sorghum disease

1. Symptoms
 The disease is confined to individual spikelets.
 The first symptom is the 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.
3.3. Major sorghum diseases and their management
1. ERGOT or SUGARY DISEASE (Claviceps sorghi or Sphacelia sorghi )

3. Disease cycle
• Primary source of infection is through the germination of sclerotia which
produce ascospores, which infect the ovaries.
• The secondary spread takes place through air and insect borne conidia, which
settle in the spikelets.
• Rain splashes also help in spreading the disease.
Favourable Conditions
• Aperiod of high rainfall and high humidity during flowering season.
• Cool night temperature (20-25 ℃) and cloudy weather during anthesis encourages
disease spread rapidly causing severe losses in hybrid seed production.
• Male sterile lines are highly susceptible.

4. 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
 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.

5. 2.ANTHRACNOSE OR RED LEAF SPOT(Colletotrichum graminicola)
Symptoms
 The fungus causes both leaf spot (anthracnose) and stalk rot (red rot) in sorghum.
 The disease appears as small red coloured spots on both surfaces of the leaf.
 The centre of the spot is white in colour 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.
 Stalk and inflorescence infection can be characterized externally by the development of circular
cankers.

7. Disease cycle
• Fungus has wide host range and survives
on Johnson grass, Sudan grass, maize,
barley and wheat.
• Also survives in seed and infected plant
debris.
• Primary infection is from the conidia
produced on the infected plant debris
and infected seed.
• Disease spread within the season is through
air borne conidia, which are produced on
first infected plants.
Favorable Conditions
• Continuous rain, temperature of 28-30℃ and
high humidity aggravates the disease.
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.
• Treat the seeds with Captan or Thiram @3 g/kg.
Spray the crop with Mancozeb @0.25% or
carbendazim@0.1% .

8. 3.RUST (Puccinia purpurea)
Symptoms
• Small reddish brown flecks on lower surface of the leaf.
• Reddish brown pustules on the both surfaces of the leaves.
• Initially pustules contain reddish powdery mass of uredospores.
• In later stages teliospores are developed which are darker & longer than the uredospores.
• Premature drying of leaves ,stunted growth of the plants is seen.
Rust on leaf Pustules on stalk Telio & Uredospores

9. Disease cycle
 The fungus is long cycled rust with Oxalis corniculata as the alternate host with aecial and pycnial stages.
 Presence of alternate host helps in perpetuation of the fungus.
 The uredospores survive for a short time in soil and infected debris.
 Air borne uredospores help in the secondary spread of the disease.
Favorable Conditions: Low temperature of 10 to 12℃ favors teliospore germination and a spell of
rainy weather favours the onset of the disease.
Management :
 Grow resistant varieties
 Remove and destroy the alternate host
 Spray the crop with Mancozeb @0.25%.
 Dusting of sulphur@25 kg/ha .

10. 4.SMUTS
• Types of Smuts
Grain smut/Kernel smut/Covered smut/Short smut
Long smut
Head smut
Loose smut
Grain smut/Kernel smut / Covered smut / Short smut -
Sphacelotheca sorghi

11. A. Grain smut/Kernel smut / Covered smut / Short smut -
Sphacelotheca sorghi
Symptoms
The individual grains are replaced by
smut sori.
The sori are oval or cyclindrical and
are covered with a tough creamy skin
(peridium) which often persists
unbroken up to thrashing.
Ratoon crops exhibit higher incidence
of disease.

12. Symptoms
 The affected plants can be detected before the
ears come out.
 They are shorter than the healthy plants with
thinner stalks and marked tillering.
 The ears come out much earlier than the
healthy.
 The glumes are hypertrophied and the earhead
gives a loose appearance than healthy.
 The sorus is covered by a thin membrane
which ruptures very early, exposing the spores
even asthe head emerges from the sheath.
B. Loose smut/ kernel smut - Sphacelotheca cruenta

13. C. Long smut - Tolyposporium ehrenbergii
Symptoms
 This disease is normally restricted to a relatively a small proportion
of the florets which are scattered on a head.
 The sori are long, more or less cylindrical, elongated, slightly
curved with a relatively thick creamy-brown covering membrane
(peridium).
 The peridium splits at the apex to release black mass of spores
(spore in groups of balls) among which are found several dark
brown filaments which represent the vascular bundles of the
infected ovary.

14. D. Head smut - Sphacelotheca reiliana
Symptoms
• The entire head is replaced by large sori.
• The sorus is covered by a whitish grey membrane of fungal
tissue, which ruptures, before the head emerges from the
boot leaf to expose a mass of brown smut spores.
• Spores are embedded in long, thin, dark colored filaments
which are the vascular bundles of the infected head.

