Practical Manual - acharya ng ranga agricultural university

<strong>Practical</strong> <strong>Manual</strong> of 

Diseases of Horticultural crops 

and 

Their Management 

COURSE No. PATH 372 

Prepared By 

Dr. B.VIDYA SAGAR 

Assistant Professor 

Department of Plant Pathology 

College of Agriculture: Rajendranagar 

and 

Dr. P. Kishore varma 



Agricultural College: Aswaraopet 

ACHARYA NG RANGA AGRICULTURAL UNIVERSITY 

College of Agriculture, Rajendranagar-500030 

2012 

1

<strong>Practical</strong> <strong>Manual</strong> of 

Diseases of Horticultural crops 

and 

Their Management 

COURSE No. PATH 372 

Prepared By 

Dr. B.VIDYA SAGAR 



College of Agriculture: Rajendranagar 

and 

Dr. P. Kishore varma 



Agricultural College: Aswaraopet 

ACHARYA NG RANGA AGRICULTURAL UNIVERSITY 

College of Agriculture, Rajendranagar-500030 

2

ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY 

DEPARTMENT OF PLANT PATHOLOGY 

Certificate 

Certified that this is a bonafied record of practical work done by 

Mr./Miss _______________________________________I.D. No. 

__________________________ in B.Sc (Ag) degree programme 

Course No. PATH – 372 title “Diseases of Horticultural Crops and 

their Management” during _______________ semester of the 

academic year _______________. 

Date: Teacher in – charge 

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S. No Title 

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INDEX 

Date of 

submission 

Remarks 

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INTRODUCTION 

Plant Pathology is a branch of biological science which deals with symptoms 

causal organisms, epidemiology and management of plant diseases. Plant diseases 

can be caused by both biotic and abiotic factors. The abiotic factors are mostly due to 

imbalance of nutrients which do not spread in the field. The biotic diseases caused 

by fungi, Bacteria, Phytoplasma, Viruses, Viroids, Phanerogamic parasites, Algae 

and Nematodes. These diseases have potential to spread from one field to the other 

and one area to the other. 

Plant diseases can be diagnosed by studying symptoms, signs and 

microscopic investigations. 

Symptom : Sign or evidence of diseased as shown by the plant or any objective 

evidence of disease is called symptom of the disease. 

Sign: Presence of the pathogen or its parts or structures or products on infected 

portions of plant. 

Syndrome: A group of several symptoms produced by pathogen in sequence. 

Symptoms and signs provide the most important evidences about the causal 

agent. Sign can point directly to causal agents. 

Each disease is cahracterised by certain symptoms and they may change in 

nature and intensity in the course of a disease and they may modify by 

environmental conditions. 

1. Symptomatology 

A. Symptoms due to the character and appearance of the visible pathogen or its 

structures or organs 

In a number of diseases the structure of the pathogen constitutes the most 

prominent symptom of the disease. Several of such symptoms described below. 

i. Downy mildews : Under humid conditions, owing to the production of 

sporangiophores and sporangia, a white or grey bloom develops on the lesions 

produced usually on the under surface of leaves. This is called the “downy 

growth”. It is generally true in downy mildews that the symptoms are less 

conspicuous than the sporangiophores en masse. 

Ex : Downy mildew of grapevine – Plasmopara vitiocola 

Downy mildew of cucurbits – Pseudoperonospora cubensis 

Powdery mildews : Enormous numbers of conidia are formed on superficial 

growth of the fungus giving the host surface a dusty or powdery appearance. Black 

minute fruiting bodies may also be seen. 

Eg : Powdery mildew of cucurbits – Erysiphe cichoracearum 

Powdery mildew of grapevine – Uncinula necator 

Powdery mildew of chillies – Leveillula tauria 

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ii. Rusts : These are diseases with rusty symptoms. The rusts appear as relatively 

small pustules of spores, usually breaking compact, and red, brown, yellow or 

black in colour. 

Eg : Powdery mildew of cucurbits – Erysiphe cichoracearum 

iii. Smuts : The world smut means a story or charcoal like power. Smut affected 

parts of the plant show a black or purplish black dusty mass. These symptoms 

usually appear on gloral organs. 

Eg : Loose smut of wheat – Ustilago tritici 

iv. White Blisters : On leaves of cruciferous and other plants there may be found 

numeroud white blister – like pustules which break open the epidermis and 

expose powdery masses of spores. Often such symptoms have been called 

white rusts. 

Eg : White rust of crucifers – Albugo candida 

White rust of amaranthus – Albugo bliti 

v. Sclerotia : A sclerotium is a compact, often hard mass of dormant fungus 

mycelium. Sclerotia are most often dark coloured. Dresence of these structures 

on the host surface helps in identification of the disease and the causal fungus. 

Eg : Ergot of rye – Claviceps purpurea 

Ergot of bajra – Claviceps fusiformis 

vii. Blotch : This symptom consists of a superficial growth giving the fruit a blotched 

appearance. Eg : Sooty blotch disease of apple – Gloeodes pomigena 

Overgrowth or Hypertrophy : The most apparent effect in some diseases is the 

abnormally increased size of one or more organs of the plant or of certain portions of 

them. This is usually the result of stimulation of the host tissues due to excessive 

growth. It is brought about by one or both of the two processes known as 

hyperplasia and hypertrophy. Hyperplasia is the abnormal increase in the size or a 

plant organ due to increase in number of cells of which the organ is composed. In 

hypertrophy the increased size of the organ is due to increase in the size of cells of a 

particular tissue. 

The over growths are of various forms in different diseases and are known by 

different names : 

a. Galls : These are malformations of more or less globose, elongated or 

irregular shape. They may be fleshy or woody. 

Eg : Club root of cabbage Plasmodiophora brassicae 

Stem gall of coriander – Protomyces macrosporus 

b. Warts : Smaller galls are called warts Eg : Black wart of potato Sunchytrium 

endobioticum 

c. Curl : Leaves are arched, puckered, twisted, curled and distorted due to 

growth in tissues in localized are of the leaf. 

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Eg : Leaf curl of peach – Taphrina deformans 

d. Proliferations : Eg : Taphrina cerasi on cherry stimulates shoot production by the 

host. 

e. Transormation of plant parts : The earheads are converted into green leaflike 

structures. 

Eg : Green ear of pearl millet Sclerospora graminicola 

Green ear of Korra 

Atrophy of Hypoplasia or dwarfing : In many diseases one of the results is 

inhibition of growth resulting in stunting or dwarfing. The whole plant may be 

dwarfed or only certain organs may be so affected. 

Spots and shot-holes : There are common necrotic symptoms of some plant diseases. 

The cells are killed in definitely limited areas and the dead tissues usually become 

some shade of brown. In many cases, other colour changes such as yellowing, 

precede the death of cells. The leaf spot diseases are numberous, the same host some 

times being affected by many types. The dead area often shrinks and soparates from 

the surrounding healthy tissues. This condition is called “shot-hole”. The shape of 

lesions on leaves and fruits may be round, angular or irregular. The dead areas are 

often surrounded by a purple, red, yellow or brown margin. 

Eg : Anthracnose of grapevine – Gloeosporium ampelophagum 

Anthracnose of mango – Colletotrichum gloeosporioides 

a. Anthracnose : Symptoms appear as circular to angular, sometimes irregular, 

spots occurring along the leaf veins, petioles, stems and fruits. The affected 

tissues are discoloured and killed resulting in characteristic lesions. 

b. Blight and blast : These refers to diseases in which death occurs in masses of 

cells suddenly. In a diseased plant, due to severity of infection the tissues are 

rapidly killed, resulting in death of foliage, blossom or other above ground plant 

parts. Such as symptom is known as blight. When the entire leaf blade, bud or 

other plant parts are involved resulting in quick death of the part of plant as a 

whole then it is know as blast. 

Eg : Early blight of potato and tomato – Alternaria solani 

Late blight of potato and tomato – Phytophthora infestans 

c. Cankers : These are symptoms expressed as necrotic lesion in the cortical tissues 

of stem, fruits or leaves. Corky growths often develop in the affected parts. 

Cankers mostly cause localized death of the tissues but in severe infections they 

may girdle the stem which may be deep seated, almost to the wood and that a 

small area of eanbium is to be killed. 

Eg : Apple canker – Nectria galligena 

d. Scab : The infection is not deep seated. Sunken lesions are produced. 

Eg : Apple scab – Venturia inaequalis 

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e. Damping-off : It is a condition in which the stem is attacked near the soil surface. 

The affected protion becomes constricted and weak, incapable of bearing the load 

of the upper portion. As a result the seedlings topple down and die. 

Eg : Damping-off tobacco, tomato, chilli, brinjal etc. – Pythium aphanidermatum 

f. Rot : The affected tissues die, decompose to greater extent, and turn brown. In 

most cases this condition is brought about by fungi which dissolve the cell walls 

more or less completely by means of enzymes. It is a gangrene of plant tissues 

which affects fleshy or woody stems, roots, fleshy leaves, flowers, buds, fruits etc. 

According to the plant organ attacked the rot may be called root rot, leaf or stem 

rot, bud-rot and fruit rot. Depending upon the type of dissolution brought about 

by the pathogen the rots may be grouped as soft rot, wet rot or dry rot. 

Eg : Bud rot of palmyrah – Phytophthora palmivora 

Fruit rot of chilli – Colletotrichum capsici 

i. Die-back : As the name indicates such diseases are characterized by dying of 

plant organs, especially stem or branches, from the tipe backwards. 

Eg : Die-back of chilli – Colletotrichum capsici 

ii. Wilts : In many diseases the most striking effect is drying or witting of the entire 

plant. The leaves and other green or succulent parts lose their turgidity, become 

flaccid and crop. This effect is usually seen first in some of the leaves. Later, the 

young growing tip or the whole plant may suddenly or gradually dry up. 

Wilting may be the result of injury to the root system, to the partial plugging of 

water conducting vessels or to toxic substances sereted by the pathogen. 

Eg : Tomato wilt : Fusarium oxysporum f.sp. lycopersici 

Guava wilt – Fusarium solani 

2. MICROSCOPIC EXAMINATION 

Diseases caused by fungi are characterized by the presence of these fungi on 

the surface of the plants or inside the plants. The presence of such pathogens at an 

active state on the surface of a plant would indicate that they are probably the cause 

of the disease. Their detection and identification can, in some cases, be determined 

with the experienced naked eye or with a magnifying lens or, more frequently, by 

microscopic examination. If no such pathogens are present on the surface of the 

diseased plants, then it will be necessary to look for additional symptoms and 

especially, for pathogens inside the diseased plant. These are usually at the margins 

of the affected tissues, at the vascular tissues, or at the base of the plant, and on or in 

its roots. 

When fungal mycelium and spores are present on the affected area of a 

diseased plant, two possibilities must be considered: 

1. The fungus may be the actual cause of the disease or 

2. It can be one of the many saprophytic fungi that can grow on dead plant tissue 

once the latter has been killed by some other cause even other fungi. 

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Determination of whether the observed fungus is a pathogen or a saprophyte 

in initiated by microscopically studying the morphology of its mycelium, fruiting 

structures and spores. From these, the fungus can be identified and can be checked 

in appropriate books of mycology or plant pathology to see whether it has been 

reported to be pathogenic or not especially on the plant correspond to those listed in 

the books as caused by that particular fungus, then the diagnosis of the disease is in 

most cases considered complete. If no such fungus is known to cause a disease on 

plants, especially one with symptoms similar to the ones under study, then the 

fungus found should be considered a saprophyte and the search for the cause of the 

disease must continue. In many cases, neither fruiting structures nor spores are 

initially present on the diseased plant tissue and therefore, no identification of the 

fungus is possible. With most fungi, however, fruiting structures and spores are 

produced in the diseased tissue if the later is placed in a glass, plastic etc “moist 

chamber”, i.e. a container in which wet paper towels etc. are added to increase the 

humidity in the air of the container. 

Symptoms Pathogen structures associated 

Downy mildews Sporangiophores and sporangia, oospores 

Powdery mildews Conidiophores and conidia, eleistothecia 

Rusts Uredosori bearing uredospores 

Teliolsori bearing teliospores 

Smuts Chlamydospores or teliospores 

White blisters 

Leaf spots 

Leaf blights 

Globose sporangia in chains 

Blast 

Anthracnose 

Shot holes 

Conidia 

Damping off Sporangia and mycelial bits 

Root rots 

Stem rot 

Charcoal rot 

Sclerotia/Pycnidia 

Fruit rot and die-back Acervuli 

(Chillies) 

Wilts Mycelium and conidia 

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Ex.No.1 Date: 

STUDY OF DISEASES OF CITRUS 

Gummosis 

Causal organism : Phytophthora palmivora, Phytophthora citrophthora 

P. parasitica (P. nicotianae var. Parasitica) 

Phytophthora syringae 

Symptoms 

1. Profuse gumming on the surface of the affected bark with droplets or gum 

trickles down the stem. 

2. Infected bark show conspicuous brown staining. 

3. Affected plants blossom heavily and die. 

4. Leaves because chlorotic, pale yellow shows malnutrition symptoms and 

veins turn yellow and premature leaf fall occur. 

5. Infection spreads both upward and downward to roots which causes fibrous 

root rot. 

6. In Manderin oranges, water soaked spots observed on leafs. 

7. On fruits, Water soaked spots also observed which the symptom referred as 

‘Brown rot’. 

Etiology 

In south India, the main cause of gummosis is recognized as Phytophthora palmivora. 

Mycelium: Intercellular with haustoria. Hyphae large and often swollen at regular 

intervals. 

Sporangiophores: Simple or branched with inverted pear shaped, rarely round and 

always terminal sporangia bearing large biflagellate zoospores. 

Oospores: Spherical, thick walled and produce secondary sporangium on 

germination 

Disease cycle 

PSI : Oospores and chlamydosores in soil. 

SSI : Sporangia / Zoospores spread through water and movement of soil. 

Management : 

Preventive measures 

Selection of proper site with adequate drainage. 

Selection of well drained soils. 

Avoid excess irrigation. 

Provision of inner ring – 45 cm around the tree trunk to prevent moist soil. 

Avoid injuries to crown roots or base of stem during cultural operations. 

Use resistant sour oranges rootstocks for propagating economic varieties. 

