SRS INSTITUTE OF AGRICULTURE AND TECHNOLOGY

(Affiliated to Tamil Nadu Agricultural University)

PAT 301 DISEASES OF FIELD AND HORTICULTURAL CROPS

AND THEIR MANAGEMENT – I (1+1)

PRACTICAL MANUAL CUM RECORD

B.Sc. (Hons.) Agriculture

COURSE TEACHER
Dr. A. PRAVEEN
Dr. M.V. RUPPAVALLI

SRS INSTITUTE OF AGRICULTURE AND TECHNOLOGY

(Affiliated to Tamil Nadu Agricultural University)
Vedasandur – 624 710
2023-2024
 SRS INSTITUTE OF AGRICULTURE AND TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University)

PAT 301 DISEASES OF FIELD AND HORTICULTURAL CROPS

AND THEIR MANAGEMENT – I (1+1)

PRACTICAL MANUAL CUM RECORD

CERTIFICATE

Certified that this is a bonafide record of work done by the student

Mr./Ms. (ID. No. ) of

III B.Sc.(Hons.) Agriculture for the course, PAT 301 - Diseases of Field and Horticultural

Crops and their Management - I (1+1) during V semester of the academic year 2023 –

2024.

COURSE ASSOCIATE COURSE TEACHER

EXTERNAL EXAMINER
 PAT 301 DISEASES OF FIELD AND HORTICULTURAL CROPS AND
THEIR MANAGEMENT- I (1+1)

PRACTICAL MANUAL CUM RECORD

Compiled by

Dr. V. Paranidharan, Professor (Plant Pathology), TNAU, Coimbatore

Dr. A. Kamalakannan, Professor (Plant Pathology), TNAU, Coimbatore
Dr. N. Revathi, Assoc. Professor (Plant Pathology), TNAU, Madurai
Dr. V.Ramamoorthy, Assistant Professor (Plant Pathology), TNAU, Killikulam
Dr. S. Sundravadana, Assistant Professor (Plant Pathology), TNAU, Coimbatore
Dr. I. Jhonson, Assistant Professor (Plant Pathology), TNAU, Coimbatore
Dr. P. Latha, Assistant Professor (Plant Pathology), TNAU, Coimbatore
Dr. T. Anand, Assistant Professor (Plant Pathology), TNAU, Coimbatore

CENTRE FOR PLANT PROTECTION STUDIES

TAMIL NADU AGRICULTURAL UNIVERSITY
2020-2021
 TAMIL NADU AGRICULTURAL UNIVERSITY

CERTIFICATE

Certified that this is the bonafide record of Selvan / Selvi

…………………………………… I.D.No. ……………………… of Vth Semester

of III B.Sc. (Hons) Agriculture during the academic year 2020 - 2021 for the

course PAT 301 Diseases of Field and Horticultural Crops and their

Management-I (1+1).

External Examiner / Course Teacher

 CONTENTS
Ex. Date of Teacher’s
Date Title of the Exercise
No. submission Signature
1. Diseases of Rice

2. Diseases of Maize and Sorghum

3. Diseases of Pearl millet, Finger

Millet and Small Millets

4. Diseases of Pigeonpea,
Urdbean, Mungbean, Soybean
and Cowpea

5. Diseases of Groundnut, Sesame

and Castor

6. Diseases of Tobacco, Jute and

Mulberry

7. Diseases of Banana

8. Diseases of Guava, Papaya and

Pomegranate

9. Diseases of Crucifers

10. Field visit

11. Diseases of Tomato, Brinjal and
Okra

12. Diseases of Sweet potato and

Beans

13. Diseases of Coconut and

Arecanut

14. Diseases of Tea

15. Diseases of Coffee

16 Diseases of Rubber and Cocoa

EX. NO. : 1 DISEASES OF RICE
DATE :
FUNGAL DISEASES
Disease name Anamorph Teleomorph Life style/
parasitism
Major Diseases

Pyricularia grisea Magnaporthe Hemibiotroph

Blast (syn : P. oryzae) grisea
(syn: M. oryzae)
Brown Spot Bipolaris oryzae Cochlibolus Necrotroph
or (Syn: miyabeanus
Sesame leaf spot Helminthosporium
oryzae)
Sheath blight Rhizoctonia solani Thanetophorus Necrotroph
cucumeris
Sheath rot Sarocladium oryzae Necrotroph
(Syn: Acrocylindrium
oryzae)
False smut/ Ustilaginoidea virens Villosiclava Biotroph
Lakshmi disease virens (floral
(Claviceps infection
virens) only)
Udbatta disease Ephelis oryzae Balansia oryzae-
sativa
Stem Rot Sclerotium oryzae Leptosphaeria Necrotrop
salvinii
Foot rot / Fusarium moniliforme Gibberella Hemibiotroph
Bakane disease/ fujikuroi
rice foolish disease
Grain discoloration Bipolaris oryzae, Curvularia lunata,
Sarocladium oryzae, Alternaria tenuis,
Fusarium moniliforme
Minor diseases

Narrow brown leaf Cercospora janseana

spot
Stackburn disease Trichoconis padwickii
(Syn. Alternaria padwickii)
Leaf smut Entyloma oryzae
Bunt / Kernel smut Tilletia horrida (T. barclayana)

BACTERIAL DISEASES
Disease name Causal organism Life style/
parasitism
Bacterial leaf blight Xanthomonas oryzae pv. oryzae Necrotroph
Bacterial leaf streak Xanthomonas oryzae pv. oryzicola Necrotroph
VIRAL DISEASES
Disease name Virus Vector Life style/
parasitism
Tungro Rice tungro virus
leaf hopper Biotroph
(Nephotettix virescens)
Grassy stunt Grassy stunt virus Plant Hopper Biotroph
(Nilaparvatha lugens)
Dwarf Rice Dwarf virus Nephotettix cincticeps) Biotroph
(ds RNA)
Ragged stunt Ragged stunt Nilaparvata lugens Biotroph
virus / Fiji virus
(ds RNA)
PHYTOPLASMAL DISEASE
Disease name Phytoplasma Vector Life style/
parasitism
Rice yellow dwarf Candidatus Nephotettix virescens Biotroph
Phytoplasma
Fungal Diseases
1. BLAST - Magnaporthe grisea
Symptoms
The fungus attacks all stages of crop growth from seedling to ear head
formation and all aerial parts of the crop. Symptoms appear on leaves, nodes,
neck of the panicle and grains. Based on the plant parts on which the
symptoms appears, blast disease is named as follows
a. Leaf blast
 Spindle or eye shaped spots, with grey centre and dark brown margin,
are produced on leaf surface. Several spots join together on the leaves
leading to leaf drying. Severely infected field shows a burnt up
appearance. Thus it is called blast disease.
b. Nodal blast
 Necrotic black lesions encircle at nodes resulting in weakening of nodal
region. All the plant parts above the infected nodes dry up.
c. Neck blast
 Dark brown to black colored spots appear at the neck region of panicle.
As a result, transport of nutrients to grains is blocked leading to chaffy
grains. The ear head breaks at the neck region.
d. Grain infection
 The grains are also infected. Dark brown spots appear on the grains.
Pathogen
Thallus - The mycelium is dark brown to olivaceous green
and septate.
Parasitism - Hemibiotroph
Asexual - Conidia are produced in clusters on long septate,
reproduction olivaceous conidiophores. Conidia are pale olive
green, three celled, pyriform, and attached to the
conidiophore at the broader base by hilum.
Sexual reproduction - Four celled ascospores are formed in perithecium.
Favourable conditions
 Application of excessive doses of nitrogenous fertilizers, intermittent
drizzles, cloudy weather, high relative humidity (93-99 %), long dew
periods with dew deposition on leaves, low night temperature (below
20C) and availability of collateral hosts.
Mode of spread and survival
 Mycelium and conidia in the infected straw and seeds are important
sources of primary inoculum. The fungus also survives on collateral
hosts viz., Echinochloa crusgalli, Panicum repens, Digitaria marginata,
Leersia hexandra. Secondary spread is through air-borne condia.
2. Brown spot or Sesame leaf spot or Helminthosporiose
Bipolaris oryzae / Helminthosporium oryza (Cochlibolus miyabeanus)
Symptoms
 The fungus attacks the crop from seedling to milky stage.
 The disease appears first as minute, sesame shaped, rectangular
brown dots. Later these spots become cylindrical or oval to circular
spots with yellow halo. Several spots coalesce and the leaf dries up.
The severely affected seedlings die.
 Grain infection shows dark brown or black spots. It causes failure of
seed germination, seedling mortality and reduces grain quality and
weight.
Pathogen
Thallus - Septate, brown colored mycelium.
Parasitism - Necrotroph.
Asexual - No asexual fruiting body. Conidiophores arise from the
reproduction
mycelium and are septate. Conidia are borne singly on the
conidiophore. They are spindle shaped or worm like that is
why they are formerly called as Helminothosporium.
Conidia are brown colored and germinate at both ends
(Bipolaris). They are multisepate (eight to many celled).
Sexual - Sexual fruiting body is called perithecium that contains
reproduction
ascus and ascospores which are long and fusiform.
Toxin - The fungus produces terpenoid phytotoxins called
ophiobolin A, (or Cochliobolin A), ophiobolin B (or
cochliobolin B) and ophiobolin I. Ophiobolin A is most toxic.
This toxin causes fungal membrane permeability and
cytotoxicity.
Favorable conditions
 Temperature of 25-30C with relative humidity above 80 % is highly
favourable. Excess nitrogen aggravates the disease incidence.
Mode of spread and survival
 The infected seeds are the primary source of inoculum. The conidia
present on infected grain and mycelium in the infected tissue are viable
for 2 to 3 years. Secondary spread is through air-borne conidia. The
fungus also survives on collateral hosts like Leersia hexandra and
Echinochloa colonum.
3. Sheath blight
Rhizoctonia solani (Sexual stage: Thanetophorus cucumeris)
Symptoms
 The fungus affects the crop from tillering to heading stage.
 Initial symptoms are noticed on leaf sheaths located near water level.
Oval or elliptical or irregular greenish grey spots are formed on the leaf
sheath. As the spots enlarge, the centre becomes greyish white and
margin turns brown or purple brown. The spots coalesce and the leaf
sheaths die showing rotting symptoms.
Pathogen
Thallus - Filamentous, septate, colored mycelium
 Parasitism - Necrotroph
Asexual reproduction - No asexual spore. Brown colored irregularly
shaped sclerotia are formed
Sexual reproduction - Rarely produce basidiospores and no sexual
fruiting body.
Favourable conditions
 High relative humidity (96-97 %), high temperature (30-32C), closer
planting and heavy doses of nitrogenous fertilizers.
Mode of spread and survival
 The pathogen survives as sclerotia or mycelium in dry soil for about 20
months but for 5-8 months in moist soil. Sclerotia spread through
irrigation water. It is a typical soil-borne pathogen.
4. Sheath rot - Sarocladium oryzae (Syn: Acrocylindrium oryzae)
Symptoms
 Symptoms are noticed only on the flag leaf sheath.
 The flag leaf sheath shows oblong or irregular spots with dark reddish
brown margin with gray centre. They enlarge and coalesce, covering
major portions of leaf sheaths.
 Partial or complete choking of panicle occurs and results in chaffy and
discolored grains. The panicles rot and abundant whitish powdery
fungal growth is formed inside the flag leaf sheath.
Pathogen
Thallus - hyaline branched and septate mycelium
Parasitism - Necrotroph
Asexual reproduction - Conidia are hyaline, single celled and cylindrical
in shape.
Favourable conditions
Closer planting, high doses of nitrogen, high humidity and temperature
around 25-30C favours disease development while, injuries made by leaf
folder, brown plant hopper and mites increase the infection.
Mode of spread and survival
 Mainly through air-borne conidia and also seed-borne.
5. False smut - Ustilaginoidea virens [Villosiclava virens]
Symptoms
 It is a sporadic disease. A few spikelets in a panicle are affected.
 Typical symptom is the replacement of rice grains by white colour, ball-
shaped fungal mycelia, namely false smut balls.
 Later during maturation, the false smut ball is covered with powdery
chlamydospores and the colour changes to yellow, green, olive green
and finally to greenish black.
Pathogen
 Chlamydospores are formed as spore balls which are spherical to
elliptical, warty and olivaceous.
 Sclerotia are formed on the false smut balls.
Favourable conditions
 Rainfall and cloudy weather during flowering and maturity.
6. Stem rot - Sclerotium oryzae (Leptosphaeria salvinii)
Symptoms
 Small black lesions are formed on the outer leaf sheath. They enlarge
and reach the inner leaf sheath also. The affected tissues rot.
Abundant small black colored, spherical shaped sclerotia are produced
on the rotted tissues. The culm collapses and lead to lodginh of plants
lodge.
Pathogen
 The mycelium of the fungus is septate and white to tan coloured.
 Sclerotia are minute, mustard seed like structures, regular spherical in
shape and black in colour.
Favourable conditions
 Infestation of leaf hoppers and stem borer and high doses of
nitrogenous fertilizers.
Mode of spread and survival
 Fungus survives as sclerotia. The sclerotia are carried through
irrigation water.
7. Foot rot or Bakanae disease - Fusarium moniliforme (Gibberella fujikuroi)
Symptoms
 Infected seedlings in nursery are lean and lanky, much taller and die
after some time.
 In the main field, the affected plants have tall lanky tillers with longer
internodes and aerial adventitious roots from the nodes above ground
level. The root system is fibrous and bushy.
 The plants are killed before earhead formation or they produce only
sterile spikelets.
 When the culm is split open white mycelial growth can be seen.
Pathogen
Asexual reproduction
 Macro and microconidia are produced.
 Microconidia are hyaline, single celled and oval.
 Macroconidia are slightly sickle shaped, and two to five celled.
 The fungus produces the phytotoxin, fusaric acid, which is non-host
specific.
Mode of spread and survival
 The fungus is externally seed-borne.
8. Udubatti (Udbatta) disease- Ephelis oryzae (Balansia oryzae-sativa)
Symptom
 Symptoms appear at the time of panicle emergence. The entire ear
head is converted into a straight compact cylindrical black spike like
structure, since the infected panicle is matted together by the fungal
mycelium. The spikelets are cemented to the central rachis and the
size is remarkably reduced.
Pathogen
 Pycnidiospores are hyaline, needle shaped and 4-5 celled.

9. Grain discoloration
 It is caused by a complex of fungal organisms namely Drechslera
oryzae, D. rostratum, Curvularia lunata, Sarocladium oryzae, Alternaria
tenuis, Fusarium moniliforme
Symptoms
 The infection may be external or internal causing discolouration of the
glumes or kernels or both. Dark brown or black spots appear on the
grains. The discolouration may be red, yellow, orange, pink or black
depending upon the organism involved. This disease is responsible for
quantitative and qualitative loss of grains.

Favourable Conditions
 High humidity and cloudy weather during heading stage.
Mode of spread and survival:
 The disease is mainly spread through air-borne conidia and
 The fungus survives in the infected grains, plant debris.
BACTERIAL DISEASES
1. Bacterial Leaf Blight - Xanthomonas oryzae pv. oryzae
Symptoms
 In seedlings, water soaked, circular, yellow spots are produced in the
leaf margin. They enlarge and coalesce leading to drying of foliage.
The bacteria enter through the cut wounds of the leaf tips of the
seedlings 1-2 weeks after transplanting or enter through the
hydathodes, and become systemic. As a result of systemic infection of
seedling, yellowing, wilting and death of entire seedling, this is called
“Kresek” symptom.
 In grown up plants, water soaked lesions appear near the leaf margin
where the hydathodes are present. The lesions enlarge both in length
and width with a wavy margin and turn straw yellow within a few days,
covering the entire leaf. These lesions can develop either on one side
or on both sides of the leaf and occasionally along the midrib. Milky
or opaque bacterial ooze are formed on young lesions in the early
morning. They dry up leaving a white encrustation.
 On panicles the disease causes grey to light brown lesions on glumes
that result in infertility and low quality of the grains.
Confirmation test for BLB: Cut the infected leaves and put them into test
tube containing water. Yellowish bacterial ooze streams out from the cut ends
into the water. After 1-2 hours, the water becomes turbid.
Pathogen
 The bacterium is gram negative, non spore forming, rod shaped with
monotrichous polar flagellum.
Favorable conditions
 Clipping of leaf tip of the seedling at the time of transplanting
 Heavy rain, heavy dew, flooding, deep irrigation water
 Severe wind and temperature of 22-30C
 Application of excessive nitrogen, especially late top dressing
Mode of spread and survival
 Primary infection/spread through seed-borne inoculum.
 Secondary infection/spread through irrigation water and rain splashed
water.
 The pathogen survives in soil and in the infected stubbles and on
collateral hosts Leersia spp. Plantago najor, Paspalum dictum, and
Cyanodon dactylon.
2. Bacterial leaf streak - Xanthomonas oryzae p.v. oryzicola
Symptoms
 Small water-soaked, translucent interveinal streaks are formed on the
leaf and the lesions enlarge lengthwise and turn brown. On the surface
of the lesions, bacteria ooze out and form small yellow bead under
humid conditions. In severe cases, the leaves wither and dry up.

