4. Pathogen:
• Biotrophic, Obligately parasitic, Basidiospores not
contained within Basidiocarp, macrocyclic
(5 possible spore types), heteroecious
• The three species of Puccinia causing rust:
Stem rust or black rust
(Puccinia graminis f. sp. tritici),
Leaf or brown rust
(Puccinia recondite f.sp. triticiana).
Stripe or yellow rust
(Puccinia striiformis f.sp. tritici)
Rust of wheat Basidiomycetes
uredianales
Pucciniaceae
www.ars.usda.gov/Main/docs.htm?docid=9757
“RUST NEVER SLEEPS”
FATHER OF GREEN REVOLUTION
DR NORMAN BORLAUG.
5. Black stem rust
Pathogen: Puccinia graminis tritici
o Uredospores are brown and oval
o Each cell of teleutospore has one pore
o Size is about 25-30x15- 20μm
o Microscopically, these red spores are covered with fine
spines
Pre disposing (environmental) factors
Warm ‐humid weather conditions with
intermittent rains.
Hot days 25‐30ºC and mild nights (15‐20ºC)
Leaf wetness from rain or dew
6. Black stem rust
Symptoms:
Sori/pustulse containing fungal spores on aerial
part of plant
Elongated to irregular shaped pustules (uredinia)
of brickred urediniospores break through the
epidermis and develop on the upper leaf surfaces,
leaf sheaths, glumes and awns.
Later in the season, pustules of black teliospores
(telia) begin to appear in infected host plants.
Long, narrow, oval pustules in the parallel
fashion
Causes defoliation, increase in transpiration water
loss
Loss of photosynthetic area, poor grain fill and
results in shriveled grains
7. Yellow rust/stripe rust of wheat
Etilogy: Puccinia striiformis f.sp tritici
Uredospores are spherical to ovate in shape, orange colored
Teleutospores are dark brown and flattened at the top when in
contact with the epidermis
Pre disposing (environmental) factors
Cool ‐humid weather conditions with intermittent rains.
Cooler climates (10‐16ºC )
Leaf wetness from rain or dew
Heavy dew or intermittent rains can accelerate the spread of
the disease
8. Yellow rust/stripe rust of wheat
Symptoms:
In the upper surface of the leaf, yellow colored pustules arises in
the linear fashion
Appearance of yellow streaks (pre-pustules)
Small, bright yellow, elongated pustules on the leaves, leaf sheaths,
Glumes and awns.
Mature pustules will break open and release yellow-orange masses
of Urediniospores
In some varieties, long, narrow yellow stripes will develop on
leaves.
Tissues may become brown and dry as the plant matures.
Severe infection can result in plant stunting.
9. Yellow rust/stripe rust of wheat
Black pustules form as the plant approaches maturity(Telia). Teliospores of stripe rust (Puccinia striiformis) (400x)
10. Yellow rust/stripe rust of wheat
Management:
Plant resistant varieties: WK 1204, Pasanglyamu
Sowing and planting wheat at optimum time (oct 15)
Apply only recommended amount of fertilizers
Apply fungicides when severe mancozeb 75% WP (Dithane M 45) 1.5-
2.0 kg per ha in 750 ltr water in 15 days interval
Or
Propiconazole 25% EC (Bonus, Bumper, Tilt 25) .75 gm per ltr.
11. Orange rust/Brown rust/leaf rust of wheat
Etiology: Puccinia triticiana (P. recondite f.sp. triticiana)
Uredospores are brown and spherical
16-28um in diameter
Predisposing factors:
Warm ‐humid weather conditions with intermittent
rains.
Hot days 25‐30ºC and mild nights (15‐20ºC)
Leaf wetness from rain or dew
Symptoms:
• Small, circular and orange-brown (rusty red) pustule
around main pustule.
• Black pustules form as the plant approaches
maturity(Telia)
• Pustules scattered over leaves.
• It appears on leaf sheath, penduncles, internodes and ear
heads.
12. Orange rust/Brown rust/leaf rust of wheat
Management: (krishi diary, 2075)
Plant resistant varieties: Vijaya, Rohini BL-1473, Gautam
Planting on optimum time (oct 15)
Apply only recommended amount of fertilizers
Apply fungicides when severe mancozeb 75% WP (Dithane M 45) 1.5-
2.0 kg per ha in 750 ltr water in 15 days interval
Or
Propiconazole 25% EC (Bonus, Bumper, Tilt 25) .75 gm per ltr.
