Diseases of sorghum and their management

Diseases of sorghum and their management

1. PRESENTATION ON DISEASES OF SORGHUM 9/19/2024 1

2. SORGHUM ( Sorghum bicolor L ) INTRODUCTION Sorghum is the world's fifth-most important cereal crop after rice, wheat, maize, and barley. Jowar or Great millet is an important food and fodder crop of India. Grown in tropical to subtropical regions of the world. India ranks second (21.5 percent), after The United States (25 percent) in production. Originated in North East Africa . About 50 diseases of sorghum are known, and around 30 diseases found in India Only 10 are of Economic importance. 9/19/2024 2

3. DISEASES OF SORGHUM a. Fungal diseases SL. NO. DISEASE CAUSAL ORGANISM 1. Grain Smut Sporisorium / Sphacelotheca sorghi 2. Head smut Sorosporium relianum 3. Long smut Tolyposporium ehrenbergii 4. Loose smut Sporisorium cruenta 5. Rust Puccinia purpurea 6. Downy Mildew/ leaf shredding disease Perenosclerospora sorghi 9/19/2024 3

4. SL. NO. DISEASE CAUSAL ORGANISM 7. Crazy top downy mildew Scleropthora macrospora 8. Ergot( Sugary disease ) Claviceps sorghi Sphacelia sorghi 9. Fusarium Stalk rot Fusarium moniliformae 10. Charcoal rot Macrophomina phaseolina 11. Cereal grain mold /Head mold Fusarium semitectum F.moniliformae Curvularia lunata 12. Anthracnose /Red Rot Colletotricum graminicola 9/19/2024 4

5. 13 . Leaf blight / stripe Exserohilum turcicum 14. Tar spot Phyllachora sacchari b. Bacterial and viral disease 1. Bacterial leaf spot or Bacterial leaf stripe Pseudomonads andropogonis Burkholderia andropogonis 2. Sugarcane Mosaic disease Sugarcane mosaic virus and sorghum mosaic virus c. Phanerogamic parasite Straiga or witch weed.( Striaga asiatica and Striaga densiflor ) 9/19/2024 5

6. Grain Smut: Sporisorium / Sphacelotheca sorghi It is also called as Covered smut, Kernel smut, and Short smut . Most common and destructive disease 25% of plants usually get infected. In the world it is present in – Asia, Australia, the USA, and Sri Lanka. Covered smut of sorghum was first time registered in Russia in 1890. In India- TN, Kar, AP, Gujarat, UP, MP. 9/19/2024 6

7. Taxonomic position Perfect stage: Sporisorium ( Sphacelotheca ) sorghi Phylum: Basidiomycota Class: Ustilaginomycetes Order : Ustilaginales Family: Ustilaginaceae Genus: Sporisorium ( Sphacelotheca ) Species: sorghi 9/19/2024 7

8. Symptoms Infected plants appear normal till the time of flowering. Grain is replaced by an oval or cylindrical, dirty grey sorus. Size of the sori larger than normal grains . Sori are oval to cylindrical 5- 15 mm long, 3- 5 mm broad dirty greyish in colour. Sori: fruiting body in which a mass of spores are produced . 9/19/2024 8

9. Sori consists of a tough membrane (peridium), long hard, central tissue called columella . Columella is made up of host tissues consisting of parenchyma and fibrous vascular bundles. Sometimes, the columella is branched at the tip Glumes are unaltered and may be found adhering to the sides of sorus . Stamens normally protruding out of the sorus. High incidence in Ratoon crops. 9/19/2024 9

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11. Etiology Sporisorium sorghi ( Spacelotheca sorghi ) Sorus is tough walled, hard, short collumella -central tissue . Dense Mass of black to dark brown smooth thick walled, single-celled spores. Measuring 5 - 9 mm in diameter fills the space between columella and peridium. On germination of smut spores. 4 celled promycellia are formed. On Which lateral and terminal sporidia are formed. Secondary sporidia is by budding . In culture, appears yeast-like growth with sporidia . Spores remain viable for more than 10 years. 9/19/2024 11