Common differentiating features between bacterial blight and bacterial

streak diseases

Bacterial blight Bacterial streak

Xanthomonas oryzae pv. oryzae Xanthomonas oryzae p.v. oryzicola
Marginal lesions are opaque against The interveinal streaks are
the light and lesions are formed at the transparent
leaf tip and margin.
Streak/ Lesion margins remain wavy Streak/ Lesion margins remain linear
Enters mainly through either wounds Enters mainly through the stomata
or hydathodes, multiplies in the and multiply in the parenchyma
parenchymatous cell and moves to tissues of the leaves. It infects mainly
the xylem vessels where active the parenchymatous cells of the
multiplication results in blight on the leaves, but is not systemic
leaves.

PHYTOPLASMAL DISEASE

1. Rice yellow dwarf - Candidatus Phytoplasma

Symptoms
 Stunting, excessive tillering with yellowish green leaves. Leaves
became soft and droop. Plants are usually sterile but some may
produce small panicles with unfilled grains.
Mode of Spread and Survival
 The phytoplasma is transmitted by plant hoppers Nephotettix virescens
and N. nigropictus with a latent period of 25-30 days.
VIRAL DISEASES
1. Tungro disease - Rice Tungro Virus (RTV)
Symptoms
 Affected plants exhibit stunting and reduced tillering. Their leaves
become yellow or orange-yellow, may also have rust-colored spots.
Discoloration begins from leaf tip and extends down to the blade or the
lower leaf portion. Flowering is delayed and panicle becomes sterile or
partially filled.
Iodine test
 Tungro infected plants can be identified by Iodine test. Ten centimeter
long leaf tip is cut in the early morning before 6 am and dipped in a
solution containing 2 g Iodine and 6 g Potassium Iodide in 100 ml of
water for 30 minutes or dip in10 ml of tincture iodine + 140 ml of water
for one hour. Tungro infected leaves show dark blue streaks.
Pathogen
The disease is caused by two morphologically unrelated viruses:
Rice tungro bacilliform virus (RTBV) [belongs to caulimoviridae family;
genus – tungro virus] RTBV is rod/bacilliform shaped with a circular double -
stranded DNA as a genome.
Rice tungro spherical virus (RTSV) [belongs to family Sequiviridae, of the
genus Waikavirus]. RTSV is spherical shaped (isometric particle) with a single
- stranded RNA. Both the particles in plant are restricted to phloem tube.
 If rice is co-infected by both of the viruses, it will show the typical
severe symptoms of yellow-orange leaf discoloration, plant stunting,
and reduced tillering and yield. On the other hand, if rice is infected
only with rice tungro bacilliform virus, it shows milder symptoms. In
contrast, rice plants will show no symptoms if they are infected only
with rice tungro spherical virus.
Mode of Spread and Survival
 Transmitted semi-persistently by the leaf hoppers Nephotettix
virescens, N. nigropictus, N. parvus, N. cincticeps.

2. Grassy stunt - Virus

Symptom
 The infected plants are markedly stunted with excessive tillering and an
erect growth habit. The leaves become narrow, pale green and small
with rusty spots. The plants may produce a few small panicles which
bear dark brown colored and unfilled grains.
Pathogen
 It has filamentous particles. Genome of the virus is RNA .
Mode of spread
 The virus is transmitted in a persistent manner by the brown plant
hopper, Nilaparvata lugens. It has a latent period of 5 to 28 days in the
vector.
Physiological disorder – Khaira disease due to Zn deficiency
Symptoms
 Symptom appears 2 to 3 weeks after transplanting. Leaves develop
brown spots, blotches and streaks on the upper leaves, plants remain
stunted and in severe cases may die.

Favorable conditions
 High soil pH (>7.0) especially in calcareous soil, low available Zn
content even though soil contains enough Zn, prolonged
submergence/flooding and low redox potential, high magnesium (Mg)
to calcium (Ca) ratio.
Ex. No. : 2 DISEASES OF MAIZE AND SORGHUM
Date:
Disease name Causal organism
MAIZE
Common Smut Sphacelotheca sorghi
Head Smut Sphacelotheca reilina
Turcicum Leaf blight (TLB) Exserohilum turcicum
Rust Puccinia sorghi
Downy mildew Peronosclerospora sorghi
Charcoal rot / Post flowering stalk rot Macrophomina phaseolina
Leaf blight Exserohilum turcicum
(syn. Helminthosporium turcicum)
SORGHUM
Downy mildew Peronosclerospora sorghi
Rust Puccinia purpurea
Anthracnose and red rot Colletotrichum graminicolum
Grain smut /covered smut/ kernel Sporisorium sorghi
smut/short smut (Syn. Sphacelotheca sorghi)
Loose smut Sporisorium cruentum
(Syn. Sphacelotheca cruenta)
Long smut Tolyposporium ehrenbergii
Head smut Sporisorium reilianum
(Syn. Sphacelotheca reiliana)
Ergot or Sugary disease Claviceps sorghi (Anamorph -
Sphacelia sorghi)
Rectangular leaf spot Cercospora sorghi
Charcoal rot Pycnidial stage Macrophomina phaseolina
Sclerotial stage Rhizoctonia bataticola
Leaf Blight Exserohilum turcicum
(Helminthosporium turcicum)
Sorghum Grain Mould / Head mould - Fusarium, Curvularia, Alternaria,
Fungal complex Aspergillus and Phoma
Witch weed – Partial root parasite Striga asiatica and S. densiflora
MAIZE DISEASES
1. Common Smut: Sphacelotheca sorghi
Symptoms
Head smut is not visible in the early stage of corn development, but
only when the corn tassel and ear appear.
Tassel symptoms
 Symptoms first become visible at the time of tassel emergence and
pollination. It is typical for head smut to attack in hot spots randomly
throughout the field, depending on where the spores were present at
the time of infection.
 Infection of the tassel may be limited to individual spikelets, or may
cover it completely. Leaf-like formations emerge, forming unusual
structures on infected tassels. No pollen is produced
Ear symptoms
 Most commonly, affected ears are round or tear-drop shaped, lacking
silks, and filled with black spores. A tangled mass of vascular strands
mingles between spore masses. Infected plants usually have no
kernels. It is common to observe excessive tillering in infected plants.
Life Cycle and Disease Development
The fungus Sphacelotheca reiliana survives over winter as spores in
the soil. Separate races have been recognized: one race limited to corn, and
another that attacks sorghums and sudangrass. Optimum conditions for corn
germination and early growth also favor the pathogen. Infection level is
increased by low soil moisture at the seedling stage of corn.
The fungus attacks seedlings by invading the young tissue, and later
the mycelium systemically develops within the undifferentiated ear and tassel
tissues. Part or all of these tissues develop into smut sori in which teliospores
are produced. Smut sori will completely replace all the kernels on the ear, and
consume most of the tassel, causing total yield loss on affected plants.
Teliospores are scattered and buried in the soil. The fungus may also be
introduced to a field by contaminated harvesting, planting or cultivation
equipment, which may transport the spores from an infected to a disease-free
field.
2.Head Smut: Sphacelotheca reilina
Symptoms
 Symptoms are usually noticed on the cob and tassel.
 Large smut sori replace the tassel and the ear. Sometimes the tassel is
partially or wholly converted into smut sorus. Under such conditions the
Individual spikelets on tassels may form shoot like growths, or the
entire tassel may develop into leaf like structures.
 The smutted plants are stunted in growth, produce little yield and
remain greener than that of the rest of the plants.
Pathogen
 Smut spores are produced in large numbers which are reddish brown
to black, thick walled, finely spined, spherical or slightly irregular.
Favourable Conditions
 Low temperature favours more infection and this fungus also infects
the sorghum crop and vice versa.
Mode of Spread and Survival
 The smut spore retains its viability for two years. The fungus is
externally seed-borne and soil-borne. The major source of infection is
through soil-borne chlamydospores.
3. Turcicum Leaf blight (TLB) - Exserohilum turcicum
Symptoms
 The fungus affects the maize plant at young stage.
 Small yellowish round to oval spots are seen on the leaves. The spots
gradually increase in area into bigger elliptical spots with straw to
grayish brown colour centre and dark brown margins. The spots
coalesce to form bigger spots and gives blighted appearance. The
surface is covered with olive green velvetty masses of conidia and
conidiophores.
Pathogen
 Conidiophores are in group, geniculate, mid dark brown, pale near the
apex and smooth.
 Conidia are distinctly curved, fusiform and pale to mid dark golden
brown with 5-11 pseudosepta.
Favourable Conditions
 Optimum temperature for the germination of conidia is 8 to 27C
provided with free water on the leaf. Infection takes place early in the
wet season.
Mode of Spread and Survival
 It is a seed-borne fungus. It also infects sorghum, wheat, barely, oats,
sugarcane and spores of the fungus are also found to associate with
seeds of green gram, black gram, cowpea, varagu, Sudan grass,
Johnson grass and Teosinte.
4. Rust: Puccinia sorghi
Symptom
 Brown pustules: Circular to elongate golden brown or cinnamon
brown, powdery, erumpent pustules appears on both leaf surfaces. As
the crop matures brownish black pustules containing dark thick walled
two celled teliospores will develop. In severe cases, infection spreads
to sheaths and other plant parts.
Pathogen
 Heteroceious rust
 Uredospores single celled, echinulate and yellowish brown. The
uredospores are pedicellate, elliptical or oval, thin walled, echinulate
and brown in colour with 4 to 5 germ pores. Club shaped paraphyses
are also found in uredosorus.
 The teliospores are reddish or brown in colour and two celled, rounded
at the apex with one germ pore in each cell. The teliospores
germinate and produce promycelium and basidiospores.
 Alternate hosts - Oxalis europea, O. corniculata and O. stricta.
 Basidiospores infect Oxalis corniculata (alternate host) where
pycnial and aecial stages arise after infection. Aeciospores carried by
wind and infect maize.
Mode of Spread :
 Primary spread thgrough alternate host and
 Secondary spread through wind borne uredospores.
5. Downy mildews

Sorghum downy mildew - Peronosclerospora sorghi

Philippine downy mildew - Peronosclerospora philippinensis
Java downy mildew - Peronosclerospora maydis
Sugarcane Downy mildew - Peronosclerospora sacchari
Brown stripe Downy mildew - Sclerophthora rayssiae
Rajasthan downy mildew - Peronosclerospora heteropogoni
Among the above downy mildews, sorghum downy mildew prevailing in
Tamil Nadu.

Symptoms
 Development of chlorotic streaks on the leaves. Plants exhibit a
stunted and bushy appearance due to shortening of the internodes.
White downy growth is seen on the lower surface of leaf. Downy
growth also occurs on bracts of green unopened male flowers in the
tassel. Small to large leaves are noticed in the tassel. Proliferation of
auxillary buds on the stalk of tassel and the cobs is common and called
as Crazy top.

Pathogen
Mycelium - Non-septate, inter cellular
Parasitism - Systemic and obligate
Sporangiophores Short and stout, branch profusely into series of
pointed sterigmata which bear hyaline, oblong or
ovoid sporangia (conidia). Sporangia germinate
directly and infect the plants
oospores In advanced stages, oospores are formed which are
spherical, thick walled and deep brown.
Mode of spread
 Primary spread through oospores in soil and seed-borne
 Secondary spread by sporangia.
6. Charcoal rot / post flowering stalk rot (PFSR)-Macrophomina phaseolina
Symptoms
 The affected plants exhibit wilting symptoms.
 The stalk of the infected plants can be recognized by greyish streak.
The pith becomes shredded and grayish black minute sclerotia develop
on the vascular bundles.
 Shredding of the interior of the stalk often causes stalks to break in the
region of the crown. The crown region of the infected plant becomes
dark in colour. Shredding of root bark and disintegration of root system.
Pathogen
 Fungus produces large number of round and black sclerotia. Sclerotia
are black and globular to irregular in shape.
 Pycnidia appear on the stalks.
 Pycndiospores are colourless, oval and single celled and borne in
black flask shaped pycnidia.
Favourable Condition:
 Post flowering and grain filling stage.
 Warm temp 36 – 40oC and low moisture.
Mode of spread and survival
 Primary spread – Sclerotia in infected crop debris.
 Secondary spread – Wind-borne pycnidiospores.
7. Leaf blight – Exserohilum turcicum (syn. Helminthosporium turcicum)
Symptoms
 Elongated spindle shaped necrotic lesions appear on leaves. Infection
is first seen on lower leaves. Complete burning of foliage in severe
cases. Also called as Northern leaf blight.
Pathogen
 Mycelium branched, septate, inter and intra cellular.
 Conidiophores arise in groups, long, unbranched, slightly curved,
septate, geniculate and yellowish brown.
 Conidia borne singly, distinctly curved, fusiform, long, 3-7 septate.
Favourable Condition
 Cool and humid climate.
Mode of spread and survival
 Primary spread through dormant mycelia in plant debris.
 Secondary spread through wind-borne conidia.
8. Aspergillus rot / Aflatoxin contamination rot:
 Aspergillus flavus and A. parasiticus. Aspergillus ear rot is one of the
most important diseases in maize crop. The fungus produces a
mycotoxin known as aflatoxin (B1, B2, G1 and G2) - inside the
diseased maize kernels. The presence of aflatoxin will affect grain
quality, marketability and livestock health (if the grain is consumed).
Favourable Condition:
 Aspergillus ear rot is commonly observed during hot, dry years on
stressed plants (such as those exhibiting symptoms of nutrient
deficiency or drought stress). Feeding damage from ear-invading
insects also contributes to disease development and aflatoxin
contamination.

SORGHUM DISEASES
1. Downy mildew - Peronosclerospora sorghi
Symptoms
 Abundant white downy growth occur on the under surface of the
leaves, corresponding to the upper surface of the leaf, yellowing. The
infected plants show streaks on surfaces of the upper leaves. Due to
formation of oospores along the streaks, necrosis of tissues occurs and
the streaks turn brown. Inter-veinal tissues disintegrate resulting in
typical leaf shredding symptom.
Pathogen
Thallus - The mycelium is filamentous inter-cellular,
hyaline, non-septate and branched. It produces
haustorium
Parasitism - Biotrophs, systemic
Asexual reproduction - The sporangiophores emerge through stomata
singly or in clusters, they are swollen, short,
upright branches bearing sporangia. Sporangia –
 direct germination
Sexual reproduction - Sexual spores are oospores that present between
fibrovascular strands of shredded leaves.
Oospores are thick walled, brown in color and
round shaped
Favourable conditions
 Cool (20 -23C) and moist weather (>90 % RH) favors the disease.
Mode of spread and Survival
 Primary spread - Oospores in soil (viable for 3-4 years) and seed-borne
 Secondary spread - Air-borne sporangia
 Survives as oospores in soil and crop debris
2. Rust- Puccinia purpurea
Symptoms
 The pathogen affects the all stages of crop growth. Raised pustules
(Uredosori) appear on both surfaces of leaf as purplish elliptical spots
which rupture to release reddish powdery masses of uredospores. The
pustules lie parallel to the veins. Teliospores develop in the old
uredosori which are darker. The pustules may also occur on the leaf
sheaths, stalks and on the inflorescence.
Pathogen
 Parasitism – Biotroph, heterocious, macrocyclic.
 Basidiospores infect Oxalis corniculata (alternate host) where pycnial
and aecial stages arise after infection.
 Urediospores and teliospores are formed in the sorghum.
Favorable conditions
 Rainy weather
Mode of spread and survival
 Uredospores survive only for a short time in soil and infected debris.
Presence of alternate host helps in perpetuation of the fungus.
3. Anthracnose and red rot - Colletotrichum graminicolum
Symptoms
 The fungus causes both leaf spot (anthracnose) and stalk rot (red rot)
in sorghum.
  Affect all aerial parts – leaves, leaf sheaths, stalk, earhead, and seed.
 The disease appears as small red or purple spots on both surfaces of
the leaf. The centre of the spot is white in colour encircled by brown
margin. Numerous small black dots are seen on the white surface of
the lesions which are the fruiting bodies (acervuli).
 Red rot can be characterized externally by the development of circular
cankers in the stalk and the inflorescence.
 Infected stem when split open shows red discolouration.
Pathogen
Mycelium : It is localized in the lesion and forms the stroma
beneath the epidermis
Conidiophores : Short (hyaline) and pointed, septate, dark coloured
setae
Conidia : It is sickle shaped, thin walled, single celled, hyaline and
measures 45-55μ. Conidia contain centrally or laterally
placed oil globule
Perithecia : Ostiolate having limited number of asci, which contains
typically eight spores, which are one or two celled with
a central oil globule.
Favorable conditions
 Continuous rain, temperature of 28-30° C and high RH
Mode of spread and survival
 Spread through seed and air-borne conidia and infected plant debris