13. Rust of wheat
Particular Stem rust Brown/leaf Yellow /stripe (30-50%)
Affected sites Terai Foot Hills/ inner terai Midhills (300-1500m)
Major occurance March –April (high
temp. 25 d. C)
Feb-March Jan- Feb
Alternate host Barbery Thalictrum spp./Anchusa sps. Barberry
Collateral host Aegilops, Agropyron Aegilops, Agropyron Baeberry, Aegilops,
Agropyron
Resistant wheat var Vijaya, BL3503,
BL3235, Danphe,
Tillotama
Vijaya, Rohini BL-1473, Gautam WK 1204, WK1123 BL1813,
NL 297, Passang lahmu
, Gaura
15. Rust of wheat
Conducive factors:
Later stage of crop growth, High
nitrogen fertilizer, 11-21*C , RH^,
airborne
Though their optimum environmental
conditions are slightly different, these
rusts are present globally, wherever
wheat is grown
They are often present together in
one plant, during different growth
stages of wheat in different severities.
Stripe rust Stem rust Leaf rust
20. Rust of wheat
Management
• Sanitation
• Early planting
• Use resistant varieties: Vijaya, Gautam, NL 297, WK 1204.
(varietal mixture)
• 2-3 Foliar spray of mancozeb 75%WP (DM-45) 1.5-2 kg per
ha in 750 lt water in 15 days interval or propicunazole 25%
EC (Tilt 25, Bonus, Bumper) @ 0.75 gm per litre plantavex-
20 @ 1lt/ha, Bayleton@ 500gm/ha
• Use balance use of NPK
21. Loose smut of wheat
Disease of hills and terai, internally seed borne
Causal agent: Ustilago nuda var. tritici (Syn. U. segetum var. tritici)
The teliospores are single celled and formed irregularly from fertile
hyphae.
Teliospores are olivaceous brown, spherical to oval, measures 5-
9μm in diameter
Conducive factor:
16-22*C/ 60-80% RH
Intermittent rain during flowering
Basidiomycetes
Ustilaginales
Ustilaginaceae
http://ohioline.osu.edu/ac-fact/0012.html
22. Loose smut of wheat
Symptoms:
Every ear of the affected plants is converted into a black mass of
spores and no grains are formed.
The infected heads emerge from the boot one to three days earlier
than those of healthy plants.
As a rule, all the glumes (chaff) and grain in a smutted head are
completely transformed into black powder.
This sooty mass is composed almost entirely of millions of
teliospores.
The spores are quickly dispersed by the wind during the flowering
period of normal heads, and by harvest only an erect bare rachis
remains.
All of the floral parts of the head, except for the rachis and pericarp
membrane, are invaded by mycelium of the fungus and converted
into loose aggregates of smut spores (teliospores).
23. Loose smut of wheat
Disease cycle and epidemiology:
Internally seed borne, monocyclic /resting mycelium
activated/teliospore
Pathogens overwinter as dormant mycelium in
cotyledon of infected kernels
When infected kernels begin to germinate, the
myceliums activates and grow intercellularly in
seedlings till it reaches to ear head formation.
Mycelium enters young spikelets and establish in seed
embryo.
After infection convert into black teliospores.
Secondary spread: Teliospore liberates in air and
lands on flowers, germinates through stigma and
through ovary wall establishes in seed embryo and
remains dormant.
25. Loose smut of wheat
Disease Management: (PPD, 2075)
Use healthy seeds
Seed treatment (hot water/fungicide-solarization) --tilt/ agrosan GN, Vitavex-200 2 gm or
Tebuconazole 2% DS (Cavit, Raxil) 1 gm per kg seed of wheat
Resistant varieties: Annapurna -4, BL-1135, Bansipali 808, Punjab, Pradesh
Scouting and Smutted head destruction
Hot water treatment at 20ºC for 5 hrs. then transferred into 49ºC for about 1 min. and
again 52ºC for 11 min. (20ºC for 5 hrs. → 49ºC for 1 min. → 52ºC 11 min.) and
immediately place in cold water.
Solar treatment: Soak the seeds in cool water for 4 hrs. followed by spreading and drying
of seeds in bright sun (44ºC) for 4 hrs. in the afternoon.
26. Hill/Common/Stinking Bunt
of wheat
o The disease is ranked second after rusts in world-wide
importance (Hoffmann 1982; Wiese 1987).
