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Diseases of wheat and their management
- 1. Dr. Shivam Singh AssistantProfessor Department of Plant Pathology School of Agriculture, LPU Diseases of wheat
- 2. Fungal diseases 1. Yellowrust: Puccinia striiformis 2. Brown rust: Puccinia recondita 3. Black rust: Puccinia graminis tritici 4. Loose smut: Ustilago nuda tritici 5. Common bunt: Tilletia tritici and Tilletia laevis 6. Karnal bunt: Tilletia indica 7. Powdery mildew: Erysiphe graminis 8. Flag smut: Urocystis tritici 9. Foot rot: Pythium graminicolum 10. Leaf blight: Alternaria triticina
- 3. Bacterial disease 1. Bacterialleaf streak and black chaff: Xanthomonas campestris pv. undulosum Viral disease 1. Barley yellow dwarf: Barley Yellow Dwarf Virus (BYDV) 2. Barley yellow streak mosaic: Barley Yellow Streak Mosaic Virus (BYSMV) 3. Barley yellow striate mosaic: Barley Yellow Striate Mosaic Virus (BYSMV)
- 4. Symptoms • The pustulescontain yellow to orange-yellow urediospores, usually form narrow stripes on the leaves. • The teliospores are also arranged in long stripes and are dull black in colour. • Pustules also can be found on leaf sheaths, necks, and glumes. 1. Yellow rust or Stripe rust Causal organism: Puccinia striiformis It is heteroecious rust but the alternate host is still unknown.
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- 6. Pathogen • Uredospores areyellow, spherical to oval, measuring 23-35 × 20-35 µ, with a hyaline, minutely echinulate spore wall with 6-16 germ pores. • Teleutospores are dark brown, two celled, thick walled flattened at the top and measure 35-63 × 12-30 µ. Uredospores Teleutospores (Teliospores)
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- 8. Survival and spread •The inoculum survives in the form of uredospores /teliospores in the northern hills during off season on self sown crop or volunteer hosts. • Spread occur through uredospores from hills. Favourable conditions • Temperature (10-20°C) • High humidity (>80%)
- 9. Symptoms • The pustulesare circular or slightly elliptical, smaller than those of stem rust, usually do not coalesce, and contain masses of orange to orange-brown Urediospores. • Mainly found on the upper surfaces of leaves and leaf sheaths and occasionally on the neck and awns. 2. Leaf or Brown or Orange Rust Causal organism: Puccinia recondita It is heteroecious rust and the alternate host is Meadow-rue (Thalictrum sp.)
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- 11. Pathogen • Uredospores arebrown, spherical, minutely echinulate, measuring 20-35 µ in diameter and bearing 7-10 germ pores. • Teleutospores are two celled, smooth, oblong, thick walled and brown with a rounded apex and measure 35-56 × 12-23 µ. Uredospores Teleutospores (Teliospores)
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- 13. Survival and spread •The inoculum survives in the form of uredospores /teliospores in the northern hills during off season on self sown crop (stubbles) or volunteer hosts. • Spread occur through uredospores from hills. Favourable conditions • Temperature (20-25°C) with free moisture (rain or dew).
- 14. Symptoms • Pustules aredark reddish brown in colour, occur on both sides of the leaves, on the stems and on the spikes. • Pustules are usually separate and scattered, and in heavy infections they coalesce. • Prior to pustule formation, "flecks" may appear. 3. Stem or Black Rust Causal organism: Puccinia graminis tritici It is heteroecious rust and the alternate host is Barberry (Berberis sp.)
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- 17. • Before thespore masses break through the epidermis, the infection sites feel rough to the touch and gives a ragged and torn appearance. Pathogen • Uredospores are brown, oval shaped, thick walled, borne singly on stalks, measure 25-35 × 17-20 µ and bearing 4 germ pores. • Teleutospores are dark or chestnut brown, two celled, smooth and thick walled with a rounded apex and measure about 40-46 × 15-20 µ.
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- 20. Survival and spread •The inoculum survives in the form of uredospores /teliospores in the northern hills during off season on self sown crop (stubbles) or volunteer hosts. • Spread occur through uredospores from hills. Favourable conditions • Temperature (20°C) • Moisture (>70-80%).
