PATH 372 Diseases of Horticultural Crops

COURSE MATERIAL FOR PATH 372 

DISEASES OF HORTICULTURAL CROPS AND THEIR MANAGEMENT 

Prepared By 

DR. P. KISHORE VARMA, 

ASSISTANT PROFESSOR, 

DEPARTMENT OF PLANT PATHOLOGY 

AGRICULTURAL COLLEGE, 

ASWARAOPET 507 301 

1

DISEASES OF HORTICULTURAL CROPS 

LECTURE 1 

CITRUS 

Citrus Phytophthora Phytophthora nicotianae var. parasitica, P. palmivora, 

Gummosis citrophthora, P. hibernalis, P.syringae, P. cactorum 

Citrus Diplodia 

Gummosis 

Diplodia natalensis 

Citrus Dry root rot Fungal complex (Fusarium sp., Diplodia., etc) 

Citrus Scab Elsinoe fawcetti 

Citrus Canker Xanthomonas axonopodis pv. citri 

Citrus Tristeza Citrus tristeza virus 

Citrus Greening Candidatus Liberibacter asiaticus 

Citrus Felt Septobasidium pseudopedicillatum 

1) Gummosis: Phytophthora nicotianae var. parasitica, P. palmivora, P. citrophthora, 

P. hibernalis, P.syringae, P. cactorum 

Economic importance: Gummosis is widespread in Punjab and Assam. Lemons are 

highly susceptible compared to grapefruit, rough lemons and sweet orange. In South 

India, it is common in the sweet orange. 

Symptoms 

Disease starts as water soaked large patches on the basal portions of the stem near 

the ground level 

First symptoms are dark staining of bark which progresses into the wood. 

Bark in such parts dries, shrinks and cracks and shreds in lengthwise vertical 

strips. 

Bark at the base is destroyed resulting in girdling and finally death of the tree. 

Later profuse exudation of gum from the bark of the trunk occurs. There may be a 

considerable amount of gum formation in sweet oranges, but relatively little in 

grapefruit. 

Infection extends to crown roots. 

Prior to death, the plant usually blossoms heavily and dies before the fruits 

mature. 

Favourable conditions 

Prolonged contact of trunk with water as in flood irrigation; water logged areas and 

heavy soils predispose the disease. Incidence is more in black soils than in light soils; 

high water table leads to high incidence. The disease is severe in high rainfall areas. 

Mode of spread and survival 

The fungus survives as oospores or as dormant mycelium. Sporangia and zoospores 

spread by splashing rain water and irrigation water. 

2

Management 

Preventive measures: 

Selection of proper site with adequate drainage and high budding (30 to 46 cm or 

above). 

Provision of an inner ring about 45 cm around the tree trunk to prevent moist 

soil. (Double ring method of irrigation) 

Avoid irrigation water from coming in direct contact with the trunk. 

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

Use resistant sour orange rootstocks for propagating economic varieties 

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

60 cm above the ground level at least once a year. 

Curative measures: 

Scrape the diseased portion with a sharp knife. 

Protect the cut surface with Bordeaux paste followed by spraying of 0.3% fosetyl- 

AL reduces the spread. 

Soil drenching with 0.2% metalaxyl and 0.5% Trichoderma viride commercial 

formulation is also effective. 

2) Diplodia gummosis: Diplodia natalensis (Perfect stage: Physalospora rhodina) 

Economic Importance: Occurs commonly in Andhra Pradesh, Tamil Nadu and Uttar 

Pradesh. It is common on Sathgudi and Batavian oranges, mandarins and lemons in 

A.P. and Tamil Nadu. 

Symptoms: 

Profuse gumming on the upper portions of the trunk, branches and twigs. 

Infection starts at growth cracks or ridges at crotches. 

Gum oozes out from the cracks developed on the diseased portion. 

From bark, the infection spreads to wood which dries and becomes 

discoloured. 

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

course of time. 

Sometimes branches break at the infected portion. 


Reduced tree vigour, insect damage, malnutrition and old age predispose the disease. 


Black pycnidial bodies appear on the diseased bark which gets removed in flakes. 

The disease spreads through dissemination of pycnidiospores or conidia by air, 

rain and insects 

Management 

The tress should be kept in a vigorous growing condition. 

Wound in the bark especially on limbs and forks should be scraped and protected 

with Bordeaux paste. 

