DISEASES OF SESAMUM.pptx

Major diseases of Sesamum

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

2. 1.FUNGAL DISEASES Charcoal rot Powdery mildew Stem and seedling blight Wilt Alternaria leaf blight Leaf spot 2

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. 3

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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. 5

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. 6

7. Pathogen Macrophomina phaseolina (Anamorph) Rhizoctonia bataticola (sclerotial stage) The fungus produce dark brown septate mycelium showing constrictions at the hyphal junctions. 7

8. D isease cycle 8

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. 9

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. 10

11. 5.Roguing of severely infected plants and spot drenching with carbendazim (0.5g/L or 0.05%) 11

12. 2.Powdery mildew 12

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. 13

14. Pathogen Erysiphe cichoracearum Fruiting body of Erysiphe cichoracearum 14

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. 15

16. Epidemiology Dry humid weather and Low relative humidity are the favourable conditions for the spread of disease. 16

17. Management Removal of infected plant/plant parts. Spraying wettable Sulphur @2.5kg/ha or dusting at 25kg/ha at 25 days intervals. 17

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. 18

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. 19

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 20

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. 21

22. Epidemiology The predisposing factors are, Prolonged rainfall Low temperature (25˚C) High relative humidity (above 90 per cent ) 22

23. Management Use of healthy seeds. Seed treatment with captan or thiram at 2g/kg seed. Avoiding continuous cropping of sesamum in the same field. Roguing of infected plants and destruction of infected crop debris. Spraying with fungicides like mancozeb,copper oxychloride [email protected]% immediately after the symptom development and repeating the application 2-3 times at fortnightly intervals. Give 2-3 spray of zineb@2kg/L at fortnightly intervals starting with the first appearance of the disease. 23

24. 4.Wilt The disease affects all stages of crop. Fusarium wilt on passionfruit. 24

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. 25

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. 27

28. Epidemiology The fungus requires warm moist environment. 28

29. Management Sanitation in the field involving collection and destruction of infected crop debris,roguing of infected plants etc. Use of clean and disease free seeds collected from healthy plants. Seed treatment with captan/carbendazim@2g/kg seed. Use of biological control agents like Trichoderma viride for seed treatment@4g/kg seed Application of FYM/green manure @10t/ha or neemcake 250kg/ha. 29

30. 5. Alternaria leaf blight 30

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 . 31

32. Pathogen Alternaria sesami The mycelium of the fungus is dull brown and septate 32

33. Disease cycle 33

34. Epidemiology Low temperature (20-25˚C ) High relative humidity Cloudy weather 34

35. Management Destruction of infected crop debris. Seed treatment with carbendazim 2g/kg seed. Foliar spraying with mancozeb 0.2-0.4% at fortnightly intervals. 35

36. 6 . Leaf spot 36

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. 37

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 38

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. 39

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. 40

41. 2.BACTERIAL DISEASES Bacterial leaf spot Bacterial blight 41

42. 1. Bacterial leaf spot 42

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. 43

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. 44

45. Epidemiology The bacterium is seed borne and soil borne.Therefore,secondary spread is through rain splash and wind. Management Use of disease free seed. Crop rotation atleast for 3 years. Spraying 0.3% copper fungicides or antibiotics like streptomycin sulphate @100g/ha 45

46. 2. Bacterial leaf blight 46

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 47

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. 48

49. Management Remove and burn infected plant debris. Seed treatment with Agrimycin (0.025%) for 9h. 49

50. VIRAL DISEASE-Leaf curl 50

51. Symptoms Downward curling of leaves is the most conspicuous symptom. 51

52. Pathogen Sesamum leaf curl virus Vector: Bemisia tabaci (Tobacco whitefly) 52

53. Management Soil application of phorate 10G@10kg/ha Spraying with metasystox 25EC@1ml/L 53

54. SESAMUM PHYLLODY- Phytoplasma Phyllody is used to denote a condition where in the all floral parts are transferred to green leafy structures. 54

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. 55

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 56

57. Management Roguing of infected plants in the field as soon as the symptoms are noticed. Apply metasystox 25EC@1ml/L water or malathion 50EC(1ML/l) Delaying sowing time reduces the incidence of the disease. 57

58. REFERENCE D iseases of crop plants and their management By: Peethambaran Publisher: Thiruvanathapuram Kerala Agricultural University 2011 AESA based IPM – Sesame By:NIPHM,Hyderabad 58

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