Major diseases of Sesamum

1. DISEASES OF SESAMUM
FARZANA HARIS
2017-20-002 1

2. 1.FUNGAL DISEASES
1. Charcoal rot
2. Powdery mildew
3. Stem and seedling blight
4. Wilt
5. Alternaria leaf blight
6. Leaf spot
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3. 1.Root rot/Stem rot/Charcoal rot
• Disease may appear at early or later stages of crop growth.
• Infected seeds when planted cause seedling infection and leads to seedling blight.
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4. 4

5. Symptoms
• In mature plants, the stem portion at the soil line shows dark brown lesions that
deepen and cause shredding and collapse.
• The disease symptom starts as yellowing of lower leaves, followed by drooping and
defoliation starting from base upwards.
• Blighting starts from margin of leaves and proceeds inward.
• Roots also shows rotting.
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6. • Black pinhead like pycnidia develop and cause premature splitting of pods.
• The rotten root and stem bear hard resting structures/sclerotia of the fungus.
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7. Pathogen
Macrophomina phaseolina(Anamorph)
Rhizoctonia bataticola(sclerotial stage)
• The fungus produce dark brown septate mycelium showing constrictions at the
hyphal junctions.
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8. Disease cycle
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9. Epidemiology
• The pathogen survives in seed, soil and as sclerotia in soil.
• High temperature(30°C or <)and continued dry condition followed by high moisture
favor disease development.
• The fungus spreads primarily through sclerotia/pycnidia seen in seed and through
wind borne or rain splashed conidia.
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10. Management
1.Use of healthy, disease free seeds.
2.Seed treatment
a. with fungicides like captan/thiram(4g/kg) or carbendazim(2g/kg)
b. with Trichoderma viride @4g/kg seed.
3.Application of FYM @10T/ha or neemcake 250kg/ha
4.Clean cultivation by destroying infected crop debris.
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11. 5.Roguing of severely infected plants and spot drenching with carbendazim (0.5g/L
or 0.05%)
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12. 2.Powdery mildew
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13. Symptoms
• Greyish white powdery patches appear initially on upper surface of leaves in the
form of circular spots.
• Later it covers the entire surface of leaves,flowers,capsules and stem.
• In extreme severe condition stem and leaves get malformed.
• The coating changes to shades of dark brown/black due to development of sexual
fruiting bodies/cleistothecia.
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14. Pathogen
Erysiphe cichoracearum
Fruiting body of Erysiphe cichoracearum
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15. Disease cycle
• The Pathogen is an obligate parasite and disease perennates through cleistothecia in
the infected plant debris in soil.
• The ascospores from the cleistothecia cause primary infection.
• The secondary spread is through wind-borne conidia.
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16. Epidemiology
• Dry humid weather and Low relative humidity are the favourable conditions for the
spread of disease.
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17. Management
1. Removal of infected plant/plant parts.
2. Spraying wettable Sulphur @2.5kg/ha or dusting at 25kg/ha at 25 days
intervals.
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18. 3. Stem and seedling blight/Phytophthora blight
• Affect the plants at any stage from seedling to flowering stages but especially
serious at the seedling stage.
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19. Symptoms
• Water soaked lesions appear at the base of stem near the soil line.This area
becomes black and encircles the base, causing girdling and death of the plants.
• Leaves are also water soaked and further spread causes withering of leaves.
• Other aerial parts like flowers, capsules and seeds are also affected.
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20. Pathogen
Phytophthora parasitica var.sesame
• The fungus produces non-septate, hyaline mycelium.
• The sporangiophores are hyaline and branched sympodially and
bear sporangia.
• The sporangia are hyaline and spherical with a prominent apical
papilla.
• The oospores are smooth, spherical and thick walled.
Cleared tissue of young fruit
showing hyphae
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21. Disease cycle
• The fungus can survive in the soil through dormant mycelium and oospores.
• The seeds also carry the fungus as dormant mycelium, which causes the primary
infection.
• Secondary spread of the disease is through wind-borne sporangia.
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22. Epidemiology
The predisposing factors are,
• Prolonged rainfall
• Low temperature (25˚C)
• High relative humidity (above 90 per cent)
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23. Management
1. Use of healthy seeds.
2. Seed treatment with captan or thiram at 2g/kg seed.
3. Avoiding continuous cropping of sesamum in the same field.
4. Roguing of infected plants and destruction of infected crop debris.
5. Spraying with fungicides like mancozeb,copper oxychloride etc@0.3-0.4%
immediately after the symptom development and repeating the application 2-3
times at fortnightly intervals.
6. Give 2-3 spray of zineb@2kg/L at fortnightly intervals starting with the first
appearance of the disease.
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24. 4.Wilt
The disease affects all stages of crop.
Fusarium wilt on passionfruit.
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25. Symptoms
• The disease appears as yellowing, drooping and withering of leaves.
• These symptom start from base and progress upwards.
• The plants gradually wither, show wilting symptoms leading to drying.
• The infected portions of root and stem show long, dark black streaks of vascular
necrosis.
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26. Pathogen
Fusarium oxysporum f.sp. sesami
• The fungus produces white/pink colored septate mycelium that later produces
asexual spores or conidia.
• Microconidia are single celled and falcate.
• Sometimes,chlamydospores are also produced.
microconidium and chlamydospore 26