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Painting Bordeaux paste or with ZnSO4, CuSO4, lime – 5 :1:4 to a height of about 

60 cm above the ground level once a year. 

Bud union should be 30-45 cm above the soil level. 

Soil treatment : With sodium tetra thio carbonate (ENZONE) 

Pre-harvest spray : Captan 0.2 %, or Metalaxyl – 0.2 % 

Fruits : Treat fruits with chlorine or sodium orthophenyl phenate to prevent post 

harvest spoilage. 

Curative measures: 

Scoop the diseased bark portion with a little portion of healthy tissue with a 

sharp knife. 

Protect the cut surface with Bordeaux paste followed by spraying 0.3 %, Fosetyl – 

Al 0.1 % reduces spread. 

Soil drenching: With Metalaxyl 0.2 % or 0.5 % or Trichoderma viride Commercial 

formulation is also effective. 

Biocontrol with commercial formulations of Pseudomonas fluorescence, T. viride, 

VAM (Vascular Arbuscular Mycorhizoa) along with farm yard manure. 

Resistant varieties : Root stock – Rangapur lime 

Diplodia gummosis Diplodia natalensis, Physalospora rhodina 

Symptoms 

Profuse gumming on upper portions of trunk, branches & twigs. 

Infection starts at growth cracks or ridges at Crotches. 

Gum Oozes out from Cracks developed on diseased portion. 

The infection spreads from bark to wood, which ultimately dries and become 

discoloured. 

Large limbs are killed and if left unchecked the whole tree may be killed in 

course of time. 

Affected branches break at infected portion. 

Etiology 

Conidiomata: Pycnidia black, single, globose, immersed, erumpent and ostiolate. 

Conidiophores: Simple and slender. 

Conidia: Dark, two celled, ellipsoid or ovoid. 

Management 

Maintain balanced nutrition to keep the pruning of infected branches. 

Maintain trees in vigorous condition. 

Wounds in bark especially on limbs & forks should be scraped and protected 

with Bordeaux paste. 

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Spraying with 0.1 % Carbendazim on affected limbs and forks useful to 

restrict disease spread. 

Spraying insecticides like Monocrotophos 1.6ml/litre of water to control 

insects. 

Twig blight 

Symptoms 

Colletrotrichum sps., Diplodia sps ,Fusarium sps. 

Shedding of dry leaves, die back of small twigs. 

Formation of gum at the base of dead twigs. 

Black pycnidial bodies on affected bark (Diplodia). 

Etiology 

Colletotrichum 

Conidiomata: Acervuli seen in epidermis beneath the cuticle. Acervuli disc or 

cushion shaped, waxy, sub-epidermal typically with dark setae or spines at the edge 

or among the conidiophores. 

Conidiophores: Simple, elongate and are produced within the cavity of acervulus. 

Conidia: Hyaline, one-celled, ovoid or oblong. 

Management 

Pruning of twigs before rainy season & spray with Carbendazim – 0.1 % 

Dry root rot Diplodia natalensis, Macrophomina phaseolina, 

Fusarium solani 

Symptoms 

Bark of bigger roots decay & extends to wood. 

Later bark becomes dry and shredded and remain dry root emits foul odour. 

Finally tree dies. 

Affected tree gives heavy crop with small sized fruits before the death. 

Favourable conditions 

Injuries to root 

Hardpan formation. 

Formation 

Poor aeration 

Direct contact of water with trunk. 

Management 

Cut infected roots and paste with Bordeaux Mixture spray. 

Addition of green manure 

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Drenching soil – with Carbendazim 0.1 % followed by Mancozeb – 0.25 % at 

monthly interval. 

Application of neem cake followed by drenching with 0.5 % Trichoderma viride 

formation + 0.2 % copper oxychloride in early stages. 

Citrus Scab Elsinoe fawcetti 

Symptoms 

Produced on leafs and fruits. 

Lesions are small semi translucent dots in early stages and become sharply 

defined. 

Pustules with flat and some what depressed at the centre the opposite surface 

corresponding to the warty growth shows circular depression with pink or 

reddish centre. 

Affected leafs wrinkled, distorted, stunted and misshapen. 

On fruits lesions consist of corky projection which often breaks into scab. 

Etiology 

Ascostroma: Simple, innate, intra or sub-epidermal, partially erumpent at maturity, 

small pulvinate to crustose. 

Asci: Ovoid bearing 1-3 septate, oblong to elliptical and hyaline to yellowish 

ascospores 

Management 

Pruning and destruction of diseased leafs, twigs, branches and fruits followed 

by spray with copper oxy chloride – 0.3 % or Bordeaux Mixture 1 % or 

Carbendazim – 0.1 % 

Canker: Xanthomonas axonopodis pv. citri 

Symptoms 

Symptoms appear on leaves, twigs, thorns and fruits. 

On leaves the initial symptoms appear as small, round water soaked, 

translucent spot of yellow brown colour, with raised convex surface on both 

surface. 

Such spots are surrounded by yellow halo. 

On maturity, surface become white, or grayish, finally rupturing in the centre 

giving crater. 

Cankerous growth encircles the twigs causing die back of twig. 

On fruits spots of canker similar to leaf appear but without yellow halo. 

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Etiology 

The bacterium is rod shaped, Gram negative, aerobic, non-spore forming and is 

motile by single polar flagellum. Bacterial colonies on beef agar are circular, straw 

yellow, slightly raised and glistening. 

Management 

Field sanitation. 

Removal of affected plants. 

Collect and burn defoliated twigs, leafs, fruits. 

Use disease free nursery stock. 

Spray – 1 % Benomyl or 1 % Bordeaux mixture. 

Spray – Streptocycline – 1 g + COC – 0.3 % - three sprays. 

Control leaf minor – Spraying Monocrotophos – 0.5 % 

Fortnight spraying of Neem cake extract solution 

Tristeza: Citrus Tristeza Virus 

Symptoms 

Stem pittings are seen on woody trunk. 

Honey comb like inner pittings on innerside of bark. 

Yellow brown stain below bud union. 

Plants bear heavy small sized fruits and insipid. 

Trees look like chlorotic & sick in early stage, gradually leaf defoliation takes 

place resulting dieback and death of plant. 

Intermittent vein clearing vein flecks in young leafs in typical symptoms – 

Acid lime. 

Diseased trees usually blossom heavily. 

Sweet oranges – specific symptom – honey combing. 

Tristeza infected citrus trees on sour orange rootstocks cause phloem necrosis 

at graft union. 

Grape fruit and acid lime – susceptible irrespective root stock. Lime 

susceptible as seedling on any root stock. 

Etiology 

Virions filamentous, not enveloped, usually flexuous with a clear modal length of 

2000 nm and 12 nm wide. Genome consists of single-stranded RNA. Total genome 

size is 17-20 kb. 

Disease cycle 

PSI : Infected plant wood, Disease transmitted by Grafting and Budding. 

SSI : Aphids (Black citrus aphid) : Toxoptera citricida, Myzus persicae 

Dodder – Cuscuta reflexa, Virus – Not seed borne 

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Management 

Strict quarantine measures to be enforced. 

Use certified bud wood free CTV. 

Use of nucellar seed lings. 

Remove all diseased trees as and when disease noticed. 

Fresh plantings to be taken with virus free materials on tolerant root stocks. 

Cross Protection: Incorporating the mild strain to prevent the attack by severe 

strain of virus. 

Avoid Sweet orange & mandarin susceptible root stock and use resistant root 

stock Rough lemon, Trifoliate orange, Rangapur lime 

Heat therapy: Exposing bud wood to 35-400 C for 85 to 107 days. 

Spray Monocrotophos – 0.05 % to control vector. 

Greening: Candidatus Liberobacter asiaticus 

Fastidious phloem limited Bacterium, Obligate gram negative bacterium. 

Symptoms: 

Chlorosis of the leaves, the yellow tissue on lamina scattered as green islands. 

Yellow areas on leaf blade surrounded by the midrid at one side and another 

side by lateral veins. 

Heavy leaf fall – onset of summer. 

Often new flush may come out leaves formed are short, upright, chlorotic 

with green veins on green blotches on leaves. 

The affected trees stunted with pronounced leaf and fruit drop. 

Twigs die back. 

Internodal distance between branches reduced which gives bushy appearance 

of branches. 

The fruits are small, lopsided with oblique columella. Affected fruits are low 

in Juice content and high in acid. 

The Seeds are poorly developed, aborted and dark coloured. 

Etiology 

Rod shaped cells, 0.2 to 0.5µm in diameter by 1 to 4µm in length with undulating or 

rippled cell wall without flagella 

Disease cycle 

PSI : Survives in wild and cultivated species. 

SSI : Spreads by Psyllids – Diaphorina citri, Vegetative propagation. 

Management 

Eradication and removal of affected trees. 

Insect control by Dimethoate – 0.2 % or Monocrotophos – 1.6 ml / lit. or 

Phosphomidon 1 ml / lit 

Acephate – 1 gm / lit. 

15

Application of Tetracycline – 500 ppm to suppress the effect of disease. 

Spray Carbendazim – 0.1 % 

The Seedlings are exposed to moist hot air at 47 0C for 4 hours or 430 C for 6 

hours – Reduces / Suppresses pathogen. 

Phanerogamic parasite 

Dodder: Cuscuta subinclusa, Cuscuta asiatica 

Complete stem parasite 

Seeds of parasite germinate in soil near to the host plant. It reaches the host, 

entwined around the branches and flowers of host plant and produces haustoria and 

draws nutrition from host plant. 

Etiology 

Stem: Cream yellow to orange, thread like, leafless stem devoid of green pigment 

Leaves: Represented by minute functionless scales 

Flowers: Tiny white, pink or yellow flowers in clusters 

Control 

Mechanical suppression and Spray Bordeaux Mixture 1 % 

Answer the following simple questions: 

1. Which disease of citrus is aggrievated by insects? 

2. What is meant by thermotherapy? Give examples of diseases which 

controlled by this method. 

3. The neem cake extract was used in controlling the disease? Substantiate it? 

4. What is cross protection and how it works in the management of plant 

viruses? 

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Ex.No.2 Date: 

STUDY OF DISEASES OF MANGO 

Mango 

Powdery mildew: Oidium mangiferae 

Symptoms 

White or superficial powdery growth on inflorescence, stalks of inflorescence, 

fruits and leaves. 

Floral axis become black and showing die back symptoms. 

If the fruit is already set it may drop off prematurely at pea size. 

Etiology 

Mycelium: Hyaline, branched and superficial with septate hyphae 

Conidiophores: Simple, erect with 2 or more basal cells 

Conidia: Hyaline, unicellular, elliptical and borne singly or rarely in chains of two 

Management : 

Spray 0.3 % of wettable sulphur or Dinocap – 0.1 % 

Resistant varieties Totapuri, Neelam 

Anthracnose: Glomerella cingulata 

Symptoms : 

Symptoms appear on leaves, twigs, inflorescence and fruits. 

On Leaves : Oval to irregular or circular grayish brown spots. Affected leaf tissues 

dry up and drop off giving the leaf ‘shot hole’ appearance. 

On Stem : Similar spots on young stems enlarge and cause girdling and drying of 

the stem, Die back symptom. 

On Fruit : Black depressed spots developed on the skin of the ripened fruits. 

Etiology 

Perithecia: More or less compounded, sub-spherical, with prominent ostiolar hair 

Asci: Subclavate, often slightly pedicellate and fugacious 

Ascospores: Hyaline, 1-celled, allantoid 

Management 

Field sanitation 

Spray COC – 0.3 % before flowering. Or Carbendazim – 0.1 % at peanut 

stage. 

Hot water treatment at 550 C for 5-16 minutes 

Fruit dip in Benomyl 100ppm. 

17

Malformation: Fusarium moniliformae var. Subglutinans 

Symptoms 

Bunchy top: Formation of bunch of thick small shoot lets with small leaves 

on four to five months old plants, which gives an appearance of bunchy 

top. 

Vegetative malformation: induces the excessive vegetative branches with 

short internodes, at the top of seedlings that gives a bunchy top 

appearance. 

Floral malformation: shows variation in panicle formation, with 

Etiology 

The presence of chains of microconidia and the absent of chlamydospores are the 

diagnostic characters of Fusarium moniliforme. 

Microconidia: Fusoid to clavate, becoming one septate and produced in chains from 

subulate lateral phialides 

Macroconidia: Fusoid, thin walled, 3-7 septate 

Chlamydospores: Absent, but globose stromatic initial cells may be present in some 

cultures 

Reasons are 

1. Physiological 

2. Viral 

3. Acarologocal 

4. Fungal 

Management 

Removal of infected parts. 

Spray 0.1 % Carbendazim 

Spray 200 ppm NAA (October) 

Control mites using acaricides like Dicofol – 0.3% 

Spray mangiferin after pruning. 

Bacterial Leaf spot / black spot: Xanthomonas campesrtis pv. mangiferae-indicae 

Symptoms: 

On Leaves : Water soaked black spots surrounded by Chlorotic halo 

Several spots join to form Cankerous patches resulting in severe 

defoliation 

On Twigs : Black elongated elliptical lesions 

On Fruits : Water soaked spots turn brown ultimately black. 

Management 

Eradication of infected plant parts. 

18

COC – 0.3 % + Streptocycline – Spray 

Bio control agent : Bacillus coagulans is effective. 

Resistant variety : Keshar, Bombay green 

Sooty mould: Capnodium ramosum 

Symptoms 

Observed in dense orchards with low sunshine. 

It not parasite by it self. Grows on the excretion of insect like Mealybugs, leaf 

hoppers etc. 

Black sooty growth covers the entire leaf surface reducing photosynthesis. 

Management 

Spray Acepheate – 1.5 ml / lit – 15 days interval or carbaryl. 

Spraying Starch 5% solution. (1 kg of starch 20 litres of water) 

Redrust: Cephaleuros virescens 

Symptoms 

Observed on leaves, petioles and twigs. 

Spots brick red in colour, raised and velvety in nature. 

After shedding zoospores, spots turn to creamy white. 

Etiology 

The alga after a period of vegetative growth develops two types of sporangia. Those 

formed directly on the thallus are sessile and thick walled with orange pigments. 