12. Epidemiology Externally seed borne spores germinate with seeds. Smut sori are broken during threshing and get lodged on the surface of the seeds. Remain dormant until the next season and germinate along with the germination of seeds. Infection: Seedling infection through radicle or mesocotyl. Systemic infection . Hyphae acculate in the immature ovary, smut spores are formed completely in the ovary converting into smut sori . Conditions: temp 25⁰C, medium to low soil moisture. 9/19/2024 12

13. Management Use of disease-free seeds and cobs. Crops sown early in the season i.e. by early June usually escape disease incidence. Solar heat treatment : The seeds are soaked in cold water for 4 hours . Then the seeds are dried under direct sunlight. The spores, which have initiated the germination process, are killed by direct exposure to sunlight. Seeds are immersed in 0.5% Formalin for 2 hours and dried quickly Alternatively treated in 0.5 -3% CuSo4 solution for 10 min then dried and sown. 9/19/2024 13

14. Use of host plant resistance : Milo, Hageri , Feterita , shantung carries a resistance gene. Resistant varieties. CSH.5, CSH.7-R, CSH.9, RSV.1-R, SDM.9, SPL.102, SPV.115, SPV. 138, SPV.245, SPV.297, T.29/1, PJ.7 K, PJ.23 K, Nandyal and Bilichigan are resistant to this disease. Seed treatment with sulfur @4 g /kg of seeds . Thiram or Copper Carbonate or captan @2-4 g/kg of seeds. Carboxin or Vitavax - 2g/Kg of seed . 9/19/2024 14

15. 2. Head Smut: Sphacelotheca reiliana The Head smut of sorghum was found in Russia for the first time in 1911. The disease has been reported from Madhya Pradesh, Andhra Pradesh, Maharashtra, and Uttar Pradesh states of India. Symptoms The inflorescence is totally destroyed in the infected plants. Infected plants appear normal till the time of flowering. In rare cases, partial damage has been seen. The entire inflorescence is converted into a big sorus about 10-13 cm in length, 4-6 cm in breadth. A thin white membrane encloses the sorus in its early stages but during emergence through the boot leaf, the membrane is ruptured and is exposed . 9/19/2024 15

16. Columella is absent but a network of vascular tissue is present. At harvest time only a thin network remains and spores dispersed by wind. Normal inflorescence replaced by sorus, fully covered with greyish-white membrane emerges from the boot leaf. Infects leaves and stalk causing inflorescence prolification and leaves rosette. Airborne spores resemble a smoky cloudy around the head . 9/19/2024 16

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18. Etiology Sorosporium relianum . Angular to spherical, dull brown with minutely papillated spore wall and 10 -16 mm in diameter . Teliospores gathered easily in glomerules and sprout into 3–5 celled basidia (laterally and apically growing into sporidia). Spores survive upto 2 year . Infection takes its origin from infected ground (soil borne) and seeds . 9/19/2024 18

19. Epidemiology Infection at the time of flowering . Pathogen may be externally seed-borne . Soil borne: young seedling infection at a temperature of about 21- 28⁰C . Moisture content 15 -25%. Systemic infection.. Covering of entire floral tissue converted into sorus . Green fodder yield loss up to 19 - 34%. The survival of the spores in soil depends on soil temp and soil moisture . There will be more disease at relatively high soil temp (25⁰C) and low soil moisture than in wetter and cooler soils. Crops retained in clay loam soils which have higher soil moisture than in silty or sandy loam soils. 9/19/2024 19

20. Management Collect smutted heads in paper bag and dip in boiling water to reduce inoculum potential for the following crops. Seed treatment with Carboxin @ 2g /kg of seeds . Sanitation Crop rotation Rouging of affected plants in the field Seed treatment- captan @ 2g/kg of seed . 9/19/2024 20

21. 3 .Long Smut : Tolyposporium ehrenbergii Long smut has been reported in Africa and Asia. In India, it occurs in Tamilnadu , Karnataka, Telugu Desam, Maharashtra, Madhya Pradesh, and Uttar Pradesh. Symptoms: Relatively small portion of florets infected. Infection during booting leaf stage . Individual and only a few grains are transformed into smut sori . Spore mass is cylindrical, elongated, slightly curved with relatively thick creamy brown membrane . Sorus consists of a thick membrane and Columella absent . Sori longer than other 2 smuts . Measuring 4 cm in length 6-8 mm in width . 9/19/2024 21