- 21. Management • Mixed croppingand crop rotation. • Avoid excess dose of Nitrogen. • Sulphur dusting @ 35-40 kg/ha • Spray Mancozeb @ 2g/lit or Zineb @2.5 kg/ha or Propiconazole @ 0.1 %. • Grow resistant varieties like PBW 343, PBW 550, PBW 17, Lerma Rojo, Safed Lerma, Sonalika and Chotil. • Spray of 1 litre butter milk + 1 litre cow urine along with 8 litres of water.
- 22. Symptoms • The entireinflorescence is commonly affected, except rachis, and appears as a mass of olive-black spores, initially covered by a thin grey membrane. • Once the membrane ruptures, the head appears powdery. • The powdery mass of spores is blown off by wind, leaving behind only the central rachis. 4. Loose Smut Causal organism: Ustilago nuda tritici This is internally seed borne disease.
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- 24. Pathogen • The smutspores are very minute, pale, olive-brown, spherical to oval in shape, measure about 5-9 µ in diameter and are adorned with minute echinulations on the wall. • They germinate readily in water, each spore producing 1 four-celled germ tube (promycelium).
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- 27. Survival and spread •The disease is internally seed borne, where pathogen infects the embryo in the seed. • Primary infection occurs by sowing infected seeds. Favourable conditions • Infection is favoured by cool and humid conditions during flowering period of the host plant.
- 28. Management • Solar heattreatment or hot water treatment of seed. • Rogue out diseased ear heads and destroy them by burning. • Grow resistant varieties like Raj 2296, K-8027, K- 8251, HW-657, HW-240, Raj-6276, VL-646, VL-719 etc. • Treat the seed with Vitavax @ 2g/kg seed before sowing.
- 29. Symptoms • The fungusattacks seedling of 8-10 days old and become systemic and grows along the tip of shoot. • At the time of flowering, hyphae concentrate in the inflorescence and spikelets and transforming the ovary into smut sorus of dark green colour. • The diseased plants mature earlier and all the spikelets are affected. 5. Common Bunt or Hill Bunt or Stinking Smut Causal organism: Tilletia tritici (syn. T. caries) and Tilletia laevis (syn. T. foetida) This is externally seed borne disease.
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- 31. Pathogen • Reticulate, globoseand rough walled. • No resting period. • Germinate to produce primary sporidia.
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- 33. Survival and spread •The spores on the seed surface germinate along with the seed. • Each produces a short fungal thread terminating in a cluster of elongated cells. • These then produce secondary spores which infect the coleoptiles of the young seedlings before the emergence of the first true leaves. • In India, disease occurs only in Northern hills, where wheat is grown. Favourable conditions • Temperature of 18-20˚C. • High soil moisture.
- 34. Management • Adopt shallowsowing. • Grow the crop during high temperature period. • Treat the seeds with carboxin or carbendazim at 2g/kg. • Grow resistant varieties like Kalyan Sona, S227, PV18, HD2021, HD4513 and HD4519.
- 35. Symptoms • In aninfected plant, not all the ears are affected and in an infected ear, only a few grain (5-6) are being infected and changed into sori. • The sori are always irregularly distributed on the infected ear. • On the maturity of the grains, the outer glumes in a spike spread out and the bunted grains may be observed. 6. Karnal Bunt Causal organism: Tilletia indica (syn. Neovossia indica) This disease was first reported from Karnal (Haryana).
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- 38. Survival and spread •The disease is seed borne and sowing of infected seeds is the source of primary infection. Favourable conditions • Temperature of 18-20˚C. • High soil moisture.
- 39. 7. Powdery Mildew Causalorganism: Erysiphe graminis Symptoms • Greyish white powdery growth appears on the leaf, sheath, stem and floral parts. • Powdery growth later become black lesion and cause drying of leaves and other parts.
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- 42. Pathogen • Fungus producesseptate, superficial, hyaline mycelium on leaf surface with short conidiophores. • The conidia are elliptical, hyaline, single celled, thin walled and produced in chains. • Dark globose cleistothecia containing 9-30 asci develop with oblong, hyaline and thin walled ascospores.
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- 46. Survival and spread •Fungus remains in infected plant debris as dormant mycelium and asci. • Primary spread is by the ascospores and secondary spread through airborne conidia. Favourable conditions • Cool and moderate temperature (20-21˚C). • High humidity (>70%).
- 47. Management • Crop rotation •Removal of plant debris. • Avoid excess dose of Nitrogen. • Use of resistant varieties. • Spray wettable sulphur 0.2% or carbendazim @ 500 g/ha.