4. Grain smut/covered smut/ kernel smut/short smut

Sporisorium sorghi (Syn. Sphacelotheca sorghi)
Symptoms
 Most of the grains are converted into smut sori and they are larger than
normal grains. Grains are converted into sac or sori and are oval or
conical covered with a tough membrane which persists up to thrashing.
At the time of thrashing, the skin ruptures and releases black powdery
mass of smut spores. Ratoon crops exhibit higher incidence.
Favourable condition
 Warm temperature of 20-32oC and wet soil moisture favour the disease
incidence.
Mode of spread and survvival
 Survives in the seed because it is externally seed borne (viable for
more than 13 years).
 Primary spread – seed-borne spores.
 Secondary spread and air-borne spores.
5. Loose smut - Sporisorium cruentum (Syn. Sphacelotheca cruenta)
Symptoms
 All florets / spikelets in an infected head are smutted. Each spikelet is
converted into the smut sorus covered with thin membrane. The
membrane covering the sorus ruptures prior to head emergence and
release black powdery teliospores. All the spores are released leaving
the central columella in the spikelet.
Favorable conditions
 Soil temperature 10-35oC and moist soil.
Mode of spread and survival
 Externally seed-borne and soil-borne in dry regions.
6). Long smut - Tolyposporium ehrenbergii
Symptoms
 Usually a few spikelets in an ear affected. The sori are very prominent,
long, and curved with creamy brown thick membrane.
Favourable condition
 Warm temperature of 20-32oC and wet soil moisture favour the disease
incidence.
Mode of spread and survvival
 The spores are viable for two years. Air borne
7. Head smut - Sporisorium reilianum (Syn. Sphacelotheca reiliana)
Symptoms
 The entire inflorescence is either completely or partially replaced by a
large cylindrical sorus covered with thick membrane which rupture
 before the emergence of the head and the spores are blown away, the
dark filaments network of vascular tissues are exposed.
Favorable conditions
 Soil temperature: About 27-31 oC and moist soil
Mode of spread and survival
 The spores are viable for two years. Seed and soil-borne.
Pathogen
Thallus - Dimorphic thallus (mycelia form and yeast like growth)
Parasitism - Biotroph and cause systemic infection
teliospores - Called as smut spore. They are oval, brown with thick
walled and single celled
Basidiospores Sexual spores
8. Ergot or Sugary disease - Claviceps sorghi (Sphacelia sorghi)
Symptoms
 The disease is confined to individual spikelet. Honey dew like creamy
sticky liquid oozes out from the infected florets. The honey dew is
colonized by saprophytic fungi giving a blackened appearance. Under
favourable conditions, long straight or curved, light brown hard sclerotia
(Ergot) are produced from the infected florets.
9. Rectangular leaf spot - Cercospora sorghi
Symptoms
 Usually the lower leaves are first attacked. The symptoms appear as
small leaf spots which enlarge to become rectangular lesions on the
leaf and leaf sheath. The lesions are mostly isolated and limited by
veins. Severe spotting results in premature drying of leaf. The colour of
the spots varies from red, purple and brown depending upon the
variety.
Favourable conditions
 Cool moist weather, high humidity high rainfall.
Mode of spread and survival
 The disease spreads through air-borne and seed borne conidia.
10. Charcoal rot of Sorghum
Macrophomina phaseolina (Rhizoctonia bataticola)
Symptoms
 Charcoal rot is a major disease in the dry land sorghum-growing
regions. Charcoal rot becomes conspicuous near crop maturity or
moisture stress during the pre-flowering period.
 Fungus invades the crown through roots and disorganizes the cortical
tissues of lower internodes near the soil level resulting in internal
shredding at and above the ground line. The shredding can be
observed by splitting the stalk.
 Lower stem becomes soft and weak, leading to lodging. Stem split
open and vascular fibres are seen to be clearly separated and heavily
coated with small hard black sclerotia, hence named as charcoal rot.
Pathogen
Thallus - Filamentous, branched, septate, coloured (black)
mycelium.
Parasitism - Necrotroph
Asexual reproduction - Asexual fruiting body -Pycnidia is dark brown,
globose with an ostiole. Inner wall of the pycnidium
is lined with pycnidiophore bearing pycnidiospore.
Pycnidiospores are hyaline, thin, one celled, rod or
oval shaped.
Sexual reproduction - No sexual stage.
Resting bodies - Irregular, black coloured sclerotia which are
microscopic.
Host plants - The pathogen affects several crops such as major
food crops (maize, sorghum, pulse crops (common
bean, green gram, blackgram), fiber crops (jute,
cotton), and oil seed crops (soybean, sunflower,
sesame).
Mode of spread and survival
 Survival and spread through soil-borne sclerotia.
11. Leaf Blight – Helminthosporium turcicum
Symptoms
 The spots are long elongated spindle shaped with straw coloured
centre and deeply pigmented margin. The spots enlarge and coalesce
to form large patches.
2. Sorghum grain mould / Head mould - Fungal complex
Fusarium, Curvularia, Alternaria, Aspergillus, Phoma
Symptom
Grain mould occurs on grains when there is rain during flowering and
grain filling. Cultivars with white grain are particularly affected by this disease.
Grain mould drastically reduces both quantity and quality of the grain and
affects germination of seeds. Moulded grain may contain certain mycotoxins.
There are 3 types of infected grain:
 Severely infected grain fully covered with mold.
 Normal-looking grain with slight discoloration.
 Apparently normal grain with no external symptoms.
The moulded grain show pink, orange, gray, white, or black discoloration
depending on the fungus involved.
Mode of spread and survival
 Spread through air borne conidia.
 Survive as parasites and saprophytes in the infected plant debris.
Favourable condition
 Wet weather during flowering and grain filling.
13. Witch weed – Striga asiatica and S. densiflora
Symptoms
 The root exudates of sorghum stimulate the seeds of the parasite to
germinate and infect its root. Striga plants (15-30 cm height) occur in
clusters of 10-20/plant. It produces flowers, fruits and seeds. Each fruit
contains minute seeds which survive in soil for several years. Severe
infestation of the parasite causes yellowing and wilting of the host
plant. Infected plants are stunted and may die prior to seed setting.
 S. asiatica produces red-pink flowers S. densiflora produces white
flowers
EX.NO : 3 DISEASES OF PEARL MILLET, FINGER MILLET AND
Date : SMALL MILLETS

PEARL MILLET/ CUMBU

Name of the diseases Causal organism

Downy mildew Sclerospora graminicola
Rust Puccinia penniseti/ Puccinia substriata
Smut Moesziomyces penicillariae
(Tolyposporium penicillariae)
Ergot or Sugary disease Claviceps fusiformis

FINGER MILLET (RAGI) AND SMALL MILLETS

Name of the diseases Causal organism
Fungal diseases
Ragi Blast Pyricularia grisea
Seedling blight or Leaf blight Drechslera (Helminthosporium) nodulosum
(Sexual stage: Cochliobolus nodulosum)
Wilt Sclerotium rolfsii
(Sexual stage : Corticium rolfsii)

Viral Diseases
Disease name Virus Vector Life style/
parasitism
Mosaic Sugarcane mosaic virus Aphid Biotroph
Mottle streak Rhabdo virus Hopper Biotroph
Streak Maize streak virus Hopper Biotroph

1. Downy mildew -Sclerospora graminicola

Symptoms
 Infection is mainly systemic and symptoms appear on leaves (downy
mildew) and inflorescence (green ear). The initial symptoms appear in
seedlings at three to four leaf stages.
  The affected leaves show profuse downy white growth consisting of
sporangiophores and sporangia of the pathogen occurs predominantly
on the under surface of the leaves. Corresponding to the upper surface
of the leaf, yellowing or patches of light green to light yellow colour
discoloration occur. The yellow discolouration often turns to streaks
along veins.
 Each florets of the inflorescence of infected plants gets completely or
partially malformed into green leaf like structures, giving the typical
green ear symptom.
Pathogen
 Characters of the pathogen are the same as described in sorghum
downy mildew. Exception is the sporangia.
 Sporangia of Sclerospora show indirect germination that is zoospores
are produced inside the sporangia and then infect the crop. Whereas in
the Peronosclerospora sporangia show direct germination that is
sporangium itself germinate and infect the crops without production of
zoospores.
2. Smut - Moesziomyces penicillariae (Syn: Tolyposporium penicillariae)
Symptoms
 The pathogen infects few florets and transforms them into plump sori
containing smut spores. The smutted grains are initially bright green
later colour changes to dirty black in colour containing smut spores.
The smutted grains are two to three times bigger than the normal grain.
Favourable conditions
 High humidity and successive cropping with cumbu.
Mode of spread and survival
 It survives as spore balls in the soil that serves as primary source of
inoculum.
 Secondary spread is by air-borne smut spores.
3. Rust - Puccinia penniseti / Puccinia substriata
Symptoms
 Symptoms first appear mostly on the distal half of the lamina.
  Raised reddish rusty pustule (urediosori) appear both upper and under
surface but appear more on the upper surface. The pustules may be
formed on leaf sheath. stem and on peduncles.
 Later, black colored telial formation takes place on leaf blade, leaf
sheath and stem. Brownish uredia are exposed at maturity while the
black telia remain covered by the epidermis for a longer duration.
Pathogen
As described in sorghum rust
 The pathogen is macrocyclic and heterocious. Uredinial and telial,
stages occur on pearl millet. The spermagonial/pycnial and aecial
stages are seen on brinjal (alternate host).
 Uredospores are oval, elliptic, sparsely echinulated and pedicellate.
Teliospores are dark brown in colour, two celled, cylindrical to club
shaped, apex flattered, broad at top and tapering towards base.
Favourable Conditions
 Closer spacing
 Presence of abundant brinjal plants and other species of Solanum viz.,
S.torvum, S. xanthocarpum and S. pubescens.
Mode of Spread and Survival
 Air-borne uredospores are the primary source. The uredial stages also
occur on several species of Pennisetum.
4. Ergot or Sugary disease -Claviceps fusiformis
Symptoms
Symptoms are the same as described in sorghum ergot.
Honey dew stage:
 The symptom is seen by exudation of small droplets of light pinkish or
brownish honey dew from the infected spikelets. Under severe infection
many such spikelets exude plenty of honey dew which trickles along
the earhead. This attracts several insects.
Ergot stage:
 In the later stages, the infected ovary turns into small dark brown
sclerotium which projects out of the spikelet.
Pathogen
As described in sorghum ergot disease.
Mode of Spread and Survival
As described in sorghum ergot disease.
 The role of collateral hosts like Cenchrus ciliaris and C. setigerus in
perpetuation of fungus is significant. The fungus also infects other
species of Pennisetum.
Minor diseases
Grain mould- Fusarium and Curvularia spp.
 Grain affected by complex of several fungi. Grains covered with white,
pink or black moulds.
Blast -Pyricularia grisea.
Diamond shaped to circular lesions with dark brown margins and grey
center. Lesions are surrounded with yellow halo.
DISEASES OF FINGER MILLET (RAGI) AND SMALL MILLETS
1. Ragi Blast - Pyricularia grisea
Symptoms
 Symptoms of ragi blast are the same as described in rice blast. The
pathogen attacks the crop from seedling stage to the time of grain
formation.
 The lesions are spindle shaped with greyish green centre and brown
margin. Under humid conditions, an olive grey overgrowth of fungus is
seen on the centre of the spot. Later the centre become whitish grey
and disintegrates. Nodal infection causes blackening of the nodal
region.
 Neck infection shows black discolouration at the neck region.
 Infection may also occur at the basal portions of the panicle branches
including the fingers. The affected portions turn brown and ears
become chaffy and only few shriveled grains are formed.
Pathogen, Favourable conditions, mode of spread and survival and
management
As described in rice blast
2. Seedling blight or Leaf blight Drechslera (Helminthosporium) nodulosum
(Sexual stage: Cochliobolus nodulosum)
Symptoms
 The pathogen affects both seedling and the adult plants.
 Minute, oval, light brown lesions on the young leave and become dark
brown. Several such lesions coalesce to form large patches of infection
on the leaf blade. The affected blades wither prematurely and the
seedlings may be killed. Linear oblong and dark brown spots appear on
the leaves of grown up plants. The leaves give blightening appearance.
 The pathogen also attacks the nodal region causing black lesion.
 While nursery infection causes heavy damage due to the seedling
blight, neck infection causes heavy chaffiness and severe loss in grain
yield.
Pathogen
Hypha - Brown and septate.
Asexual reproduction - Conidiophores are long, septate, dark brown in
colour, often branched and geniculate.
Conidia are straight ovoid, pale to dark golden
brown, 5-7 pseudoseptate.
Sexual reproduction - It produces spherical perithecia and asci contain
1 to 8 ascospores.
Favourable conditions
 Optimum temperature for infection is 30-32C and 80-90% relative
humidity, rains during ear head emergence.
Mode of spread and survival
 Primary spread is through seed-borne inoculum and the secondary
spread by air-borne conidia.
3. Wilt -Sclerotium rolfsii (Sexual stage: Corticium rolfsii)
Symptoms
The infected plants become pale, chlorotic and stunted.
 The fungus attacks basal stem portion and later the leaf sheath and
culm. The infected portion becomes soft and dark brown in colour. A
whitish mycelial mass can be seen on the basal stem and on the nodal
 portions. On the surface of the lesions, small spherical, dark coloured
sclerotia are formed.
Pathogen
 The mycelium of the fungus is septate and white to tan coloured.
 Sclerotia are minute, mustard seed like structures, regular spherical in
shape and black in colour.
Favourable conditions
 High soil moisture and high temperature (more than 30C).
Mode of spread and survival
 The fungus survives in the soil as sclerotia and spreads through
irrigation water and implements.
4. Mosaic/Mottle streak/ streak
Mosaic : Sugarcane mosaic virus -aphid transmitted
Mottle streak : Rhabdo virus - hopper transmitted
Streak : Maize streak virus -hopper transmitted
Symptoms
 The virus affected plants are stunted and pale green in colour.
Chlorotic mottles/streaks appear on leaves that are continuous or
discontinuous. Early infection leads to reduction of tillers and grain
formation.
Favorable Conditions
 The disease is high in April-May sown crops due to high population of
hoppers viz., Cicadulina bipunctella and C. cinai.

Minor diseases
Downy mildew: Sclerospora macrospora: Green ear symptom, Proliferation
of spikeles.
Smut: Melanopsicum eleusinis: Grains are converted into enlarged greenish
to dirty black sori.
EX. NO. : 4 DISEASES OF PIGEONPEA, URDBEAN, MUNGBEAN AND
DATE : COWPEA

PIGEONPEA
Fungal Diseases
Name of the diseases Causal organism
Wilt Fusarium udum
Powdery mildew Leveillula taurica
Leaf spot Cercospora cansescens
Viral Diseases
Disease name Virus Vector Life style/
parasitism
Sterility mosaic Pigeon pea sterility mosaic Mite Biotroph
virus (Aceria cajani)
URDBEAN AND MUNGBEAN
Fungal diseases
Name of the diseases Causal organism
Dry root or Charcoal rot
Sclerotial stage Rhizoctonia bataticola
Pycnidialstage Macrophomina phaseolina
Powdery mildew Erysiphe polygoni
Rust Uromyces phaseoli typica
Leaf spot Cercospora canescens
Viral Diseases
Disease name Virus Vector Life style/
parasitism
Yellow Mosaic Mung Bean Yellow whitefly Biotroph
Mosaic virus (Bemisia tabaci)
Leaf crinkle Leaf crinkle virus whitefly Biotroph
(Bemisia tabaci)
SOYBEAN
Fungal diseases
Name of the diseases Causal organism
Anthracnose Colletotrichum lindimuthianum
Root rot Macrophomina phaseolina
Rust Uromyces appendiculatus
Leaf spot Cercospora cruenta
Powdery mildew Erysiphe polygoni
Viral Diseases
Disease name Virus Vector Life style/
parasitism
Mosaic Soya bean mosaic Aphids Biotroph
virus (Myzes persicae)
COWPEA
Fungal diseases
Name of the diseases Causal organism
Dry root rot Macrophomina phaseolina
Wilt Fusarium oxysporum f. sp. tracheiphilum
Leaf spot Cercospora sojana
Viral Diseases
Disease name Virus Vector Life style/
parasitism
Mosaic Cowpea mosaic virus Aphids Biotroph
Aphis craccivora,
A. gossypii,
A. fabae and
Myzus persicae

