Disease of sorghum

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1. Sorghum bicolor Diseases of Sorghum TA-2009-085 Vikas Kumar Dhiraj

2. S.N Diseases Causal organism 1 Anthracnose or Red leaf spot Colletotrichum graminicola 2 Rust Puccinia purpurea 3 Ergot or Sugary disease Claviceps sorghi or Sphacellia sorghi 4 Head Mould / Grain Mould / Head Blight Several Fungal genera 5 Leaf Blight or Leaf Stripe Exserohilum turcicum or Trichometasphaeria turcica Syn : Helminthosporium turcicum or Drechslera turcicum 6 Grain Smut / Kernal Smut / Covered Smut / Short Smut Sphacelotheca sorghi Sporisorium sorghi 7 Charcoal Rot / Hollow Stem / Stalk Rot Blight Macrophomina phaseolina 8 Downy Mildew or Leaf Shredding Peronosclerospora sorghi 9 Phanerogamic Parasite ( Striga or Witch Weed ) Striga asiatica or Striga densiflora

3. Anthracnose : Colletotrichum graminicola Symptoms : Small red coloured spots on leaf. Whitish centre encircled by red , purple or brown margin. Numerous small black dots are seen on the white surface of the lesions which are the fruiting bodies (acervuli) of the fungus, Many lesions coalesce and kill large leaf portions. In midrib region, elongate elliptical , red or purple regions with black acervuli are formed Development of circular cankers on Stalk and inflorescence Infected stem when split open shows discoloration, which may be continuous over a large area or more generally discontinuous giving the stem a marbled appearance . Disease cycle Primary Infection : Fungus present in Seed, and IPD Collateral host: Johnson grass, Sudan grass, maize, barley and wheat Secondary Infection : Wind born Conidia

4. Management Destruction of infected plant debris and collateral hosts Crop rotation with non-host crops Grow resistant varieties like SPV 162, CSV 17, Texas Milo and Tift sudan etc Treat the seeds with Captan or Thiram @3 g/kg. Spray the crop with Mancozeb @0.25% or [email protected]%

5. Symptoms Small reddish brown flecks on the lower surface of the leaf Pustules ( uredosori ) appear on both surfaces of leaf as purplish spots which rupture to release reddish powdery masses of uredospores . The pustules are elliptical and lie between and parallel with the leaf veins. Pustules are surrounded by a reddish or yellow halo Teliopores develop later sometimes in the old uredosori or in teliosori , which are darker and longer than the uredosori Rust : Puccinia purpurea Disease cycle Primary Infection : long cycled rust Alternate host Oxalis corniculata ( aecial and pycnial stage ) Secondary Infection : Wind born uridospores

6. Favourable Conditions Low temperature 10 to 12 C rainy weather Management Grow resistant varieties like CSH 5, SPV 13, 81, 126, PSH 1, CSV 17, etc. Remove and destroy the alternate host Oxalis corniculata . Spray the crop with Mancozeb @ 0.25% Dusting of sulphur@25 kg/ha Oxalis corniculata

7. Symptoms The disease is confined to individual spikelets . Secretion of honey dew (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 honey dew is colonized by Cerebella sorghivulgaris which gives the head a blackened appearance . Under favourable 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. Ergot or Sugary disease : Claviceps sorghi or Sphacelia sorghi Disease cycle Primary infection : Sclerotia germinates & produce ascospores Secondary Infection : Air and insect born conidia & conidia also spreads through Wind splash rain water Favourable Conditions High rainfall High humidity during flowering season. Cool night temperature (20-25 0C) Cloudy weather during anthesis Male sterile lines are highly susceptible .

8. Management Adjust the date of sowing so that the crop does not flower during the periods of high rainfall and high humidity. Grow resistant varieties like SPV 191, CSH 5 , SPH 1 and CS3541. Deep summer ploughing Soaking seeds with 2% saline solution will aid to remove ergot infested seeds, as ergot infested seeds will float in the salt solution. Seed treatment with fungicides such as Captan or Thiram@4g/kg seed Spray Ziram (or) Zineb (or) Captan (or) Mancozeb @0.2% at emergence of earhead (5-10 per cent flowering stage) followed by a spray at 50 per cent flowering and repeat the spray after a week, if necessary. Control of ergot with fungicides such as Propiconazole or Tebuconazole has proved to be cost effective in seed production plots.

9. Symptoms If rains occur during the flowering and grain filling stages, severe grain moulding can occur. Infected grains are covered with pink or black mold and such grains disintegrate during threshing process. Fusarium semitectum and F.moniliforme develop a fluffy white or pinkish colouration. C. lunata colours the grain black. Fungi from many genera have been isolated from the infected sorghum grains and the most frequently occurring genera are Fusarium , Curvularia , Alternaria , Aspergillus , Cheatomium , Rhizopus , Helminthosporium and Phoma . Moldy grains contain toxic mycotoxins and are unfit for human consumption and cattle feed. Disease cycle The fungi mainly spread through air-borne conidia. The fungi survive as parasites as well as saprophytes in the infected plant debris. Favourable Conditions Wet weather following the flowering favours grain mould development and the longer the wet period the greater the mould development. Compact ear heads are highly susceptible. Head mould / Grain mould / Head blight

10. 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 milky stage .

