Diseases of Wheat and their management

Stem Rust Puccinia graminis f.sp. tritici

Leaf Rust Puccinia recondita
Stripe Rust Puccinia striiformis
Loose Smut Ustilago tritici
Kernal Bunt Tilletia indica (syn. Neovossia indica)
Tundu disease or yellow slime disease Anguina tritici (Nematode) + Corynebacterium tritici
Powdery Mildew Blumeria graminis f. sp. tritici
Soil-Borne Wheat Mosaic: Soil-Borne Wheat Mosaic virus

1. Black or stem rust: Puccinia graminis tritici

Symptoms
 The first symptom of rust infection is flecking of leaves, leaf sheaths, culms and floral
structures.
 Appearance of reddish-brown-black pustules on stems, leaves, leaf sheath and floral
structures.
 When large number of uredosori burst, other affected parts appear brownish-like that
of a rusted iron.
 In case of severe infections, plants are stunted; they produce small spikes and
shrivelled grains or no grains at all.
Pathogen:
Black stem rust is heteroecious cycle rust. It requires more than one host species to
complete its life cycle. The uredial and telial stages occur on wheat, barley and some grasses
and the pycnial and aecial stages on the species of Berberis (Barbery) and Mahonia, the
alternate hosts.
Diseases cycle:
 The source of inoculum for black rust comes from south, i.e., Nilgiri and Pulney
hills. The possibilities of the fungus surviving on ratoon tillers or self sown wheat plants,
late and off season wheat crops and certain grasses growing in cool areas particularly in the
foot hills of Himalayas in the North, the Nilgiris and Pulney hills in the South appear to be
great. The grasses, viz., Briza minor, Bromus patula, Brachipodium sylvaticum and Avena
fatua, harbor the fungus in the off-season.

Management:

 Eradication of self sown wheat plants and weed hosts

 Adjust time of sowing.
 Grow resistant varieties like Kalyanasona, Sonalika, Choti Lerma, Lerma Rojo, Safed
lerma, NP 700 & 800.
 Avoid late sowing
 Balanced application of nitrogenous fertilizers
 Seed dressing with Plantavax@0.1% followed by two sprays with the same chemical.
 Spray twice or thrice with Zineb@0.25% or Mancozeb@0.25% or Plantavax@0.1% , at
15 days interval.
2. Leaf, brown or orange rust : Puccinia recondita
Symptoms
 The first symptom of the disease is the appearance of minute, round, orange sori,
irregularly distributed on the leaves, rarely on the leaf sheath and stem.
 The sori turn brown with maturity. As the disease advances, the telial stage may be
found in the same pustule.
 The telia are small, oval to linear, black and covered by the epidermis. The telia are
also found on the leaf sheath. Severe rusting of leaves causes reduction in yield.
Disease cycle:
The fungus, Puccinia recondita, is heteroecious. The uredial and telial stages appear on
wheat and some other grasses and aecial and pycnial stages on species of Thalictrum. In
Russia, Isopyrum fumaroides is known to act as a natural alternate host. The uredospores are
brown, spherical and minutely echinulate with 7-10 germ pores. Teleutospores are smooth,
oblong, thick walled and brown with a rounded and a prominent thickened apex.
Management:
 Grow resistant varieties like Sonalika, NP 700 & 800, Lerma Rojo and Safed Lerma.
 RH-124, an Indofil product is very specific to brown rust (or) spray Dithiocarbamates like
Zineb@0.25% or Mancozeb@0.25%
 Seed dressing with Plantavax@0.1% followed by two sprays with the same chemical

3. Yellow or stripe rust: Puccinia striformis

Symptoms:
 The uredosori appear as bright yellow pustules chiefly on the leaves. But in severe
infections they may be seen on leaf sheaths also.
 The sori are elongated and are arranged in linear rows between the veins of the leaf
and hence it is referred as stripe rust.
 The sori are mostly sub-epidermal and are remained covered by the epidermal layer
and break only at the time of crop maturity.
Disease cycle:
 Uredospores are yellow, spherical to oval with a spiny wall. The teleutospores are dark
brown, two celled, thick walled and flattened at the top..
 The fungus overwinters in its uredial stage. It may overwinter on volunteer wheat
plants at an altitude of about 1500 to 1800 meters in the Himalayas.
 The uredospores germinate after a period of dormancy and form a source of inoculum
for early sown wheat crop.
  Some weeds like Agropyron semicostatum, Bromus catharaticus, Bromus japonicus
and Hordeum murinum also serve as primary source of inoculum.
 Secondary infection is by wind borne uredospores.
Management:
 Grow resistant varieties like Lerma Rojo, Safed Lerma, Sonalika and Choti Lerma
 Spray plantavax@0.1%
 Removal and destruction of weed hosts
Difference between Stem rust, Leaf rust and Stripe rust
Characters Stem rust Leaf rust Stripe rust