PIGEONPEA
1. Wilt: Fusarium udum
Symptoms
 Gradual or sudden wilting from bottom to top.
 Leaves initially pale, loose their turgidity and droop (withering).
 Entire plants wilt or die within few days. Disease occur in patches.
 Vascular browning seen indicating xylem plugging with mycelia.
 Affected plants cannot be easily pulled out.
Pathogen
Mycelium - Hyaline, septate
Microconidia - Hyaline, small, elliptical or curved, single celled or
two celled
Macroconidia - Hyaline, thin walled, linear, curved or fusoid, pointed
at both ends with 3-4 septa.
Chlamydospores - Thick walled, spherical or oval, terminal or intercalary
singly or in chains of 2 to 3.
2. Powdery mildew- Leveillula taurica
Symptoms
 Powdery patches on the lower surface corresponding yellow patches
on upper surface.
 Premature defoliation.
Pathogen
Mycelium - Intercellular
Haustoria - Absorbs nutrition
conidiophores - Which arise through stomata, are hyaline, long, non
septate, slender and rarely branched and bear
single conidium at the tip.
conidia - Hyaline, single celled and elliptical or clavate.
cleistothecia Black, globose with simple myceloid appendages.
They contain 9-20 cylindrical asci. Each ascus
contains 3-5 ascospores which are also hyaline and
unicellular.
3. Leaf spot: Cercospora cansescens
Symptoms
 Light brown spots bound by veins on under surface of the leaves.
 Premature defoliation.
Pathogen
 The fungus produces large number of whip-like, hyaline, 7-9 septate
conidia in groups on the conidiophores which are light to dark brown in
colour.
Viral disease
1. Sterility mosaic (Pigeon pea sterility mosaic virus)
Symptoms
 Plants stunted due to shortening of internodes and look chlorotic.
 Auxiliary buds grow, crowded at the top giving bushy appearance.
 Leaves become small and crinkled with mild mottle to severe mosaic.
 Ring spot symptom seen.
 Plants become sterile
Vector : Mite - Aceria cajani.
URDBEAN AND MUNGBEAN
1. Dry root or Charcoal rot: Sclerotial stage: Rhizoctonia bataticola
Pycnidial stage: Macrophomina phaseolina
Symptoms
 Occurs in patches, plants wilt and dry suddenly.
  Yellowing and dropping of leaves.
 Infected plants can be easily pulled out.
 Grayish black sunken lesion leading to bark shredding.
 Dark brown sclerotia seen on roots and black minute pycnidia on
stem.
 Rotting of roots.
Pathogen
 Survives as sclerotia in soil and in infected plant debris.
2. Powdery mildew- Erysiphe polygoni
Symptoms
 Oidium type White powdery growth on the upper surface of leaves.
 In advanced stages powdery growth turns brown and leaves drop off
prematurely.
Pathogen
Mycelium - Ectophytic
Haustoria - Absorbs nutrition- epidermal cells
Conidiophores - Conidiophores arise vertically from the leaf surface,
bearing conidia in short chains.
Conidia - Conidia are hyaline, thin walled, elliptical or barrel
shaped or cylindrical and single celled
Chasmothecium Appear as minute, black, globose structures with
myceloid appendages. Each chasmothecium contains
4-8 asci and each ascus contains 8 ascospores
which are elliptical, hyaline and single celled.

3. Rust: Uromyces phaseoli typica

Symptoms
 Small, round reddish brown powdery pustules on lower surface of
leaves.
 Premature defoliation.
Pathogen
 It is autoecious, long cycle rust and all the spore stages occur on the
same host. The uredospores are unicellular, globose or ellipsoid,
 yellowish brown with echinulations.
 The teliospores are globose or elliptical, unicellular, pedicellate,
chestnut brown in colour with warty papillae at the top. Yellow
coloured pycnia appear on the upper surface of leaves. Orange
coloured cupulate aecia develop later on the lower surface of leaves.
The aeciospores are unicellular and elliptical.
4. Leaf spot: Cercospora canescens
Symptoms
 Well defined, reddish brown spots with grey center bounded by veins.
 Shot hole symptoms seen.
Pathogen
 The fungus produces clusters of dark brown septate conidiophores.
 The conidia are linear, hyaline, thin walled and 5-6 septate.
VIRAL DISEASES
1. Mung Bean Yellow Mosaic (Mung Bean Yellow Mosaic virus)
Symptoms
 Small irregular yellow patches in between veins giving mosaic
mottling.
 Yellowing covers the entire leaf.
 Brown necrotic spots are also seen.
Vector : white fly – Bemisia tabaci
2. Leaf crinkle (Leaf crinkle virus)
 Plants stunted. Leaves crinkling, curling and puckering.
 Leaves dark green with thick lamina and veins.
 Inflorescences malformed. Flowers sterile.
Vector : white fly (Bemisia tabaci) sap and also through seed.
DISEASES OF SOYBEAN
1. Dry root rot – Macrophomina phaseolina
Symptoms
 The disease symptom starts initially with yellowing and drooping of the
leaves.
 The leaves later fall off and the plant dies with in week.
  Dark brown lesions are seen on the stem at ground level and bark
shows shredding symptom.
 The affected plants can be easily pulled out leaving dried, rotten root
portions in the ground. The rotten tissues of stem and root contain a
large number of black minute sclerotia.
Pathogen
 The fungus produces dark brown, septate mycelium with constrictions
at hyphal branches. Minute, dark, round sclerotia in abundance.
 The fungus also produces dark brown, globose ostiolated pycnidia on
the host tissues. The pycnidiospores are thin walled, hyaline, single
celled and elliptical.
2. Wilt - Fusarium oxysporum f. sp. tracheiphilum
Symptoms
 Symptoms do not appear until the plants are about six weeks old.
 Initially a few plants are noticed with pale green flaccid leaves which
soon turn yellow.
 Growth is stunted, chlorosis, drooping, premature shedding or
withering of leaves with veinal necrosis often occurs and finally plant
dies within 5 days.
 Brownish, purple discoloration of the cortical area is seen, often
extends throughout the plant.
3. Leaf spot – Cercospora sojana
Symptoms
 Light to dark gray or brown areas varying from specks to large
blotches appear on seeds.
 The disease primarily affects foliage, but, stems, pods and seeds may
also be infected.
 Leaf lesions are circular or angular, at first brown then light brown to
ash grey with dark margins.
 The leaf spot may coalesce to form larger spots. When lesions are
numerous the leaves wither and drop prematurely.
 Lesions on pods are circular to elongate, light sunken and reddish
brown.
VIRAL DISEASES
1. Mosaic - Soybean mosaic virus (SMV)
Symptoms
 Diseased plants are usually stunted with distorted (puckered, crinkled,
ruffled, narrow) leaves.
 Pods become fewer and smaller seeds. Infected seeds get mottled
and deformed.
 Infected seeds fail to germinate or they produce diseased seedlings.
Virus
 It is caused by Soybean mosaic virus - a potyvirus.
 Flexuous particles 750 - 900nm long, ssRNA genome.
Vector: Aphids (Myzes persicae)
DISEASES OF COWPEA
1. Anthracnose : Colletotrichum lindimuthianum
Symptoms
 Spotting on pods.
 Water soaked lesions appear later becoming brown and circular
depressed with dark center. Acervuli seen.
2. Mosaic
Sypmtoms
 Mosaic mottling with dark green vein– banding, leaf distortion,
blistering, stunting and reduced leaf lamina.
Pathogen
 Cowpea mosaic virus (CPMV) is a plant virus of the comovirus group.
It is an RNA containing virus with isometric particles about 28 nm in
diameter. Its genome consists of 2 molecules of positive sense RNA
(RNA-1 and RNA-2) which are separately encapsidated.
Vectors : Aphid - Aphis craccivora, A. gossypii, A. fabae and Myzus persicae
3. Bacterial blight : Xanthomonas phaseoli
Sypmtoms
 Water-soaked light yellow spots on lower surface of leaves.
 Spots enlarge into reddish brown angular to circular necrotic
spots with chlorotic halos.
  In severe infection shot holes formed.
 Infection also seen on stem, pods and seeds.
Pathogenic characters:
 Bacteria is gram negative, rod shaped bacteria. It enters into the host
through wounds or natural opening. It spreads through water,
propagating materials, pruning tool etc.
4. Root rot : Macrophomina phaseolina
5. Rust : Uromyces appendiculatus
6. Leaf spot : Cercospora cruenta
7. Powdery mildew : Erysiphe polygoni
EX. NO. : 5 DISEASES OF GROUNDNUT, SESAME AND CASTER
DATE :
1. Tikka leaf spot Cercospora arachidicola (Mycospherella arachidis)
SYMPTOMS
 Affects all aerial parts – mostly on leaf.
 Occurs early in crop season – 3 to 4 weeks after sowing.
 Irregular reddish brown spots with yellow halo.
 Leaves shed prematurely and yield reduced.
Pathogen
 The fungus is both intercellular and intracellular.
 The fungus produces abundant sporulation on the upper surface of
the leaves.
 Conidiophores are olivaceous or yellowish brown in colour, short, 1
or 2 septate, unbranched and geniculate and arise in clusters.
 Conidia are sub hyaline or pale yellow, obclavate, often curved 3-12
septate, 35- 110 x 2.5 - 5.4 um in size with rounded to distinctly
truncate base and sub-acute tip.
 The fungus in its perfect stage produces asci in pseudothecia which
are globose or broadly ovate with papillate ostiole. Asci are
cylindrical to clavate and contain 8 ascospores. Ascospores are
hyaline, slightly curved and two celled, apical cell larger than the
lower cell.
Cercospora personata (Mycospherella berkeleyii)
 Spots appear 5 to 7 weeks after sowing.
 Dark brown circular spots without yellow halo.
 The lower surface lesions carbon black.
 Severe infection – leaf shed prematurely and yield reduced.
Pathogen
 The fungus produces both intercellular and intracellular mycelium.
 The conidiophores are long, continuous, 1-2 septate, geniculate, arise
in clusters on lower surface of leaves and are olive brown in colour.
 The conidia are cylindrical or obclavate, short, measure 18-60 x 6-
10um, hyaline to olive brown, usually straight or curved slightly with 1-
 9 septa, but mostly 3-4 septate.
 The fungus in its perfect stage produces asci in pseudothecia which
are globose or broadly ovate with papillate ostiole. Asci are
cylindrical to ovate, contain 8 ascospores. Ascospores are 2 celled
and constricted at septum and hyaline.
3. Rust: Puccinia arachidis
Symptoms
 Infection seen on 6 weeks old crop. Brick red pustules on lower
surface of leaf.
 Upper surface necrotic brown spots.
 Pustules seen on leaf and stem. Dark coloured teliosori appear which
produces teliospores.
 Leaves dry, drop prematurely, seeds small and shriveled.
Pathogen
 The fungus produces both uredial and telial stages.
 Uredial stages are produced in abundance on groundnut and
production of telia is limited. Uredospores are pedicellate,
unicellular, yellow, oval or round and echinulate.
 Teliospores are dark brown with two cells.
 Pycnial and aecial stages have not been recorded and there is no
information available about the role of alternate host.
4. Collar rot or seedling blight or crown rot : Aspergillus niger
 Pre–emergence rot : Rotting of seed, becomes soft and watery.
Germination affected.
 Post emergence rot : Circular brown spots occurs on the cotyledons of
seedling. Brown spots on collar region become soft and rots. Collapse
of seedling and stem shredding are seen.
Pathogenic characters:
 The mycelium of the fungus is hyaline to sub-hyaline.
 Conidiophores arise directly from the substrate and are septate,
thick walled, hyaline or olive brown in colour. The vesicles are
mostly globose and have two rows of hyaline phialides viz., primary
and secondary phialides.
  The conidial head are dark brown to black. The conidia are globose,
dark brown in colour and produce in long chains.
1. Root rot : Macrophomina phaseolina
 Reddish brown lesion above soil level.
 Leaves and branches droop – death of plants.
 Shredding of bark.
 Black sclerotia in infected tissues.
 Blackening of shells.
Pathogen
 The fungus invades the host both inter and intra-cellularly.It grows
rather fast, covering large areas of the host tissues and eventually
killing them in a short time.
 It produces numerous sclerotial bodies on the host tissue,which
measure about 110- 130µ in diameter.
 Often the pycnidial stage is produced on the host.the pycnidia are dark
brown, ostiolate and of varying size.The pycniospores are elliptical, thin
walled, single celled, hyaline and measure 10-42×6-10µ.
6. Peanut spotted wilt / Bud necrosis/ Groundnut ring mosaic / TSWV:
 Ring spot, mottling and rugosity of leaves. Leaflets size reduced and
distorted.
 Necrotic spots on stem and leaf. Bud necrosis.
 Pods wrinkled with black lesions on testa.
Pathogenic characters
It is caused by Groundnut bud necrosis virus (GBNV). The
virus particles are spherical, 30 nm in diameter, enveloped, ssRNA with
multipartite genome.

7. Rossette - Groundnut rosette assistor virus (GRAV), Groundnut

rosette virus and Groundnut rosette satellites
 The affected plants are characterized by the appearance of dense
clump or dwarf shoots with tuft of small leaves forming in a rosette
fashion.
 The plant exhibits chlorosis and mosaic mottling.
  The infected plants remain stunted and produce flowers, but only a
few of the pegs may develop further to nuts but no seed formation.
Pathogenic characters
The disease is caused by a complex mixture of viruses viz.,Groundnut
rosette assistor virus (GRAV), Ground nut rosette virus and Groundnut
rosette satellites is an isometric, not enveloped and 28nm diameter
(reported from India) and it gives no overt symptom in groundnut.
Groundnut rosette virus is with ssRNA genome, which becomes packaged in
GRAV virious and thus depends on it for aphid transmission, but produces
no overt symptoms in groundnut. The groundnut rosette satellites are
satellite RNAs that control the symptoms and cause the different types of
rosette (chlorotic, green and mosaic).

DISEASES OF SESAME / GINGELLY

1. Root rot/ Stem rot/ Charcoal rot : Macrophomina phaseolina
Rhizoctonia bataticola
 Dark brown lesions at the collar region,
 Yellowing, drooping and defoliation of leaves,
 Shredding of bark. Rotten roots and stem tissues harbours sclerotia.
 Plant easily pulled out.
 Pods Infected and open prematurely.
 Pycnidia seen on infected capsules and seeds.
Pathogenic characters:
The fungus produces dark brown, septate mycelium showing constrictions
at the hyphal junctions. The sclerotia are minute, dark black and 110-
130um in diameter. The pycnidia are dark brown with a prominent ostiole.
The conidia are hyaline, elliptical and single celled.

2. Leaf blight : Alternaria sesami

 Small,circular reddish brown spots with concentric rings on leaves.
 Dark brown lesions on petioles,stem and capsules.
 Blighting of leaves,defoliation ,splitting, of capsules and shriveled
 seeds.
Pathogenic characters:
The mycelium of the fungus is dull brown and septate and produce
largenumber of pale grey-yellow conidiophores which are straight or
curved. The conidia are light olive coloured with transverse and
longitudinal septa. There are around 3-5 septate and conidia are borne in
chain over short conidiophore.
3. Powdery mildew : Erysiphe cichoracearum
 White powdery growth on upper surface later turn grayish forming
cleistothecia.
 Flowers and young capsules affected .Premature shedding.
Pathogenic characters:
The fungus produces hyaline, septate mycelium which are extophytic and
send haustoria into the host epidermis. Conidiophores arise from the primary
mycelium and are short and non septate bearing conidia in long chains. The
conidia are ellipsoid or barrel-shaped, single celled and hyaline.
The chasmothecia are dark, globose with the hyaline or pale brown
myceloid appendages. The asci are ovate and each ascus produces 2-3
ascospores, which are thin walled, elliptical and pale brown in colour.
4. Phyllody : Phytoplasma disease
Vector Jassid – Orosius albicinctus.
 Floral parts transformed into green leafy structure – Phylloid structure.
 Small leaves and malformed flowers cluster at the top. Flower sterile.
 Stamens leaf like, anthers green and ovary transformed into shoot like
structure.
 Plants with reduced internodes – gives bushy appearance.
5. Wilt : Fusarium oxysporum f.sp sesami
The disease appears as yellowing, drooping and withering of leaves.
 The plants gradually wither, show wilting symptom leading to drying.
 The infected portions of root and stem show long, dark black streaks of
vascular necrosis.
Pathogenic characters:
The fungus produces macroconidia, microconidia and chlamydospores.
Macroconidia are falcate shape, hyaline and 5-9 celled. Microconidia are
hyaline, thin walled, unicellular and ovoid. The dark walled chlamydospores
are also produced.
6. Stem blight : Phytophthora parasitica var sesami
 Black coloured lesions appear on the stem near the soil level.
 The disease spreads further and affects branches and may girdle the
stem, resulting in the death of the plant.
 Leaves may also show water-soaked patches and spread till the leaves
wither. Infection may be seen on flowers and capsules.
 Infected capsules are poorly developed with shriveled seeds.
Pathogenic characters:
The fungus produces non-septate, hyaline mycelium. The sporangiophores
are hyaline and branched sympodially and bear sporangia. The sporangia are
hyaline and spherical with a prominent apical papilla. The oospores are
smooth, spherical and thick walled.
7. Bacterial leaf spot : Xanthomanas campestris pv sesami
 Initially water-soaked spots appear on the undersurface of the leaf and
then on the upper surface.
 They increase in size, become angular and restricted by veins and dark
brown in colour.
 Several spots coalesce together forming irregular brown patches and
cause drying of leaves.
 The reddish brown lesions may also occur on petioles and stem.
Pathogenic characters:
The bacterium is a Gram negative rod with a monotrichous flagellum.