Etiology: Tilletia caries and tiletia foetida
Conducive factor:
5-15* C, Moist
Disease cycle:
Externally seed born/ soil borne (Teleospore-25 yr)
Basidiomycetes
Ustilaginales
Tilletiaceae
27. Hill/Common/Stinking Bunt of wheat
Symptoms:
Plants with common bunt may be moderately stunted but infected plants
cannot be easily recognized until near maturity and even then it is
seldom conspicuous.
After initial infection, the entire kernel is converted into a sorus
consisting of a dark brown to black mass of teliospores covered by a
modified periderm, which is thin and papery.
The sorus is light to dark brown and is called a bunt ball.
The bunted heads are slender, bluish-green and may stay greener longer
than healthy heads.
The bunt balls change to a dull gray-brown at maturity, at which they
become conspicuous.
The fragile covering of the bunt balls are ruptured at harvest, producing
clouds of spores. The spores have a fishy odor (trimethiamine) so
referred as “stinking smut.”
29. Hill/Common/Stinking Bunt
of wheat
Disease Management:
Seed treatment (fungicide/washing) Systemic fungicides like carboxin,
vitavax and benlate @ 2.0 g/Kg seed and Tilt (propioconazole) 25 EC @ 0.1% are
used for seed treatment. A combination of vitavax with thiram is very effective
for disease control
Resistant varieties: HB-383, HD-2012, Kalyan sona, PV 18, IWP
127/129
Affected head destruction
Crop rotation
Shallow sowing
30. Karnal/partial Bunt of wheat
Importance:
• Karnal bunt is so named because it was discovered in 1931
on wheat grown near Karnal, India by Mitra.
• Since then, it has been found in all major wheat-growing
states of India, as well as in Pakistan, Iraq, Mexico, and
Afghanistan.
Etilogy: Tilletia indica (braclayana) [syn. Neovossia indica
(Mitra) Mundkur]
• Teliospores are dark brown to black in colour.
• Ellipsoidal to spherical in shape.
• Characteristic apiculus and episore is reticulate with curved
spines.
Pre disposing factors/Conducive factor:
15-20*C/ 60-80% RH
Intermittent rain
Q
Basidiomycetes
Ustilaginales
Tilletiaceae
31. Karnal/partial Bunt of wheat
Symptoms:
Karnal bunt is difficult to identify in the field. Developing
wheat kernels are randomly infected and usually only
partially converted to the fungus and hence, called partial
bunt.
The disease is not usually noticed until the grain is threshed
and partially smutted kernels are exposed. Generally a few
florets per spike are affected.
While diseased seeds usually retain a partial seed coat, the
embryo and part of the endosperm have been converted to
masses of small black spores, which emit a fishy odor
trimethylamine).
32. Karnal/partial Bunt of wheat
Disease cycle and epidemiology:
Primary source: Smut spore germinate in the
soil producing a large number of needle
shaped primary sporidia (primordia) and sickle
shape secondary sporidia
Secondary spread: air borne secondary
sporidia infect ovary.
34. Karnal/partial Bunt of wheat
Management:
Use healthy seeds
Rotational cropping
Resistant varieties Kalyan sona, HD 2012
Infected head destruction
Crop rotation
Foliar spray of PCNB, Bavistin and DM-45 @ 0.2% or Hexaconazole 0.1% on anthesis
Seed treatment
(a) Hot water treatment:
The seeds are first soaked in water for five hours at 20°C , the water is drained off and then they are treated with
hot water at 49°C for about a minute and finally with hot water at 52°C for 11 minutes.
Immediately after the hot water treatment , the seeds are cooled off by dipping in cold water and dried. The
dormant mycelium inside the seed dies off by this treatment.
(b) Use of systemic fungicides:
Fungicides like carboxin, vitavax , and benlate @ 2.0 g/Kgseed and propioconazole @ 0.1% are used for seed
treatment to reduce the pathogen infectivity.
A combination of vitavax with thiram is very effective for disease control.
35. Flag smut of Wheat
Pathogen: Urocystis agropyri (Syn. U.tritici)
Symptoms and Signs:
Flag smut :
A smut fungus, causing a smut in cereals, affects leaves, leaf
sheath, culm and stems, and is characterized by chains of
sori (linear sori) within the plant tissue that later rupture
releasing black masses of spores.
These streaks have a greasy appearance. Diseased plants
remain stunted and produce excessive numbers of tillers.
There is a twisting of affected leaves which droop down like
a flag and finally wither away.
37. Flag smut of Wheat
Disease cycle and
epidemiology:
The disease is seed as well as soil
borne.
38. Flag smut of Wheat
Management:
Cultural:
Shallow planting is better than deep planting to reduce infection,
probably because the seedling is in a susceptible stage for a shorter
period of time.