Some are produced on special sporangiophores consisting of thick, rigid, septate 

hairs, swollen into a vesicle at the tip. Each vesicle carries 3 to 6 sporangia bearing 

orange and ovoid zoospores which swim actively by means of cilia. 

Disease cycle 

PSI : Sporangia 

SSI : Wind borne Zoospores 

Management 

Spray COC + Teepol @ 0.5 % each. 

Phanerogamic parasites: 

Symptoms 

Partial stem parasite. 

Dendrophthoe ampullaceus 

(=Loranthus) 

Germinate on twigs and produce bulged haustoria help in absorption of 

water nutrients 

Point of attachment show hypertrophy. 

19

Etiology 

Stem is thick, erect or flattened at the nodes and appears to arise in clusters at the 

point of attack. The place at which the haustorium penetrates often swells to form 

tumors which vary ion size according to the age of the parasite. The flowers are 

borne in clusters which are long and tubular in shape and usually greenish white or 

red in colour. The fruit is fleshy and contains a solitary seed. 

Management 

<strong>Manual</strong> removal. 

Apply Bordeaux paste at cut ends. 

Post harvest rots 

Diplodia stem end rot Diplodia natalensis 

Symptoms : Area around stem end of fruit turns to cement colour due to rotting 

and become soft. 

Management 

Post harvest spray with Benomyl 

Hot water dip at 520 C for 3 minutes 

Black mould rot Aspergillus niger 

Symptoms : Yellowing of base and affected regions turn to big circular black rot. 

Management 

Fruit dip in Benomyl 

Cold storage 


1. Name the disease that develops in transit conditions? 

2. differentiate the anthracnose and bacterial leaf spot 

20

Ex.No.3 Date: 

STUDY OF DISEASES OF BER, GUAVA AND SAPOTA 

Ber: 

Powdery mildew: Oidium erysiphoides var. ziziphi 

Symptoms 

Flowers and fruits are affected. 

Powdery mass appear on young leaves and fruits. 

Severely affected leaves shrink and defoliate. 

On fruits, light brown to dark brown discolouration occurs. 

Infected fruits become corky, crack, misshapen, underdeveloped and finally 

drop prematurely. 

Etiology 

Mycelium is ectophytic with white upright conidiophores. On the conidiophores 

cylindrical, single celled, hyaline and barrel shaped conidia are produced in chains. 

Survival and Spread 

P.S.I.: Pathogen survives in bud wood of host plant. 

S.S.I: Air borne conidia. 

Management 

Spray Dinocap @ 0.1 % or Wettable Sulphur @ 0.2 % during first and third 

weeks of November. 

Two sprays of Carbendazim @ 0.2 % at 25 days interval, starting from the 

time when the fruits are of pea size followed by Dinocap @ 0.1 % at 10-15 days 

interval. 

Add Teepol or Sandovit to the fungicide solution. 

Spray Calixin – 0.1 % (ANGRAU). 

Resistant varieties : Safeda selected, glory, Dhaka 1 and Dhaka – 2. 

Guava 

Wilt: Fusarium oxysporium f.sp. psidii 

F. solani 

Symptoms 

Yellowing and browning of leaf. 

Death of branches on one side. 

Girdle stem and whole plant wilt. 

Etiology 

The short simple phialides producing the microconidia together with the presence of 

chlamydopores is the distinguishing character of Fusarium oxysporum. 

Microconidia: Oval to ellipsoidal, cylindrical, straight or curved, produced from 

simple, short lateral phialides often grouped into sporodochia. 

21

Macroconidia: Generally 3-5 septate, thin walled, fusoid 

Chlamydospores: Globose, formed singly or in pairs, intercalary or on short lateral 

branches. 

The long phialides, branched and elaborate microconidiophores and the shape of 

macroconidia distinguishes F. solani from F. oxysporum. 

Disease cycle 

PSI : Chlamydospores in diseased tissue of roots. 

SSI : Conidium by water and soil borne. 

Management 

Application of lime or gypsum @ 1 kg / plant. 

Margosa seed cake – 10 kg / plant. 

Metasystox – 0.1 % 

Resistant varieties: Apple Guava 

Sapota 

Flat limb: Botryodiplodia theobromae 

Lasiodiplodia theobromae 

Symptoms 

Affected branches flattened twisted, having rough appearance. 

Bunchy appearance of leaves at top of limb. 

Etiology 

Conidiomata: Eustromatic, immersed or superficial, globose, carbonous, uni- or 

multicellular, thicjk walled with dark brown hyphae over the surface, usually with 

cylindrical necks 

Ostiole: Absent, dehiscence by irregular rupture 

Conidiophore: Absent 

Conidiogenous cells: Holoblastic, determinate, discrete, cylindrical, hyaline, smooth 

with no sympodial proliferation 

Conidia: Acrogenous, hyaline when young, later becoming dark brown with one 

thick transverse septum at the middle, thick walled, ellipsoid, base truncate with 

indistinct longitudinal striations from apex to base often mixed with hyaline, 

immature conidia. 

Control 

Cut infected twigs and apply Bordeaux Mixture. 

22

Ex.No.4 Date: 

STUDY OF DISEASES OF PAPAYA, BANANA AND POMEGRANATE 

Papaya 

Powdery Mildew: Oidium caricae 

Symptoms 

White powdery patches with diffused mycelium on both surfaces of leaf. 

Affected areas become chlorotic with dark margin. 

Etiology 

Mycelium is hyaline, septate and haustoria develop in epidermal cells. Conidia are 

hyaline, granular and 14-19 x 28-30µ. 

Control 

Spray Wettable sulphur – 0.3 % or Dinocap – 0.1 % 

Foot Rot (Damping off / Foot Rot / Stem Rot) 

Causal organism: Pythium aphanidermatum; Rhizoctonia solani 

Symptoms 

Water soaked brown patches appear at base of stem which girdle the base 

turn to dark brown. 

Terminal leaves yellow droop off acropetally. 

Base of stem portion gets dried up and when split open shows honey comb 

like appearance. 

Etiology 

Mycelium: Intracellular with much branched hyphae up to 10 µm wide, hyaline and 

coenocytic 

Sporangia: Lobulate with bud like outgrowths at the apex of which a bladder like 

vesicle is formed at the time of germination. Later, 30-45 biflagellate zoospores are 

formed within the vesicle at 25-300C. Oospores: Terminal, globose, smooth and aplerotic 

Antheridia: Mostly intercalary, sometimes terminal, broadly sac shaped, 1-2 per 

oogonium, monoclinous or diclinous. 

Colonies on corn meal agar with cottony aerial mycelium, on potato-carrot agar with 

some loose aerial mycelium without a special pattern. 

Disease cycle 

PSI – Oospores in soil debris, Rhizoctonia survives as Sclerotia 

SSI – Zoospores by soil and water. 

Management: 

Seed treatment with captan or Metalaxyl 

Avoid ill drainage / low lying areas for cultivation. 

23

Soil drenching with cheshunt compound – 0.3 % 

Spray Bordeaux Mixture (6:6:50) 

Mosaic: Papaya mosaic virus, Carica Mosaic Virus-1 

Papaya Ring Spot Virus(PRSV) 

Symptoms: 

Disease appears as profuse mottling and puckering of young leaves. 

Such plants are stunted and show degeneration. 

The top most leaves shows malformation and reduction in size and become 

tendril like structures in severe cases (Shoe string). 

Number of lobes per leaf increased but thin and distorted. 

Conspicuous dark green spots and elongated streaks appear as water soaked 

areas on petioles and stem. 

Fruits are reduced in size and number. 

Etiology 

Virions filamentous not enveloped, usually flexuous with a clear modal length of 530 

nm. Virions contain 7 % nucleic acid and 93 % protein. Genome consists of single 

stranded linear RNA. Genome unipartite and total genome size is 6.656 kb. TIP: 73- 

76 °C, LIV: 180 days, and DEP: log10 minus 4. Leaf sap contains many virions. 

Disease cycle 

Survives on wild Carica sps. 

Transmission through grafting. 

Aphids. 

Management: 

Use healthy plant material. 

Spray groundnut oil – 0.1 % 

Leaf curl: Tobacco leaf curl virus or Nicotiana virus -10 

Symptoms 

Leaf margins rolled downwards, upward giving inverted cup shaped 

appearance. 

Veins thickened and turn dark green. 

Leaves leathery brittle, twisted petiole. 

Etiology 

Tobacco leaf curl virus 

Virions geminate; not enveloped; 18 nm in diameter; dimers 30 nm in length. 

Genome consists of single stranded circular DNA. Total genome size is 5.4 kb. 

24

Disease cycle 

Wild host – tobacco, tomato, chillies, transmission through grafting. 

White fly – Bemisia tabasi 

Management: Roguing and Spray neem oil. 

Anthracnose: Colletotrichum papayae 

Symptoms 

Brown superficial discolouration of skin which develops into circular, slightly 

sunken area. 

Lesions coalesce with sparse mycelial growth pinkish mycelium at Centre 

giving bull’s eye appearance. 

Etiology 

Conidiomata: Acervuli seen in epidermis beneath the cuticle. Acervuli disc or cushion 

shaped, waxy, sub-epidermal typically with dark setae or spines at the edge or among 

the conidiophores. 

Conidiophores: Simple and elongate and are produced within the cavity of acervulus. 

Conidia: Hyaline, one-celled, ovoid or oblong 

Disease cycle 

PSI : Dormant mycelium or Ascospores. 

SSI : Air borne conidia 

Management: 

Spray Mancozeb – 0.2 % 

Fumigation with benzylisothiocynate. 

Dipping of fruits in food grade wax. 

BANANA 

Sigatokoa leaf spot: Mycospherella musicola 

Symptoms 

Early symptoms appear on the third or fourth leaf from the top i.e. on young 

leaves. 

Pale yellow or greenish yellow streaks running parallel to vein on both 

surfaces. 

Spindle or eye shaped spots with grayish centres and dark brown margins 

surrounded by yellow halo lead to tearing of leaves. 

Spots are mostly seen along the edge of the leaf with defined margin and 

possess dark brown to black margin spots coalesce and whole leaf blade dries 

up. 

On the upper surface of the spots, Fructifications of the fungus appear as 

black specks. 

25

If the fruits are nearing maturity at the time of heavy infection, the flesh 

ripens unevenly and individual bananas appear undersized and angular in 

shape, their flesh develops a buff pinkish colour and they store poorly. 

Etiology 

This fungus produces fascicles of asci in very small, ostiolate, spherical locules in 

multilocular peritheciod structures known as pseudothecia. 

Pseudothecia: Small and immersed in the host tissue bearing asci with 8 ascospores 

Ascospores: Hyaline or pale green with a median septum 

Management 

Removal and destruction of affected leaves followed by spraying with 

Bordeaux Mixture (0.1 %) + linseed oil (2 %) or benlate (0.1 %). 

Preventive : Captan 0.2 % or eight sprays of 1 % Bordeaux mixture 0.1% 

depending on weather conditions. 

Wetting agent such as teepol or sandovit added at the rate of 1 ml / lit of 

water. 

Use of disease free suckers for planting. 

Dip suckers in Benomyl solution for 30 min. 

Spray Bordeaux Mixture – 0.1 % or Chlorothalonil 0.2 % or Propicanazole 

0.1 % or Hexacanazole – 0.2 % 

Panama wilt: Fusarium oxysporum f.sp. cubense. 

Symptoms 

Conspicuous symptoms usually appear on at least 5 months old banana 

plants although 2-3 months old plant are also killed under highly favourable 

conditions. Sudden wilting of plant and leaves. 

Initially yellowing appears first in the outer or older leaf sheath. 

Such leaves break at petiole and hang down along the pseudostem. 

Longitudinal splitting of Pseudostem and discoloration vascular bundles. 

Affected plants give characteristic odour of rotten fish. 

Young leaves may not dry up but remain erect and they also get affected 

under severe cases. (Heart leaf alone remains upright) 

Young suckers also develop the disease and rarely develop external 

symptoms. 

Affected plants do not produce bunches, even if produced fruits are 

malformed and ripen prematurely or irregularly. 

Roots of diseased Rhizomes are frequently blackened and decayed. 

Etiology 

The short simple phialides producing the microconidia together with the presence of 

chlamydopores is the distinguishing character of Fusarium oxysporum. 

26

Microconidia: Oval to ellipsoidal, cylindrical, straight or curved, produced from 

simple, short lateral phialides often grouped into sporodochia. 

Macroconidia: Generally 3-5 septate, thin walled, fusoid 

Chlamydospores: Globose, formed singly or in pairs, intercalary or on short lateral 

branches. 

Disease cycle 

PSI : Chlamydospores in soil debris or Infected Rhizomes. 

SSI : Spread as micro and macro conidia through irrigation water or through root 

contact. 

Management 

Maintain field sanitation. 

Use of disease free suckers for planting. 

Avoid ill drained soils and prefer slightly alkaline soils (7-7.5 pH) for 

cultivation. 

Flood fallowing for 6 to 24 months. 

Application of Pseudomonas fluorescence application. 

Treat pits with lime before planting – 2 kg / pit. 

Dipping suckers in Carbendazim (0.1 %) solution before planting. 

Soak planting material in Benomyl – 0.1 % 

Soil drench with 0.1 % Carbendazim or 0.01 % vapam. 

Avoid Zn deficiency 

Growing resistant (Cavendish varieties) : Basrai (Vamanakeli) 

Poovan (Karupura chakkara keli), Red banana, Moongil 

Dwarf varieties are generally resistant. 

Bunchy Top: Curly top / Cabbage top Banana Bunchy top virus (BBTV) 

Symptoms 

First as dots on midrib on lower surface of leaf which enlarge and join to form 

elongated streaks, measure 2.5 cm length and 0.75 cm width. 

Lower leaves are small and chlorotic curl upwards, stand upright and become 

brittle and clustered / crowded at apex giving Bunchy appearance. 

Green streaks range from a series of dark green dots to continuous dark green 

line. 

Marginal chlorosis and curling of leaves. 

Petioles fail to elongate. 

Plants show marked stunting. 

27

Etiology 

Virions isometric; not enveloped; 18-20 nm in diameter; rounded in profile without a 

conspicuous capsomere arrangement. Genome consists of single stranded circular 

DNA of three parts. 