3

Gummed portions of affected bark should be removed and the cut surface 

protected. 

Spraying with 0.1% carbendazim on the affected limbs and forks is useful to 

restrict the disease spread. 

3) Dry root rot: Fungal complex (Fusarium sp., Diplodia natalensis and 

Macrophomina phaseolina) 

Economic Importance: Dry root rot is a major problem in all citrus growing areas of 

Andhra Paradesh in both sweet orange and acid lime. It is also common in North 

Arcot district in Tamil Nadu and in Mandarins in Wynad 

Symptoms: 

The disease is characterized by moist decay of root bark in the early stages. Later, 

the bark becomes dry and shredded with hard dead wood underneath. 

The affected trees show yellowing of foliage and bare necks. 

The flowering is increased and the affected trees bear a heavy crop of small sized 

fruits. The affected roots emit a foul odour and the tree finally dies. 

Peeling of bark of the affected roots and formation of black sclerotia on the root 

surface is also common 


Excessive moisture, direct contact of water with trunk, poor aeration, heavy soils, and 

frequent injuries to roots, excessive manuring at long intervals and close planting 

favour dry root incidence. Lack of sufficient moisture or inadequate supply of 

nitrogen may also lead to this disease. Defective soil, hard pan formation below the 

second foot and unfavourable soil-air-moisture relationship in the subsoil leads to 

inadequate oxygen at root zone which is primarily responsible for the incidence of dry 

root rot. 

Management: 

Cut and destroy the diseased roots, if only one or two roots are affected and the 

tap root and crown are still in good condition. The cut surface should be protected 

with Bordeaux paste. 

Avoid deep ploughing or digging which are likely to injure roots 

Leaf mulch in the tree basins during the dry season helps in conserving the soil 

moisture and thereby reduces disease incidence 

Spray with Urea (4.5 kg in 450 litres of water) to reduce disease intensity 

Drench the soil with 0.25 carbendazim + 0.25% Mancozeb at the rate of 1 litre per 

m 2 of the tree basin in early stage of infection 

Apply 10 kg of neem cake followed by soil drenching with 0.5% Trichoderma 

viride formulation + 0.2% copper oxy chloride in the early stages of infection 

4) Scab / Verucosis: Elsinoe fawcetti (I.S: Sphaceloma fawcetti) 

Economic Importance: In India this disease is reported from Bengal, Punjab, Assam, 

Karnataka, Uttar Pradesh and Andhra Pradesh. It is one of the common diseases of 

sour oranges, rough lemon, tangelos and Pummelo. In Andhra Pradesh it is severe on 

Rangapur lime. The sweet oranges are mostly resistant to the disease. 

4

Symptoms: 

The disease attacks leaves, twigs and fruits. 

The lesions on leaves in early stages consist of small, semi-translucent dots 

which become sharply defined pustular elevations usually on the underside, flat or 

somewhat depressed at the center. The opposite surface corresponding to the 

warty growth shows a circular depression with a pink to red centre. In later 

stages, leaves often become distorted, wrinkled, stunted and mis-shapened. 

The twigs also develop similar lesions and the affected twigs are ultimately killed. 

On the fruit, lesions consist of corky projections which often break into scab 

affecting larger areas on the fruits. The surface becomes rough and distorted. 

The market value of the fruits is considerably reduced, though the fungus rarely 

affects the fruit flesh below the skin. 


Young leaves are highly susceptible. 

The fungus infects tissues only when the surface is wet and prefers temperature of 

16 to 23 0 C. The disease is a problem under low temperature and high humidity 

conditions 

Mode of survival and spread 

The fungus survives the off-season as ascospores 

The secondary spread is through air borne conidia 

Management: 

The diseased leaves, twigs and fruits should be collected and destroyed 

Spray with 0.3% COC or 1.0% Bordeaux mixture or 0.2% Difolaton or 0.2% 

chlorothalonil at 15 days interval. 

5) Citrus canker: Xanthomonas axonopodis pv. citri 

Economic Importance: In India, citrus canker is endemic and occurs in all the citrus 

growing areas. It is reported from Punjab, Tamil Nadu, Andhra Pradesh, Karnataka, 

Rajasthan, Madhya Pradesh, Assam, and Uttar Pradesh. Acid lime is highly 

susceptible to canker. 