A 1‐ or 2‐year break in wheat cropping may be beneficial.
Resistance:
Use resistant cultivars or at least avoid very susceptible cultivars
Chemical
Seed treatment : Systemic fungicides like carboxin, vitavax and
benlate @ 2.0 g/Kg seed and Tilt (propioconazole ) 25EC @ 0.1%
39. Helminthosporium Leaf Blotch/Spot Blotch
Importance: In Nepal, it appears in terai region 60 to
300 masl however it is becoming problematic in inner
terai, midhills and yield loss of 20-30% is reported.
Etilogy: Bipolaris sorokiana/ B. brizae telemorph:
Cochliobolus sativus (Helminthosporium sativum) Syn.
Drechslera sorokiniana
Epidemiology
Seed and soil borne
Warm, high temperature 25 °C and RH favors
Bipolaris
40. Helminthosporium Leaf blight/H. leaf Blotch/Spot Blotch
Symptoms
Bipolaris symptoms common in seed, leaves,
stem and roots while Drechslera common in
leaves and stem and less in seed
Small brown spots initially, blighted appearance
when spots coalesce
During tillering disease initiate from the lower
leaves then spreads to whole plant with increase in
the temperature.
Finally disease infection will be all over the plants
41. Helminthosporium Leaf Blotch/Spot Blotch
Management: (krishi diary,2075; PPD)
After crop harvest burn all the previous crop debris
Use of enough organic manures and cultivate wheat in fertile land
Use of healthy seeds
Seed treatment –Carbendazim 37.5 % WP + Thiram 37.5 % 2gm or
tebuconazole 2% DS 1 gm per kg seed or vitavax-200 2 gm per kg seed
Use of balanced dose of fertilizers and compulsory use potassium fertilizers
Planting at optimum date
Planting resistant varieties: Triveni, Achyut, Rohini, Brikuti,
Aaditya, Bijaya, Gautam
When disease appears propiconazole 15 EC 1 ml per litre in 2 weeks
interval spray 3 times
42. Tan spot/Yellow leaf spot/blotch of cereals
Etiology: Pyrenophora tritici-repentis Syn. Helminthhosporium tritici-repentis
Syn. Drechslera tritici-repentis
Produces two types of spores.
Asexual spores known as conidia are produced mainly in maturing lesions on
leaves
Conidia are hyaline (non-pigmented) to light brown, cylindrical, and have one to
nine transverse septa.
The conical tapering of the basal cell of the conidium which gives the
appearance of a snake head, is diagnostic of D. tritici-repentis.
Sexual spores known as ascospores are produced in pseudothecia. Each
pseudothecium contains saclike cells called asci in which meiosis followed by
mitosis occur leading to formation of eight ascospores per ascus.
Mature ascospores are yellow-brown and oval to globose. Each mature
ascospore has three transverse septa, and the median cells may have a
longitudinal septum
43. Tan spot of cereals
Symptoms:
The key diagnostic feature of tan spot is tan lesions
with a yellow margin.
Mature tan spot lesions often have a dark area in the
center.
Lesions may merge as they expand, resulting in large
sections of diseased leaf tissue.
The fungus that causes tan spot survives in the debris
of previous wheat crops and produces small, black
reproductive structures in the spring.
44. Tan spot of cereals
Disease cycle andepidemiology :
• P. tritici-repentis survives intercrop periods as pseudothecia on host
residue, which is considered the main source of primary inoculum.
• Other sources of inoculum mainly in the form of conidia include
infected seed, volunteer wheat, and other grass species.
• Pseudothecia develop and mature on wheat straw in the fall and
winter.
• In the spring, ascospores are discharged from pseudothecia and cause
primary infections on leaves. They are dispersed by wind.
• Rainfall, high relative humidity, and temperatures above 10°C (50°F)
favor ascospore discharge. Conidia produced in maturing lesions on
leaves serve as secondary inoculum.
45. Tan spot of cereals
Management:
Fungicides in the strobilurin and triazole classes provide very good to
excellent control of tan spot. They include azoxystrobin, pyraclostrobin,
metconazole, propiconazole, prothioconazole, tebuconazole,
prothioconazole + tebuconazole, metconazole + pyraclostrobin,
propiconazole + azoxystrobin, and propiconazole + trifloxystrobin.
46. Alternaria leaf blight of wheat
Etiology: Alternaria triticina
Symptoms:
The disease appears in the field when the crop is 7-8 weeks old.