Disease cycle 

PSI : Virus survives in banana plant and suckers. Heliconia sp (collateral host) 

SSI : By banana aphid. Pentalonia nigronervosa. 

Management 

Domestic and quarantine measures. 

Periodical roughing of infected plants. 

Use of only certified banana suckers for plantings. 

The new crop should be regularly inspected and the diseased plants 

destroyed as soon as noticed. 

Eradication of al infected suckers by spraying with Kerosene or injecting 

herbicide, 2, 4-D. 

Vector control with systemic insecticides Phosphomidon @ 1 ml / lt or methyl 

Demeton @ 2 ml / lt. 

Killing infected plants using 50 g Gammoxine and Feranoxone in stem 

alternatively + 100 ml Kerosene / plant. 

Spray Dimethoate – 2 g / lit pesticide. 

Moko disease (Bacterial wilt) Ralstonia Solanacearum; 

Pseudomonas or Burkholderia 

Symptoms 

Symptoms start on rapidly growing young plants. 

Similar to panama wilt. 

Yellowish discoloration of inner leaf lamina. 

Wilting and blackening of suckers. 

Breaking of petiole and rapid wilt. 

Characteristic discolouration of vascular Bundles is concentrated near centre of 

Pseudostem. 

Greyish brown bacterial Ooze is seen when the pseudostem of affected plant is 

cut transversely. 

Premature ripening of fruit. 

Brown dry rot is found within fruits of infected plants (Characteristic 

symptoms). 

Death of whole plant. 

Pseudostem has no smell when cut open as in panama wilt. 

28

Etiology 

Stictly aerobic, 1-many polar flagella, non-fluorescent and produce water soluble 

brown pigment on complex media. Polyhydroxybutyrate (PHB) is accumulated as 

cellular reserve and can be detected by Sudan Black staining on nutrient-rich media. 

Biochemical parameters: Levan not formed from sucrose; gelatin hydrolysis negative 

or weak; starch and esculin not hydrolysed, nitrate reduced by nearly all strains, 

many produce gas (denitrification), oxidative metabolism of glucose only, no growth 

at 4°or 40°C; growth is weak at pH 8 with no growth at pH 4 or 9; oxidase and 

catalase positive; arginine dihydrolase, lecithinase (egg yolk) and lipase negative. 

Disease cycle 

PSI : Through diseased plant suckers use for planting. 

SSI : bacterial cells through irrigation water, implements and by insects. 

Transfer through infected crops, insects, irrigation water. 

Management 

Strict plant quarantine and phytosanitary measures. 

Use of healthy planting material. 

Exposure of soil to sunlight during dry hot weather. 

Eradicate infected plants and suckers killing in situ by application of 

herbicides. 

Disinfestation of tools with formaldehyde (1:3) diluted with water. 

Crop rotation and providing good drainage. 

Fumigation of infected site with Methyl Bromide. 

Soil application of Pseudomonas fluorescens is effective. 

Soil application of bleaching powder. 

Pomegranate 

Cercospora leaf spot: Cercospora punicae 

Symptoms 

Leaves brown to black circular spots with yellow halo enlarge become dark 

brown. 

On flowers minute dark circular spots on sepals. 

On fruits – black circular spots. 

Black and elliptic spots appear on the twigs. 

Affected areas in the twigs become flattened and depressed with raised edge. 

Such infected twigs dry up. 

In severe cases whole plant dies. 

Etiology 

Conidiophores: Dark, simple, arises in clusters and burst out of leaf tissue. 

Conidiophores are clustered, dark coloured and have knee bends. 

29

Conidia: Long and slender (filiform), needle shaped, multicellular, hyaline and 

several celled having a scar at the base 

Management 

Pruning and destruction of diseased twigs. 

Application of Thiophanate methyl – 0.1 % or Chlorothalonil – 0.2 % or 

Mancozeb – 0.2 % 

Anthracnose Colletotrichum gloeosporioides 

Symptoms 

On leaves spots appear as small i.e. Dull violet and black leaf spots with 

yellow hallow. 

Spots surrounded by yellow margins. 

Infected leaves turn yellow and drop off. 

On fruits: Small irregular lesions on the fruits. 

Reduction in market value. 

Fruits initially circular brown to dark brown with sunken centers. 

Etiology 

Myycelium: Narrow, sparsely septate hyphae which are initially hyaline and later 

turns slightly dark in colour 

Conidiomata: Acervuli containing numerous closely packed conidiophores which 

partially raise the epidermis 

Conidia: Hyaline, broadly oval to oblong with rounded ends, non-septate and 

sometimes contains 1-2 globules. On germination, conidial germ tubes form dark 

appressoria 

Management 

Spray Carbendazim @ 0.1 % or Thiophanate – methyl @ 0.1 % 

Mancozeb @ 0.2 % at fortnightly intervals. 

Bacterial leaf spot Xanthomonas axonopodis pv. punicae 

Symptoms 

On leaves minute water soaked, brown to dark brown, circular spots 

surrounded by yellow halo appears. 

Such leaves are distorted and malformed. 

Severely infected young leaves shed. 

On Stem the disease starts as brown to black spots around the nodes. 

Such branches are girdles and crack at nodes and break down. 

On fruits brown to black raised oily spots appear on the pericarp with L or Y 

shaped cracks. 

30

Management 

Clean cultivation and strict sanitation in orchard. 

Select cuttings from healthy field. 

Spray COC – 0.1 % with Streptocycline sulphate – 200 ppm. 

Spray Bordeaux mixture @ 1 % along with antibiotic. 


1. Which cultural practices are useful and helpful in the management of banana 

diseases? List out such practices and substantiate it. 

2. Differentiate the panama and moko wilt of banana. 

3. Explain the role of quarantine in management of banana diseases? 

31

Ex.No.5 Date: 

STUDY OF DISEASES OF GRAPE AND APPLE 

Grape: 

Powdery mildew Uncinula necator (Oidium tuckeri) 

Symptoms : Powdery growth mostly on the upper surface of the leaves. 

Malformation and discolouration of affected leaves. 

Discolouration of stem to dark brown. 

Floral infection results in shedding of flowers and poor fruit set. 

Early berry infection resulting in shedding of affected berries. 

Powdery growth is visible on older berries and the infection results in the 

cracking of skin of the berries. 

Etiology 

Mycelium: Ectophytic with slender, branched septate hyphae 

Conidiophores: Simple and erect bearing a chain of 3-4 conidia 

Conidia: Oval in shape and measure 25-30 x 15-17 microns 

Cleistothecia: Black, almost round with flattened top and the peridium is covered 

with 8-25 septate appendages which are coiled at the distal end 

Management 

Dust sulphur – 300 mesh (1st when new shoots are 2 weeks old, 2nd prior to 

blossoming, 3rd which the fruits are half ripe). 

Prophylactic spray with Bordeaux Mixture 1 % toward of other diseases, also 

help to check this disease. 

Spraying Wettable Sulphur @ 0.3 % or Karathane or Calixin @ 0.1 %. 

Morestan @ 0.03 % sprayed at 4 days interval starting from last week of 

December to 1st week of March. 

Downy mildew Plasmopara viticola 

Symptoms 

Irregular, yellowish, translucent spots on the upper surface of the leaves. 

Correspondingly on the lower surface, white, powdery growth of fungus 

appears. 

Affected leaves become yellow and brown and gets dried. 

Premature defoliation of leaves 

Tender shoots dwarfed. 

Brown, sunken lesions on the stem. 

White growth of fungus on berries which subsequently becomes leathery and 

shrivels. 

Later infection of berries results in soft rot symptoms. 

No cracking of the skin of the berries. 

32

Etiology 

Mycelium: Intercellular, consists of coenocytic, thin walled hyaline hyphae 

producing spherical haustoria 

Sporangiophores: Branching of sporangiophore is almost at right angle to the main 

axis and at regular intervals. From the apex of each branch 2-3 sterigmata arise and 

bear sporangia 

Sporangia: Thick walled, oval or lemon shaped 

Zoospores: Pear shaped with two apical flagella 

Oospores: Thick walled, produced mostly in tissues adjacent to the midrib and 

germinate buy producing a germ tube that bears an apical sporangium. 

Management 

The disease can be effectively managed by giving 3-5 prophylactic sprays 

with 1 % B.M. or Aliette 0.2 % or Metalaxyl + Mancozeb 0.3 to 0.4 %. 

Sanitation 

Vine should be kept high above ground to allow circulation of air by proper 

spacing. 

Pruning (April-May and September and October) and burning of injected 

twigs. 

Spraying Difolatan or captan 0.2 % at 15 days, interval (5-6 sprays) or Zineb or 

COC @ 0.3 %. 

Anthracnose / Bird’s eye disease Gloeosporium ampelophagum 

Symptoms 

Visible on leaves, stem, tendrils and berries. 

Young shoots are more susceptible than leaves. 

Circular, greyish black spots with yellow halo appear. 

Later the centre of the spot becomes grey, sunken and fall of resulting in a 

symptom called ‘shot hole’. 

Black, sunken lesions appear on young shoots. 

Cankerous lesions on older shoots, Girdling and death of shoots occur 

Infection on the stalk of bunches and berries result in the shedding of 

bunches and berries respectively. 

Sunken spots, with ashy grey centre and dark margin on fruits (Bird eye 

symptom). 

Mummification and shedding of berries. 

Etiology 

Conidiomata: Acervuli sub-epidermal, erumpent, disc or cushion shaped and waxy 

(no setae or spines). 

Conidiophores: Simple and variable in length. 

Conidia: Hyaline, one-celled, ovoid to oblong and sometimes curved 

33

Management 

Removal of infected twigs 

Selection of cuttings from disease free areas and dipping them in 3% FeSO4 

solution for ½ an hour before planting. 

Spraying Bordeaux mixture 1% or COC@ 0.2% or carbendazim@0.1%. 

Grow resistant varieties like Banglore blue, Golden muscat, Golden queen and 

Isabella. 

Alternaria leaf spot Alternaria vitis 

Symptoms 

More seen on mature leaves, start as water soaked areas particularly on the lower 

side, when grow in size. 

They are brown in colour, zonate or concentric circular in the spot. 

When the disease is progress, these areas become necrotic some times fall off (or) 

appear with cracks also. 

The disease increase with relative humidity. 

Etiology 

Conidiophores: Dark, simple, rather short or elongate, 1-3 septate, bearing a simple 

or branched chain of conidia. 

Conidia: Dark, muriform, typically with both transverse and longitudinal septa. 

Conidia are usually borne in chains and are said to be catenulate. 

Management 

Proper care in the orchard. 

Spraying Ziram (Cuman L) 0.2 % 

Hexaconazole (or) Iprodine (Rovral) 0.2 % 

Spray COC-0.3 % repeated during October-November at 7 days interval or 

Bitertanol 0.2 %. 

Rust Phakopsora vitis 

Physopella ampelopsis 

Symptoms 

Orange coloured sori on the under surface of the leaf. 

Under severe infections, the entire leaf surface is covered by sori and 

defoliation occurs. 

Etiology 

Uredospores: Binucleate with hyaline or coloured walls, echinulate and are borne 

singly on pedicel 

Teliospores: Found in several layers, sessile, single celled with one germ pore and 

not echinulate 

Management 

Spray Zineb @ 0.2 % or dust sulphur @ 25 kg/ha. 

34

Grey mould rot Botrytis cinerea 

Symptoms 

Loosening of skin from flesh of fruits. 

Soft watery mass of decayed tissue in a slightly intact brown skin. 

Powdery grey mould appears on the fruits. 

Fruits shrivel and turn dark brown. 

Etiology 

Conidiophores: Long, slender, branched, septate, apical cells enlarged or rounded 

bearing clusters of conidia on short sterigmata. Entire structure resembles a grape 

bunch. 

Conidia: Hyaline or ash coloured, grey in mass, one-celled, globose to ovoid 

Disease cycle 

PSI : On dormant vines/fallen berries. 

SSI : Spread through contact/conidia at the time of storage transport. 

Apple: 

Scab Venturia inaequalis (I.S: Spilocaea pomi) 

Symptoms 

Scab appears on leaves, petioles, blossoms and fruit. 

Symptoms on leaves develop first on lower surface of leaves of fruit spurs later 

spread to the upper surface. 

Lesions are velvety – brown to olive spots, which turn black with age. The 

margin of lesions are feathery and indefinite, but later distinct limits are evident. 

Severe infection causes heavy defoliation. 

On fruits small rough black circular lesions appear on the skin and become corky 

with age. 

Early infection results uneven growth of the fruit and cracks on skin and flesh. 

Etiology 

Ascocarp: Pseudothecia spherical, dark brown to black with a short beak and distinct 

ostiole 

Asci: 50-100 per ascocarp, slightly spatulate, thin walled with short stalk bearing 8 

ascospores 

Ascospores: Two celled, oval, yellowish with the upper cell shorter and somewhat 

wider than the lower cell 

Disease cycle 

PSI: Ascospores formed from pseudothecia. 

SSI: Wind borne conidia. 

35

Management 

Clean cultivation 

Spray captan @ 0.2 % or Dodine @ 0.25 % at short intervals after petal fall. 

Single application of Difolaton @ 0.3 % at green bud stage followed by captan 

@ 0.2 % at petal fall. 

Spray schedule 

Ist spray : Silver tip stage : 0.2 % Captafol (or) 0.3 % captan. 

II spray : Pink bud – 0.2 % captan (or) 0.3 % Mancozeb. 

IIIrd spray at petal fall – 0.5 % Carbendazim. 

IV spray : After 10 days – 0.2 % Captan. 

Vth spray : 15 days after – Mancozeb 0.3 % 

Fruit set – 0.15 % Captafol 

Resistant varieties : Emira, Red free, Ambstraking, Ambroyal, Ambrich and 

Ambred. 

Powdery mildew Podosphaera leucotricha 

Symptoms 

Appear soon after the buds develop into new leaves and shoots. 

Small patches of white or grey powdery masses on under surface of leaves. 

Leaves grow longer and narrow than normal leaves and the margin is curled. 

Twigs covered with powdery mass. 

Affected fruits remain small and deformed and tend to develop roughened 

surface. 

In nursery plants, formation of wood is affected. 

Etiology 

Mycelium is ectophytic and persistent forming saccate haustoria in the epidermal 

cells. Conidiophores bear a long chain of hyaline, oval or ellipsoid conidia. 