Symptoms: 

Canker appears on leaves, twigs, petioles, branches, fruit stalks, fruits and thorns. 

When it is severe, trunk and roots are also affected. 

But the symptoms are most conspicuous on leaves, twigs and fruits. 

The lesions appear as minute water soaked round, yellow spots which enlarge 

slightly and turn brown, eruptive and corky. 

On acid lime and sweet orange they are about 2 to 3 mm in diameter. These 

pustules are surrounded by a characteristic yellow halo. 

Canker lesions on the fruit do not possess the yellow halo as on leaves. Several 

lesions on fruit may coalesce to form a patch. The crater-like appearance is more 

marked on fruits than on leaves. 

The market value of the fruits is considerably reduced by the canker spots, though 

such infections are mostly confined to the fruit skin. 

5

Due to severe infections of the leaves there may be defoliation, and severe 

infections of the twig and stem may cause die-back symptoms. 

The plants also remain stunted and fruit yields are reduced considerably. 

Favourable conditions: Free moisture for 20 minutes at 20-30°C initiates the disease. 


Survives in infected leaves for 6 months. 

Bacteria overwinters in leaf, twig and fruit canker lesions 

Citrus leaf miners (Phyllocnistis citrella) helps in the dissemination of the 

pathogen 

Spread by rain splashes. 

Management 

Prune out and burn all canker infected twigs before monsoon 

Periodical spraying of bactericides along with an insecticide 

Use canker tolerant varieties like “Tenali selection” and “Balaji” 

Select seedlings free from canker for planting in main field 

Spray Streptocycline (1g) + Copper oxy chloride (30g) in 10 litres of water at 

fortnightly intervals for effective management of canker in citrus nurseries 

Three sprayings of Streptocycline (1g) + Copper oxy chloride (30g) in 10 litres of 

water at an interval of 20 days during rainy season is effective for leaf canker 

Fruit infection can be prevented by two sprays of Streptocycline (1g) + Copper 

oxy chloride (30g) in 10 litres of water at marble stage followed by another spray 

30 days later 

Control leaf miner when young flush is produced. 

6) Tristeza or quick decline: Citrus Tristeza Virus (CTV) 

Economic Importance: This disease was first reported in Citrus aurantifolia and C. 

sinensis from Italy and Florida in the U.S.A. In India, tristeza is present in Andhra 

Pradesh, Tamil Nadu, Karnataka, Madhya Pradesh, Maharashtra, Punjab, Bihar, West 

Bengal and Sikkim. 

It affects all kinds of citrus plants but primarily orange, grapefruit and lime. Tristeza 

symptoms consisting of a quick or chronic tree decline are particularly common and 

severe on trees propagated on sour orange root stocks. The name “Tristeza” was 

suggested to describe the sad appearance of the diseased citrus trees. Kagzi lime and 

Nasnaran are indicator plants for CTV detection. 

Symptoms: 

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Tristeza affected trees look chlorotic and sickly in the early stages. Gradually the 

leaves drop and the defoliated twigs show die-back. The declining trees die 

gradually but sometimes apparently healthy trees die suddenly. 

Vein clearing or vein flecks (elongated translucent area) in young leaves of acid 

lime is seen intermittently when viewed against light (characteristic symptom). 

In sweet orange, the specific symptom of tristeza is honeycombing, a fine pitting 

of inner face of bark in the portion of trunk below the bud union. In acid lime 

which is highly susceptible to the disease, vermiform or linear pits appear in the 

woody cylinder. 

Tristeza infected citrus trees on sour orange rootstocks cause phloem necrosis at 

the graft union 

Diseased trees usually blossom heavily. Trees with stem pitting are stunted and 

set less fruits. The fruits are of smaller size and of poor quality (insipid fruits). As 

the fruits develop, the tree wilts partly or completely. 

Grapefruit and acid lime are susceptible irrespective of root stock. 

Pathogen: Tristeza is a highly flexuous filamentous virus 2000nm long and 10-12nm 

in width. The virus is restricted to only phloem tissue and is a member of 

Closterovirus group. CTV has ss +ve sense RNA of 20 K nucleotides as its genome. 


The disease primarily spreads through grafting and budding. Under field conditions, it 

is transmitted by the black citrus aphid, Toxoptera citricida. The virus is not seed 

borne. 