Leaves show reddish brown localized oval spots which become
irregular with bright yellow margin.
Heavily infected fields display a brunt appearance.
47. Alternaria leaf blight of wheat
Disease cycle and epidemiology:
25ºC temp. coupled with high humidity.
Primary source: Fungus is seed borne externally.
Secondary spread: Air borne conidia.
Management:
Pre soaking of seeds in water for 4 hrs. followed by 4 hrs.
water treatment at 52ºC for 10 minutes.
Spraying of mancozeb (D.M-45) @ 0.2 %
48. Septoria tritici blotch/ speckled leaf blotch
Pathogen: Septoria tritici
This fungal disease causes tan, elongated lesions on wheat leaves.
Lesions may have a yellow margin, but the degree of yellowing varies
among varieties.
The dark, reproductive structures produced by the fungus are key
diagnostic features and can often be seen without magnification.
This disease is also known as speckled leaf blotch.
Management:
Genetic resistance, foliar fungicides, crop
rotation.
50. Fusarium head blight/ Scab of wheat
Importance: Severe levels of infection can cause yield losses of
more than 50% and significant reductions in grain quality.
Etiology: Fusarium graminearum
Disease cycle and Epidemiology:
Favored by warm, wet weather during and after flowering.
Symptoms:
Bleached heads or individual spikelets
Superficial pink/orange mycelium/spores
Bleached heads contain scabby seed (tombstones).
Diseased spikelets may have a dark brown discoloration at the
base and an orange fungal mass along the lower portion of the
glume
Grain from plants infected by Fusarium head blight is often
shriveled and has a white chalky appearance.
51. Fusarium head blight/ Scab of wheat
Management:
No resistant varieties
Plant varieties that differ in flowering times
Bury crop residue
Chopping corn stalks down helps
Crop rotation ( not corn or grain sorghum)
Foliar fungicides are not effective
52. Fusarium root, crown, and foot rots
Fusarium root, crown, and foot rots cause patches of
wheat to die prematurely, resulting in areas of white
heads within a field.
Infected plants are typically brown at the base and
have poor root development.
During advanced stages of the disease, the Fusarium
fungus often produces a pink, cottony growth inside
the lower portions of the stem.
Often, the disease is most severe after prolonged
periods of dry weather.
Management:
Crop rotation, control grassy weeds.
53. Powery mildew of wheat
Etiology: Erysiphe graminis tritici
The conidia are elliptical, hyaline, single celled,
thin walled and produced in chains
Fungus produce septate, superficial, hyaline
mycelium on leaf surface with short conidiophores
Disease cycle and Epidemiology:
Fungus remains infected in plant debris as
dormant mycelium
Favorable temperature is 20-21°C and High RH
54. Powery mildew of wheat
Symptoms:
Greyish white powdery growth appears
on leaf, sheath, stem and floral parts
Glumes and awns also can be infected
when disease is severe.
Fungal growth is largely limited to
outer plant surfaces and can be easily
wiped away by rubbing a finger across
affected area.
Powdery growth later become black
lesion and Drying of leaves and Other
parts
55. Powery mildew of wheat
Management:
o Burning of the crop stubbles
o Deep ploughing of the field during summer days
o Apply recommended dose of fertilizers
o Use of resistant varieties: BL 1413, WK 1204, Aaditya, Gautam
and Bijaya
o In severe condition apply sulfur @ 0.5 kg per ropani in 15 days
interval
56. Cephalosporium stripe
Plants infected with Cephalosporium stripe have pronounced yellow stripes running the full length of
the leaf blade.
The center of the yellow stripe may have a long, brown streak that extends onto the leaf sheath.
Splitting the stem of infected plants often reveals small, brown streaks within the node tissue.
Cephalosporium stripe also can cause areas of stunted, irregular growth within a field.
Often, infected plants die prematurely, causing patches of white heads within a field.
Management:
Genetic resistance, crop rotation, control grassy weeds.
57. Wheat blast
Etiology: Magnaporthe oryzae Triticum pathotype
(MoT)(synonym Pyricularia oryzae Triticum pathotype
and Pyricularia graminis-tritici)
Importance: WB was first identified in in Brazil in
1985, The disease was confined to South America until
its discovery in Bangladesh in 2016 and more
recently in India.
A phylogenomics and populations genetics study
indicated that the disease did not evolve independently
in South Asia, but was probably cause by an incursion of
a South American lineage of MoT (Islam et al., 2016
58. Wheat blast
Symptoms:
WB is primarily a head disease.