Cleistothecia formed are densely gregarious, black with a single ascus and 

dichotomously branched appendages. 

Management 

Sanitation of orchard. 

Prebloom spray with lime sulphur (1:60). 

Spray Dinocap @ 0.05 % or wettable sulphur. 

Resistant varieties : Maharaja chunth and golden Chinese (apple cultivars), 

Yantarka Altaskya, Dolgoe (Crab apple cultivars). 

36

Fire blight Erwinia amylovora 

Symptoms 

Initial symptoms are noted on flowers which are water soaked, shrivel, turn 

brown to black either fall off or remain on the tree. 

On leaves brown to black areas developed along the midrib and main veins 

(or) along the margins (or) in between the major veins. As a result of this 

leaves curl, shrivel and hang down. 

Twigs also curl and blight, bark of the twig turns brownish, black, shrinks and 

becomes harden. 

Branches exhibit a cankerous growth. 

Branches above the point of infection die. 

On fruits water soaked areas late turn brown, shrivels and mummified, finally 

become, black and remain attached to the branches. 

Under humid conditions milky coloured, sticky droplets of bacterial 

exudation noticed on fresh infection. 

Oozing is in excess form a layer on plant parts. 

Etiology 

E. amylovora has cells 1.1-1.6 x 0.6-0.9 μm in size, Gram-negative short rods, with 

rounded ends, motile by many peritrichous flagellae. Bacteria enter the plant through 

blossoms, natural openings (stomata, lenticels, hydathodes) or wounds, carried by 

insects or by wind-driven rain. 

Disease management 

Pruning all blighted and dried twigs during winter. 

Cutting diseased branches, cankerous areas at least 10 cm below the lowest 

point of infection and burnt. 

Cutting blighted twigs, suckers and root sprouts in summer about 30 cm 

below visible infection. 

Disinfection of tools after each cut with mercury chlorides (0.1 %). 

Control of insects to restrict the spread of bacteria using insecticide. 

Monocrotophos (1.6 ml/l); Dimethoate (2 ml/l). 

Application of antibiotic streptomycin. 

Crown gall Agrobacterium tumefaciens 

Symptoms 

Small out growth on stem and root near soil line. 

Galls are spherical, white or flesh coloured (young stage) 

Galls become hard and corky on woody stems, knobby and knotty. 

Affected plants stunted with chlorotic leaves. 

Etiology 

Strictly aerobic rods with polar or sub-polar flagellation (sparsely peritrichous) 

37

Management 

Regulatory measures. Crop rotation with maize or other grain crops. 

Avoid injuries to roots or lower stem parts. 

Penicillin or vancomycin – partial control. 

Agrobacterium radiobacter (strain K-84) applied to fresh wounds. 

38

Ex.No.6 Date: 

DISEASES OF CHILLI, BRINJAL AND BHENDI 

Dieback and fruit rot Colletotrichum capsici 

Symptoms 

Dieback : Flowers become pale yellowish, twigs dry and die out showing 

dieback symptoms. Glistening white or dull white lesions are appear on diseased 

portion with dark brown borders. On the centre of the lesions, pin head size, raised 

black fruiting bodies i.e. Acervuli of fungus present. 

Fruit rot: Circular dark brown (or) black sunken areas which contain pinpoint 

raised black bodies in concentric fashion fruits become white (or) straw 

coloured. They are called ‘Bleached fruits’. 

Etiology 

Mycelium: Septate and both inter- and intracellular 

Conidiomata: Acervuli, hemispherical with scattered dark brown and several septate 

setae 

Conidia: Born singly at the tip of conidiophores, unicellular, falcate, hyaline with 

narrow ends 

Disease Cycle: 

PSI : Seed borne in nature, cultural host – turmeric 

SSI : Wind borne or rain water spread conidia. 

Management: 

Seed treatment with Thiram, Captan, Mancozeb 

Spray Carbendazim – 0.1 % 

Resistant variety – LCA – 357 

Damping off: Pythium aphanidermatum 

Symptoms : Two types : 1. Pre emergence; 2. Post emergence 

Seen in crops where nursery is taken up. 

Base of the seedling appears water soaked pale diseased portion brake at the 

point of infection and topple over plant become white and papery. 

Etiology 

Mycelium: Intracellular with much branched hyphae up to 10 µm wide, hyaline and 

coenocytic 

Sporangia: Lobulate with bud like outgrowths at the apex of which a bladder like 

vesicle is formed at the time of germination. Later, 30-45 biflagellate zoospores are 

formed within the vesicle at 25-300C. Oospores: Terminal, globose, smooth and aplerotic 

Antheridia: Mostly intercalary, sometimes terminal, broadly sac shaped, 1-2 per 

oogonium, monoclinous or diclinous. 

39

Management 

Use of optimum seed rate 650 g/40 cents 

Seed treatment: Thiram or captan or Mancozeb 2-3g/Kg seed. 

Prophylactic application of fungicides 

Spray COC 0.3% or 0.2 % Metalaxyl 

Cheshunt compound – 0.3 % soil drench 

Cercospora leaf spot Cercospora capsici 

Symptoms 

On leaves circular, initially brown spots, mature spots have brown or black 

border and whitish (or) grayish centre. 

Chlorosis of the leaves and they drop off. 

Central dead portion of the spot necrotizes and appear cracked. 

Etiology 

Stromata well developed with sub-hyaline to coloured acicular conidia produced on 

conidiophores 

Management 

Antracol – 0.2 % alternated at 10-15 days gap. 

Hexaconazole – 0.1 % 

Powdery mildew Leveillula taurica 

Symptoms 

Powdery growth appears on lower side of leaves corresponding upper 

surface becomes yellow. 

Affected twigs dry and fruits mis-shapen. 

Etiology 

Conidial stage: Oidiopsis type 

Mycelium: Endophytic 

Conidiophores: May be branched or unbranched, erect, septate, hyaline and emerge 

through stomata. 

Conidia: Produced singly and cylindrical in shape with a blunt or pointed tip 

Ascocarp: Cleistothecia with myceloid appendages and several asci 

Management 

Sulphur dusting 10-12 kg/acre or wettable Sulphur 0.25 – 0.3 % 

Spraying of Dinocap – 0.1 %, Tridemefon, Hexaconazole. 

Spray Tridemorph repeated at 10-15 days gap 2-3 times. 

40

Bacterial leaf spot Xanthomonas campestris pv. vesicatoria 

Symptoms 

On leaves: Water soaked translucent area formed and become brown/black 

having chlorotic (or) yellow halo. 

Individual spots appear black greasy shiny or oil nature. 

Chlorosis of leafs occurs and diseased portions are raised. 

On fruits circular (or) irregular area with water soaked halo. Green fruits 

greatened. 

Etiology 

X. vesicatoria is an aerobic, mobile, Gram-negative rod, occurring singly or in pairs, 

0.6 x 1.0-1.5 μm, with a single polar flagellum. On yeast dextrose chalk agar and 

nutrient dextrose agar, colonies are large, smooth-domed, mucoid-fluidal and yellow 

with entire edges. X. vesicatoria is sensitive to triphenyl tetrazolium chloride and is 

oxidative. 

Management 

Taking sprayings in form of antibiotics and along with fungicides. 

Streptocyclin sulphate, COC @ 30 g (Blitox -50) + Antibiotic (1 g) should be 

mixed in 10 l and repeated at fortnightly interval. 

Choanephora blight Choanephora cucurbitarum 

Symptoms: 

Flowers turn brown to black and then rot. The rotting spreads downward 

rapidly, affecting buds and tender leaves. Wet rot develops on affected parts. 

Infected parts of the stem appear and green and the bark easily peels off. 

Etiology 

Sporangiophores: Unbranched, often bent or circinate below the sporangium, 

hyaline, becoming darkened above 

Sporangia: Spherical to slightly flattened, initially white and later turns black in 

colour with a persistent sporangial wall breaking from above to below in to two 

equal parts 

Sporangiospores: Faintly striate, light coloured to brown with hyaline hair-like 

bristles, 1-1.5 times as long as spores 

Sporangiophores consists of primary vesicle from which secondary vesicle arise on 

short stalks which bear single spored sporangiola termed as conidia 

Management: 

Spray Hexaconazole 0.2% 

41

Mosaic complex: 

Symptoms 

TMV: Mild systemic mosaic and curling, stunting. Alternation of normal green with 

light green patches. 

CMV: Mosaic, narrowing, yellowing, chlorotic or necrotic ring spots on leaves. 

Transmitted by aphids. 

Disease cycle 

PSI : Wide host range, mechanical transmission 

SSI : Vectors , Aphids, 

Management 

Seed treatment with Tri sodium orthophosphate (150 g/l) 

Tolerant varieties – Bagyalaxmi LCA-305, Bhaskar. 

Management of vectors –Monocrotophos 1.5ml or Dimethoate 

Granular insecticides Carbofuran 10-12kg/ha 

Seed treatment with Imidacloprid 

Growing of border crops jowar, maize, bajra (2 rows) 

Avoid mono cropping 

Rogue out and destroy the infected plants. 

Brinjal 

Little leaf Phytoplasma 

Symptoms 

The most characteristic symptom is reduction in leaf size. 

Leaves are narrow, soft, smooth and yellow 

Newly formed leaves are much more shorter 

Internodes of stem shortened 

Axillary buds get enlarged but petioles and leaves also remain shortened. 

This gives bushy appearance mostly there is no flowering but if flowers are 

formed they remain green. 

Fruiting rare. 

Disease cycle: 

The organism has been transmitted to Datura, tomato and tobacco. 

It occurs in nature on Datura fastuosa and Vinca rosea 

Natural transmission – vector Hishimonas phycytis perennation of organism 

through – weed hosts 

Management: 

Severity of disease can be reduced by destruction of affected plants and 

spraying of insecticides. 

Metasystox, Malathion 0.1% have been recommended for vector control. 

42

Bacterial wilt Pseudomonas solanacearum 

Symptoms: 

Sudden wilting of plants. 

Drooping of young top leaves and shoots. 

Water soaked streaks on the infected stem 

Management: 

Crop rotation with French bean- finger millet 

Phomopsis blight and fruit rot Phomopsis vexans 

Symptoms: 

On young seedlings the stem is girdled slightly above the soil level, the plants 

topple over and die. 

The stem lesion is dark in colour with grey centre bearing pycnidia. 

On leaves, circular to oval brown spots which later become irregular in shape 

appear. The centre of the spots become grayish with dark margin and 

contains pycnidia. 

On fruits, the infection begins as watery soft decay and becomes black. Such 

fruits are mummified. 

Etiology 

Pycnidia dark coloured, ostiolate, immersed, erumpent and nearly globose bearing 

simple conidiophores with conidia. Each Pycnidium contains two types of single 

celled conidia, α-conidia (oval to fusoid) and β-conidia (filiform and curved or 

curved stylospores). 


PSI: Pycnidia in the infected tissue 

SSI: Conidia spread by wind. 

Management: 

Hot water treatment of seeds at 500C for 30 minutes. 

Spraying Difolatan or captan 0.2%. 

Deep summer ploughing 

Bhendi: 

Yellow vein mosaic: Bhendi Yellow Vein Mosaic Virus 

Symptoms: 

The veins are yellow and interveinal areas are remain green (Vein clearing) 

In severe cases, the young leaves become chlorotic and veins become thick 

The fruits become fibrous and tough. 

43

Etiology 

The disease is caused by a complex consisting of monopartite begomovirus Bhendi 

Yellow Vein Mosaic Virus (Fy: Geminiviridae) and a small satellite DNA β component. 

Virions geminate; 16-18 nm in diameter; dimers 30 nm in length 

Geminiviruses belongs to the family Geminiviradae and have circular single 

stranded (ss) DNA genome. Most of the Begomoviruses have bipartite genome, 

termed DNA A and DNA B. The DNA A component encodes the proteins required 

for viral DNA replication , while the DNA B encodes two proteins that are essential 

for systemic movement and symptom expression 

Management: 

Management of vectors –Monocrotophos 1.5ml or Dimethoate 

Avoid mono cropping 

Rogue out and destroy the infected plants. 

Tolerant varieties: Parbahni Kranthi, Janrdhan, Haritha, Arka Anamika, Arka 

Abhay. 

Powdery mildew: Erysiphe polygoni 

Symptoms: 

White or grayish patches of powdery fungal growth, on the upper surface of 

the leaves. 

In severe infection the leaves dry up and fall off prematurely 

Etiology 

Mycelium: Ectophytic, fine, persistent and rarely thick 

Conidiophores: Septate, arise vertically from superficial hyphae and bear several 

conidia in a chain 

Conidia: Barrel shaped, hyaline, elliptical and unicellular. 

Cleistothecia: Short, black and minute with a number of mycelial appendages 

Asci: Fasciculate, ovate, nearly sessile and contain 3-8 hyaline, elliptical and 

unicellular ascospores 

Management: 

Dusting sulphur 30Kg/ha 

Spray wettable sulphur 0.3% or Dinocap 0.1% 3 – 4 times with 15 days 

interval. 

Cercospora leaf spot: Cercospora malayensis 

C. abelmoschi 

Symptoms: 

Cercospora malayensis: Brown irregular spots on the leaves 

C. abelmoschi: Black sooty angular spots on lower surface of the leaves. 

Management: Spray Mancozeb or Zineb 0.2% or Carbendazim 0.1% 

44

Ex.No. 7 Date: 

STUDY OF DISEASES OF POTATO AND TOMATO 

Potato: 

Early blight Alternaria solani 

Symptoms 

Small circular to oval dark brown to black scattered spots on lower surface of 

old leaves. These spots become large and angular. 

Later concentric rings appear on necrotic tissue giving a target board 

appearance. 

Several spots coalesce and big rotten patches appear. 

Sometimes the necrosis spreads the entire leaf. 

Sometimes the necrotic tissue drops out leaving “shot holes” in the leaves. 

Dark brown lesions on stems and petioles, which break at the point of 

infection. 

Slightly dark, sunken, circular to irregular lesions on tuber. 

Infected tubers rot under favourable conditions. 

Disease cycle 

PSI: Mycelium or conidia in infected plant debris or tubers. 

SSI: Conidia dispersed by wind, water or rain splashes. 