15. Management for all smuts
• Treat the seed with Captan or Thiram at 4 g/kg.
• Use disease free seeds.
• Follow crop rotation.
• Collect the smutted ear heads in cloth bags and bury in soil.

16. Comparison of characteristics of Four smuts of Sorghum
Character Grain smut Loose smut Long smut Head smut
Organism S. sorghi S. cruenta T. ehrenbergii S. reiliana
Ear infection All or most grains
smutted
All or most grains
smutted
Only about 2% of
grains are infected
Entire head smutted
into a single sorus
Sori Small, 5-15 × 3-5mm Small,3-18 × 2-4mm Long, 40 × 6-8mm 7.5-10cm × 2.5-5cm
Columella Short columella
present
Long columella
present
Columella
absent,but 8-10
vascular strands
present
Columella absent,
but a network of
vascular tissues
present
Spores In single round to
oval,olive-brown
In single spherical or
elliptical,dark brown
Always in
balls,globose or
angular,brownish
green
Loosely bound into
balls,spherical or
angular,dull brown
Viability of spores Over 10 years About 4 years About 2 years Upto 2years
In culture Yeast like growth
with sporidia
In colonies with
sporidia
In colonies with
masses of sporidia
In colonies germ
tubes and sporidia
Spread Externally seed-
borne
Externally seed-
borne
Air-borne Soil-borne and
Seed-borne

17. 5. LEAF BLIGHT OR STRIPE
Symptoms:
 Long elliptical necrotic lesions, straw coloured in the centre with
dark margins.
 Straw coloured centre becomes darker with the sporulation of the
fungus.
 The lesions can be several centimeters long and wide and
coalesce on the leaves, destroying large areas of leaf tissue.
 This gives the crop a distinctly burnt appearance leading to
premature drying of leaves.
 The leaf blight pathogen also causes seed rot and seedling blight
of sorghum.
 The disease appears in the form of small narrow elongated spindle
shaped spots in the initial stage.
Caused by Exserohilum turcicum or Trichometasphaeria turcica
(Syn : Helminthosporium turcicum or Drechslera turcicum)

18. Disease cycle:
• The fungus is found to persist in seed, soil
and infected plant debris.
• Seed borne conidia are responsible for
seedling infection.
• The secondary spread of the disease is
through wind-borne conidia and seed.
Favourable Conditions :
• Cool moist weather, high humidity (90 per
cent) and high rainfall.
• Management
• Use disease free seeds.
• Rotation with non susceptible crops.
• Collect and destroy infected plant debris.
• Treat the seeds 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.
• Resistant variety

19.  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.
 Moldy grains contain toxic mycotoxins and are unfit for human consumption and cattle feed.
 Fungi from many genera have been isolated from the infected sorghum grains the most frequently
occurring genera are:
Symptoms
6. Head mold/grain mold/ head blight
 Fusarium,
 Curvularia,
 Alternaria,
 Aspergillus,
 Cheatomium,
 Rhizopus,
 Helminthosporium and
 Phoma.

21. Disease cycle
• The fungi mainly spread through air-borne conidia.
• The fungi survive as parasites as well as saprophytes
in the infected plant debris.
Favorable Conditions
• Wet weather following the flowering favors grain
mold development and the longer the wet period
the greater the mold development.
• Compact ear heads are highly susceptible.
Management
 Adjust the sowing time
 Grow resistant varieties.
 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.

22. 7. PARISITIC DISEASES
Phanerogamic parasite (Striga or Witch Weed) Striga asiatica and Striga
densiflor
Symptoms
• Infestation causes yellowing and wilting of the host
• Stunted in growth and may die prior to seed setting,
• The parasite grows faster and appears at the base of
the plant.

24. Etiology
 It is a partial root parasite and occurs mainly in the rainfed sorghum.
 It is a small plant with bright green leaves, grows upto a height of 15-30 cm.
 It always occurs in clusters of 10-20/host plant.
 S. asiatica produces red to pink flowers while. S. densiflora produces white flowers .
 Each fruit contains minute seeds in abundance which survives in the soil for several years.
Disease cycle:
 The seeds remains for many years.
 The seeds germinate with roots of host.
 Seeds can germinate even one foot below soil.
 Soil temperature of 35C and soil moisture of 30 per cent is favorable for Striga infection.

25. 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.
 After germination, Striga can be removed and destroyed.
 Spray Fernoxone (sodium salt of 2, 4-D) or Agroxone (MCPA) at 450g/500 liters of water or
Praquat@1kg/ha.
 1% Tetrachloro dimethyl phenoxy acetate can be used for instant killing of Striga.