The typical symptoms range from small elliptical lesions to complete bleaching and
empty spikes (Igarashi et al., 1986, 1990).
Yield losses of 40%–100% have been reported (Igarashi, 1990).
Foliar lesions caused by MoT have also been described; however, their role and
significance in grain yield losses remain unknown (Cruz et al., 2016a; Igarashi,
1990).
Disease cycle and epidemiology:
Warm and humid conditions are required for WB development (i.e. temperatures at
25ºC with at least a 10-h wetting period) (Cardoso et al., 2008).
60. Wheat blast
Management:
Studies have indicated that the performance of foliar fungicides only reduces disease incidence by 50% (compared with non-
fungicide treatments), and that this efficiency is typically far lower in the weather conditions, described above, that favour disease
development (Maciel, 2011).
Little information is available on the chemistries used in the field, although QoI fungicides, either as the sole active ingredient
or in mixtures, have been documented for WB control in Brazil.
However, resistance to QoIs in South America has increased dramatically over the last 10 years to the point at which 90% of
tested isolates carry a resistant allele.
As such, there are no currently documented effective fungicide strategies in Brazil.
Seed treatment with fungicides has also been tested to control the initial establishment of the disease. However, the length of time
from seed germination to heading has led to questions with regard to the efficacy of seed treatments.
Nonetheless, seed treatment trials in Brazil and also the USA have proven to be successful, at least in the management of seed-
borne infections (Bocku et al., 2015; Goulart & Paiva 1991; Igarashi, 1990).
Seed treatment with fungicides has also been tested to control the initial establishment of the disease.
A more desirable approach to control WB is through the use of host genetics. Unfortunately, these approaches have been only
partially effective because of the lack of identifiable genetic resistance.
61. Glume blotch of Wheat
Pathogen: Septoria nodurum
Symptoms and signs:
Glume blotch :
Infected glumes develop gray‐brown blotches.
63. Glume blotch of Wheat
Disease cycle and epidemiology:
• The septoria leaf and glume blotch pathogen
survives within infested straw, seed and on
volunteer wheat and serves as the source of
inoculum with a new crop of wheat.
• Infections occur during periods of extended
wetness.
• Infected heads develop shriveled grain seeds.
• Aged blotches develop dark pin‐point
structures called pycnidia.
• Pycnidia are the source of infectious spores.
Pycnidia on discolored glumes are the best
sign of this disease.
64. Glume blotch of Wheat
Management:
Grow moderately resistant varieties.
Use disease-free seed (e.g. certified seed). Use seed grown in the drier
areas of the province.
Avoid excessive use of nitrogen
Crop rotation with non‐cereal crops.
General sanitation : Turn under the stubble and crop residue to reduce
disease incidence and control volunteer wheat seedlings.
Use wide row spacing and adequate but not excessive nitrogen levels.
These practices lower canopy density and
65. Stagonospora nodorum blotch
Pathogen:
Stagonospora nodorum
Symptoms:
Leaf blotch:
The lesions of Stagonospora leaf blotch are normally brown or tan,
surrounded by a thin, yellow halo.
Lesions caused by Stagonospora leaf blotch are more irregular in
shape and often have a darker color than those of tan spot.
The presence of small, honey-colored fungal reproductive structures is
diagnostic for Stagonospora nodorum blotch; however, these
reproductive structures are only visible with considerable
magnification.
Head blotch:
This disease causes dark brown or purple lesions on heads.
Lesions are often more intense at the top of the glume, with brown
streaks or blotches extending down toward the base of the spikelet.
The presence of tiny fungal reproductive structures embedded in the
tissue can confirm the diagnosis but will require significant
magnification.
67. Take-all
Pathogen:
Gaeumannomyces graminis f.
sp. tritici Syn. Ophiobolus graminis
Importance: Take-all is widespread in
monocropped areas and has been known to
cause considerable yield losses in winter
wheat and fall-sown spring wheat areas,
especially where liming or minimum tillage is
practiced.
Symptoms:
• This fungal disease causes wheat to die
prematurely, resulting in patches of white
heads in otherwise green fields of wheat.
• Plants infected by take-all normally have a
black discoloration of the lower stem
and roots.
68. Take-all
Disease development and epidemiology:
• The fungus persists on crop debris in the soil.
• Initial infections come from contact with hyphae or ascospores in the soil.
• Infection can occur throughout the crop cycle, but is favored by cool (12-18C)
soil temperatures and alkaline or nutrient deficient soils.
• Nitrate also appears to enhance disease development.