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23. Etiology Tolyposporium ehrenbergii Sori filled with black spore masses of spores, also contain 8 -10 dark filaments structure arising from the vascular tissue of the ovary . Spores are firmly United into balls . Spore germinate without rest period Viable for 2 years . 9/19/2024 23

24. Epidemiology Primary infection: soil-borne spores germinate to produces a cluster of sporidia that is spread through air . Secondary infection: By spores released from smutted ears . May settle or germinate in water drops accumulate at flag leaf sheath . Infect the opening spikelets in the panicle during later season. 9/19/2024 24

25. Management Since the inoculum is air borne seed treatment is of no use . Adjusting sowing dates. Early sowing of the crop reduces disease incidence. Crop rotation. Avoid rationing. Collecting earheads in cloth bags and dipped in boiling water. In Tamil Nadu, “Irungu cholam ” is found to be free from infection, as the glumes cover the floral parts completely. 9/19/2024 25

26. 4. Loose smut- Sporisorium cruenta It is not as common as the grain smut in most of the sorghum growing areas. It closely resembles the grain smut in its appearance . Disease reported from China, Iran, Southern Europe, Africa and the USA. In India-AP, MH, Kar, TN. The effects of the smut are not only on the grain but also on the plant growth. The grain as well as fodder yield may be reduced. 9/19/2024 26

27. Symptoms : Infected plants are stunted with thin stalks and more tillers . Early flowering, all the spikelets of the head are affected. Sori length 3 -18 mm, 2-5 mm wide, solid, long, black oftently curved pointed collumella which extend almost the length of the sorus. Collumella remains as conspicuous after spores have been blown away. The membrane of the sori ruptures easily. Apparent at the time of florescence. Fully covered with greyish white membrane, emergences from the boot leaf. 9/19/2024 27

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29. Etiology : Sporisorium cruenta Collumella bigger, longer more curved,smut spores are spherical to elliptical, dark brown . Spores measure about 5 - 10 mm in diameter . Remain viable for nearly 4 year. Resting spores remain over 3 months . 9/19/2024 29

30. Epidemiology Disease cycle : Externally Seed borne inoculum. Soil borne in dry soil . Enters into the plant through radical mesocotyl or epicotyl, Systemic infection. Smutting of ovaries at the time of ear formation. Optimum temp for spore germination and subsequent infection is 30⁰C . Soil temperature- 18-23°C. Soil humidity- 15-20%. In culture, colonies form with sporidia . 9/19/2024 30

31. Management Treat seeds with Sulphur @ 4 g / kg of seeds. Thiram and Copper Carbonate at 2-4 g / kg of seeds . Resistance Varieties : Milo and Feteria . Avoid ratooning. 9/19/2024 31

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33. 5. Rust : Puccinia purpurea Rust is a severe disease of sorghum where the crop is grown all over. In India, causing extensive damage in both dryland and irrigated crops. It is common in sorghum-growing regions like Africa, Asia, South America, and North America. Early sown crops escape rust infection , while observed mainly in late sown crops. Purple pigmented sorghum is generally susceptible to Rust. (Singh et.al., 1994). 9/19/2024 33

34. Symptoms : At all stages of crop growth, an infection common in 2 month old crop. Upper leaves are more severely affected than lower. Rust pustules appears on both surfaces of leaves , the upper side severely infected. Reddish brown pustules are minute, elliptical, 1-2 mm in diameter. Reddish brown to black telia on the lower surface of the leaves. 9/19/2024 34

35. Older leaves dry prematurely. Stunted growth is seen. In susceptible varieties pustules cover entire leaves and whole leaves tissue is destroyed. Initially pustule contains reddish powdery mass of uredospores . Later stage teliospores are of longer and darker than uredosopres are formed . 9/19/2024 35