Management: 

Strict quarantine measures to be enforced 

Use certified budwood free of CTV 

Remove all diseased trees as and when the disease is noticed. Fresh plantings 

to be taken with virus free materials on tolerant rootstocks. For sweet orange and 

mandarin avoid susceptible root stocks. 

For Andhra Pradesh, Maharashtra and Karnataka, Rangapur lime is 

recommended as a root stock resistant to Tristeza. For the Punjab region, 

Jattikhatti, Cleopatra mandarin and sweet orange are recommended as resistant 

root stocks. 

For acid lime, use seedling preimmunised with mild strain of tristeza virus (Cross 

protection). 

Periodic sprays of insecticides like Monochrotophos 0.05 % reduce s the 

secondary spread of the disease in the orchard. 

7) Greening or Huanglongbin: Candidatus Liberibacter asiaticus (Fastidious Phloem 

limited Bacterium), Obligate gram negative bacterium 

7

Economic importance: Greening disease is known to occur in Andhra Pradesh, 

Karnataka, Punjab, Uttar Pradesh, Himachal Pradesh, Rajasthan, Maharashtra, 

Jammu, Bihar, Bengal and Sikkim. The disease is more severe on sweet oranges than 

on acid lime, mandarin and grapefruits. This disease affects almost all citrus varieties 

irrespective of root stock. In India Mosambi sweet orange and Darjeeling orange 

(Citrus reticulata) are good indicator plants for greening. 

Symptoms: 

Affected trees are stunted with pronounced leaf and fruit drop. Varied chlorotic 

patterns on leaves are noticed which are persistent and cannot be corrected by zinc 

sprays. 

Reduction in leaf size is common. Many affected leaves show small circular 

green islands within the chlorotic areas. Heavy leaf fall occurs with the onset of 

summer. Often new flush may come out and leaves formed are short, upright and 

chlorotic with green veins or with green blotches on the leaves. 

Twig die-back occurs. Some branches in a tree exhibit severe symptoms whereas 

others in the same tree are apparently normal. 

Fruits show reduction in size, lopsided growth and oblique columella. 

The rind surface exposed to sun appears yellow whereas the remaining portion 

remains dull green. Diseased fruits are valueless owing to small size, distortion, 

low in juice and soluble solids, high in acid and insipid taste. 

Seeds are poorly developed, dark coloured and aborted. 

Mode of spread: 

The disease is transmitted through infected bud wood and citrus psylla, Diaphorina 

citri. The disease also transmits from citrus to Periwinkle (Catharanthus roseus) 

through dodder. 

Management 

Select certified disease-free seedlings. 

Control psyllids with insecticides like dimethoate. 

Use pathogen free bud wood for propagation. 

Raise virus free plants through shoot tip grafting 

500 ppm tetracycline spray though effective, requires fortnightly application 

which is not economic. 

8) Felt disease: Septobasidium pseudopenicillatum 

8

Symptoms: 

The disease starts with onset of monsoon in case of acid lime. 

A soft felt like fungal growth encircles the twigs and branches. 

The fungus grows over the bark and does not penetrate the surface. The growth is 

light brown to grey in colour and colonies of scale insects can be seen underneath 

it. 

This results in drying of stems. 

Management: 

Spray twice with monochrotophos 0.05% and zineb@0.25% with the onset of 

monsoon at monthly interval. 

9

LECTURE 2 

Mango 

1. Powdery mildew: Oidium mangiferae (Eyrsiphe polygoni) 

Economic importance: The disease is worldwide in distribution. Reported from India, 

Pakistan, Ceylon and South Africa. In India the disease is particularly destructive in U.P. 

Maharashtra and Karnataka severe particularly during the months of December-March, 

i.e. cooler months. 

Symptoms: 

The disease can easily recognized by whitish or grayish powdery growth on the 

inflorescence and tender leaves. 

Generally the infection starts from the inflorescence and spreads downwards 

covering the floral axis, tender leaves and stem. Leaves become twisted, curled 

and defoliate. 

Infected floral parts are severely damaged and drop off. If the fruits are set, they 

do not grow in size and may drop before attaining pea size. Fruits are sometimes 

malformed, discolored due to severe mildew attack. 

Because of poor fruits set and heavy flower and fruits drop, the loss due to the 

disease may go as high as 70-80%. 


Disease spread is favored by warm humid weather with cool nights. 

Pathogen and Disease cycle: P.S: Erysiphe polygoni -(Rare) in India. 