8. Bacterial leaf spot: Pseudomonas sesami

 The disease appears as water-soaked yellow specks on the upper
surface of the leaves.
 They enlarge and become angular as restricted by veins and veinlets.
 The colour of spot may be dark brown with shiny oozes of bacterial
 masses.
Pathogenic characters:
The bacterium is gram negative aerobic rod with one or more polar flagella.

DISEASES OF CASTOR
1. Seedling blight : Phytophthora parasitica
 Dull green lesion on cotyledonary leaves.
 Rotting of stem, withering and death of seedling.
 Black discolouration of leaves, petiole and stem.
 Defoliation of leaves.

Pathogenic characters:
The fungus produces non-septate and hyaline mycelium.
Sporangiophore emerge through the stomata on the lower surface singly or in
groups. They are unbranched and bear single celled, hyaline, round or oval
sporangia at the tip singly. The sporangia germinate to produce abundant
zoospores. The fungus also produces oospores and chlamydospores in
adverse seasons.

2. Rust : Melampsora ricini

 Orange yellow coloured raised pustules on lower surface, drying of
leaves.
 Yellow coloured upper surface.
Pathogenic characters:
The fungus produces only uredosori in castor plants and other stages
of the fungus are unknown. Uredospores are two kinds, one is thick walled
and other is thin walled. They are elliptical to round, orange-yellow coloured
and finely warty.

3. Leaf blight: Alternaria ricini

 Irregular brown spots with concentric rings seen on leaves, stem,
inflorescence and capsules.
 Premature defoliation,.capsules crack and seeds infected.
Pathogenic characters:
 The pathogen produces erect or slightly curved, light grey to brown
conidiophores, which are occasionally in groups. Conidia are produced
in long chains.
 Conidia are obclavate, light olive in colour with 5-16 cells having
transverse and longitudinal septa with a beak at the tip.

4. Brown leaf spot : Cercospora ricinella

 The disease appears as minute brown specks surrounded by a pale
green halo.
 The spots enlarge to greyish white centre portion with deep brown
margin.
 The spots may be 2-4 mm in diameter and when several spots
coalesce, large brown patches appear but restricted by veins.
Infected tissues often drop off leaving shot- hole symptoms. In
severe infections, the older leaves may be blighted and withered.
Pathogenic characters:
 The fungal hyphae collect beneath the epidermis and form a hymenial
layer. Clusters of conidiophores emerge through stomata or epidermis.
 They are septate and unbranched with deep brown base and light
brown tip. The conidia are elongated, colourless, straight or slightly
curved, truncate at the base and narrow at the tip with 2-7 septa.
Ex. No 6. DISEASES OF TOBACCO, JUTE AND MULBERRY
Date:
I. TOBACCO
Name of the disease Causal organism
Damping off Pythium aphanidermatum
Frog eye spot Cercospora nicotianae
Powdery mildew Erysiphe cichoracearum var.
nicotianae
Black shank Phytophthora parasitica var.
nicotianae
Wild fire Pseudomonas tabaci
Mosaic Tobacco Mosaic Virus (TMV)
Nicotiana virus I (Marmor tabaci var.
vulgare)
Leaf curl Nicotiana virus 10 (Ruga tabaci)
Phanerogamic parasite: Broom rape Orobanche cernua var. desertorum

II. JUTE
Name of the disease Causal organism
Root and stem rot Macrophomina phaseolina
Powdery mildew Erysiphe sp.
Anthracnose Colletotrichum sp.
Stem gall Protomyces sp.

III. MULBERRY
Name of the disease Causal organism
Powdery mildew Phyllactinia corylea
Leaf rust Peridiospora mori
Leaf spot Cercospora moricola
Sooty mould Capnodium sp.
Root knot disease Meloidogyne incognita (Root knot
nematode)

I. TOBACCO
1. Damping off: Pythium aphanidermatum
Symptoms
 Seedlings get infected at any stage in the nursery
 Sprouting seedlings are infected and wither before emergence from the
soil (Pre-emergence damping off)
 Water soaked minute lesions appear on the stems near the soil
surface, girdling the stem, spreading up and down in the stem ; stem
 rot leading to toppling over of the seedlings (Post-emergence
damping off)
Pathogen
 The fungus produces thick, hyaline, thin walled, non-septate mycelium.
 It produces irregularly lobed sporangia which germinate to produce
vesicle containing zoospores.
 The zoospores are kidney shaped and biflagellate.
 Oospores are spherical and light to deep yellow or yellowish brown
coloured.
2. Frog eye spot: Cercospora nicotianae
Symptoms
 Small ashy grey spots with brown border appear on lower leaves
 The typical spots has a white centre, surrounded in succession by
grey and brown portions, surrounded by a dark brown to black margin,
resembling the eyes of a frog
 Several spots coalesce to form large necrotic areas, causing the leaf to
dry up from the margin and wither prematurely.
Pathogen
 The mycelium is intercellular which aggregates beneath the
epidermis and produce clusters of conidiophores which emerge
through stomata.
 The conidiophores are septate, dark brown at the base and lighter
towards the top bearing 2-3 conidia.
 The conidia are hyaline, slender, slightly curved; thin walled and 2-12
septate.
3. Powdery mildew: Erysiphe cichoracearum var. nicotianae
Symptoms
 Small, white isolated patches appear on the upper surface of the leaves
and stem
 Later, it spreads fast and cover the entire lamina
 Affected leaves turn brown, wither and scorched and defoliation occurs
4. Black shank: Phytophthora parasitica var. nicotianae
Symptoms
 Roots and base of the stem gets infected
 Black discolouration of stem; blackening of roots
 When the affected stem is split open, the pith region is found to be
dried up in disc- like plates showing black discolouration
Pathogen:
 The fungus produces hyaline and non-septate mycelium.
 The sporangia, which are hyaline, thin walled, ovate or pyriform
with papillae, develop on the sporangiophores in a sympodial fashion.
 Sporangia germinate to release zoospores which are usually kidney
shaped.
 The fungus also produces globose and thick walled chlamydospores.
 Oospores are thick walled, globose, smooth and light yellow coloured.
5. Wild fire: Pseudomonas tabaci
Symptoms
 In nursery, dark brown to black spots with a yellow halo spreads
quickly causing withering and drying of leaves
 In fields, numerous water soaked black spots appear, become angular
when restricted by veins and veinlets
 In advanced stage, the entire leaf is fully covered with enlarged
spots with yellow halos
 The leaves slowly wither and dry and the entire plant gives a blighted
appearance
Pathogen:
 The bacterium produces a fluorescent pigment and a potent toxin,
called tabtoxin or wildfire toxin.
 A mere 0.05 milligrams of this toxin can produce a yellow lesion on a
tobacco leaf in the absence of bacteria.
 The bacterium produces a hypersensitive reaction when injected into
leaves of tomato and pepper.
6. Mosaic: Tobacco Mosaic Virus (TMV)
Nicotiana virus I (Marmor tabaci var. vulgare)
Symptoms
 Light discolouration along the veins of the youngest leaves
 Leaves develop a characteristic light and dark green pattern
 Dark green areas develop into irregular crumpled swellings or blisters
 Leaves puckered, thin and malformed
 Dark brown necrotic spots develop under hot weather and this
symptom is called “Mosaic burn” or Mosaic scorching”
 The virus is sap transmissible
Pathogen:
 Tobacco mosaic is caused by Nicotiana virus I (Marmor tabaci var.
vulgare).
 It is a rod shaped particle measuring 300 X 150-180μm with a central
hollow tube of about 4μm diameter.
 It is made up of centrally placed Ribonucleic acid molecules (RNA)
covered with a protein coat.
 It is capable of remaining infective when stored dry for over 50 years.
 The thermal inactivation point (TIP) of the virus is 900C for 10 minutes.
7. Leaf curl: Nicotiana virus 10 (Ruga tabaci)
Graft transmissible and Vector: Bemisia tabaci
Symptoms
 Three forms of leaf curl expression are observed
 The leaf margins curl downward towards the dorsal side and show
thickening of veins with enations on the lower surface
 Crinkle form shows curling of whole leaf edge towards dorsal side
with enations on the veins and lamina arching towards the ventral side
between the veinlets
 Curling of leaves towards the ventral side with clearing of the veins
and enations are absent
Pathogen:
 The virus is spherical measuring 35μm in diameter.
 The virus is Nicotiana virus 10 or Ruga tabaci.
8. Phanerogamic parasite:
Broom rape (Orobanche cernua var. desertorum)
 It is a total parasite
 Affected plants are stunted and show withering and drooping of
leaving leading to wilting
 The parasitic plant is an annual, fleshy flowering plant and appears in
clusters of 50- 100 shoots around the base of a single tobacco plant
 The stem is pale yellow and covered by small, thin, brown scaly leaves
Parasite
 It is a total root parasite. It is an annual, fleshy flowering plant with
a short, stout stem, 10-15 inches long.
 The stem is pale yellow or brownish red in colour and covered by
small, thin, brown scaly leaves and the base of the stem is thickened.
 White-coloured flowers appear in the leaf axils.
 The floral parts are well developed with a lobed calyx, tubular corolla,
superior ovary with numerous ovules and a large four-lobed stigma.
 The fruits are capsules containing small, black, reticulate and ovoid
seeds.
II. JUTE
1. Root and stem rot: Macrophomina phaseolina
Symptoms
 Young plants show dark, thin streaks at collar region and also on
cotyledons
 On the grown up plants, black lesions along the margins, midrib and
petioles
 In severe case, blackening of stem with bark shredding, wilting and
premature falling of leaves
 Rotting of root system
 It also infects inflorescence and capsules and produces discoloured,
black seeds
Pathogen
 Pycnidia- globose, dark brown, papillate ostiole.
 Conidiogenous cells- barrel shaped, hyaline.
  Conidia – hyaline , aseptate, cylindrical to fusiform
 Sclerotia- more common in cultures, black, smooth, hard.
2. Powdery mildew: Erysiphe sp.
Symptoms
 Powdery growth on leaves, later turn brown and wither
 Affected plants become weak and produces quality fibre
Pathogen
 The fungal growth consists of external mycelium conidiophores and
chain of conidia. The fungus is of oidium type.
3. Anthracnose: Colletotrichum sp.
Symptoms
 Yellowish brown depressed spots on stem later turns to brown and
black
 Stem girdling, wilting of plants and produces poor pods
Pathogen
 Cushion shaped acervulus is seen below epidermis or cuticle with dark
setae.
 Setae – septate, stout at base and pointed at tip, dark brown, long,
present in the periphery or in between the conidiophores.
 Conidiophores – simple, elongate, septate, hyaline to brown,
 Conidia- sickle shaped, , guttulate ( oil globule ), hyaline, single celled.
4. Stem gall: Protomyces sp.
 It produces small greenish galls on the lower stem which turn to dark
brown and crack at maturity.
III. MULBERRY
1. Powdery mildew: Phyllactinia corylea
Symptoms
 White powdery patches appear on the lower surface of leaf which is
gradually increased and cover whole leaf surface
 Affected leaves turn yellowish and defoliate prematurely
2. Leaf rust: Peridiospora mori
Symptoms
 Several small pin head shaped brown pustules appear on the lower
surface of mature leaves
  Reddish brown spot appear on the upper surface of the infected leaves
 Severely infected leaves turn yellowish and margin of the leaves
become dry
3. Leaf spot: Cercospora moricola
Symptoms
 Circular light brown spots appear on both sides of the leaves
 The adjacent spots unite together to form a larger spot
 The necrotic tissues of such spots drop out and form the characteristics
shot holes
 Highly infected leaves defoliate prematurely
4. Sooty mould: Capnodium sp.
Symptoms
 Thick black coating developed on the upper surface of the leaves
5. Bacterial leaf spot: Pseudomonas syringae pv. mori
Symptoms
 It is common during rainy season when there is high humidity and
temperature
 It shows numerous blackish brown irregular water soaked patches on
the leaves resulting in curling and rotting of leaves
6. Root knot disease: Meloidogyne incognita (Root knot nematode)
 It is one of the major diseases limiting crop production throughout the
world
 It can occur any time of the year mainly in sandy soils low in organic
matter
 Infected plants become weak and predisposed to other diseases while
severely infected plants ultimately die
 Stunted growth
 Poor and delayed sprouting
 Reduced leaf size and yield
 Formation of gall/knots on roots
 Retarded root growth
 Necrotic lesions on the root surfaces and death of active rootlets
Ex. No 7. DISEASES OF BANANA
Date:

Name of the disease Causal organism

I. FUNGAL DISEASES
Panama disease /Vascular wilt/ Fusarium oxysporum f sp. cubense
Fusarium wilt
Sigatoka leaf spot Mycosphaerella musicola
Mycosphaerella fijiensis
Anthracnose / Fruit rot Gloeosporium gloeosporioides
Freckle leaf spot Phyllosticta musarum
Cigar end rot Verticillium theobromae
II. BACTERIAL DISEASES
Moko wilt Ralstonia solanacearum Race II
Top rot or Tip over or Heart rot Pectobacterium (Erwinia) carotovorum
sub sp. carotovorum
III. VIRAL DISEASES
Disease name Virus Vector Life style/
parasitism
Bunchy top/ Curly top Musa virus-1 Black Aphids Biotroph
Pentalonia nigronervosa
Infectious Cucumber Aphids – Aphis gossypii Biotroph
chlorosis/Banana Mosaic Virus
mosaic/ Heart rot:
Banana Bract mosaic Banana Bract Aphids – Aphis Biotroph
mosaic virus gossypii

I. Fungal Diseases
1. Panama disease/Vascular wilt/Fusarium wilt : Fusarium oxysporum f sp.
cubense
Symptoms
 Kathali, Rasthali and Karpuravalli are highly susceptible varieties while
Poovan is resistant.
 Yellowing of leaf blade.
 Leaves hang around pseudostem – yellow skirt symptom.
 Longitudinal splitting of pseudostem.
 Dark brown streaks in the vascular bundles of infected suckers
radiating from centre to periphery.
Pathogen: Fungus produces 3 types of spores
 Microconidia - 1 celled, hyaline
 Macroconidia – Sickle shaped, tapered, 3-4 septate hyaline
  Chlamydospores - Terminal or Intercalary
Mode of spread: Primary: Infected sucker
Secondary: Water borne conidia and chlamydospores
2. Sigatoka leaf spot: Two types of leaf spots
Symptoms
a). Yellow sigatoka leaf spot - Mycosphaerella musicola
 Light yellow or brownish green narrow streaks along the veinlets
 Central portion necrotic, surrounded by dark brown band, yellow halo
 Rapid drying of leaves
b). Black sigatoka leaf spot - Mycosphaerella fijiensis
 Black colour rectangular spots/ linear spots on leaf lamina without
yellow halo
 Rapid drying of leaves
Pathogen: Pathogen produces branched, septate hyphae, branched,
septate cylindrical conidiophores on which brown colour, slender, 4 to 6
septate conidia in M. musicola, while brown colour, needle shaped, multi-
septate conidia in M. fijiensis. Under perfect stage, fungus produces
perithecia, asci and ascospores (1-2 celled).
Mode of spread
Primary: Ascospores from the infected plant debris
Secondary: Air borne conidia
3. Anthracnose / Fruit rot: Gloeosporium gloeosporioides
Symptoms
 Circular to irregular black sunken lesions with pinkish sporulation
appear on the fruit
 Skin of the fruit turns black and rots
 Latent infection – Pathogen infects green fruits in the field
without expression of symptoms and symptoms appear during
during ripening
Pathogen: Hyaline, septate and branched conidiophore on which cylindrical
to oval single celled, hyaline and thin walled conidia with large number of oil
globules are produced.
Mode of spread
Primary: Air borne conidia
Secondary: Spread through the contact of infected fruits
4. Freckle leaf spot : Phyllosticta musarum
Symptoms
 Large number of minute raised rusty black spots on leaf and green
fruits.
 On the centre of the spot pycnidia are produced
 Causes drying and defoliation of leaves.
 Affects the yield of fruit. Reduce the market value of fruit.
Pathogen: Pycnidia contain conidiophores and conidia. Conidiophores are
simple and elongated. Conidia are hyaline, ovoid (or) ovate (or) globose,
one celled.
Mode of spread:
Primary and secondary spread through air borne conidia
5. Cigar end rot: Verticillium theobromae
Symptoms
 Blackening of the skin, shrinkage and folding of tissues covered with
powdery coating due to sporulation
 The above symptom resembles ash end of a burning cigarette.
 Internal pulp dry and causes dry rot
Pathogen: Conidiophores are long, hyaline and septate. Hyaline, single
celled, oval shaped conidia are produced on the conidiophore in a
verticillate manner.
Mode of spread:
Primary and secondary spread through air borne conidia
II. Bacterial Diseases
1. Moko wilt: Ralstonia solanacearum Race II
Symptoms
 Rapid development of yellow discoloration of inner lamina close to
the petiole and wilting of inner leaves.
 Necrosis of unfurled heart leaf.
 Blackening of internal fruit pulp.
  Pale yellow to dark brown strands are seen on vascular bundles and
yellow slimy bacteria oozing out from the infected corm.
Pathogen: Rod shaped gram negative bacterium with single polar flagellum
(monotrichous).
Mode of spread: Primary: Infected suckers
Secondary: Bacterial carried by irrigation water
2. Top rot or Tip over or Heart rot: Pectobacterium (Erwinia) carotovorum
sub sp. carotovorum
Symptoms
 Tissue culture banana and Nendran variety are highly susceptible
 The disease will be severe during summer months.
 Rotting of basal portion of pseudostem at the point of attachment with
suckers/corm in young plants due to production of pectinase enzyme.
 Bad odour emitted from the rotten tissues.
 Swelling of pseudostem base and rotting of collar portion.
 Toppling of pseudostem affected plants.
Pathogen: Rod shaped gram negative bacterium with flagella around the cell
wall (peritrichous).
Mode of spread:
Primary: Infected suckers and soil borne bacteria
Secondary: Bacterial carried by irrigation water
III. Viral Diseases
1. Bunchy top/ Curly top /Cabbage top diseases/ Strangles: Musa virus-1
Symptoms
 Stunting of plants with reduced leaf size
 Leaves become thick, leathery/brittle with very short petiole
 Upright orientation of the leaves gives bunchy appearance
 Dark green streaks on the leaf lamina and petioles and marginal
necrosis on leaves and become sterile
 Later stage infection leads to chocking of bunches and it comes out
through piercing of pseudostem
 Yellow chlorotic streaks formed on the unopened flowers
Vector: Black Aphids – Pentalonia nigronervosa
Pathogen: Banana Bunchy Top Virus (BBTV), isometric ssDNA virus
Mode of spread: Primary: Infected suckers
Secondary: Black Aphids – Pentalonia nigronervosa
2. Infectious chlorosis/Banana mosaic/ Heart rot:
Symptoms
 Typical mosaic symptom, rolling of leaf margin, rotting of heart leaf
(heart rot)
 Leaves narrower and smaller than normal and the leaf sheath loosely
attached with pseudostem
Vector: Aphids – Aphis gossypii
Pathogen: Cucumber mosaic virus, isometric ssRNA virus
Mode of spread:
Primary: Infected suckers; Secondary: Aphids – Aphis gossypii
3. Banana bract mosaic:
Symptoms
 Spindle shaped mosaic streaks on the bracts.
 Greenish to brownish spindle-shaped streaks irregularly scattered
along leaf petioles.
 Pinkish spindle shaped lesions at the base of pseudostem, loosening
of leaf sheath and appear like travellers palm
Vector: Aphids – Aphis gossypii
Pathogen: Banana Bract mosaic virus, flexible rod shaped ssRNA virus
Mode of spread: Primary: Infected suckers
Secondary: Aphids – Aphis gossypii
Ex. No. 8. DISEASES OF GUAVA, PAPAYA AND POMEGRANATE
Date:
I. GUAVA
Name of the disease Causal organism
Wilt Fusarium oxysporum f.sp. psidii
Anthracnose Gloeosporium psidii
Sooty mould Capnodium sp.
Red rust Cephaleuros virescens