Management 

Use of disease free tubers. 

Mancozeb at the rate of 0.25 % or chlorothalonil @ 0.2 % spray at 53 DAP 

followed by 3 sprays at weekly intervals. 

Res. Varieties: K. Sindhuri, K.Jeevan (MR) 

Late blight of potato Phytophthora infestans 

Symptoms 

Circular or irregular water soaked dark green areas usually starts from leaf 

tips or edges of lower leaves. 

Under moist weather, these patches enlarge rapidly and forms brittle blighted 

areas with indefinite borders. 

Downy growth of pathogen on subsequently appears on lower surface. 

Progressive defoliation and collapse of plants under favourable conditions. 

Light brown elongated lesion on stem which later become necrotic. 

Purplish brown spots appear on skin of tubers. 

On cutting, the affected tubers show rusty brown necrosis spreading from 

surface to the centre. 

Decay of plant parts under favourable weather which emits foul smell. 

Disease cycle 

PSI: Infected potato tubers or oospores. 

45

SSI: Zoospores or sporangia dispersed by wind or water. 

Management 

Regulatory measures. 

Select healthy tubers for planting. 

Delayed harvesting. 

High ridging to about 10-15 cm height reduces tuber infection. 

Grow resistant varieties such as Kufri Jyothi, Kufri Badshah, Kufri Jeevan, 

Kufri Sherpa etc. 

Prophylactic measures 

Metalaxyl (0.1 %), Mancozeb (0.25 %) or Chlorothalonil (0.2 %), BM (1 %) can 

be applied at 7 to 10 days intervals in the hills and 10 to 15 days intervals in 

plains. 

Dip sprouted tubers in 0.2 % Metalaxyl for 30 min. 

Common scab of potato Streptomyces scabies 

Symptoms 

Small brownish and slightly raised spots on tubers. 

Spots enlarge, Coalesce and become corky. 

Lesions typically possess a raised margin and slightly depressed center. 

Characteristic symptoms have descriptive names : 

Russet scab appears on tubers as superficial tan to brown corky lesions. 

Pitted scab is characterisied by lesions with depressions beneath the tuber 

surface. 

Raised scab appears as cushion like warty lesions. 

Etiology 

Streptomycetes resemble fungi in their structure. Their branching, filamentous 

arrangement of cells form a network called a mycelium. However, S. scabies 

filaments are much smaller than fungal hyphae. S. scabies filaments are 1 µm or less 

in diameter. The filaments are vegetative and break off or fragment to form spores. 

S. scabies survives in the soil as spores in infected tissue and is spread through water, 

or infected plant material and in wind-blown soil. 

Management 

Use of disease free tubers. 

Crop rotation with wheat – oat or potato – onion – maize (4 yrs) 

Hold the soil pH at about 5.3 by addition of sulphur 

Green manuring before planting potato. 

Dipping of infected tubers in 3 % boric acid for 30 min. 

Soil application of PCNB. 

46

Powdery Scab: Spongospora subterrenea 

Symptoms: 

On tubers faintly brown, raised areas appears in groups or scattered all over 

the tubers. 

As these grow, the brown colour disappear and become jelly like. 

The epiodemic ruptures and exposes the dusty spore mass leaving the 

cavities. 

These may be circular or oval in shape. 

On roots, proliferated tissues cause galls of size up to a pea. 

Management: 

Selection of healthy tubers for planting. 

Tuber treatment with organo mercurial fungicides 

Panther, Red skin are tolerant. 

Mild mosaic/interveinal mosaic Potato virus X 

Symptoms 

Often referred as latent potato mosaic 

Light yellow mottling with slight crinkling on potato plants 

Inter veinal necrosis of top foliage 

Stunting of diseased plants. 

Symptoms are masked at temperature above 210 C. 

Leaves may appear slightly rugose where strains of PV A combines 

Etiology 


nm and 13 nm wide. Virions contain 6 % nucleic acid and 94 % protein. Genome 

consists of single stranded linear RNA. Genome unipartite and total genome size is 

6.435 kb. TIP: 68-76 °C. LIV: 40-60 days. DEP: log10 minus 5-6. Leaf sap contains 

many virions. 

Spread 

Spreads mechanically through rubbing of leaves, contact of infected plants, 

seed cutting knives, farm implements. 

Roots clubbing of healthy and diseased plants in field. 

Management 

Disease free seed tubers for planting 

Roguing of diseased plants 

Severe mosaic Potato virus Y (PV Y) 

Also called potato leaf drop streak. 

Symptoms 

47

Chlorotic streaks on leaves, petioles and stem which become necrotic. 

The leaves become necrotized and withered but remain hanging as it attaches 

to the stem by a thread. 

Interveinal necrosis and stem/petiole necrosis. 

Plants remain stunted in growth. 

Etiology 


nm and 11 nm wide. Virions contain 5.4-6.4 % nucleic acid and 93.6-94.6 % protein. 

Genome consists of single stranded linear. Genome unipartite and total genome size 

is 10.4 kb. TIP: 50-62 °C. LIV: 7-50 days. DEP: log10 minus 2-6. Leaf sap contains few 

virions. 

Survival and spread 

Infected tubers 

Spread by aphids, Myzus persicae and Aphis gossypii 

Management 

Disease free seed tubers for planting. 

Roughing of diseased plants. 

Aphid control with insecticides. Dimethoate 2 ml/l or Metasystox 2ml/L 

Rugose Mosaic PV X and PV-Y 

Symtoms: 

Plants show extremely stunting without inter veinal elongation and 

overlapped leaf lets. 

Lower leaves have black necrotic veins 

Upper leaves are mottle with light green spots. 

Other symptoms are rugose and distortion of leaves 

Tuber size is reduced. 

Spread: 

PSI: Tubers 

SSI: PV-Y through vectors. 

Management: 

Use of disease free material 

Rouging 

Vector management 

Leaf roll 

Symptoms 

Potato Leaf Roll Virus. 

Upward rolling of leaves, which have a stiff leathery texture. 

Plants stunted and have a stiff upright growth. 

48

Phloem necrosis of tubers in some varieties. 

Etiology 

Potato leafroll virus (PLRV) is the type member of the genus Polerovirus in the family 

Luteoviridae. PLRV consists of spherical particles of 24 nm. Genome is 6kb positive 

sense single stranded RNA. 

Spread 

Infected seed tubers or by aphids. 

Management 

Disease free seed tubers for planting 

Aphid control 

Potato spindle tuber Potato Spindle Tuber Viroid (PSTVd) 

Symptoms 

Plants appear erect, spindle and dwarfed. 

Leaves small, erect and leaflets dark green. 

Affected tubers small and deformed become cylindrical and elongate 

(Spindle). 

Tuber eyes are numerous and more conspicuous. 

Etiology 

The pathogen Potato Spindle Tuber Viroid(PSTV) is the first recognized viroid. PSTV 

is infectious RNA of low molecular weight, approximately 100,000 Daltons. The 

RNA is single stranded molecule of 359 nucleotides with extensive regions of base 

pairing. 

Spread 

Infected seed tubers 

Mechanically spread by knives used to cut seed tubers. 

Also transmitted by pollen and seed and contaminated mouth parts of grass 

hoppers, flea beetles and bugs. Myzus persicae 

Management 

Use of PSTVd free potato seed tubers. 

Disinfestation of cutting knives and tools with Hypochlorite solution. 

Tomato: 

Stemphylium leaf spot 

Symptoms 

Stemphylium solani 

Small brownish black specks on the under side of leaves. 

49

Later these specks develop on both leaf surfaces into grayish brown, glazed 

lesions of 3 mm or less in size. 

On older leaves lesions dry up, crack and the centers drop out leaving a shot 

hole appearance. 

Yellowing of the leaf occurs followed by defoliation of plant. 

Management 

Rouging and burning of infected plant debris. 

Foliar application of Mancozeb @ 0.25 %. 

Septoria leaf spot Septoria lycopersici 

Symptoms 

Less vigorous plants are usually attacked. 

Small round to irregular spots with a grey center and dark margin on leaves. 

Spots usually starts on lower leaves and gradually advance upwards. 

Complete defoliation of affected leaves. 

Fruits are rarely attacked. 

Disease cycle 

P.SI. : Infected plant debris or seed or solanaceous weeds. 

S.S.I. : Rain splash, wind-blown water, insect and on hands and clothing’s of 

tomato pickles. 


High humidity or persistent dew at 25 0C. Moist weather with intermittent showers. 

Management 

Seed Treatment with Mancozeb or Zineb @ 2 g/kg seed 

Spray Zineb @ 0.2 % or Mancozeb @ 0.2 % at 10 d interval 

Bacterial canker Clavibacter michiganensis sub sp. michiganensis 

Symptoms 

Disease appears as spots on leaves, stems and fruits and as wilting of leaves 

and shoots. 

White blister like spots in the margins of leaves. 

Spots become brown with age and coalesce, but do not fall off. 

Leaves wilt and curl upward. 

Birds eye like appearance of spots, which have brownish centers and white 

halos. 

The centres of white spots become slightly raised, tan coloured and rough. 

50

Large cavities in pith and cortex which extend to outer surface of stem and 

cause cankers. 

Etiology 

C. michiganensis sub sp. michiganensis is an aerobic, non-motile, Gram-positive, nonsporing, 

curved rod. C. michiganensis subsp. michiganensis develops slow-growing, 

smooth, shining, round, yellow colonies with entire margins on nutrient glucose 

agar or yeast peptone glucose agar. 

Management 

Extraction of seed through fermentation of pulp at room temperature for 72 

hrs. 

Hot water treatment of seed at 520 C. 

Three year crop rotation. 

Protection sprays with COC and streptomycin sulphate 

Tomato spotted wilt: Tospo virus 

Symptoms: 

Young leaves turn bronze and develop small dark spots 

Growing tips die back and stem terminals dried. 

Affected plant shows drooping of leaves and stunting. 

Early infection, results no fruit formation, in case of late infection fruits 

produced with chlorotic ring spots. 

On green fruits, faint concentric rings appear, on ripen fruits these turn into 

obvious rings. 

Etiology 

Virions isometric, enveloped, 85 nm in diameter, rounded in profile without a 

conspicuous capsomere arrangement. Virions contain 5 % nucleic acid, 70 % protein, 

20 % lipid and 5% carbohydrate. 

Genome consists of single stranded linear RNA. Total genome size is 17.2 kb. TIP: 45 

°C, LIV: 0.2 days (5 hours) and DEP: log10 minus 3. Leaf sap contains few virions. 

Disease Cycle: 

P.S.I: Virus perennates on weed hosts or other perennials. 

S.S.I.: Vector: Thrips tabci, Flankliniella schulzii, Scirtothrips dorsalis 

Management: 

Rouging 

Vector control 

Growing barrier crop 

Root Knot disease Meloidogyne incognita 

Symptoms: 

Yellowing of foliage, stunting and wilting of plants in hot dry periods. 

Fruits reduced in size and low yields. 

51

Seedlings fail to establish. 

Formation of root galls or knots is diagnostic symptom of root knot nematode 

infection. 

Etiology 

Meloidogyne incognita is identified by the cuticular markings in the perineal area of 

the mature female. The dorsal arch is high and may be flattened at the top. 

Female has 2 ovaries, prodelphic; adults swollen; eggs deposited in matrix secreted by six 

rectal glands, eggs not retained in female body. Female body does not form cyst. Cuticular 

striations in posterior of female form a fingerprint-like perineal pattern. Overlap of 

esophageal glands over intestine 

Male has 1 testis, but sometimes two. Male does not have caudal alae; has characteristic halftwist 

of body. 


P.S.I.: galls, eggs of nematode S.S.I.: same as above by irrigation water. 

Management: 

Crop rotation 

Use of resistant varieties, Hisar lalith, PNR-7 

Application of Carbofuran 

52

Ex.No.8 Date: 

STUDY OF DISEASES OF CRUCIFERS AND CUCURBITS 

Club Root Plasmodiophora brassicae 

Symptoms 

Symptoms become apparent in advanced stage of root infection. 

Stunting of above ground parts. 

Reduction in size of head/chlorosis. 

Roots are malformed into club like structure due to fleshy growth of roots. 

Management 

Use of seedlings from disease free fields 

Crop rotation dose not work since persist longer in soil. 

Severe in acidic soils. Add lime to soil to increase pH. (6 weeks before 

planting @ 2 T/ha) 

Avoid excess irrigation. 

Drenching soil with Brassicol (PCNB). 

Downy Mildew: Peronospora parasitica 

Severe in raddish, cabbage, cauliflower, mustard and knol-khol. 

Symptoms 

Small pale yellow angular spots on upper surface of leaves with downy 

growth on the under surface. 

Spots coalesce and leaves shrivel and dries up prematurely. 

In cabbage spots expose heads to soft rot. 

Cauliflower curds looks brownish at top. 

Stems show dark brown and depressed lesions or streaks which later develop 

growth, of fungus. 

Management 

Destruction of infected plant debris. 

Avoidance of thick sowing and excessive moist conditions. 

Spray Metalaxyl @ 0.25 % 

Spray COC @ 0.3 or Mancozeb @ 0.2 % at 10 days interval. 

Powdery Mildew Erysiphe polygoni 

Symptoms 

Seen on cabbage and cauliflower 

White powdery spots on upper surface of leaves, stems, flower parts etc. 

Finally mildew may cover the entire surface. 

Management 

Application of Dinocap @ 0.2 % or sulphur dust. 

Alternaria Leaf Spot: Alternaria brassicola; Alternaria brassicae; Alternaria raphani 

53

Symptoms 

Spots are small dark coloured. 

They enlarge some become circular and 1 mm diameter 

Under humid conditions groups of conidiophores will be formed in spot. 

Spots become concentric rings. 

Finally several spots coalesce leading to blighting of leaves. 

Fungus is seed borne and cause shriveling of seeds and poor germination. 

Linear spots also appear on petioles, stems, pods and seeds. 

Management 

Hot water treatment – 500 C for 30 minutes 

Seed treatment with agrosan. 

Foliar spray with Mancozeb @ 0.2 %, COC @ 0.3 % twice. 

Black Rot Xanthomonas campestris pv campestris 

Serious on Cabbage, cauliflower, knot-knol, mustard, raddish. 

