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
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
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
16.
17.
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
19.
20.
21.
22. Stem end rot
Water soaked areas
Brown to black color
Cause:
Phomopsis sp.
23.
24.
25.
26. Sour rot
Symptoms include a soft watery rot with leakage of berry juice,
and a distinctive vinegar smell
Cause:
Colletotrichum candidum
Under investigation
27.
28.
29.
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
31.
32.
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
34.
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
36.
37.
38.
39. Alternaria rot
more or less round, brown to black lesions
weakened tissue
Cause:
Alternaria spp.
40.
41.
42.
43.
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.
45.
46.
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
48.
49.
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
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