II. PAPAYA
Name of the disease Causal organism
Foot rot / Stem rot Pythium aphanidermatum
Powdery mildew Oidium caricae
Anthracnose Colletotrichum gloeosporioides
Papaya ring spot Papaya Ring Spot Virus
Vector: Aphids- Aphis gossypii & A.
craccivora
Papaya mosaic Carica Virus 1
Vector: White fly-Bemisia tabaci
Leaf curl Tobacco Leaf Curl Virus
Vector: White fly-Bemisia tabaci
Leaf spots Phyllosticta sulata
Cercospora papayae
Fruit rots Rhizopus stolonifer
Ascochyta caricae
Botrodiplodia theobromae

III. POMEGRANATE
Name of the disease Causal organism
Anthracnose Gloeosporium gloeosporioides
Cercospora leaf spot Cercospora punicae
Bacterial leaf spot Xanthomonas campestris pv. punicae

I. GUAVA
1. Wilt: Fusarium oxysporum f.sp. psidii
Symptoms
 Yellowing, curling and premature shedding of leaves in the terminal
branches.
 Die back at later stage
 Fruits become underdeveloped, hard and stony.

63
  Black streaks on the finer roots and complete wilting of the plant with
brown discolouration in the vascular tissues.
Pathogen: Fungus produces 3 types of spores
 Microconidia-Ovate / elongate / 1 celled, hyaline
 Macroconidia – Spindle shaped, tapered, 3-4 septate hyaline
 Chlamydospores - Terminal or Intercalary
Mode of spread:
Primary: Soil borne chlamydospores
Secondary: Water borne conidia
2. Anthracnose: Gloeosporium psidii
Symptoms
 Die back of young twigs and branches
 Circular to irregular black sunken lesions with pinkish sporulation appear on
the fruit
 Skin of the fruit turns black and rots
 Latent infection – the infection originate from the green fruits in the field and
expressed during ripening Pathogen: Hyaline, septate and branched
conidiophore on which cylindrical, single celled, hyaline and thin walled
conidia with large number of oil globules are produced.
Mode of spread
Primary: Air borne conidia
Secondary: Spread through the contact of infected fruits
3. Sooty mould: Capnodium sp
Symptoms
 Black encrustation formed on flowers, leaves ,stem and fruit
 Mycelium superficial and lives on the sugary secretion of the sucking
pests like hoppers, jassids, aphids and mealy bugs.
 Photosynthetic activity is reduced which results in reduced fruit set and fruit
fall
Pathogen: Fungus produces 5 types of conidia such as
1. Torula 2. Trichothecium 3. Coniothecium 4. Brachysporium 5. Ascospores
from Pseudothecia

64
Mode of spread
Primary and Secondary spread are through wind borne conidia
4. Red rust: Cephaleuros virescens
Symptoms
 It is an algal parasite.
 Produces small red orange raised velvety mycelial growth on the upper
surface of the leaf.
 In severe cases, symptoms seen on the fruits.
Pathogen:
 The alga produces sporangia on sporangiophore. Sporangia produce
n u me r o u s zo o sp or e s. 5-8 sporangia are found on each vesicle.
 Zoospores are involved in the disease spread.
II. PAPAYA
1. Foot rot / Stem rot: Pythium aphanidermatum
Symptoms
 Water soaked patches on stem at ground level
 Girdling of the stem
 Terminal leaves turn yellow, droop and wilt
 Due to disintegration of parenchymatous tissues at the base of the stem,
the internal tissues of the bark give a honey comb appearance
 Roots deteriorate and entire plant topples and dies
Pathogen: Coenocytic mycelium ,produces sporangiospore bearing irregular
shaped sporangia which bears the vesicle. Inside the vesicle the zoospores are
produced.
Mode of spread
Primary: Soil borne Oospores
Secondary: Water borne zoospores
2. Powdery mildew: Oidium caricae
Symptoms
 Powdery growth on undersurface of the leaves.
 Some times on upper surface. Flower stalks and fruits are also affected
and exhibit white powdery patches

65
Pathogen
 Obligate parasite produces short conidiophore and also produces
haustoria.
 Barrel shaped conidia, mycelium hyaline septate conidiophore short
hyaline and produces conidia in chains.
Mode of spread
Primary: Soil borne ascospores
Secondary: Wind borne conidia

3. Anthracnose: Colletotrichum gloeosporioides

Symptoms
 Spots seen on leaves and fruits
 Leaf : Necrotic spots on leaf
 Fruit : Circular, slightly sunken spots. Latex oozes out
Pathogen
 Hemi biotroph produces hyaline septate branched mycelia.
 Fungus produces acervuli without black setae.
 Conidia are single celled, hyaline, thin walled with full of oil globules.
Mode of spread
Primary spread and Secondary spread through wind borne conidia

4. Papaya ring spot: Papaya Ring Spot Virus

Symptoms
 Vein clearing, puckering or bulging of leaf tissues between veins.
 Margin and distal parts of leaves roll downward and inwards, mosaic
mottling, dark green blisters, leaf distortion which result in shoe string
system and stunting of plants.
 On fruits circular concentric rings are produced. If affected earlier no fruit
formation.
Pathogen: PRSV is a flexious rod shaped RNA virus belongs to potyvirus group
transmitted by Aphids in a non- persistant manner
Vector : Aphids Aphis gossypii & A. craccivora

66
5. Papaya mosaic – Carica Virus 1
Symptoms
 Chlorosis with dark green blisters on leaves
 Lamina reduced and malformed
Vector:White fly -Bemisia tabaci
6. Leaf curl – Tobacco Leaf Curl Virus
Symptoms
 Curling, crinkling and distortion of leaves, reduction of leaf lamina, rolling
of leaf margins inward and downward, thickening of veins.
 Leaves become leathery, brittle and distorted. Plants stunted. Affected
plants does not produce flowers and fruits.
Causal organism: Papaya Leaf curl virus (PLCV) is a DNA virus in the family
Geminiviridae. It is not transmitted mechanically.
Vector: Whitefly - Bemisia tabaci

7. Leaf spots
 Phyllosticta sulata
 Cercospora papayae

8. Fruit rots
 Rhizopus stolonifer
 Ascochyta caricae
 Botrodiplodia theobromae

III. POMEGRANATE
1. Anthracnose: Gloeosporium gloeosporioides
Symptoms
 Spots seen on leaves and fruits
 Leaf : Necrotic spots on leaf
 Fruit : Circular, slightly sunken spots .Latex oozes out
Pathogen: Hemi biotroph produces hyaline septate branched mycelia. Fungus
produces acervuli without black setae. Conidia are single celled, hyaline, thin
walled with full of oil globules.

67
Mode of spread
Primary spread and Secondary spread through wind borne conidia
2. Cercospora leaf spot: Cercospora punicae
Symptoms
 Light brown zonate sports appear on leaves and fruitss
 Black elliptical spots appear on the twigs
 Affected areas in the twigs become flattened and depressed with raised
edge.
Pathogen: Conidiophore are olivaceous brown, short fasciculate, sparingly
septate. Conidia are olivaceous, cylindrical and multi-septate.
Mode of spread
Primary spread through ascospores from fallen leaves and Secondary spread is
through wind borne conidia
3. Bacterial leaf spot: Xanthomonas campestris pv. punicae
Symptoms
 Dark coloured irregular spots 2-5 mm in diameter
 The leaves often distorted and malformed
 Premature dropping of leaves. The normal growth of the plant in affected
 Raised spots are seen on the fruits which are irregular.
Pathogen: Gram negative, rot, motile with single polar flagella
Mode of spread & Survival
The bacteria infect through wounds and stomatal openings. Survive in the soil.

68
Ex. No. 9. DISEASES OF CRUCIFERS
Date:
Name of the disease Causal organism
Club root of cabbage/ Finger and Plasmodiophora brassicae
toe disease
Damping off/Wire stem of cabbage Rhizoctonia solani
Black leg of cabbage Phoma lingam
Cabbage yellows/Fusarium wilt of Fusarium oxysporum sp.conglutinans
cabbage
White blisters or Rust of radish Albugo candida
Downy mildew Peronospora parasitica
Black rot Xanthomonas campestris pv.
campestris
Cauliflower mosaic Cauliflower Mosaic Virus
Vector:Aphids - Brevicoryne brassicae

1. Club root of cabbage/ Finger and toe disease: Plasmodiophora brassicae

Symptoms
 Leaves pale green to yellowish
 Plants stunted
 Fail to produce marketable heads
 Small or large spindle like, spherical, knobby or club shaped swellings on
the roots and root lets
 Diseased plants later die
Pathogen: It is a Protozoa. Plasmodium (naked protoplasm) produces primary
and secondary zoospores. zoospores are biflagellate. Sexual spores are resting
spores
Mode of spread: Primary: Resting spores; Secondary: Zoospores
2. Damping off/Wire stem of cabbage: Rhizoctonia solani
Symptoms
 Serious in nursery of cabbage
 Tissues water soaked and toppling of seedlings
 Damping off in seedling, wire stem in seedlings (plants blend or twisted
without breaking in cabbage)
 Bottom rot, head rot and root rot in older plants

69
Pathogen:
 Septate mycelium. Sclerotia are irregular brown to black.Produces terminal
and intercalay chalamydospores.
 Perfect stage: Thanatephorus cucumeris. Basidia with basidiospores are
produced
Mode of spread: Primary: Sclerotia and Basidiospores; Secondary: Water borne
sclerotia and chlamydospres
3. Black leg of cabbage: Phoma lingam
Symptoms
 Fungus attacks the crop at seedling or any stage of crop growth
 Oral, depressed, height brown canker appear near the base of stem
 Canker enlarges and girdles the stem
 Attacked roots show dark brown cankers
 Elliptical lesions appear on seed stalk and pods
Pathogen: Septate mycelium, produces pycnidia. Ascocarps bear asci with
ascospores
Mode of spread: Primary: Ascospres; Secondary: Water borne conidia
4. Cabbage yellows/Fusarium wilt of cabbage: Fusarium oxysporum
sp.conglutinans
Symptoms
 Plants show uniform yellowing
 Stem and leaves curl laterally
 Later leaves turn brown, brittle and die
 Browning of vascular system seen
Pathogen: Produces microconidia, macroconidia, and chlamydospores
Mode of spread: Primary: Chlamydospores ; Secondary: Water borne conidia
5. White blisters or Rust of radish: Albugo candida
Host: Cabbage, mustard, radish, turnip
Two types of infection: Local and systemic
 Local infection: isolated pustules or sori develop in leaves and stems.
Pustules merge to form larger patches. Host epidermis rupture after
maturity of pustules
 Systemic infection: When young stems and flowering parts are

70
 infected it becomes systemic. Stimulates hypertrophy and hyperplasia.
Results in enlarged and variously distorted organ mostly flower parts sepals
become enlarged to several times than the normal sepals. Petals enlarge
and become green pistils and anthers are distorted. Seed development is
arrested.
Pathogen: Pathogen produces sporangia. Sporangia are spherical / hyaline in
nature contains 4-8 zoospores. Sexual spore is tuberculate oospore
Mode of spread: Primary: Oospore; Secondary: Sporangia and Zoospores
6. Downy mildew: Peronospora parasitica
Symptoms
 White fluffy fungal growth on leaves, stems, seed pods. Later become
small, purplish irregular areas
 The systemically invaded tissue turns yellowish and become necrotic, dries
out
 Infection on cotyledons and hypocotyls – seedlings get killed
 Cabbage seed pots twist, curl and break opens to expose the seeds.
Pathogen:The sporangiophores are dichotomously branched at acute angles
and taper into gracefully curved pointed tips on which sporangia are borne.
Mode of spread: Primary: Oospore ; Secondary: Sporangia and Zoospores
7. Black rot: Xanthomonas campestris pv.campestris
Symptoms
 Infected young plants killed. Plants stunted
 Cotyledons turn yellow to black, hang down and drop off prematurely
 Leaves yellow with blackened veins and vein lets. Become necrotic and
brittle
 V shaped chlorotic to yellow lesions develop from the leaf margin
 Disease spreads onto the roots
 Vascular bundles become black and the fleshy tissue break down
 Cabbage heads and cauliflower curds are infected and discoloured
Pathogen: Gram negative, rod shaped bacterium with single polar flagellum
Mode of spread: Wind driven rain splashes carry bacteria from infected to healthy
leaves, Twigs and fruits

71
8. Cauliflower mosaic:
Symptoms
 Leaves are mottled with a pattern of light and dark green
 Plants are stunted, central leaves smaller
 Mild infection leads to production of a small and poor quality heads
 Infected plants die.
Causal organism: Cauliflower mosaic virus, Double strand DNA virus
Transmission: Aphids - Brevicoryne brassicae

72
Ex. No. 10. FIELD VISIT
Date:

73
EX. NO. : 11 DISEASES OF TOMATO, BRINJAL AND OKRA
DATE :

TOMATO
Fungal Diseases
Name of the diseases Causal organism
Damping off Pythium aphanidermatum
Fusarial wilt Fusarium oxysporum f.sp.lycopersici

Verticillium wilt Verticillum dahliae, Verticillum albo-atrum

Early blight Atternaria solani
Late blight Phytophthora infestans

Bacterial Diseases
Name of the diseases Causal organism
Wilt Ralstonia solanacearum
Canker Clavibacter michiganense

Viral diseases
Disease name Virus Vector
Tomato mosaic seed and sap
Tomato Spotted / Tomato spotted wilt Thrips (Thrips tabaci,
Bronzy Wilt virus (TSWV) Scirtothrips dorsalis)
Leaf curl Tobacco Leaf Curl White fly
Virus (TLCV) (Bemisia tabaci)

BRINJAL
Fungal Diseases

Name of the diseases Causal organism

Fusarial wilt Fusarium oxysporum f.sp.lycopersici
Verticillium wilt Verticillum dahliae
Alternaria leaf spot Alternaria solani
Phomopsis blight and fruit rot Phomopsis vexans

74
Bacterial Diseases
Name of the diseases Causal organism
Wilt Ralstonia solanacearum
Canker Clavibacter michiganense

PHYTOPLASMA DISEASE
Disease name PHYTOPLASMA Vector
Little Leaf Leaf hoppers (Hishimonas phycitis)
and grafting

BHENDI
Fungal Diseases
Name of the diseases Causal organism
Wilt Fusarium oxysporum f.sp.vasinfectum
Powdery mildew Golovinomyces cichoracearum
Alternaria leaf spot Alternaria solani

Viral diseases
Disease name Virus Vector Life style/
Parasitism
Vein Clearing / Bhendi Yellow vein Whitefly Biotroph
Yellow Vein Mosaic
mosaic virus (Bemisia tabaci)

TOMATO
1. Damping off - Pythium aphanidermatum
Symptoms
 Pre-emergence damping off: Seeds infected – rots and loss in
germination
 Post-emergence damping off: Affected seedling pale and collapse
suddenly
 Toppling down of seedling

75
Pathogen
 Pythium produces coenocytic mycelium with sporangiophore bearing
lobed sporangia.
 The sporangia put forth vesicle which bears the zoospores.
 Sexual spore is oospore.
Mode of spread:
 Primary and secondary: Soil borne oospores and chlamydospores
 Secondary: Water borne Zoospores
2. Fusarial wilt- Fusarium oxysporum f.sp.lycopersici
Symptoms
 Plants stunted, yellowing of lower leaves
 Leaves droop, wilt and die
 Vascular brown discolouration
Pathogen
 Mycelium is septate, hyaline initially and turn to cream colour later.
 Produces microconidia, macroconidia and chlamydospores
Mode of spread
 Primary : Soil borne chlamydospores
 Secondary: Wind borne spores, surface drainage water and
agricultural implements
3. Verticillium wilt- Verticillum dahliae, Verticillum albo-atrum
Symptoms
 Plants stunted growth
 Leaves – Dark green patches – with interveinal and marginal yellowing
 Leaves wilt, dry and fall off.
 Brown/pink discoloration in xylem vessels
 Many adventitious root develop
Pathogen
 Conidiophores are abundant, erect, hyaline and vertically branched,
3 to 4 phialides arises from each node.
 Conidia borne on the apex of conidiophore are single, eliptical to
cylindrical, hyaline.