36. Taxonomic position Perfect stage : Puccinia purpurea Phylum: Basidiomycota Class : Pucciniomycetes Order : Pucciniales Family : Pucciniaceae Genus : Puccinia Species : purpurea 9/19/2024 36

37. Etiology Causal Organism : Puccinia purpurea . Both the Uredial and telial stages are seen . Uredospores : singly on stalk, oval or elliptical, dark brown echinulate 27-43 mm in diameter, short lived. Teleutospores : Formed both in older uredo sori and telio sori, long stalks or pedicels, reddish brown 2-celled. Measuring 40-50 ×22 -30 mm Germinates readily. Retains viability for many months. 9/19/2024 37

38. Epidemiology Disease cycle : Fungus is long cycled rust with Oxalis corniculate as the alternate host with pycnial and aecial stages. Uredospores survive for a short time in soil and plant debris . Secondary spread: Airborne uredospores . The teliospores germinate and produce promycelium and basidiospores. Basidiospores infect Oxalis . Low temperature of 10 – 12 °C favours teliospore germination, a spell of rainy weather favours the onset of disease. Yield loss from 29 - 69% under certain conditions .( Bandyopadhyaya ,1986 ; Hepperely ,1990). 9/19/2024 38

39. Management Dust sulphur at 35 days after sowing ( 20kg/ ha ) Repeat twice at 10-day interval (25 – 35 kg/ha). Spray Tridemorph after 35 days of sowing @ 5 -7 ml/ litre of water. Repeats at 10 days intervals. Spray Mancozeb 1 kg/ha . Repeat application after 10 days. Remove and destroy the alternate host Oxalis corniculata Grow resistance Varieties: CH5, SPV 13,81, 126, PSH 1, CSV -17 . Oxalis corniculata 9/19/2024 39

40. 6. Downy Mildew or Leaf shredding disease: Peronosclerospora sorghi First reported by Butler from India ( Butler,1907) Occurrence in many Asian and African countries and Italy. Incidence is more in fodder sorghum than grain stage. Later reported in tropical and sub-tropical zones. In India- TN, AP, Kar, MP, MH and UP. Prevails more in the Delta region of Andra Pradesh. 9/19/2024 40

41. Symptoms : Symptoms vary depending upon the growth stage of the crop at which infection occurs. Primary or systemic infection: seedling stage Affected seedlings have pale yellow, narrow leaves covered with downy growth consisting of sporangia. Abundant Downy white growth is produced on the lower surface of leaves. White streaks on leaves of 5-6 old seedlings, later brown streak or necrosis due to the formation of oospores in vascular bundles of the leaves. 9/19/2024 41

42. Later chlorotic streaks developed on upper surface of leaves and turn to brown on advanced condition - leaf Shredding symptoms- tear along the veins( after oospore formed in the vascular bundles.) Infection at early Stage : No ear head formation . Infection at later stage : older leaves shed and younger leaves remain normal. Occasionally green ear symptoms. Infected parts are stunted and sterile . In the standing crop the healthy plants are infected due to secondary infection by Sporangia to 60-70 days old plants . 9/19/2024 42

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44. Etiology Causal Organism: Sclerospora sorghi (Recent- Perenosclerospora ) Phylum- Oomycota Class- Oomycetes Order – Sclerosporales Family – Sclerosporaceae Genera – Sclerospora (8 genera) Species: sorghi 9/19/2024 44

45. Systemic in young host plant. Obligate parasite. Intercellular, non septate present in parenchyma tissue of the roots, stem, and mesophyll tissue of the leaves. Draws nutrient from haustoria. Sporangiophore: Young stout with many upright branches. Sporangia bears at tip. Direct germination of sporangia. Sporangia –hyaline, globose 15-29 µ diameter Sexual Spores : Thick-walled oospores formed in the interveinal space of mesophyll of leaves .Remains viable for 3 or more years. 9/19/2024 45

46. Epidemiology Primary source of inoculum: Soil-borne oospores, Dormant mycelium, and oospores in seeds. Secondary source of inoculum: Air borne sporangia . Fungus attacks maize but not Bajra and Ragi Weeds. Temperature: 21 - 25 ° C. High moisture (Humid conditions) and high organic matter increase disease incidence. Relative humidity : 98%, light drizzling and cool weather . 9/19/2024 46

