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:
bacterium Clavibacter
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
Surrounding environment
Temperature
Relative humidity
Chilling injury
Mechanical injury
pH of the produce
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:
Nature of disease
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 Modified atmosphere
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