76
Mode of spread
 Primary: Soil borne chlamydospores and dormant mycelium from plant
debris
 Secondary: Water borne conidia
4. Early blight: Atternaria solani
Symptoms
 Circular to angular dark brown to black spots with concentric rings
 Stem girdling
 Shedding of immature fruits
Pathogen
 Conidia is of muriform shape, multiseptate and characterized by the
presence of both vertical and horizontal septations (transverse septation)
and a long narrow beak at the tip of the conidia.
Mode of spread
 Primary and secondary: Dormant mycelium from plant debris
 Secondary: Wind borne conidia and also spread through rain splash

5. Late blight- Phytophthora infestans

Symptoms
 Brown to purplish black lesion
 Blighting of foliage
 Russet brown marbled areas on green fruits
Pathogen
 Mycelium is hyaline, coenocytic.
 Sporangiophores are slender, hyaline and branched, produces hyaline
pear shaped sporangia with papilla. It releases biflagellate zoospores.
 Anthredium is amphigynous in nature.
 Sexual spores are oospores.
Mode of spread
 Primary: Soil borne dormant oospores and mycelium from plant debris
 Secondary: Wind bone sporangia and zoospores

77
BACTGERIAL DISEASES
1. Bacterial wilt: Ralstonia solanacearum Race II
Symptoms
 Yellowing of plants, stunted, downward ceiling of leaflets
 Excessive adventitious roots produced
 Plants collapse and die
 Xytem blackening
 Bacterial ooze seen
Pathogen
 Rod shaped with tuft of polar flagella and gram negative
Mode of spread
 Primary: Bacteria from infected plant debris
 Secondary: Water borne bacteria

2. Bacerial canker: Clavibacter michiganense

Symptoms
 Small numerous minute brown- black color spots appear on the leaves.
 Drying of Leaves at the harvest and flowering stage due to bacterial and
fungal infection.
 Black - brown color cankerous spots on the infected tomato fruits.
Pathogen
 Aerobic, non-sporulating, gram-positive plant pathogenic bacteria with no
flagella

VIRAL DISEASES
1. Tomato mosaic
Symptoms
 Light and dark green mosaic mottling
 Plants stunted
 Leaves distorted like ‘fern leaf’
 Internal necrosis of fruit
Pathogen
 Tomato mosaic virus (TMoV)
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Mode of spread
 Primary and secondary: seed borne and sap transmissible

2. Tomato Spotted / Bronzy Wilt

Symptoms
 Thickening of veins, with concentric rings
 Bronzing of leaves
 On fruits, pale red or yellow areas with circular marking
 Shape affected with no seeds
 Lycopene content is reduced
Pathogen
 Tomato spotted wilt virus (TSWV)
Mode of spread
 Thrips tabaci, Scirtothrips dorsalis
3. Leaf curl
Symptoms
 Plants are severely stunted with shoots becoming erect
 Leaflets become reduced in size and pucker
 Leaves curl upwards, become distorted and have prominent yellow
margins.
 Flowers wither and plant will become sterile
Pathogen
 Tobacco Leaf Curl Virus (TLCV)
Mode of spread
 Through vector White fly - Bemisia tabaci
PHYTOPLASMA DISEASE
Tomato big bud
Symptoms
 Swollen green buds that are atypically large and don’t set fruit.
 Stems of the afflicted plants thicken while the foliage becomes distorted
and yellow.
 Transmitted by cuscuta, grafting and leaf hopper- Orasius argentatus

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Pathogen
 Tobacco Leaf Curl Virus (TLCV)
Mode of spread
 Through dodder, grafting and leaf hopper – Orosius argentatus
BRINJAL
1. Fusarial wilt- Fusarium oxysporum f.sp.lycopersici
Symptoms
 Plants stunted, yellowing of lower leaves
 Leaves droop, wilt and die
 Vascular brown discolouration
Pathogen
 Produces microconidia, macroconidia and chlamydospores
Mode of spread:
 Primary: Soil borne chlamydospores
 Secondary: Water borne conidia
2. Verticillium wilt - Verticillum dahliae
Symptoms
 Pale yellow patches in the interveinal areas
 Drooping of old leaves, complete drying, leaves drop leaving barren
branches
 Curling of leaf lamina
 Browning of vascular tissue
Pathogen
 Conidiophores are abundant, erect, hyaline and vertically branched,
3 to 4 phialides arises from each node.
 Conidia borne on the apex of conidiophore are single, eliptical to
cylindrical, hyaline
Mode of spread
 Primary: Soil borne chlamydospores and dormant mycelium from plant
debris
 Secondary: Water borne conidia

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3. Alternaria leaf spot - Alternaria solani
Symptoms
 Leaf spots are characterized by the presence of concentric rings.
 Spots are mostly irregular.
 Coalesce to cover large area of the leaf.
 Defoliation of the severely affected leaves.
Pathogen
 Hyphae septate, branched, dark coloured
 Conidiophores are short and dark in colour
 Conidia beaked, obclavate, formed singly, olive brown, muriform, both
horizontal and vertical septation with long beak
Mode of spread
 Primary: Soil borne dormant mycelium from plant debris
 Secondary: Water borne conidia
4. Phomopsis blight and fruit rot - Phomopsis vexans
Symptoms
Seedlings
 Blighting of young seedlings with dark brown lesion on stem
 Girdling of stem
 Toppling of seedling
Leaf: brown oval spots – centre grey with pycnidia
Fruit: become soft and watery and later block and mummified
Pathogen
 Conidiophores in the pycnidia are hyaline bearing hyaline one celled
subcylindrical condia.
 Another type of conidia called stylospores are filiform, curved hyaline and
septate.
Mode of spread
 Primary: Soil borne chlamydospores and dormant mycelium from plant
debris
 Secondary: Wind borne conidia

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BACTERIAL DISEASE
1. Bacterial Wilt- Ralstonia solanacearum
Symptoms
 Water soaked areas on stem
 Dropping of leaves and shoots
 Sudden wilting
 Bacterial ooze: in the form of milky white stream
Pathogen: Rod shaped with tuft of polar flagella and gram negative
Mode of spread: Infected plant debris

PHYTOPLASMA DISEASE
LITTLE LEAF
Symptoms
 Reduction in size of leaves, petiole, lamina
 Leaves become sessile, thin, soft and pale green
 Growth of axillary buds stimulated
 Shortening of internodes – gives bushy appearance
 Floral parts modified into green structures
 No fruits formed – plants sterile
 If fruits formed, mummified and cling on plants
Pathogen
 Mycoplasma like organism
Mode of spread
 Leaf hoppers - Hishimonas phycitis and grafting

BHENDI
1. Wilt - Fusarium oxysporum f.sp.vasinfectum
Symptoms
 Yellowing, stunting of plants
 Wilting and rolling of leaves
 Dark brown vascular discolouration
 Plant dies

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Pathogen
 Produces microconidia, macroconidia, and chlamydospores
Mode of spread
 Primary: Soil borne chlamydospores
 Secondary: Water borne conidia

2. Powdery mildew - Golovinomyces cichoracearum

Symptoms
 White powdery growth on upper surface of the leaf, latter tunes grey
 Affected leaves dry and fall off prematurely
Pathogen
 Ectophytic mycelium producing chain of single celled, hyaline barrel
shaped conidia arranged in a basipetal succession (catenate).
 Sexual fruiting body is chasmothecium which bears asci and ascospores.
Mode of spread
 Primary: Air borne conidia
 Secondary: Ascospores from the infected debris

VIRAL DISEASES
1. Vein Clearing / Yellow Vein Mosaic
Symptoms
 Clearing of small veins
 Yellow area extend into the interveinal portions
 Leaf become chlorotic, veins thickened
 Plants stunted
 Few small malformed fruits and fruits fibrous and tough
Pathogen
 Bhendi Yellow vein mosaic virus, gemini vius made up of DNA and
protein, always present as twin particles
Mode of spread
 Vector: Whitefly - Bemisia tabaci

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EX. NO. : 12 DISEASES OF SWEET POTATO and BEANS
DATE :
SWEET POTATO

Name of the diseases Causal organism

Stem rot, wilt and surface rot Fusarium oxysporum f.sp. batas
Cercospora leaf spot Cercospora ipomoeae
White rust/blister Albugo ipomoea-panduratae

BEANS

Fungal diseases
Name of the diseases Causal organism
Anthracnose Colletotrichum lindemuthianum
Ashy stem blight Macrophomina phaseolina
Powdery mildew Erysiphe polygoni
Rust Uromyces phaseoli typica

Bacterial disease
Name of the diseases Causal organism
Halo blight Pseudomonas phaseolicola

SWEET POTATO
1. Stem rot, wilt and surface rot – Fusarium oxysporum f.sp. batas
Symptoms
 Yellowing of youngest leaves.
 The vascular system becomes blackened causing stem to darken
internally. This darkening may extend several cm along stems.
 Infected plants wilt, collapse and die.
 Infected tubers have blackened ring about 6mm under the skin and
develop surface rot with shallow, sunken, circular lesions in storage
 Plants produced from these tubers are likely to be diseased.
Pathogen
Produces micro conidia, macro conidia and chlamydospores
Mode of spread
Primary: Soil borne chlamydospores;
Secondary: Conidia

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2. Cercospora leaf spot - Cercospora ipomoeae
Symptoms
 Appear as circular, ovoid or irregular yellowish brown spots 1 to 9mm in
dia. Later the spots become deep brown. The spot coalesce and form
larger patches covering major portion in the leaf blade.
Pathogen
 Conidiophores bears conidia which are sub hyaline to coloured, obculate
Mode of spread
Primary : Ascospores from the infected plant debris
Secondary : Wind borne conidia

3. White rust/blister – Albugo ipomoea-panduratae

Symptoms
 Presence of chlorotic or yellowish blotches, initially roundish to angular
where they are limited by veins, on the upper surface of leaves.
 On the lower surface, white creamy pustules produced corresponding
upper surface yellow discoloration.
 Complete yellowing and pre mature shedding of leaves

Pathogen
 The mycelium is intracellular with typical knob-like haustoria.
 The sporangiophores are hyaline, club shaped, unequally curved at the
base. The sporangia are produced in chains. They are short, cylindrical,
with more rounded terminal, hyaline and smooth
 The oospores are light yellowish brown with papillate epispore and
curved ridges.
Mode of spread
Primary spread by oospore and secondary spread by zoospore

BEANS
1. Anthracnose: Colletotrichum lindemuthianum
Symptoms
 Black sunken lesions on pods.

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  Centre of each lesions show pinkish black spore mass.
 Discolouration of seeds
Pathogen
 Mycelium is branched, septate, conidia are borne on short conidiophores.
 Conidia are 1-celled, hyaline, oblong, cylindrical with rounded ends.
Mode of spread
Primary spread: Infected seed; Secondary spread: Conidia

2. Ashy stem blight: Macrophomina phaseolina

Symptoms
 Black sunken lesion at ground level near the base of the cotyledons
 Lesions turn grey and numerous black pycnidia seen
 Leaf infection seen and the plant ultimately die.
Pathogen
Septate mycelium producing pycnidial fruiting body producing
pycnidiospores
Mode of spread
Primary spread: Infected seed; Secondary spread: Conidia
3. Powdery mildew- Erysiphe polygoni
Symptoms
 White powdery patches on the upper surface of the leaves.
 Drying of leaves
Pathogen
 Septate mycelium producing oidium type of conidia and
conidiophores.
 Sexual fruiting body: Chasmothecium with many asci and ascospores
Mode of spread
Primary spread: ascospores; Secondary spread: Conidia
4. Rust- Uromyces phaseoli typica
Symptoms
 Small pale spots which become yellow with a small dark center
 These spots enlarge and produce brick-red rust spores to spread the
disease

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  Lesions develop black (overwintering) spores later in the season due to
production of teliospores
Pathogen
 Uredospores: Single celled, brown coloured with echinulations.
 Teliospores: Single celled, brown with thickened apex
Mode of spread
Primary spread: Uredospores from volunteer plants
Secondary spread: Uredospores

Bacterial diseases
Halo blight - Pseudomonas phaseolicola
Symptoms
 brown spots with large pale yellow halo
 The bacterial fluid found in these lesions is cream or silver colored.
 Systemic plant infection produce stunted plants with small chlorotic
trifoliolate leaves
 Pod symptoms consist of red or brown lesions which may appear water
soaked.
Pathogen
Gram negative, rod shaped bacterium with tuft of flagella at one end
Mode of spread
Primary spread : Soil borne bacteria;
Secondary spread: Bacteria spread through rain flash and Irrigation water

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EX. NO. : 13 DISEASES OF COCONUT and ARECANUT
DATE :

COCONUT

Fungal diseases
Name of the diseases Causal organism
Bud rot Phytophthora palmivora
Basal stem rot /thanjavur wilt / bole rot Ganoderma lucidum
Grey leaf blight Pestalotia palmarum
Stem bleeding Ceratocystis paradoxa

Phytoplasmal diseases
Disease name Phytoplasma Vector Life style/
parasitism
Kerala wilt or root wilt Phytoplasma Lace wing bug Biotroph
(Stephanitis typicus)
TATIPAKA DISEASE Phytoplasma

Viroid disease : kadang kadang

Micronutrient deficiency : Pencil point

ARECANUT
Name of the diseases Causal organism
Anabe roga or basal rot Ganoderma lucidum
Mahali disease Phytophthora arecae
Yellow leaf spot Colletotrichum, Helminthosporium, Alternaria

1. Bud rot- Phytophthora palmivora

Symptoms
 5- 20 years old trees susceptible
 Heart leaf becomes brown, finally breaking of heart leaf
 Leaf loose luster and turn yellow
 Crown rots and emit foul smell. Central shoot can be easily pulled

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Pathogen
 Non-septate hyaline mycelium.
 Sporangiophores bear pear shaped sporangia which releases reniform
biflagellate zoospores.
 Sexual spores are oospores and
 Resting spores are chlamydospores
Mode of spread:
Primary : Oospores
Secondary : Zoospores

2. Basal stem rot /thanjavur wilt / bole rot- Ganoderma lucidum

Symptoms
 Susceptible stage -10-30 years
 Yellowing, withering and drooping of the outer fronds, leaf hang around
stem
 Young leaves do not unfold properly
 Soft rot occurs in bud with bad smell.
 Bleeding patches near the base of the trunk leading to death of tissues.
Advances to 3- 5 feet high.Tree dies.
 Fungal fruiting bodies (Bracket) are produced near the base of the trunk.
Pathogen
 Produces semi cirucular basidiocarp .
 The upper surface of the basidiocarp is tough, shining, light to dark brown
with concentric furrows.
 The lower surface is white and soft with numerous minute pores.
 The pores represent the hymenial tubes which are lined with basidia.
 The basidia bears the basidiospores on sterigmata.
Mode of spread
Primary : Rhizomorph
Secondary : Basidiospores

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3. Grey leaf blight: Pestalotia palmarum
Symptoms
 On older leaves minute yellow spots surrounded by greyish margin.
 Centre of the spots turn greyish white with dark brown margin with yellow
halo.
 Grey necrotic patches formed with acervuli.
 Complete drying giving blighted appearance
Pathogen
 Conidia produced inside the black acervuli amidst sterile setae.
Conidiophores hyaline, short and simple and bear five celled conidia.The
middle three celled are dark coloured while the end cells are hyaline with 3-
5 slender elongated appendages at the apex of the spore.
Mode of spread
Primary spread and Secondary spread through conidia from infected plants.