11. The leaf blight pathogen also causes seed rot and seedling blight of sorghum. Small narrow elongated spindle shaped spots in the initial stage. Later they extend along the length of the leaf becoming bigger. On older plants - Long elliptical necrotic lesions , straw coloured in the centre with dark margins. Many lesions coalesce on the leaves, destroying large areas of leaf tissue giving the crop a distinctly burnt appearance leading to premature drying of leaves . Leaf blight or leaf stripe Exserohilum turcicum or Trichometasphaeria turcica (Syn : Helminthosporium turcicum or Drechslera turcicum ) Symptoms Primary Infection : Fungus present in Seed, Soil and IPD Secondary Infection : Seed or Wind born Conidia Disease cycle Cool moist weather, High humidity ( 90 % ) High rainfall Favourable Conditions

12. Use disease free seeds. Crop Rotation with non susceptible crops Collect and destroy IPD Seed Treatment with Captan or Thiram at 4 g/kg. Spray the crop with [email protected]% at the age of 40 days and the spraying have to be repeated twice at 15 days interval Tift -Sudan is resistant to this disease Management

13. Symptoms Grain smut/Kernel smut / Covered smut / Short smut Sphacelotheca sorghi or Sporisorium sorghi The disease appears at the time of grain formation in the ear. The individual grains are replaced by smut sori ( dirty white to gray ) and are covered with a tough white cream to light brown skin ( peridium ). The glumes are unaltered and may be found adhering to the sides of the sorus . Sometimes the stamens may develop normally protruding out of the sorus . Ratoon crops exhibit higher incidence of disease. Disease cycle Primary Infection : Externally seed borne and systemic Secondary Infection : Wind born Sporidia

14. Use disease free seeds. Grow resistant varieties like T 29/1, PJ 7K, PJ 23K, Nandyal and Bilichigan . Treat the seed with fine sulphur powder @0.5% or Captan or Thiram @0.3 %. Follow crop rotation. Collect the smutted ear heads in cloth bags and dip in boiling water. MANAGEMENT

15. Sudden Wilting and Death of the diseased plant resulting in Lodging. If the infected stalk is split open, the pith is disintegrated with longitudinal shredding of the tissue into fibers . Small black sclerotial bodies are seen in the infected tissues. The stem, breaks near the ground level. Premature ripening takes place and the heads are poorly developed. Charcoal rot or hollow stem or stalk rot blight Macrophomina phaseolina Favourable conditions Soil temperature 35 C Moisture stress conditions preceding crop maturity High dose of nitrogenous fertilizers Symptoms Primary Infection : sclerotial bodies present in the Soil, IPD, Weed Host Secondary Infection : sclerotial bodies carried through Rain or irrigated water Disease cycle

16. Thin plant population ( 60,000 plants/ha ) Collected and burning of infected plants along with trash Avoid moisture stress at flowering Grow resistan t varieties like E-36-1, CSV 5, CSH 7-R, SPV 126 and SPV 193. Management

17. Symptoms Downy whitish growth is produced on the lower surface of the leaves. White streaks appear on both the surfaces of the leaves. The tissues then tear along the streaks causing Leaf shredding of the leaves. The tissue then turns brown in colour. Numerous oospores are found in the shredded leaves. The affected parts are stunted and sterile . Disease cycle Primary Infection : Oospores present in the Soil. mycelium , seeds Secondary Infection : air-borne sporangia . Favourable Conditions Relative humidity 100 % Optimum temperature 21-23 C Light drizzling Cool weather Downy Mildew or Leaf shredding : Peronosclerospora sorghi

18. Destroyal of affected plants by burning before oospore formation, reduce the inoculum potential Crop rotation with other crops like pulses and oilseeds . Grow Tolerant varieties like CSH 2, CSV 5, SPV 101, 165 and 190. Seed Treatment with Metalaxyl (Apron 35 SD) @4g/kg seed Spray Metalaxyl ( Ridomyl MZ) @0.2% or Mancozeb @0.25% Management

19. Symptoms Phanerogamic parasite ( Striga or Witch Weed ) Striga asiatica , Striga densiflora Disease cycle Primary Infection : Seeds present in the Soil. Secondary Infection : Favourable Conditions Soil temperature 35 C soil moisture 30 % Sorghum root exudates stimulate the seeds of the parasite to germinate. Parasite attach to the Host root by haustoria and grow below the soil surface and produce underground stems and roots for about 1-2 months. The parasite grows faster and appears at the base of the plant. Severe infestation causes Yellowing and wilting of the host leaves. Stunted growth and may die prior to seed setting, if the infection occurs early

20. Management Hand weeding of the parasites before flowering. Crop rotation with cowpea , groundnut and sunflower . Mixing of Ethrel with soil triggers germination of Striga in the absence of host. Spray Fernoxone (sodium salt of 2,4-D) or Agroxone (MCPA) at 450g/500 liters of water or Praquat @ 1 kg/ha. 1 % Tetrachloro dimethyl phenoxy acetate can be used for instant killing of Striga, if water is in scarce . Tetrachloro dimethyl phenoxy acetate