47. Management Deep tillage, deep ploughing, and burying the crop . debris to reduce soil-borne infection. Crop rotation- pulses and oilseeds. Roughing of infected plants at an early stage. Adjusting of sowing dates. Seed treatment with Metalaxyl ( 4% )+ Mancozeb 64% WP ( Ridomil gold) @ 4 g / kg of seeds + foliar spray @ 2 g / litre of water at 30, 40, and 50 days after sowing . Ressistence Genotype: QL - 3 Tolerant varieties : CSH 2, CSV 5, SPV 101, 165 and 190. 9/19/2024 47

48. 7. Crazy top downy mildew- Scleropthora macrospora . Symptoms: Young sorghum plants develop mottle leaves resembling mosaic virus infection. Subsequently leaves turn thick, stiff, twisted, and curled, Yellow occurs later. Occurs in fields in low spots where water stands. No leaf Shredding occurs . Infected plant tillers profuse, and usually survive without producing grains. 9/19/2024 48

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50. Causal Organism: Scleropthora macrospora . Soil borne infection. Entire head replaced by leaf material. It mimics with Zn deficiency symptoms . Sometimes confuses with herbicide injury . Occurs where standing water in the field prevails for a longer time . Submersion of top leaves shows crazy top symptoms . 9/19/2024 50

51. Management Deep tillage, deep ploughing, and burying the crop . debris to reduce soil-borne infection. Crop rotation- pulses and oilseeds. Roughing of infected plants at an early stage. Adjusting of sowing dates. Seed treatment with Metalaxyl ( 4% )+ Mancozeb 64% WP ( Ridomil gold) @ 4 g / kg of seeds + foliar spray @ 2 g / litre of water at 30, 40, and 50 days after sowing . Ressistence Genotype: QL - 3 Tolerant varieties : CSH 2, CSV 5, SPV 101, 165 and 190. 9/19/2024 51

52. 8. Ergot( Sugary disease )- Claviceps sorghi Sphacelia sorghi Mc.Rae first described this disease from Tamil Nadu . Infected spikelets start exudating small droplets of pinkish or light honey-coloured fluid called the Honeydew stage . It starts after 1 – 2 weeks after flowering . CK 60 A male sterile line is highly susceptible. In South India prevalent during Oct to January when cold weather prevails at crop maturity. Alkaloids: Ergotoxin ( holy fire, st. antonys fire- Ergotism), Ergometrine, Ergotamine. 9/19/2024 52

53. Symptoms The disease is confined to individual spikelets . Secretion of honeydew (creamy sticky liquid) from infected florets. The honey dew secretion attracts large number of insects and ants which help in spreading the disease. Often the honeydew is colonized by Cerebella sorghivulgaris which gives the head a blackened appearance. Under favorable conditions, grain is replaced by long (1-2cm), straight or curved, cream to light brown, hard sclerotia. At the base of the affected plants white spots can be seen on the soil surface, denoting the drops of honey dew which had fallen on the soil. 9/19/2024 53

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55. Etiology Casual Organism : Claviceps sorghi ( Spaceolotheca sorghi ) Phylum –Ascomycota Class- Pyrenomycetes Order- Hypocreales Family- Clavicepitaceae Genus – Claviceps 3 stages : Sphacelia or honeydew stage: which represents the conidial stage. Sclerotial - resting stage. Ascogenous or perithecial stage. 9/19/2024 55

56. Sclerotial bodies contain alkaloids like ergotin , ergotamine, ergometrine. Fungus is septate mycelium. Honey dew is concentrated conidia that are single-celled, hyaline, elliptical, or oblong in shape. Slightly constricted in the middle. Sclerotial bodies produced by the fungus are 10 - 12mm long and 2mm thick, hard and tough Perithecial stage. 9/19/2024 56

57. Epidemiology PSI: Scelotial bodies mixed with seeds or fallen on soil germinate and produce ascospores which infect the ovary. Secondary spread through air and insect-borne conidia which is settled in spikelets and rain flashes . Coincidence of germination of sclerotial bodies with anthesis stage of crop. Air bone spores infect spikelets . 9/19/2024 57