Mycelium branched, hyaline, superficial, septate, haustoria lobate. Conidia hyaline, 

unicellular, elliptical, borne singly or rarely in chains of two, conidiophores simple, erect 

with two or more basal cells. 

Mode of spread: 

Dissemination is by wind and the progress of the disease in the orchard is along the 

direction of wind. 

P.I: Through infected plant debris by conidia 

S.I: Wind borne conidia of Oidium mangiferae. 

Management 

Can be controlled with two preventive sprays with wettable sulphur 0.3% once before 

the flowers open and 2 nd after the fruit set. 

Dusting twice or thrice with fine sulphur will check the disease. 

10

Spraying with Karathane 0.1% or cosan 0.1% before flowering and after fruit set 

(peanut stage). 

Resistant varieties: Neelum, Zardalu, Banglora, Torapari-khurd and Janardhan pasand 

2. Anthracnose: Colletotrichum gloeosporioides 

Economic importance: SATTAR and MALIK in 1939 observed the disease in 

several districts of Punjab. Since then it has been found in all mango – growing tracts 

of the country. 

Symptoms: 

The fungus produces leaf spots, blossom blight, wither tip, twigs blight and fruit rot. 

On leaves initially circular, light yellow brown spots are produced which soon enlarge 

with dark brown to black margins. If infection is severe individual spots coalesce 

leading to twisting of foliage and premature defoliation. 

The disease spreads rapidly during rainy season and covers the tender twigs and floral 

axis causing them to wither. 

Spots appear on fruits near the stem end as small brown areas that enlarge rapidly and 

become black. In some cases the areas involved are in the form of streaks running 

down from the stem end. Fruit pulp beneath the spots become hard followed by 

cracking and decay at ripening. 

The decay is confined to the skin of the fruit except in late stages where it penetrates 

the flesh in shallow areas. Infected fruits may also drop off prematurely. 

The latent infection is carried from the field and develops further which causes rotting 

in the storage. Neelum and Banglora are more susceptible. 

Disease cycle : 

P.I: Mainly through previous season infected leaves, defoliated branches, mummified 

flowers and flower brackets. 

S. I: Mainly due to rain splash or wind driven rain water. 

Favourable conditions: Temperature of 25°C and R.H 95-97% 

Management 

Avoid over-crowding of orchards 

Tree sanitation is important. Diseased twigs are to be pruned and burnt (along with 

fallen leaves.) 

Spray carbendazim or Topsin M (0.1%) or Chlorothalonil (0.2 at 14 days intervals 

until harvest. 

11

Before storage, treat the fruits with hot water (50-55°C), for 15 minutes or dip in 

Benomyl solution (500ppm) or Thiobendazole (1000ppm) for 5 minutes or expose 

them to ammonia and sulphur dioxide gases. 

3) Mango Malformation: Fusarium moliliforme var. subglutinans 

Economic importance: 

This is one of the severe diseases of mango and is important in North India. It appears 

in and around Hyderabed & Medak Districts. 

In A.P. this was first noticed in Aragonda village in 1971. 

In India it is known to occur in U.P., Maharashtra, Haryana, Bihar, Punjab and A.P. 

particularly severe in U.P. causing much damage. 

In North West India nearly 50% incidence on orchards were recorded. 

Where as in north East and south the incidence may go up to 10%. Coastal areas are 

free from the disease. 

Symptoms: 

There are two types of symptoms namely floral malformation and vegetative 

malformation. 

Vegetative malformation: There is a proliferation of infected tissue. The affected plants 

develop excessive vegetative branches which are of limited growth, swollen and have 

short internodes. 

These dwarf branches are of various sizes which are often produced on the top of 

young seedlings giving a bunchy top appearance. The axillary buds of dwarf 

branches are unusually enlarged. 

Vegetative malformation is more pronounced in young seedlings and seedling trees 

than in grafted plants. 

Floral malformation: The flowering panicles instead of coming out as a normal one 

turns into just compact bunch of hard flowers. Individual flower is greatly enlarged 

and has a large disc. 

The inflorescence gets hypertrophied. The percentage of bisexual flowers in 

malformed panicles is very low. 

The malformed heads dry up in black masses and persist on the trees for a long time. 