Synonym Black stem rust Brown rust Yellow rust

Causal organism P. graminis tritici P. recondita P. striformis

Occurrence South and north India All wheat growing North India
regions of India
Infection Stem Leaf, leaf sheath Leaf, leaf sheath
Pustule color Dark brown Orange Bright yellow
Pustule Irregular/scattered Scattered Arranged in stripes
arrangement
Uredospores Pedicillate Non-pedicillate Non-pedicillate
Uredospores Oblong/oval Globose Globose/elliptical
Teliospores Two celled Two celled, Flattened or Two celled, Flattened
Pointed or oval tips round tips or round tips

4. Loose smut :Ustilago nuda tritici

Symptoms:
 The symptoms are evident only at the time of emergence of the panicle from boot
leaf.
 All the spikelets in a panicle transform into a mass of black powdery spores. The
infected panicle emerges two days earlier than healthy and the spores are covered
with the silvery membrane.
 This thin membrane gets ruptured exposing the mass of black spores.
 Telispores are easily blown by wind leaving the bare rachis.
Management:
 Grow resistant varieties kalyanasona, PV 18, WG 307 and HD 450.
 Hot water treatment (Jensen, 1908): Soak the seed in cold water for 4 hours and
thenimmerse the seed in hot water at a temperature of 132 0F or 520C for about 10
minutes and dry the seed in shade before sowing.
 Solar seed treatment (Luthra and Sattar, 1934): Soak the seed in water for 4 hours (8
AM to 12 Noon) and expose the seed to the hot sun for 4 to 5 hours (from 12 Noon to 5
PM) on cement or rocky surface. This can be practiced in the areas where the summer
temperatures are high (42-440C).
 Anaerobic seed treatment (USA): Soak the seeds for 2-4 hours in water between 60-
700F and keep the moist seeds in air tight containers for 65-70 hours and there after dry
the seed.
 Seed treatment with systemic chemicals like vitavax@0.2% or Benlate@0.2%

5. Karnal bunt: Neovossia indica (formerly Tilletia indica)

Symptoms:
 The infection is usually confined to a few grains in the spike with irregular
arrangement.
 In some cases the infection may spread to only a part of the grains. In severe cases,
the grain is reduced to black shiny sac of teliospores. As the grains mature the outer
glumes spread and the inner glumes expand, exposing the bunted grains.
 The bunt balls are first enclosed by the pericarp but when it bursts the masses of bunt
spores are exposed.
 The bunt affected plants emits a foul smell which is mainly due to the presence of
Trimethyl amine.
Diseases cycle:
 The teliospores in soil germinate producing primary sporidia. The sporidia become air
borne and deposit on leaves of host plants.
 The infection mostly starts from the embryonal end and spreads along the grain
suture.
 The disease progresses systemically to other florets within an infected spikelet.
 The pericarp ruptures during threshing and teliospores deposit in soil and adhere to
the surface of the seed.
Favourable conditions

 Moderate temperatures (19-230C), high humidity (>70%) and cloudiness or rainfall

during anthesis favours disease development in susceptible host varieties.
Management:
 Grow tolerant varieties, viz., WL 1562, HD 2281, etc. Use resistant sources like wild
species of Aegilops and Triticum, HD 2329, HD 29 and HD 20 for breeding
programme.
 Follow strict quarantine measures
 Use disease free seed for sowing
 Judicious application of nitrogenous fertilizers
 Adjust date of sowing
 Intercropping with Gram or Lentil
 Seed treatment with Copper carbonate or Thiram@3g/kg seed
 Spray with Carbendazim@0.1% or Carboxin@0.2% or Mancozeb@0.25% or
Bitertanol