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59. Management Adjust the sowing time. Grow resistant varieties like GMRP 4, GMRP 9, GMRP 13 and tolerant varieties like CSV 15. Seed disinfestation with [email protected]% will prevent seedling infection. Spray Mancozeb (0.25%) or captan (0.2%) or captan 2g + Aureofungin 200ppm per liter , in case of intermittent rainfall during earhead emergence, a week later, and during the milky stage. 9/19/2024 59

60. 9. Fusarium Stalk rot : Fusarium moniliformae Symptoms: Significant lodging may or may not occur. Reduced head size and stalk deterioration . Infects roots, crown, and internodes. Shredded inner stalk, tissue color turns to purple, red, and tan . Severe in low land tropical areas. Symptoms during the senescence phase i.e. , kernels are in the blister stage to the stage when dry matter is maximum . 9/19/2024 60

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62. 10. Charcoal rot: Macrophomina phaseolina The same shredded appearance as Fusarium occurs, but black dusty discolouration is present. Plant dry prematurely, disintegration of pith with straw-coloured internodes . Small pin head-like black colour pycnidia on the infected rind of the stalk. Prevalent in drier water stress areas with higher temperature of ( 37°C) during grain filling stages. High application of Nitrogen fertilizers. Survives in plant debris 9/19/2024 62

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64. Management Choose good hybrids with good roots and stalk length, stay green characteristics and post freeze lodging resistance . Reducing seedling rates, especially for charcoal rot. Too thick stands promote thinner stalks, leads to lodging Use no-till to increase soil moisture availability. Balance soil fertility of Pottasium and Chloride . 9/19/2024 64

65. Avoid excess nitrogen, Manage stress factors viz, compaction, plant population, weeds, herbicides , stress. Timely harvest, crop rotation with paddy or wheat. Seed treatment with Carbendazim or Thiram @ 3g/kg of seeds Psuedomonas straita @ 25g/kg + Trichoderma harzianum @ 6 g / kg of seeds. 9/19/2024 65

66. 11. Cereal grain mold /Head mold On improved short and medium-duration cultivars that mature during the rainy season under humid climatic conditions. Late maturing Varieties escape grain mold . Disese severe in India because of cultivation of white grain, bold-seeded hybrids, and Varieties. Severe implication on grain quality and productivity . Symptoms : Fusarium semitectum and F.moniliformae , Grain infected with these fungi develop a fluppy white or pinkish colouration. Curvularia lunata colors the grain black. Etiology : Many fungi genera infected from sorghum seeds include Fusarium, Curvularia , Alternaria, Aspergillus, Chaetomium, Phoma , Rhizopus, and Helminthosporium . 9/19/2024 66

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68. Disease cycle: Spread through air borne conidia. Fungi survive as parasites as well as saprophytes in the infected plant debris. Wet weather following the flowering favors mold grain development and the longer the wet period greater the mold development . Compact earhead more susceptible . Management: Grow resistance var. GMRP 4 GMRP 9 tolerant Varieties CSV 15.Red and Bronze grains have more resistance due to higher tannin levels . Seed disinfection with thiram @0.3% to prevent seedling infection . Spray Mancozeb( 0.25%) or Captain ( 0.2%), Captain 2 g+ Aureofungin 200 ppm per litre in case of intermittent rainfall during earhead emergence, a week later, and during the milky stage. 9/19/2024 68

69. 12. Anthracnose /Red Rot : Colletotricum graminicola First reported from Togo West Africa. In India, it occurs on forage Sorghum in moderate to severe form and sporadically on grain Sorghum . Northern and Western India on forage Sorghum, in Central and Southern India on grain Sorghum. Symptoms : small red colour spots on the leaf . Whitish centre encircled by red, or purple, brown margin . Numerous black spots are seen on the white surface which are fruiting bodies ( acervuli ). Many lesions coalesce and kill the large leaf portion. 9/19/2024 69