Disease cycle: 

P. I: Through malformed inflorescence 

S. I: Either by air borne conidia or by conidia carried by eriophid mite Aceria 

mangiferae 

Management: 

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1. Use of disease free planting material and prophylactic spray of insecticides and 

fungicides. 

2. Pruning of diseased parts along with basal 15-20 cm apparently healthy portions. 

3. Spray Captan (0.2%) or Benomyl (0.1%). 

4. Spray napthelene acetic acid (NAA) 200 ppm during first week of October. 

4) Bacterial leaf spot: Pseudomonas mangiferae- indicae 

Economic importance: The first description of bacterial leaf spot was given by Patel et 

al in 1948 from Maharashtra. In India the disease occurs in Delhi, Tamil Nadu and other 

states 

Symptoms: 

Symptoms are seen on leaves and fruits. 

On the leaves initially slightly water soaked yellowish, translucent irregular spots 

are formed towards leaf tip which enlarge soon and become dark brown with a 

yellow halo. 

These dark spots are limited by veins and become angular resulting in cankerous 

raised lesions. 

Spots appear all over the lamina. 

Under high humid conditions these spots fuse, leaves turn yellow and drop down 

prematurely. 

Longitudinal cracks develop on petioles. 

On green twigs, dark lesions of infection spread to inflorescence stalks. 

When fruits are attacked, water soaked lesion develop and turn dark brown to 

black. 

The affected fruits become yellow with deep cracks severely affected fruits are 

shed prematurely. 

Disease cycle: Primary infection is through infected leaves, branches, and fruits. 

Secondary infection occurs by wind driven rain and rain splash. 

Management: 

Forthrightly spray of 1% B.M. or Agrimycin - 100 or Paushanycin or Plantomycin 

(200ppm) or Streptomycin 

Resistant variety: Bombay green 

5) Sooty mould: Capnodium ramosum 

Symptoms: 

Black encrustation seen on upper surface of the leaves affecting the 

photosynthetic activity. 

Superficial growth of the fungus on the flowers, both tender and old leaves, stem 

and fruits. 

Black encrustation forms on the fruits; appearance is lost yielding low price. 

Pathogen grows and thrives on the sugary or honey dew secretions of plant 

hoppers. 

13

Mode of spread: Diseased leaves serve as primary inoculum. Scale insects and aphids, 

Lecanium hemisphaericum, L. viride, L. nigrum, Hemilecanium imbricans and Pulvinaria 

Psidii. 

Management: 

Controlling of plant hoppers by spraying Carbaryl (2g/lt) or Phosphomidon 0.03% 

Spray dilute solution of starch or maida 5% (Boil 1 kg of maida or starch in 5 litres of 

water, cool and dilute to 20 litres), which dries up and comes off in flakes, removing 

along with it the sooty mold growth. 

6) Red rust: Cephaleuros virescens (algae) 

Economic importance: In India it has been observed in Bihar, Karnataka and U.P. The 

disease appeared in an epidemic form in orchards of Tarai in 1956. Reduction in 

photosynthetic activity and defoliation as a result of algal attack lower vitality of the host 

plant. 

Symptoms: 

The disease is characterized by red rusty spots on the leaves and young twigs 

The spots are initially circular, slightly elevated and later coalesce to form irregular 

spots. 

The upper surface of the spot consists of numerous unbranched filaments of the 

pathogen which project through the cuticle. Some of the filaments represent the sterile 

hairs while others the fertile ones 

Initially the spots are greenish-grey in colour and variety in texture, but later on the 

surface bears reddish-brown appearance. 

Disease cycle: Common in close plantations. High moist conditions favour the 

development of fruiting bodies. 

P.I.- Zoospores. 

Management: 

Avoid close plantations 

Spray Bordeaux mixture 1-2% or Fytolan / Blitox 0.5% or lime sulphur 0.1% 

7) Loranthus 

Symptoms: 

Loranthus is a partial stem parasite. Loranthus seeds are disseminated by birds on to 

the stems of the host. 

Loranthus seeds do not require a host germination stimulus and will germinate 

spontaneously. 

14

The seedling radicle is negatively phototrophic and thus grows towards a dark surface 

(often the host branch). 

The first attachment structure formed is called a holdfast. The haustorium from the 

holdfast eventually connects to the host xylem. 

Parasite removes water and mineral nutrients from the host. 

When in contact with the host cambium, the loranth haustorium induces the formation 

of additional wood that enlarges into fluted columns. 