4. Stem bleeding: Ceratocystis paradoxa

Symptoms
 Oozing of reddish brown fluid from cracks of stem. Tissues decay
 Black crust formed
 Vigour of tree affected and yield reduced. Trees dies
Pathogen
 Produces two types of conidia.
 Macroconidia are spherical, dark green and produced
exogenously.
 Microconidia are produced endogenously inside the long cells
of conidiophores .
 Produces perithecia with a long neck with ostiole lined with appendages.
Asci bear the ascospores.
Mode of spread
 Primary spread and Secondary spread through conidia from infected plants

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PHYTOPLASMA DISEASES
KERALA WILT OR ROOT WILT: Phytoplasma disease
Symptoms
 Flaccidity of leaves i.e leaves curve abnormally inwards, resembling ribs of
animals
 Yellowing and marginal necrosis of leaflets.
 Wilting of leaves, shedding of buttons, crown size reduced.
 Cracks, discolouration and rotting of roots.
Pathogen: Phytoplasma
Vector: Lace wing bug – Stephanitis typicus

PENCIL POINT: Micronutrient deficiency

Stem tapers gradually, trunk remains barren like a pointed pencil.

ARECANUT
1. Anabe roga or basal rot - Ganoderma lucidum
Symptoms
 Yellowing of leaves
 Leaves dry, droop and fall off.
 Stem brittle and easily breaks.
 Oozing of dark fluid. Bracket shaped fructification appears.
 Roots affected and the central tissues of trunk dark brown and emit musty
smell.
 Xylem affected and the trees die.
Pathogen
 It produces basidiocarp with stipe. The basidiocarp is metallic brown in
colour.
 The clamp connection are profusely seen in older hyphae.

Mode of spread
Primary: Rhizomorph Secondary: Basidiospores

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2. Mahali disease - Phytophthora arecae
Symptoms
 On nuts water soaked lesions, nuts loose luster and rots
 Shedding of immature nuts.
 Large vacuoles in affected nuts with dark brown radial strands.
Pathogen
 Mycelium is inter and intracellular, hyaline, aseptate, produce
amphigynonus antheridium.
 The oospores are smooth and spherical
Mode of spread:
Primary: Oospores Secondary: Zoospores

3. Yellow leaf spot: Colletotrichum, Helminthosporium, Alternaria

Symptoms
Yellow specks appear on leaves with yellow halo. Seedlings stunted.
Mode of spread: Wind borne conidia

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EX. NO. : 14 DISEASES OF TEA
DATE :

Name of the diseases Causal organism

Blister blight Exobasidium vexans
Grey blight Pestalotia theae
Red rust Cephaleuros mycoides
Brown root disease Fomes lignosus
Black root disease Rosellina arcuta
Red root disease Poria hypolateritia
Armillaria root rot Armillaria mellea

1. Blister blight - Exobasidium vexans

Symptoms
 Small pale pinkish spots on the leaves
 Upper surface of the leaf spot becomes light green and depress into a
shallow cavity and the underside bulges correspondingly forming blister
like swelling covered with white growth of fungus
 Later stages blister turns dark brown and shrinks to flattened patch.
 In stem, spots without blisters are formed and damages stem, leaves and
buds wither
Pathogen
 Sexual spores - basidiospores and asexual spores - conidia.
 Early infections are caused by conidial stage.
 In the later stage, drying of leaf produces basidia.
 The hyphae gets aggregated and seen as a mass. At the terminal end of
hypha, elliptical bicelled conidia are borne.
Mode of spread
Primary spread: Basidiospores from infected seedlings from abandoned
nursery.
Secondary spread: Basidiospores from infected plants.

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2. Grey blight - Pestalotia theae
Symptoms
 Minute brownish spots on older leaves, soon turn grey
 Spots are irregular and have fine concentric lines
 Black dots of acervuli seen on older spots
 Leaves distorted and die back symptom
Pathogen
 Conidia produced inside the black acervuli amidst sterile setae.
 Conidiophores hyaline, short and simple and bear five celled conidia.
The middle three celled are dark coloured while the end cells are hyaline
with 3-5 slender elongated appendages at the apex of the spore.
Mode of spread
Primary spread and Secondary spread through conidia from infected plants.

3. Red rust - Cephaleuros mycoides

Symptoms
 It is an algal parasitic or epiphytic
 Orange yellow , roughly circular patch on the upper surface of the leaf.
 The penetrating filament may extend laterally between epidermis and
adjacent layer.
Pathogen
 The fungus produces sporangia on sporangiophore.
 Sporangia produce numerous zoospores. Zoospores are involved in the
disease spread. 5-8 sporangia are formed on each vesicle
Mode of spread
Primary spread and Secondary spread through zoospores from infected plants

ROOT ROT DISEASES

1. Brown root disease - Fomes lignosus
Symptoms
 The roots of the tea bush are encrusted with a mass of earth and small
stones cemented to the root by the mycelium

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Mode of spread
Primary and secondary spread through Rhizomorph and root contact

2. Black root disease: Rosellina arcuta

Symptoms
 Black strands adhere to the roots as loose cob – webby mass
 Star like sheets of white mycelium on the collar region
Mode of spread:
Primary and secondary spread through Rhizomorph and root contact

3. Red root disease - Poria hypolateritia

Symptoms
 Flat, black, rhizomorph on infected portion
 Branched markings on the surface of the wood
 Root mottled appearance of red and white
 Bark softened and wood discoloured as bluish black.
Mode of spread
Primary and secondary spread through Rhizomorph and root contact

4. Armillria root rot - Armillaria mellea

Symptoms
 Bushes wilt and turn chlorotic, affect collar region; Bark cracks
 Sheets of creamy coloured mycelium accompanied by flattened brown
rhizomorph.
 Sporophores produced on collar region, death of whole plants
Pathogen
 Flattened brown rhizomorphs are produced.
 Basidiospores from the sporophore infect the host
Mode of spread
Primary and secondary spread through Rhizomorph and root contact

95
EX. NO. : 15 DISEASES OF COFFEE
DATE :

Name of the diseases Causal organism

Leaf rust or oriental leaf disease Hemileia vastatrix
Collar rot Rhizoctonia solani
Black rot or koleroga or thread blight Corticium salmonicolor
Anthracnose or die back Colletotrichum coffeanum
Brown eye spot Cercospora coffeicola
Rosellina root rot / maya disease Rosellina arcuta
Brown root / stump rot Fomes lignosus
Red root disease Poria hypolateritia
Santavery root disease Fusarium oxysporum f.sp. coffea

1. Leaf rust or oriental leaf disease - Hemileia vastatrix

Symptoms
 Orange yellow uredosori on the lower surface of the leaf.
 Defoliation of leaves.
 Severe rust causes dieback of young shoots.
Pathogen
 Fungus produces teliospores and uredospores.
 Uredospores a r e reniform (orange segment like) in shape.
Uredospore’s upper surface is echinulated and lower surface is smooth
and thick walled. Teliospores/Teleutospores are thick-walled, smooth turnip
shaped.
 Aecial and Pycnial stages are not known.
Mode of spread
Primary spread: Uredospres from seedlings infected leaves from
abandoned nursery and Teliospores from infected leaves
Secondary spread: Wind borne uredospores

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2. Collar rot - Rhizoctonia solani
Symptoms
 1 to 3 months seedlings affected
 Pre-emergence damping off: seed rotting poor germination
 Post-emergence damping off: collar region brown discolouration, seedling
collapses and die
Pathogen
 Septate mycelium.
 Sclerotia are irregular brown to black.
 Produces terminal and intercalary chalamydospores.
 Perfect stage: Thanatephorus cucumeris.
Basidia with basidiospores are produced
Mode of spread
 Primary spread : Sclerotia
 Secondary spread : Wind borne basidiospores

3. Black rot or koleroga or thread blight - Corticium salmonicolor

Symptoms
 Dark brown or black decaying leaves, twigs and berries
 The affected leaves get detached and hang down by means of slimy
fungal strands.
 Fungal strands run along twig and petiole
 Defoliation and berry drops
Mode of spread
Primary : Sclerotia
Secondary : Wind borne basidiospores

4. Anthracnose or die back - Colletotrichum coffeanum

Symptoms
 Circular or irregular greenish spots on leaves
 Dark colour sunken spot on berries, berries fail to mature (kattekai)
 Die back of twigs

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Pathogen
 It produces acervuli which is rounded or irregular in shape.
 Conidiophores are simple, septate.
 Conidia are cylindrical, non-septate with oil globules.
Mode of spread
Primary : Ascospores from dried fallen leaves
Secondary : Wind borne conidia

5. Brown eye spot - Cercospora coffeicola

Symptoms
 On leaves circular necrotic spots with dark brown margin and pale brown
centre. Necrotic spots increase in size and shot hole symptom seen.
 On berries sunken necrotic spots appear, skin of the affected berries
show a purple halo around necrotic spots.
 Berry turns black, dries and finally shed.
Pathogen
 Conidia are multiseptate and sub cylindrical.
Mode of spread
Primary : Ascospores from dried fallen leaves
Secondary : Wind borne conidia

6. Rosellina root rot / maya disease - Rosellina arcuta

Symptoms
 Cambium tissues are attacked at the base of the tree at ground level and
roots affected. Heartwood affected and black sheet formed
Mode of spread
Primary and secondary spread through Rhizomorph and root contact
7. Brown root / stump rot - Fomes lignosus
Symptoms
 Affected plants show slight wilting and yellowing of leaves.
 Leaves wither and bushes die suddenly.
 The tap root and main laterals are found encrusted with a thick coating
of black charcoal like powdery patches. Roots become brittle.

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Mode of spread
Primary and secondary spread through Rhizomorph and root contact

8. Red root disease - Poria hypolateritia

Symptoms
 Aerial symptoms are similar to brown root disease. Root system show
red encrustations which is the fungal rhizomorph.
 If the affected root is washed, it appears deep red in colour.
Mode of spread
 Primary and secondary spread through Rhizomorph and root contact

9. Santavery root disease: Fusarium oxysporum f.sp. coffea

Symptoms
 Sudden wilting, yellowing of leaves followed by defoliation and death of
aerial parts.
 Discoloration of the collar region and inner portions of root.
Mode of spread
 Primary and secondary spread through rhizomorph and root contact

99
EX. NO. : 16 DISEASES OF RUBBER and COCOA
DATE :

RUBBER
Name of the diseases Causal organism
Powdery mildew Oidium heveae
Abnormal leaf fall Phytophthora palmivora
Secondary leaf fall Glomerella cingulata
Pink diseases Corticium salmonicolor

COCOA
Name of the diseases Causal organism

Seedling blight
Phytophthora palmivora

Phytophthora palmivora, P. megakarya,

Black Pod rot
P. citrophthora and P. capsici
Stem Canker
Phytophthora palmivora
Vascular Streak Dieback (VSD)
Oncobasidium theobromae
Cherelle Rot
Colletotrichum gloeosporioides

1. Powdery mildew: Oidium heveae

Symptoms
 White powdery growth on tender leaflets, reduce photosynthetic efficiency.
 Severely infected leaf lets curl, crinkle and vedge roll inwards and fall off.
 Petioles alone remain to the twigs giving a broom stick appearance.
Pathogen
 Mycelium hyaline and septate.
 Conidiophores bear chain of conidia
Mode of spread
Primary : Ascospores from chasmothecium
Secondary : Wind borne conidia

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2. Abnormal leaf fall - Phytophthora palmivora
Symptoms
 Initially water soaked lesions seen on leaves
 Leaves turn coppery red , young leaf and buds affected
 Shedding of leaves prematurely during June-Aug
 Branches shows die – back symptom
 Fruit rot, rotting of bark. Reduction in latex yield
Pathogen
 Mycelium non septate, hyaline and produces sporangiophores which bear
numerous pear shaped sporangia which releases zoospores.
 Sexual spores are oospores.
 Chlamydospores are resting spores.
Mode of spread
Primary : Oospores and Chalmydospores
Secondary : Wind borne zoospores from sporangia

3. Secondary leaf fall - Glomerella cingulata

Symptoms
 Numerous minute, circular brown spots on leaves
 Thick brown margin and central tissues turn white
 Young leaf lets crinkled and shed quickly
 Young green stem attacked
 Green pods affected and cause rotting and seen Numerous acervuli
Pathogen
 Mycelium septate and hyaline at first and later becomes light brown.
Conidiophores bear single celled oblong conidia.
 Perithecia bear ascus which contains eight ascospores.
Mode of spread
Primary : Ascospores
Secondary : Wind borne conidia

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4. Pink diseases - Corticium salmonicolor
Symptoms
 Young twigs and branches affected
 Fungal growth encircles the stem and penetrates the bark
 Bark splits and peels off
Pathogen
 Hyphae hyaline when young and turn light brown with age.
 It Produces basidia and basidiospores.
 At later stage fungus form sclerotia and found scattered all over the
diseased parts.

COCOA
1. Seedling blight - Phytophthora palmivora
Symptoms
 Symptoms develop on the leaves and stem of seedlings or budded plants.
 On leaves, small water soaked lesions appear which later coalesce in the
blighting of leaves.
 On stem, water soaked lesions develop initially and later turn to black
colour.
 Stem infections develop any point on the stem causing the death of
seedlings.
Pathogen
 Mycelium non septate, hyaline and produces sporangiophores which bear
numerous pear shaped sporangia which releases zoospores.
 Sexual spores are oospores.
 Chlamydospores are resting spores.
Mode of spread
Primary : Oospores and Chalmydospores
Secondary : Wind borne zoospores from sporangia

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2. Black Pod rot - Phytophthora palmivora, P. megakarya, P. citrophthora
and P. capsici
Symptoms

 Chocolate brown spot, which spreads rapidly and entire surface of

the pod.
 Whitish growth of fungus consisting of fungal sporangia is produced
over the affected pod surface.
 Affected pods turn brown to black.
 Internal tissues as well as the beans become discolored

Pathogen

 Mycelium non septate, hyaline and produces sporangiophores which bear

numerous pear shaped sporangia which releases zoospores.
 Sexual spores are oospores.
 Chlamydospores are resting spores.
Mode of spread
Primary : Oospores and Chalmydospores
Secondary : Wind borne zoospores from sporangia
3. Stem Canker - Phytophthora palmivora
Symptoms

 Cankers appear either on the main trunk, jorquettes or fan branches.

 Greyish brown water soaked lesion on the outer bark.
 A reddish brown liquid oozes out from these lesions, which later dries
up to form rusty deposits.
 Tissues beneath the outer lesion show reddish brown discoloration due
to rotting.

Pathogen
 Mycelium non septate, hyaline and produces sporangiophores which
bear numerous pear shaped sporangia which releases zoospores.
 Sexual spores are oospores.
 Chlamydospores are resting spores.

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Mode of spread
Primary : Oospores and Chalmydospores
Secondary : Wind borne zoospores from sporangia

4. Vascular Streak Dieback (VSD) - Oncobasidium theobromae

Symptoms

 Yellowing of one or two leaves on the second or third flush behind the
growing tip.
 Diseased leaves fall within a few days of turning yellow and the other
leaves on the shoot show similar symptoms.
 Infected shoot is split lengthwise there is always a characteristic brown
streaking.

Pathogen: Perfect stage: Thanatephorus theobromae

. Basidia with basidiospores are produced
Mode of spread: Primary: Rhizomorph
Secondary: Basidiospores

5. Cherelle Rot - Colletotrichum gloeosporioides

Symptoms

 Shriveling and mummifying of some young fruits are a familiar sight in

all cocoa gardens.
 Fruits lose their lustre and in four to seven days they shrivel.
 Fruits may wilt but do not abscise.
 Many other factors like insects, diseases, nutrient competition and over
production may also be associated with this problem.

Pathogen
 It produces acervuli which is rounded or irregular in shape.
 Conidiophores are simple, septate.
 Conidia are cylindrical, non-septate with oil globules.
Mode of spread
Primary : Ascospores from dried fallen leaves
Secondary : Wind borne conidia
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