6. Tundu disease or yellow slime disease

Anguina tritici (Nematode) + Corynebacterium tritici
Symptoms:

 Twisting of the stem, distortion of the ear head and rotting of the spikelets with a
profuse oozing of yellow liquid from the affected tissues.
 The ooze contains masses of bacterial cells.
 The nematode alone causes winkling, twisting and various other distortion of the
leaves, stem and produce small round galls on the leaves.
 In the distorted earheads dark galls are found in place of kernels.
 When the bacterium is associated with the nematode, the disease symptoms are
intensified at the flowering stage and yellow ear rot sets in due to combined action of
the nematode and bacterium.
 The earhead becomes chaffy and the kernels are replaced by dark nematode galls
which also contain the bacterium.
 The infected plants produce more tillers than the healthy ones. Another interesting
feature is the early emergence of ears in the nematode infected plants which is about
30 to 40 days earlier than the healthy ones.
Diseases cycle:

 The disease starts from the seeds contaminated with the nematode galls. When such
contaminated seeds are sown in the field, they absorb moisture from the soil and the
larvae (juveniles) escape from the galls and climb upon the young wheat plants.
 At the time of flowering, the nematodes enter the floral parts and form galls in the
ovaries.
 When once the nematode is inside the tissues of the ovary, the bacterium becomes
active and causes rotting.
 The yellow ooze coming out of the rotting earhead provides the inoculum for the
secondary spread of the disease which is favoured by wind and rain.
Management:
 Sow gall free seeds. Separate the galls from the seed by floating in brine at 160 g of
sodium chloride in liter of water.
 Wheat, barley or oat should not be sown in the infested soil.
 Spray the crop with streptocycline, 1g in 10 liters of water.

7. Powdery Mildew: C. A :Blumeria graminis f. sp. tritici

Symptoms:

 Powdery mildew produces a white to gray cottony fungal growth on the upper leaf
surface
 This disease may occur on any above ground plant part, but it is usually most
prevalent on the upper surface of the lower leaves.
 The conspicuous white to gray patches of fungus appear early in the growing season.
 When powdery mildew is severe, the entire leaf turns yellow and dies
 Small, black fungal fruiting bodies (Cleistothecia) may be seen immersed in the gray
fungal tissue later in the season
 Powdery mildew can cause severe blighting of the upper leaves and can attack the
head of susceptible varieties.
Favourable conditions:
 The disease is favored by temperatures between 10 0C and 21 0C.
 The disease usually declines after flowering, when temperatures rise above 24 0C.
 Powdery mildew can infect plants in the fall and survive in the invaded tissue during
the winter. Early infection can result in reduced tillering of susceptible varieties.
Thus, spores may come from earlier infections within the field or from fields farther
away.
  Dense stands, high nitrogen fertility, and rapid plant growth increase susceptibility.\
Management:
 Field Monitoring: Check fields periodically and early in the season.
 Genetic Control: Use of resistant varieties is the best way to control wheat losses to
powdery mildew.
 Chemical control is possible with fungicides such as Wettable sulphur
Triadimefon and Propiconazole.
8. Soil-Borne Wheat Mosaic
Symptoms
 The primary host for soil-borne wheat mosaic virus is the wheat plant, Triticum
aestivum, although the virus can also affect rye, barley, and triticale.
 Symptoms include chlorotic leaf mottling or leaf mosaic, rosetting, stunting,
streaking, and blotching of leaves.
 The mosaic and mottling symptoms may range from mild green to yellow, and leaves
may sometimes also have dashes, parallel streaks, reddish streaking, and necrosis at
the tips.
 Diseased fields are often uneven in appearance of symptoms especially in low wet
areas. This is because the drainage pattern of water on the field is used by the virus to
infect plants.
 The Soil-borne Wheat Mosaic Virus uses the fungal-like protist Polymyxa graminis,
an endoparasitic slime mold as a vector.
Management:
 Cultivar resistance to the virus is the most practical strategy to control the disease.
 Examples of resistant wheat cultivars include the Hawk and Newton cultivars.
 Chemical control in soil fumigants provide control against the vector P. graminis, but
these fumigants are not feasible economically in use of small grains.
 The sanitation of machinery is important to avoid the introduction of the virus into
new areas by soil transport, and sanitation is a more economical option for the
management of disease.