Sorghum bicolor

Diseases of Sorghum

TA-2009-085

Vikas Kumar Dhiraj

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 turcicaSyn: Helminthosporium turcicum orDrechslera turcicum

6 Grain Smut / Kernal Smut / Covered Smut / Short Smut

Sphacelotheca sorghiSporisorium 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

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 cyclePrimary Infection : Fungus present in Seed, and IPD

Collateral host: Johnson grass, Sudan grass, maize, barley and wheat

Secondary Infection : Wind born Conidia

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 carbendazim@0.1%

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 cyclePrimary Infection : long cycled rust

Alternate host : Oxalis corniculata (aecial and pycnial stage)

Secondary Infection : Wind born uridospores

Favourable Conditions

Low temperature 10 to 120C 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

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 cyclePrimary infection : Sclerotia germinates & produce ascosporesSecondary Infection : Air and insect born conidia & conidia also spreads through Wind splash rain water Favourable Conditions1. High rainfall2. High humidity during flowering season.3. Cool night temperature (20-25 0C)4. Cloudy weather during anthesis5. Male sterile lines are highly susceptible.

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.

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

Management

Adjust the sowing time Grow resistant varieties like GMRP 4, GMRP 9, GMRP 13 and tolerant varieties like CSV

15. Seed disinfestation with Thiram@0.3% 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.

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 IPDSecondary Infection : Seed or Wind born Conidia

Disease cycle

• Cool moist weather, • High humidity (90 %) • High rainfall

Favourable Conditions

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 Mancozeb@0.25% 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

Symptoms

G r a i n s m u t / K e r n e l s m u t / C o v e r e d s m u t / S h o r t s m u tS p h a c e l o t h e c a s o r g h i o r S p o r i s o r i u m s o r g h i

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 systemicSecondary Infection : Wind born Sporidia

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

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 hol low stem or stalk rot bl ightMacrophomina phaseo l ina

Favourable conditions Soil temperature 35 0 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

Thin plant population (60,000 plants/ha)

Collected and burning of infected plants along with trash

Avoid moisture stress at flowering

Grow resistant varieties like E-36-1, CSV 5, CSH 7-R, SPV 126 and SPV 193.

Management

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 0 C Light drizzling Cool weather

Downy Mildew or Leaf shredding: Peronosclerospora sorghi

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%

M a n a g e m e nt

Symptoms

Phanerogamic parasite (Str iga or Witch Weed )Striga asiatica , Striga densiflora

Disease cyclePrimary Infection : Seeds present in the Soil.Secondary Infection :

Favourable Conditions Soil temperature 350 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 toseed setting, if the infection occurs early

Management1. Hand weeding of the parasites before flowering.

2. Crop rotation with cowpea, groundnut and sunflower.

3. Mixing of Ethrel with soil triggers germination of Striga in the absence of host.

4. Spray Fernoxone (sodium salt of 2,4-D) or Agroxone (MCPA) at 450g/500 liters of water or Praquat @ 1 kg/ha.

5. 1% Tetrachloro dimethyl phenoxy acetate can be used for instant killing of Striga, if water is in scarce.

Tetrachloro dimethyl phenoxy acetate