- 48. 8. Flag Smut Causalorganism: Urocystis tritici or U. agropyri Symptoms • The symptoms can be seen on stem, clum and leaves from late seedling stage to maturity. • The seedling infection leads to twisting and drooping of leaves followed by withering. • Grey to grayish black sori occurs on leaf blade and sheath. • The sorus contains black powdery mass of spores.
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- 50. Pathogen Aggregated spore balls,consisting 1-6 bright globose, brown smooth walled spores surrounded by a layer of flat sterile cells.
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- 52. Survival and spread •The disease is seed and soil borne. • Smut spores are viable for more than 10 years. • Primary infection occurs by sowing infected seeds or by resting spores present in the soil. Favourable conditions • Temperature of 18-24°C. • Relative humidity (65% and above).
- 53. Management • Crop rotation •Removal of plant debris. • Seed treatment with carboxin at 2g /kg. • Grow resistant varieties like Pusa 44 and WG 377.
- 54. 9. Foot rot Causalorganism: Pythium graminicolum / P. arrhenomanes Symptoms • The disease mainly occurs in seedlings & roots and rootlets become brown in colour. • Seedlings become pale green and have stunted growth.
- 56. Pathogen • Mycelium iswell developed and coenocytic,. • Fungus produces sporangia and zoospores. • The sexual spores are the oospores, borne singly which are moderately thick walled. Disease Cycle
- 57. Survival and spread •Pathogen survives in soil. • Primary spread occurs through soil and irrigation water. Favourable conditions • Wet weather and high rainfall. Management • Follow crop rotation • Removal of plant debris. • Seed treatment with carboxin or carbendazim @2 g /kg.
- 58. 10. Leaf Blight Causalorganism: Alternaria triticina, A. alternata and Bipolaris sorokiniana Symptoms • Reddish brown oval spots appear on young seedlings with bright yellow margin. • In severe condition, several spots coalesce to cause drying of leaves.
- 60. Survival and spread •Primary spread is by externally seed-borne and soil borne conidia. • Secondary spread by air-borne conidia. Favourable conditions • Temperature of 25°C. • Relative humidity (>70%). Management • Seed treatment with carboxin or carbendazim @2 g /kg. • Spray with Mancozeb or Zineb @2 kg/ha.
- 61. 11. Bacterial leafstreak and black chaff Causal organism: Xanthomonas campestris pv. undulosum or Xanthomonas translucens pv. undulosa Symptoms • Initially, small and linear water soaked area may develop on the leaf blades and sheath. • Later, lesions elongate and coalesce into irregular, narrow yellowish and brownish stripes. • Spikes are blighted and turn black. • Cream to yellow coloured slime or droplets appear on the leaves.
- 63. Pathogen • Xanthomonas isa genus of Proteobacteria and is a Gram negative. • It is motile by a single polar flagellum and it can grow in temperature range from 4ºC to 37ºC. Survival and spread • The bacterium survives in and on seeds and may also persist on crop residue and in soil. • It can be transmitted by splashing water, plant to plant contact and insects. • Volunteer and grassy weeds also are sources of inoculums.
- 65. Favourable conditions • Wetweather, irrigation water and rainfall. • Temperature of 25-30ºC. Management • Crop rotation. • Bury infected plant parts. • Removal of volunteer and grassy weeds. • Avoid overirrigation. • Use of disease free seed. • Use of resistant cultivars like Blade, Cromwell, Faller, Howard, Knudson etc.
- 66. 12. Barley yellowdwarf Causal organism: Barley Yellow Dwarf Virus (BYDV) Symptoms • The most common symptom is stunting due to reduced internode length and root mass of infected plants is also often reduced. • The most conspicuous symptom is loss of green colour in leaves, mostly found on older leaves and later water- soaked areas are found on the leaves. • Leaves typically turn yellow or red or purple in colour. • Other symptoms include upright and stiff leaves and serrated leaf borders, reduced tillering and flowering, sterility and failure to fill kernels.
- 69. Pathogen • This virusis typically 25-28 nm in diameter and hexagonal in outline. • It has ssRNA (single-stranded ribonucleic acid) genome. Transmitted by Aphids (Sitobion avenae and Rhopalosiphum padi). Favourable conditions • High light intensity and relatively cool temperatures (15-18ºC)
- 71. Management • Late sowing. •Removal of volunteer plants and grassy weeds. • Use of disease free seed. • Use of resistant varieties. • Use of Imidacloprid or Thiamethoxam.