Management:
Crop rotation
control grassy weeds.
69. Foot rot
Pathogen: Pythium graminicolum and
P. arrhenomanes
This fungus produces sporangia, zoospores
and oospores.
70. Foot rot
SYMPTOMS:
The disease mainly occurs in seedlings
Roots and rootlets become brown in color
Seedlings becomes pale green and have stunted
growth
Wet weather and high rainfall is favorable
72. Bacterial streak/Black chaff
Pathogen: Xanthomonas campestris pv. Translucens, Syn. X. translucens, X.
campestris pv. undulosa
Symptoms:
Early symptoms of bacterial streak include small, watersoaked areas between leaf veins.
These water-soaked areas become tan streaks within a few days.
When the disease is severe, streaks may merge to form large, irregular areas of dead
tissue.
When dew is present, the bacteria causing this disease may ooze from the lesions and dry
to form a clear, thin film.
This film flakes easily and is visible when the leaf is viewed from different perspectives.
Disease development and epidemiology:
The bacterium can be seed borne and persists on crop residues in the soil, tolerating warm
as well as freezing temperatures.
Free moisture is required for infection and spread of the broken epidermal tissue.
The disease is spread by splashing rain, plant contact, and insects.
Management:
Avoid highly susceptible varieties.
73. Basal Glume Rot and Bacterial Leaf Blight
Pathogen: Pseudomonas syringae pv. atrofaciens Syn. Pseudomonas
atrofaciens
Symptoms:
The leaves, culms, and spikes of wheat and triticale can be infected.
On the spikelets, lesions generally start at the base of the glume and
may eventually extend over the entire glume. Diseased glumes have a
translucent appearance when held toward the light. Dark brown to black
discoloration occurs with age.
Under wet or humid conditions, a whitish gray bacterial ooze may be
present.
Stem infections result in dark discoloration of the stem; leaf
infections result in small, irregular, water-soaked lesions.
Disease development and epidemiology:
The pathogens survives on crop debris, as well as various grass hosts.
It is disseminated by splashing rain or by insects, and can be seed
borne.
74. Bacterial Spike Blight (Yellow Ear Rot)
Pathogen: Corynebacterium tritici
Symptoms:
• A yellow exudate on the spikes is indicative of bacterial spike blight.
• When dry, the exudate is white.
• Often the spikes and necks will emerge as a distorted, sticky mass.
• The early leaves may also be wrinkled or twisted.
• This bacteria is associated with the nematode Anguina tritici in some regions.
Disease development and epidemiology:
• The bacteria persists in organic material in the soil.
• It attacks wheat when it comes in contact with the plant apex within the leaf
whorl, and this transmission is often facilitated by the nematode A. tritici.
76. Seed gall nematode of wheat/Ear cockle/Tundu disease of
wheat
Importance:
Known to be present in the entire major wheat
growing areas of the world, more common in Europe,
Asia, Africa and India.
This nematode very often present in association with
the bacterium (Corynebacterium tritici) causing
tundu disease of wheat.
Etiology: Anguina tritici
77. Seed gall nematode of wheat
Symptoms:
The symptoms appear on all the aboveground parts; stems, leaves and floral
parts.
The infected adult plants or seedlings are more or less severely stunted and their
leaves show characteristic rolling or twisting.
A rolled leaf often traps the next emerging leaf or the inflorescence within it and
causes it to become looped or bent and badly distorted.
Stems are often enlarged near the base frequently bent and generally stunted.
Diseased heads are shorter and thicker than normal ones with their glumes
spread apart by the nematode filled grain galls.
A diseased head may have one or few or all kernels transformed into nematode
galls.
The diseased heads remain green longer than the normal ones and galls are shed
of the heads more rapidly than kernels.
79. Seed gall nematode of wheat
Disease cycle and epidemiology:
They lay eggs and all the juvenile and adult stages are produced in seed galls. They can survive upto 28
years in galls under dry condition.
Each gall contains 10,000 to 30,000 or even more larvae.
The galls fallen to the ground or sown with seed soften during warm, moist weather and release
second stage infective juveniles.
They swim upward in presence of film of water and feed ecto-parasitically on the tightly compact
leaves near the growing point, causing the leaves and stems malformed.
As the inflorescence begins to form, the juveniles enter the floral primordia and produce third and
fourth juveniles within 3-5 days of invasion.
The infected floral primordia become seed galls each containing about 80 or more adult males and
females.
Each female lay up to 2000 eggs within freshly formed galls over several weeks so that each gall contains
10,000 to 30,000 eggs.