70. In the midrib region elongated elliptical red or purple regions with black acervuli are formed. 9/19/2024 70

71. Etiology Causal Organism : Colletotricum graminicola (anamorph) Syn : Glomerella graminicola ( telomorph ) Mycellium of the fungus localized in the spot. Acervuli with setae arise through epidermis . Conidia are hyaline, single celled, vacuolate and fulcated . 9/19/2024 71

72. Disease Cycle: primary infection, inoculum present in seeds, collateral host like Maize, Wheat, Barley, Johnson grass, Sudan grass. Secondary infection: Wind-borne Conidia . Management: Destruction of plant debris and collateral hosts. Crop rotation, Grow resistance var, SPV 162, CSV 17, Texas, Milo, Tift Sudan . Treat seeds with Captain or Thiram @ 3 g / kg of seeds. Spray the crops with Mancozeb @0.25 % and Carbendazim @ 0.1 %. 9/19/2024 72

73. 13. Leaf blight/stripe: Exserohilum turcicum Symptoms: Long elliptical necrotic lesions, straw coloured in the centre with dark margins . Straw coloured centre becomes darker with sporulation . Lesions coalesce entire leaves like burnt appearence , leading to premature drying of leaves. Same pathogen also causes seed rot or seedling blight of sorghum . Appears in the form of small narrow elongated spindle shaped spots in initial stage. 9/19/2024 73

74. Etiology : Causal Organism, Excerohilum turcicum or ( Trichometasphaeria turcica) Syn : Helminthosporium tursicum , Dresclera tursicum Conidiophores emerge through stomata and are long, olivicious , septate geniculate. Conidia olivious brown 3 - 8 septate and thick-walled . 9/19/2024 74

75. Disease Cycle: The fungus found to persist in seeds, soil, infected plant debris. Seed borne conidia responsible for seedling infection. Secondary spread: wind borne conidia and seeds. Cool moist weather, high humidity( 90%) and high rainfall . Management: Use of disease free seed , and crop rotation. Treat seeds with Captain or Thiram @ 4 g / kg of seeds . Spray Mancozeb @ 0.25% at the age of 40 days. Repeated twice at 15 days intervals. Tift Sudan’s resistance to disease. 9/19/2024 75

76. 14. Tar spot: Phyllachora sacchari Physical fruiting body, ascomata developing on the leaf. Larger necrotic spots develop on ascomata, originating from water soaked brown lesions, with brown rings . Creating the fish-eye symptom . Spreads from lowest leaves to upper leaves, leaf sheath, and husk of the developing ear. 9/19/2024 76

77. b. Bacterial disease 1. Bacterial leaf spot or Bacterial leaf stripe Pseudomonads andropogonis Smith ( stapp) Burkholderia andropogonis Smith Gillis et.al Initially lesions are small ( 1 cm long), interveinal lesions . Lesions are red, purple, and yellow depending reaction of a host . Water-soaking tissue not observed in field conditions. Lesions occur on the kernel, peduncle, rachis, pith of stalks. 9/19/2024 77

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79. 2. Viral disease Sugarcane Mosaic disease Sugarcane mosaic virus and sorghum mosaic virus . Mosaic symptoms, necrotic stripe on leaves SCMV sub group viruses are of potyvirus genus . Alternate host: Johnson grass, setaria grass . Spreads through aphids, infected seeds, and mechanical inoculum . 9/19/2024 79

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82. c. Phanerogamic parasite Straiga or witch weed. ( Striaga asiatica and Striaga densiflor ) Symptoms: yellowing and wilting. Stunted may die prior to seed setting. Parasite grows faster and appears at the base of the plant . Etiology It is a partial root parasite, attached to the host root by haustorium. Grow below the soil surface and produce under ground stems and roots for about 1-2 months . Disease Cycle: infection through seeds present in soil. Soil temperature of 35°C and moisture 30% are favourable. 9/19/2024 82

83. Management : Hand weeding before parasite flowers . Crop rotation with Cowpea, Groundnut, and Sunflower . Mixing of ethrel with soil triggers germination of seeds . Spray fernoxone ( Sodium salt of 2, 4 D ) Agrosone ( MCPA ) @450 g/ 500 litres of water. 9/19/2024 83

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