Symptoms 

Spots initially appear near the leaf margins as chlorotic or yellow areas which 

extend to veins and midrib forming characteristic ‘V’ shaped chlorotic spots. 

Veins and veinlets turn brown and finally black. 

Vascular blackening extends beyond affected veins to midrib, petiole and 

stem. 

In advanced stages the infection may reach the roots systems and causes 

blackening of vascular bundles. 

Bacterial ooze can also be seen on affected parts. 

If infection is early plant will die. 

If infection late, plant succumb to soft rot and die. 

Disease cycle 

PSI: Bacterium internally seed and soil borne, Survives on plant debris 

SSI: Bacterium through irrigation water or Wind splashed rain 

and also by mechanical means. 

Management 

Seed Treatment with HgCl2 solution for 30 minutes or 

Agrimycin/Aureomycin – 0.01 %, 0.01 % 

Hot water treatment of seeds at 500 C – 30 minutes for killing the seed borne 

inoculum followed by 30 minutes dip in streptocycline 100 ppm. 

Spray Agrimycin – 100, streptomycin – 50 ppm at transplanting, curd 

formation and pod formation. 

Crop rotation – 2-3 years with non cruciferous crops. 

Drenching – seed bed with 5 % formalin. 

54

Antibiotic solution in nursery bed. 

Resistant varieties: Cabbage, cabaret, defender, gladiator, pusa muktha. 

Cauliflower: Pusa Ice; Pusa snow ball. 

White Rust: Albugo candida 

Symptoms 

White shiny raised blisters (pustules) on lower surface of leaves, stems and 

flowers. 

Pustules coalesce to form irregular patches. 

Epidermis ruptures exposing white spore may which gives the pustule a 

powdery appearance. 

Distortion of floral parts including petals, pistils and anthers due to 

hypertrophy and hyperplasia. 

Management 

Sanitary measures 

Crop rotation 

Destruction of weeds 

Spray 0.8 % BM or any copper fungicide 

CUCURBITS 

Powdery mildew Erysiphe cichoracearum, Sphaerotheca fuligena 

Host range: Pumpkins, cucumber, bottle gourd, ridge gourd, coccinia 

Bitter gourd less affected 

Symptoms 

Whitish or dull grey, tiny powdery growth on foliage, stems and young 

growing parts. 

Superficial growth ultimately covers entire leaf area. 

Diseased areas turn brown and dry leads to premature defoliation and death. 

Fruits remain undeveloped and are deformed. 

Management 

Dusting sulphur or spray: Calixin 0.1 %; Karathane – 0.2 % 

Downy mildew: Pseudoperonospora cubensis 

Host range : Muskmelon, sponge gourd, bitter gourd etc. 

Symptoms 

Yellow angular spots appear on upper surface of leaves. 

Corresponding lower surface of these spots shows a purplish downy growth in 

moist weather. 

Spots turn necrotic with age. 

Diseased leaves become yellow and fall down. 

Disease plants get stunted and die. 

55

Fruits produced may not mature and have poor taste. 

Management 

Destruction of cucurbitaceous weeds around field. 

Spray Metalaxyl @ 0.2 % or chlorothalonil @ 0.2 % 

Spray Zineb @ 0.3 at 10 days interval. 

Cercospora leaf spot: Cercospora citrullina; Cercospora melonis; 

Cercospora lagenarium 

Common on water melon, musk melon and cucumber. 

Symptoms 

Minute water soaked spots mostly on leaves. 

Spots enlarge rapidly and becomes circular to irregular with pale brown tan or 

white centers and purple to almost black margins. 

Spots coalesce to form blotches. 

Leaf may dry and die presenting the leaf a scorched appearance. 

Stems and fruits are also attacked. 

Management 

Maintain good soil drainage and good aeration between veins. 

2-3 protective sprays with zineb @ 0.2 %. 

56

Ex.No.9 Date: 

STUDY OF DISEASES OF BETELVINE AND ONION 

Betel vine: 

Wilt: Sclerotium rolfsii 

Symptoms: 

Darkening of the stem at the foot of the plant, near ground level. 

The leaves turn yellow, become flaccid and droop off. 

Ultimately the whole vine wilts and dries up. 

The darkened portion of the stem becomes shrinked , soft and turn black. 

On the affected stem portion, white ropy fan shaped mycelial strands 

developed. 

Brown to dark brown sclerotia appears on the infected portion 

Management: 

Sanitation 

Crop rotation with rice, tobacco 

Soil drenching of Bordeaux Mixture 1% or Iprodione 1% 

Biological control Trichoderma harzianum+ oil cakes 500Kg/ha/year 

Fusarium wilt: Fusarium solani 

Symptoms: 

Plants show the yellowing of leaves and wilts gradually. 

Often sudden wilting and drying up entire plant takes place 

Vascular discoloration of plant. 


P.S.I.: Chlamydospores survive in soil 

S.S.I.: Conidia through irrigation water 

Management: Same as above 

Root rot and Leaf spot: Phytophthora capsici 

Symptoms: 

On leaves, circular, water soaked spots which later increase in size and cover 

the whole area resulting in rotting of the leaf. 

In moist weather, the light brown to dark brown zonations alternating each 

other is formed. 

Roots and rootlets become brown to black colour and such vines finally dry or 

die. 

Management: 

Use healthy cines for planting 

Seed vine cuttings dip in 5% Bordeaux mixture for 10minutes. 

Sanitation 

Crop rotation with sorghum / maize 

Soil drenching with 1% Bordeaux Mixture 

Foliar spray with 5% Bordeaux mixture. 

57

Anthracnose: Colletotrichum capsici 

Symptoms: 

Small, black circular specks under the bark of the stem. 

Later these grow rapidly in size, and forms narrow streaks. 

The part of the plant above the point of infection wilt and dry. 

On the leaves, circular spots with brownish black centre and yellow halo. 

Infected leaves fall off prematurely. 

Powdery Mildew: Oidium piperis 

White to light brown powdery patches appear on lower surface of the leaves, 

later these increase in size. 

Management: 

Application of sulphur dust @28- 34 Kgs/ha 

Spray Bordeaux Mixture 0.5% 

Bacterial Leaf Spot Xanthomonas campestris pv. beticola 

Symptoms: 

Minute water soaked lesions appear on all over the leaf blade which delimited 

by veins. 

These coalesce to form large irregular brown spots. 

The affected leaves defoliate prematurely. 

Management: 

Application of Antibiotic solution. 

ONION 

Purple blotch Alternaria porri 

Symptoms 

Symptoms begin on upper half of leaf as white spots surrounded with a 

yellow halo. 

Spots enlarge, become elliptical to irregular with concentric zonation, 

purplish to black in colour. 

Leaf breaks at point of infection. Several spots coalesce causing brightening of 

foliage. 

Similar symptoms are formed on inflorescence stalk. 

Bulbs if infected during harvest time which will subsequently rotted during 

storage. 

Disease cycle 

Survives as conidia in seed and debris, spreads through air borne conidia. 

Management 

Seed treatment with Thiram and Captan 3 g / kg. 

Spray Mancozeb 0.25 %, chlorothalonil – 0.2 % 

Spray Iprodione – 0.1 % 

Smudge Colletotrichum Circinans 

58

Symptoms 

Symptoms are present chiefly on scales of bulbs and small leaves attached to 

bulbs. 

On infected scales of bulb subcuticular dark green later turning to black 

stroma are produced which is called as smudge. 

Stroma arranged in concentric circles, in outer surface. Acervuli and setae are 

produced. 

Under moist conditions pink masses of conidia are produced. Inner scales of 

bulbs are also attacked. 

The spots are whitish in colour, with pink sporulation. 

Disease cycle 

Spreads through conidia, rain and water movement. 

Management: 

Protection from rains after harvest is necessary. 

Crop may be sprayed with 0.2 % Zineb or Maneb at 7 to 10 days interval to 

reduce inoculum. 

Drying of bulbs before storage should be by hot air at 37 to 48 0 C. 

Smut Urocystis cepulae 

Symptoms 

The symptoms first appear on cotyledonary leaves, as small discoloured 

patches and which get thickened and burst open liberating masses of black 

chlamydospores. 

Such infected seedlings usually get killed within 3-4 weeks after infection. 

However, the seedlings that survive show severe stunting. 

Control 

Treat the seeds or bulbs with Thiram, Carboxin 3 g/ kg. 

Avoid monocropping. 

Drench in patches with Carboxin 0.1 % or Propiconazole 0.1 % 

Storage rot : Aspergillus niger 

Symptoms: 

Diseased bulbs show black masses on the scales 

Severely blackened outer scales are unfit for cooking. 

59

Ex.No.10 Date: 

STUDY OF DISEASES OF BEANS 

BEANS 

Anthracnose: Colletotrichum lindemuthianum 

Symptoms 

All the above ground parts are affected. Characteristic symptoms appear on 

pods. 

On cotyledons spots are sunken dark brown or black with pink spore mass. 

Seedling infection results in collapse of seedling. 

Spots on leaves appear on lower side and are black. Later these may also 

appear on upper surface. 

Black, sunken, circular spots of varying sizes appear on pods. 

The centre of these spots later turns grey or pink due to sporulation of the 

pathogen. 

The border of these spots appears raised. 

Management 

Use healthy seed for planting. 

Seed treatment with Carbendazim. 

Protect the crop by spraying 0.2 % Benlate or Bavistin or Zineb or Maneb @ 2 

kg/ha at 7-10 days interval. 

Rust: On beans : Uromyces phaseoli typica 

Cowpea : U. phaseoli vignae 

Urd bean : Uromyces appendiculatus 

Autoecious rust i.e. produces all the stages on bean plant. 

Symptoms 

The symptoms mostly appear on leaves. 

The rust pustules appear on either sides but more common on lower surface. 

The Uredosori are minute, roundish, slightly raised and reddish brown 

coloured. These contain rust spores. 

Later in the season with the formation of teliospores, the sori turn dark brown 

or black. 

Diseased leaves may wither or fall off. 

Management 

Protect the crop with Mancozeb or Zineb @ 2 kg / ha or Wettable sulphur @ 

0.3 %. 

Common bean mosaic: Bean Common Mosaic Virus. 

Symptoms 

Leaves show mosaic pattern i.e. light green areas alternate with dark green 

areas. 

Diseased leaves become rough, show blisters on the leaf lamina. 

Leaf size, petiole length and plant height reduced. Leaves curl down ward. 

60

Diseased plants produce fewer pods which are smaller in size. 

Seeds become smaller, malformed and aborted. 

Etiology 

Virions filamentous not enveloped, usually flexuous with a modal length of 847-886 

nm and 12-15 nm wide. Virions contain 5 % nucleic acid and 95 % protein. 

Genome consists of single stranded linear RNA. Genome unipartite and total 

genome size is about 10 kb. TIP: 60 °C. LIV: 1-4 days. DEP: log10 minus 3-4. Leaf sap 

contains few virions. 

Disease cycle 

Seed, sap, graft and aphid transmissible. 

Aphis craccivora, Macrosiphum pisi, Aphis gossypi, A. medicaginis, Myzus persicae 

and Brevicoryne brassicae. 

Management 

Use of disease free seed. 

Vector control with insecticides. 

Yellow mosaic: Bean Yellow Mosaic Virus. 

Symptoms 

Yellow areas alternate with dark green areas of the leaf blade. 

Younger leaves show more severe symptoms and may be completely 

diseased. 

Leaves completely turn yellow and gradually become necrotic. 

Pod formation is reduced and if produced, they are deformed having 

shriveled and undersized seeds. 

Etiology 


nm and 12-15 nm wide. Virions contain 5 % nucleic acid and 95 % protein. 

Genome consists of single stranded linear RNA. Genome unipartite and total 

genome size is 10 kb. TIP: 65 °C. LIV: 2-7 days. DEP: log10 minus 3-5. Leaf sap 

contains few virions. 

Disease cycle 

P.S.I : Collateral hosts. 

S.S.I.: Whitefly, Bemisia tabaci. 

Not transmitted by sap, seed and pollen. 

Host range: French bean, soybean, Redgram, Eclipta alba, Xanthium strumarum 

etc. 

Management 

Remove collateral hosts and destroy. 

Use resistant varieties. 

Spray Metasystox @ 0.1 % for vector control. 

61


STUDY OF DISEASES OF COCONUT AND OILPALM 

Coconut: 

Ganoderma basal stem rot: Ganoderma lucidum; G. applanatum 

Symptoms 

Older leaves droop and wither and remain suspended around the trunk for 

several months. 

Younger leaves remain green for some time. 

Tree becomes barren due to suppression of inflorescence. 

Diseased tree dies slowly and often the stem cracks, giving out dark brown 

ooze. 

In advanced cases the fungus produces the fruiting structures along the sides of 

the basal trunk. 

Pathogen 

Pathogen produces hyaline mycelium with frequent clamp connections. It produces 

ellipsoid, slightly thick walled chamydospores which may be terminal or intercalary. 

The fruiting body is perennial, usually lateral and is corky at first becoming woody 

later. Basidiospores are thick walled brown and truncated at one end. 

Management 

Dig isolation trenches of about 50 cm wide and in deep, 2-3 m away from 

diseased palm to prevent spread of fungus. 

Trenches dug for replanting should be filled with FYM and 5 kg neem cake. 

Apply FYM and neem cake (5-10 kg) to each tree during June – July months. 

Also apply 2 kg Single super phosphate and 3 kg MOP in two splits, once in 

July and again in November. 

Apply 40 litres of 1 % Bordeaux solution in basin of each tree, yearly once, 

during August – September. 

Curative measures 

Root feeding with Tridemorph (6 ml in 25 ml of water), 3-4 times in a year, in 

early stages of infection. 

Bud rot: Phytophthora palmivora 

Symptoms 

Yellowish green discolouration of the heart leaf or crown leaf. 

The basal tissues of the leaf rot quickly and can be easily separated from the 

crown. 

Spindle withers and droop down. 

Older leaves develop irregular, water soaked spots which are sunken in 

nature. 


High R.H. 

Temperature 18-20 0 C. 

Rainfall Increases the disease. 

Presence of insect wounds etc. 

62

Management 

Spray copper fungicides (Bordeaux Mixture @ 1 % or COC @ 0.3%) after onset 

of monsoon to prevent infection. 