The adults die soon after the eggs are laid. The eggs hatch producing first stage larvae and molt soon
producing second stage juveniles by the time of crop harvest.
80.
81. Seed gall nematode of wheat
Management:
Clean nematode free seeds must be used for sowing.
Seed treatments: Contaminated seeds can be cleaned by sieving and floating in fresh water. The
seeds are placed in 20% common salt solution and stirred vigorously. The galls being lighter float on
the water and can be removed.
Hot water treatment is also recommended. The seeds are soaked in water for 4-6 hours at room
temperature and then put in 54 °C for 10 minutes.
Crop rotation with barley and oat for 2-3 years is also found effective.
Cultural practices like early sowing of seeds and use of resistant variety have also been proved
useful for the management of this nematode.
Chemical treatment with nematicides such as nemaphos, aldicarp or thionazin @ 10 kg a.i./ha has
been found effective in heavily infested soil.
82. Cereal Cyst Nematode
Importance:
Significant yield losses can occur when nematode
populations are high.
All wheat cultivars are susceptible, but some do not
support cyst formation.
Etiology: Heterodera avenae
Symptoms:
Cereal cyst nematodes are more readily detected on seedlings than
on adult plants.
The roots of infested plants develop frequent branches and
swellings (cysts).
The cysts are off-white when young, turning dark brown as they
age.
Seedlings weakened by nematodes often are invaded by soil-
borne pathogens, especially root and crown rots.
83. Cereal Cyst Nematode
Disease cycle and epidemiology:
Larvae in moist soil penetrate roots near the
growing point and grow into adults.
Cell enlargement, root swelling, and root
branching occur as the nematodes mature.
Cysts are formed as the nematodes continue to
develop into egg-producing adults.
:
84. Cereal Cyst Nematode
Management
Regulatory methods plant quarantine
measures and seed tuber certification
Cultural methods –
Following the crop rotation of 4 years with
legumes could reduce the population up to
95%.
Chemical control – Soil sterilization with
fumigants or application of systemic
nematicides @ 2 kg a.i./ha is effective to check
the nematode.
Use of resistant varieties
86. Barley yellow dwarf (byd)
Pathogen: barley yellow dwarf virus
Spread by at least 20 aphids spp.
Major aphids: oat bird-cherry, corn leaf, english grain, greenbug, and
rice root aphid
Five prominent strains of bydv: rmv, rpv, mav, pav, sgv
Symptoms:
Temperatures of approximately 20ºC are favorable for disease development and
symptoms appear approximately 14 days after infection.
Symptoms usually do not show up until spring.
Stunted, poorly tillered across a field.
Affected plants show a yellowing or reddening of leaves, stunting, an upright
posture of thickened stiff leaves, reduced root growth, delayed (or no) heading,
and a reduction in yield.
The discoloration is often more intense near the tip of affected leaves, giving
them a flame-like appearance.
Barley yellow dwarf often occurs in patches within a field.
87. Barley yellow dwarf
Control:
Avoid early planting.
There are no resistant varieties.
Use insecticides to control fall aphids.
88. Wheat Spindle Streak Virus (WSSV)
Pathogen: Wheat Spindle Streak Virus
(WSSV)
Spread by the soil-borne Fungus Polymyxa
graminis
Symptoms:
Wheat spindle streak mosaic causes a
yellowndiscoloration to wheat seedlings.
This yellow discoloration is often most
intense in the wettest areas of a field.
Leaves of infected plants have long, yellow
streaks that are slightly wider in the middle
than at their ends.
Management:
Use resistant varieties.
Damage is usually not severe, especially when
temperatures stay above 65 F.
89. Wheat streak mosaic
Pathogen: Wheat streak mosaic virus
Symptoms:
• Leaves of plants infected with wheat streak mosaic have a bright yellow
streaking.
• Symptoms are often most severe near the leaf tip.
• The virus that causes wheat streak mosaic survives in volunteer wheat and is
spread by wheat curl mites.
• Disease severity is greater when plants are infected by more than one virus.
Management:
• Control volunteer wheat
• delay planting date
• genetic resistance
• avoid planting near maturing corn.
90. Summary of Wheat Disease Control Practices
Plant after Oct. 15.
Use recommended resistant varieties.
Treat seed with fungicide and insecticide to control aphids in the fall.
Wheat after corn may provide inoculum for scab
Burn down any “green bridge” 2 weeks before planting.
Treat with foliar fungicides when wheat prices and disease conditions
warrant their use.