27. Disease cycle
• The fungus survives in the soil in the infected plant debris.
• It is also seed-borne and primary infection occurs through infected seeds or through
chlamydospores in soil.
• The secondary infection may be caused by conidia disseminated by rain splash and
irrigation water.
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28. Epidemiology
The fungus requires warm moist environment.
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29. Management
1. Sanitation in the field involving collection and destruction of infected crop
debris,roguing of infected plants etc.
2. Use of clean and disease free seeds collected from healthy plants.
3. Seed treatment with captan/carbendazim@2g/kg seed.
4. Use of biological control agents like Trichoderma viride for seed
treatment@4g/kg seed
5. Application of FYM/green manure @10t/ha or neemcake 250kg/ha.
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30. 5. Alternaria leaf blight
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31. Symptoms
• Water soaked spots appear on leaves which gradually turn yellow and necrotic.
• The dead portions of leaf have concentric zonation spots that extend on leaf
petiole, resulting in severe defoliation.
• Stem and pods also show lesions and blighting. This causes breaking of stem and
premature bursting of capsules.
• Seeds are shrivelled.
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32. Pathogen
Alternaria sesami
The mycelium of the fungus is dull brown and septate
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33. Disease cycle
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34. Epidemiology
• Low temperature (20-25˚C)
• High relative humidity
• Cloudy weather
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35. Management
1. Destruction of infected crop debris.
2. Seed treatment with carbendazim 2g/kg seed.
3. Foliar spraying with mancozeb 0.2-0.4% at fortnightly intervals.
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36. 6. Leaf spot
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37. Symptoms
• The disease first appears on the leaves as minute water-soaked lesions, which
enlarge to form round to irregular spots of 5-15 mm diameter on both the leaf
surface.
• The spots coalesce to form irregular patches of varying size leading to premature
defoliation.
• The infection is also seen on stem and petiole forming spots of varying lengths.
• Dark linear spots also occur on pods causing drying shedding.
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38. Pathogen
Cercospora sesami
Cercospora sesamicola
The hypha of the fungus is irregularly septate, light brown and thick walled.
Conidia are elongated, broad at the base and tapering towards the apex.
Conidiophore of Cercospora
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39. Disease cycle
• The fungus is externally and internally seed-borne.
• The fungus also survives in plant debris.
• Primary infection may be from the seeds and infected debris.
• The secondary spread is through wind-borne conidia.
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40. Management
• Grow resistant/tolerant variety like TKG-21.
• Early planting i.e. immediately after onset of monsoon.
• Follow intercropping system of sesamum + pearl millet (3:1)
• Destruction of plant debris.
• Treat the seeds with Carbendazin or Thiram at 2g/kg.
• Spray with Mancozeb at 2kg/ha.
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41. 2.BACTERIAL DISEASES
1. Bacterial leaf spot
2. Bacterial blight
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42. 1. Bacterial leaf spot
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43. Symptoms
• The disease appears as water-soaked yellow specks on the upper surface of the
leaves.
• They enlarge and become angular as restricted by veins and veinlets. The color of
spot may be dark brown with shiny oozes of bacterial masses.
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44. Pathogen
Pseudomonas sesami
The bacterium is gram negative aerobic rod with one or more polar flagella.
Disease cycle
The bacterium remains viable in the infected plant tissues. It is internally seed borne
and secondary spread through rain splash and storms.
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45. Epidemiology
The bacterium is seed borne and soil borne.Therefore,secondary spread is through
rain splash and wind.
Management
1. Use of disease free seed.
2. Crop rotation atleast for 3 years.
3. Spraying 0.3% copper fungicides or antibiotics like streptomycin sulphate
@100g/ha
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46. 2. Bacterial leaf blight
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47. Symptoms
• Small water soaked spots develop in the cotyledons of seedlings that are
germinated from infected seeds.
• On mature plants,dark brown to black angular spots develop on the leaves and
later spots enlarge and coalesce to cause leaf blight.
• The blighted leaves are shed prematurely
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48. Pathogen
Xanthomonas Sesami
The bacterium is a Gram negative rod with a monotrichous flagellum.
Disease cycle
• The bacterium survives in the infected plant debris and in seeds.
• The secondary spread is by rain water.
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49. Management
1. Remove and burn infected plant debris.
2. Seed treatment with Agrimycin(0.025%) for 9h.
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50. VIRAL DISEASE-Leaf curl
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51. Symptoms
Downward curling of leaves is the most conspicuous symptom.
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52. Pathogen
Sesamum leaf curl virus
Vector:Bemisia tabaci(Tobacco whitefly)
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53. Management
1. Soil application of phorate 10G@10kg/ha
2. Spraying with metasystox 25EC@1ml/L
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54. SESAMUM PHYLLODY-Phytoplasma
• Phyllody is used to denote a condition where in the all floral parts are transferred
to green leafy structures.
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55. Symptoms
• The symptoms starts with vein clearing of leaves .
• The disease manifests itself mostly during flowering stage, when the floral parts
are transformed into green leafy structures, which grow profusely.
• The flower is rendered sterile.
• The veins of phylloid structure are thick and prominent.
• The plant is stunted with reduced internodes and abnormal branching.
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56. Pathogen
• It is caused by pleomorphic mycoplasma like bodies present in sieve tube of
affected plants, now designated as a phytoplasmal disease.
• The vector,Orosius albicinctus (leaf hopper)transmits this disease.
Orosius species
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57. Management
1. Roguing of infected plants in the field as soon as the symptoms are noticed.
2. Apply metasystox 25EC@1ml/L water or malathion 50EC(1ML/l)
3. Delaying sowing time reduces the incidence of the disease.
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58. REFERENCE
• Diseases of crop plants and their management
By: Peethambaran
Publisher: Thiruvanathapuram Kerala Agricultural University 2011
• AESA based IPM – Sesame
By:NIPHM,Hyderabad
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