby more susceptible to fungus
• Vegetables are less acidic thereby susceptible to bacteria
• 5-10 per cent of total postharvest losses
• Crops like banana are more susceptible
• Diseased fruits produce more ethylene

3. Common postharvest diseases
• Infection may occur either in preharvest or post
harvest
• Infection may occur through
a. direct penetration through skin
b. natural openings
c. injuries

4. Common postharvest diseases are:

5. Gray mold
Soft, light brown areas on the fruit which enlarge rapidly
Fruits are covered with gray, dusty spores, which give the disease
its name "gray mold."
Cause:
Botrytis cinerea

9. Black rot
larger brown, dead but firm areas
Cause:
Physalospora obtusa

12. Bitter rot
circular brown spot is the first symptom
Cause:
Glomerella cingulata

14. White rot bitter rot

15. Blue mold
Soft, watery spots
The decayed portions are sharply separated from the healthy
tissues
The spots range in color from brown to pale straw
Show all possible variations in size
Cause:
Penicillium expansum

18. Anthracnose
whitish, water soaked lesions up to 3 mm in diameter
Infected fruit eventually dry down to form hard, black,
shriveled mummies.
Cause:
Colletotrichum acutatum

22. Stem end rot
Water soaked areas
Brown to black color
Cause:
Phomopsis sp.

26. Sour rot
Symptoms include a soft watery rot with leakage of berry juice,
and a distinctive vinegar smell
Cause:
Colletotrichum candidum
Under investigation

30. Fusarium rot
• Symptoms of Fusarium fruit
rot vary depending on the
Fusarium species:
• F. graminum, F. acuminatum,
F. culmorum, and F.
moniliforme produce a distinct
reddish or purplish
pigmentation in the diseased
area
• F. semitectum, F. equiseti, F.
scirpi, and F. solani produce
brown internal lesions; a cross
section of a mature lesion
reveals a dry, brown, spongy
rot

33. Wet rot
Fruits rot rapidly and white fungal mold appears on the infected area
the heads are white to brown but turn purplish-black within a few days
water-soaked and soft
An entire fruit can rot in a 24 to 48 hour period
Symptoms usually begin on the blossom end of the fruit.
Cause:
Choanephora cucurbitarum

35. Brown rot
first appears as small, circular brown spots that increase
rapidly in size
Infected fruit eventually turn into shriveled, black mummies
that may drop or remain attached to the tree through the
winter.
Brown rot can be serious on injured fruit such as cherries split
by rain.
Cause:
Monilinia fructicola

39. Alternaria rot
more or less round, brown to black lesions
weakened tissue
Cause:
Alternaria spp.

44. Ring rot
appearing as only a broken, sporadically appearing dark line, or as
a continuous, yellowish discoloration
Causes:
1. bacterium Clavibacter
2. Pythium spp.

47. Bacterial soft rot
softening and water soaking
yellow initially, turning brown as the disease
these organisms generally appear just before or at the time of
harvest or in storage.
Cause:
Erwinia carotovora

50. Factors affecting development of infection
1. Surrounding environment
2. Temperature
3. Relative humidity
4. Chilling injury
5. Mechanical injury
6. pH of the produce
7. Ripening conditions….etc

51. Control of PHD
It depends on:
– The ability of treatment
– Level of infection
– Sensitivity of host produce
To control PHD understanding of:
1. Nature of disease
2. Conditions promotes occurrence
are important

52. Control methods
• Chemical
• Physical
• Biological

53. Chemical method
• Different chemicals are used for different
diseases
• Benzimidazole fungicide
• Guazatine fungicide
• Chlorine, wash water
• Sulphur dioxide, grape guard
• Fungicide should be applied within 24 hours
of harvest

54. The success of chemical control depends on:
The depth of infection
The growth rate of infection
Temperature
Humidity
Depth to which chemical can penetrate
Spray load of chemical

55. Physical method
• Low and high temperature
– Hot water dip (50-55 °C)
• Modified atmosphere
• Irradiation
• Good sanitation

56. Biological
• BioSaver (pseudomonus syringea [29.8%])to
control postharvest rots of pome fruits, gray
mold, blue mold
• Aspire (yeast) (Candida oleophila) to control
postharvest rots of citrus fruits, green mold

57. Thank you