Stem bleeding: Ceratocystis paradoxa 

Syn : Ceratostomella paradoxa 

Ophiostoma paradoxa 

Symptoms 

Characterised by reddish brown ooze from the cracks near the base of the 

trunk. 

The fluid dries up to form black encrustations with brownish orange margins. 

Pathogen 

The fungus produces two types of conidia. Macroconidia are produced on 

conidiophores, either singly or in chains. They are spherical or dark green in colour. 

Microconidia (endoconidia) are produced endogeneously indise the long cells of 

conidiophores and cell ruptures when mature and release the microconidia in long 

chain. The pathogen also produces hyaline perithecia with clavate asci and hyaline 

ascospores. 

Management 

Chisel out affected tissues and dress the wound with coal tar or Bordeaux 

paste. 

In older trees, after draining the fluid, cavities can be stuffed with a mixture of 

Charcoal and sawdust. 

Cover the lower part of trunk with coal tar or Bordeaux paste to prevent the 

disease. 

Tatipaka disease Phytoplasma 

Symptoms 

Development of abnormally large crown with dark green inner leaves and 

higher yield. 

The palms continue to yield for 2-3 years. 

Subsequently the crown becomes smaller in size and stem begins to taper. 

The leaves give a fascinated appearance due to unfolding of leaflets. 

Leaves turn pale and bend abnormally. 

Affected tree produces smaller bunches with atrophied barren nuts. 

Severely damaged palms are barren with silky crowns and slight tapering 

trunk. 

Management 

Remove and destroy affected trees. 

Avoid using nuts from infected tree for raising seedlings. 

Avoid transport of nursery seedlings from infected areas. 

Grey blight: Pestalotiopsis palmarum 

Symptoms 

Grayish brown spots surrounded by a brown band on leaves. 

63

Spots coalesce into irregular necrotic patches. 

Complete drying and shriveling of leaf blade, when infection is severe. 

Pathogen 

The fungus produces conidia inside the acervuli. The acervuli are black in colour, 

cushion shaped, sub-epidermal and break open to expose conidia and black sterile 

structures, setae. The conidiophores are hyaline, short and simple, bear conidia at the 

tip singly. The conidia are five celled, the middle three cells are dark coloured, while 

the end cells are hyaline with 3-5 slender, elongated appendages at the apex of the 

spore. 

Management 

Remove older affected leaves and burn. 

Spray foliage with Bordeaux Mixture @ 1 % COC or captan @ 0.2 %. 

OIL PALM: 

Bunch rot: Marasmius palmivora 

Symptoms 

The fungus grows on bunches as white mycelial mat and it causes the rotting 

of pericarp and also the mesocarp leading to wet rotting of fruits and 

shedding. 

Disease cycle 

Survives as Basidiospores. 

Spreads through Basidiospores. 

Control 

Remove the aborted flowers, dried inflorescence and diseased leaf bits from 

bunches. 

Spray Carbendazim @ 0.1 %. 

Provide conditions suitable for pollination. 

Spear rot: Phytoplasma 

Symptoms: 

Chlorosis of young whorl leaves and followed by necrosis. 

Rotting of spear leaves and reduction in leaf size. 

In severe cases, trunk become taper and inflorescence emergencies arrested. 

Management: Rouging of affected plants and planting of barrier trees. 

64


STUDY OF DISEASES OF TEA, COFFEE, TURMERIC AND GINGER 

TEA 

Blister blight of tea: Exobasidium vexans 

Symptoms 

Initially oily, yellowish, translucent spots appear on the tender leaf and turn 

deep red shiny blisters. 

The circular spot gradually enlarges to 3to 13 mm diameter, bulged on the 

under surface of the leaf with a concave trough the depression on the upper 

surface. 

Leaves become curled and distorted. 

First flush of 2-3 young leaves are attached and the young shoots and buds 

are killed. 

Mature leaf is not affected. 

In nursery infection, seedlings are stunted with many thin stems instead of a 

single stalk. 

Repeated attacks cause death of seedlings. 

Badly affected nurseries will have to be abandoned. 

Succulent leaves and green shoots of newly pruned tea are most susceptible. 

Basidiospores cause secondary infection. 


Relative humidity > 83 % for 7 to 10 days favours disease. 

Temperature above 350 C inhibit the disease. 

Bushes in low, moist and shady localities suffer more. 

Pruned trees with new flush is highly susceptible. 

Management 

Seedlings should be protected in nursery by weekly sprays of COC @ 0.3 %. 

Spray, a mixture of 210 g COC + 210 g Nickel chloride per ha at 5 days 

intervals from June-September and 11 day intervals in October-November. 

Mancozeb, Tridemorph, Triadimefon and Pyracarbolid (sicarol) offers good 

disease control under field conditions. 

COFFEE 

Coffee rust: 

Symptoms 

Hemileia vastatrix 

Small, pale yellows spots on the upper surface of the leaves usually around 

the margins. 

Later masses of orange uredospores appear on the under surfaces. 

65

The fungus sporulates through the stomata rather than breaking through the 

epidermis, so it does not form the pustules typical of many rusts. 

The powdery lesions on the undersides of the leaves can be orange, yellow to 

red. Orange in color. 

The centers of the spots eventually dry and turn brown, while the margins of 

the lesions continue to expand and produce uredospores. 

Infection slowly progresses upward in the tree. 

The infected leaves drop off prematurely, leaving long expanses of twigs 

devoid of leaves. 

Pathogen 

The fungus is mostly intercellular drawing food from cells through haustoria. It 

produces uredospores and teleutospores on club-shaped erumpent stalks rising 

through the stomata. Uredospores are reniform, with an orange segment like 

appearance, the convex side echinulate and the lower or concave side smooth. Telial 

stage develops in the same spot producing turnip like, hyaline thich walled 

teleutospores. 

Disease cycle 

P.S.I.: Survive as mycelium or Uredospores in infected leaves. 

S.S.I.: Uredospores dispersed by wind and water. 

Pycnial and aecial stages are not known. 

Management 

Spray the bushes once with Bordeaux Mixture @ 0.5 % or COC @ 0.25 % and 

subsequently 2-3 times during monsoon. 

Spray Triadimefon @ 0.05 %. 

Collect diseased leaves and destroy. 

TURMERIC 

Leaf spot: Colletotrichum capsici 

Symptoms 

On leaves, elliptic to oblong spots of different sizes appear on both the 

surfaces, but more on upper surface. 

Spots gradually increase in size and attain a length of 4-5 cm and breadth of 2- 

3 cm. 

Mature spots have grayish center with dark brown margins surrounded by a 

yellow halo. 

Central portion of the spot becomes thin and papery. 

Management 

Remove and destroy affected plants. 

Treat rhizomes with COC @ 0.25 % solution. 

Spray Carbendazim @ 0.1 % or Mancozeb @ 0.25 % during August-December. 

Leaf blotch: Taphrina maculans 

Symptoms 

66

Appearance of large number of spots on both surfaces of leaf. 

Spots first appear as pale yellow discolourations which gradually turn to 

reddish brown. 

Spots lie between leaf veins and are rectangular, coalesce to form big irregular 

patches. 

Management 

Collect and destroy diseased leaves. 

Spray mancozeb @ 0.25 % or COC @ 0.25 % at 20 days interval. 

Ginger: 

Rhizome rot: Pythium spp. 

Symptoms: 

Sprouts fail to grow, pre emergence damping off noticed. 

Leaves appear pale green, turn yellow and wither. 

Soft water soaked translucent lesion appears at collar region. 

Rhizomes soft decompose putrifide except fibrovascular tissue. 

Roots rot similarly. 

Favorable factors: 

High rainfall 

Poor drainage 

Mimigrella insects 

Management: 

Selection of healthy seed 

Rhizome treatment with Metalaxyl 0.2% 

Soil drenched with COC 0.3% or Metalaxyl 0.2% 

Control of insects. 

Leaf spot: Phyllosticta zingiberi 

Symptoms: 

Minute yellowish, oval to elongate spots on leaves which turn into white, 

black borders, with papery with halo. At the centre of spots, minute 

pycnidium appears. 

Management: 

Application of COC 0.3% or Mancozeb 0.25% 

67

Ex.No. 13 Date: 

STUDY DISEASES OF MULBERY, ROSE, JASMINE AND CHRYSANTHEMUM 

Mulbery 

Powdery mildew: Phyllactinia guttata; P. corylea; P. suffulata 

Symptoms 

Lesions appear as whitish patches on the lower surface of the leaves. 

Gradually they turn yellowish brown to black patches. 

Powdery patches cover the entire leaf surface which is unsuitable for feeding 

the silk worms. 

The whitish powdery material seen on the leaves consists of the fungal 

hyphae, conidia, conidiophores and cleistothecia. 

Management 

Remove and destroy infected plant debris. 

Spray wettable sulphur @ 0.2 %. 

Mosaic: Virus 

Symptoms 

Mottling, puckering, curling and cupping of leaves. 

Reduction in leaf size. 

Stunting of plants. 

Disease cycle 

Resistance varieties like Ichinose, Oshimasho and Kosen. 

Vector control. 

ROSE 

Powdery mildew: Sphaerotheca pannosa var. Rosae 

Symptoms 

Rolling of leaf margins with the onset of sprouting season. 

Affected leaves become curled and distorted. 

The infected leaves show grayish powdery fungal growth. 

Badly infected flower buds fail to open. 

Infected floral parts become discoloured, dwarfed and dried. 

Management 

Collect and destroy infected plant debris. 

Four sprays with wettable Sulphur @ 0.3 % or Carbendazim @ 0.1 % or 

Dinocap @ 0.1 % at 10 days interval. 

Resistant varieties: Ashwini, Ambika, Angeles, American pride, Surabhi. 

Black spot: 

Symptoms 

Diplocarpan rosae 

68

Dark brown tar coloured spots with fringed borders. 

Spots coalesce forming large patches. 

Infected leaves turn brown and defoliate. 

Fungus may also attack stems and flowers of rose bushes. 

On stems, infected areas are blackened with blistered appearance dotted with 

pustules. 

Management 

Spray Tridemorph @ 0.025 % or benomyl @ 0.1 % at weekly intervals starting 

with the sprouting of the plants till new foliage appears. 

Die back: 

Symptoms 

Diplodia rosarum 

Infection starts from the pruned surface of the twigs. 

The infected portion becomes brown to dark brown or black. 

Infected twig dries from tip downwards. 

Infection spreads from twig to main stem and roots and finally whole plant is 

killed. 

Older plants and neglected bushes are more frequently attacked. 

Management 

Diseased twigs should be carefully removed and destroyed. 

After pruning the cut end should be protected with Chaubattia paste. 

Spray Difolatan @ 0.2 % or Mancozeb @ 0.2 % or Chlorothalonil @ 0.2 % in 

early September and late October. 

Resistant varieties: Blue moon, red gold, summer queen etc. 

JASMINE 

Rust: 

Symptoms 

Uromyces hobsonii 

Leaves, stems and inflorescence are affected. 

Blisters or tumours and other abnormalities may be produced on the infected 

plant parts. 

Orange coloured pustules on both surfaces of leaf but predominantly on lower 

surface. 

Chlorosis and defoliation of leaves under severe conditions. 

Infected portions become hypertrophied. 

Yellow or orange coloured cankers on stem and twigs. 

Infected flower buds are swollen and deformed. 

Flower production is highly reduced. 

Splitting of bark of affected branches and subsequent death of branches. 

69

Pathogen 

Autoecious rust. 

Spermagonial stage is usually not observed. 

Management 

Remove and destroy affected plants or plant parts to avoid further spread. 

Spray oxy-carboxin or Mancozeb @ 0.2 % 

CHRYSANTHEMUM 

Blotch: Septoria chrysanthemella 

Symptoms 

Blackish brown circular to irregular spots on leaves which later from large 

patches. 

Patches are surrounded by chlorotic hallows. 

Later the centers turn grayish and the leaves remain small and curl. 

Management 

Spray Carbendazim @ 0.1 %. 

Resistant varieties: Alpana, Sarad and Flirt. 

Chrysanthemum stunt: Viroid 

Symptoms 

Small and paler plants and flowers. 

Some flowers appear bleached and are inferior in quality. 

Flowers from diseased plants open 7 to 10 days earlier than healthy ones. 

Axillary buds grow prematurely and produce number of branches and 

stolons. 

White specks and yellow blotches on leaves of some varieties. 

Disease cycle 

P.S.I.: Viriod survives in infected plants. 

S.S.I.: Spread through sap and knives or tools used during pruning or 

pinching plants, taking cuttings and cutting the flowers. 

Management 

Use certified viriod free stocks. 

Remove and destroy infected plants. 

Wilt: Fusarium oxysporum f.sp. Chrysanthemi 

Symptoms 

Disease is characterized by chlorosis of one or more leaves. 

Drooping of leaves and wilting of the affected plants. 

Black necrotic spots appear on the stem. 

Vascular discolouration. 

70

Creamy mycelial growth of the pathogen is seen on the collar region under 

humid conditions. 

Disease cycle 

P.S.I : Soil borne fungus or through cuttings. 

S.S.I. : Conidia dispersed through irrigation water. 

Management 

Cuttings should be obtained from disease free plants. 

Long crop rotation. 

Crosandra : 

1) Wilt – Fusarium solani 

Symptoms 

Usually observed one month after transplanting in patches 

Leaves of infected plants become pale and droop 

Leaf margins show pinkish brown discolouration 

Discolouration spreads to midrib in 7 to 10 days 

Stem portion gets shrivelled 

Dark lesions noticed on the roots extending upto collar region which results in sloughing 

of cortical tissue 

Disease cycle 

P.I: Chlamydospores survive in soil 

S.I: Microconidia dispersed through irrigation water 


Incidence is more in presence of root lesion nematode, Pratylenchus sp., and 

Helicotylenchus dihystera 

Management 

Remove and destroy affected plants 

Soil application of phorate @1g/plant on 10 th day of transplanting for nematode 

management 

Soil drench with Carbendazim@0.1% or COC@0.25%. Repeat soil drenching after 3-4 

weeks 

71

Ex. No. 14&15 Date: 

FIELD VISIT AND COLLECTION OF DISEASE SPECIEMENS 

72

Practical Manual - acharya ng ranga agricultural university

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