Management: 

Pruning of affected branches 

Periodic removal of mistletoes from infected branches and stems 

Ethephon effectively controls mistletoes in some situations 

Inject copper sulphate and 2,4-D into affected branches 

Spray of diesel oil emulsion in soap water 

15

LECTURE 3 

DISEASES OF BER 

1. Powdery mildew – Oidium erysiphoides f.sp. zizyphi 

The disease is noticed generally at the end of October and prevails from 

November to April 

Symptoms 

Powdery mass appears on young leaves and fruits 

Severely affected leaves shrink and defoliate 

Small white pwdery growth appear on young fruits which later enlarge and 

coalesce and finally turn brown to dark brown in colour 

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

prematurely 

Survival and spread 

P.I: Budwood of host plant 

S.I: Air-borne conidia 


Warm humid conditions with R.H more than 90% 

Management 

Spray Dinocap@0.1% or Wettable S@0.2% during first and third weeks of Nov 

Two sprays of carbendazim@0.2% at 15 days interval, starting from the time when 

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

Add Teepol or Sandovit to the fungicide solution 

DISEASES OF GUAVA 

1. Wilt – Fusaium oxysporum f.sp. psidii, F. solani, Macrophomina phaseolina, 

Cephalosporium sp., Gliocladium roseum and Verticillium alboarum. 

Economic importance: It was first reorted in 1935 from Allahabad. Jhoty et al., in 

1984 reported that seven thousand acres of land in A.P under guava cultivation was 

reduced to half the land value by the presence of the disease. 

Symptoms 

The affected plants show yellow colouration with slight leaf curling at the terminal 

branches, becoming reddish at the later stage and subsequently premature shedding 

of leaves takes place. 

Twigs become bare and fail to bring forth new leaves or flowers and eventually dry 

up. Fruits of all the affected branches remain underdeveloped, become hard, black 

and stony. 

The entire plantr becomes defoliated and dies. A few plants also show partial 

wlting, which is very common symptom of wilt in guava. 

16

The finer roots show black streaks which become prominent on removing the bark. 

The roots also show rotting at the basal region and the bark is easily detachable 

from the cortex. 

The cortical regions of the stem and root show distinct discolouration and damage. 

Light brown discoloration is noticed in vascular bundles. Brak splitting can be seen 

in wlted plants in later stages. 

The disease can be catagorized into slow wilt and sudden wilt. In slow wilt, plant 

takes several months or even a year, to wilt after the appearance of initial 

symptoms and in sudden wilt, infected plant wilts in 15 days to one month. 

Favourable conditions: 

pH 6.0 is optimum for disease development. Both pH 4.0 and 8.0 reduces the 

disease. 

Disease is more in clay loam and sandy loam compared to heavy soil. 

Higher disease incidence in monsoon period. 

Disease appears from august and increases sharply during September-October. 

The presence of nematode, Helicotylenchus dihystera 

Management 

Cultural: 

Proper sanitation of orchard. 

Wilted plants should be uprooted, burnt and a trench of 1.0-1.5m should be dug 

around the tree tunk. Treat the pits with formalin and cover the pit for three days 

and then transplant the seedlings after two weeks. 

While transplanting seedlimgs avoid damage to the roots. 

Maintain proper tree vigour by timely and adequate manuring, inter-culture and 

irrigation. 

Intercropping with turmeric or marigld. 

Soil solariztion with transparent polythene sheet during summer months. 

Application of oil cakes like neem cake, mahua cake, kusum cake supplemented 

with urea. Apply 6kg neem cake + 2kg gypsum per plant. 

Judicous ammendments of N and Zn. 

Host Plant Resistance: 

Resistant variety: Apple guava 

Guava species, Psidium cattleianum var. lucidum and Syzigium cumini (Jamun) are 

resistantr to wilt. 

Psidium cattleianum (P. molle), P. quianense, Chinese guava (P. friedshthalianum) 

and Phillippine guava are recommended as resistant root stocks 

Biological: 

Aspergillus niger strain AN 17, Trichoderma viride, Trichoderma harzianum and 

Penicillium citrinum can used as biocontrol agents 

Chemical: 

Stem injection with 0.1% water soluble 8-Quinolinol sulphate 

Drench with 0.2% Benomyl or Carbendazim, four times in a year and spray twice 

with Measystox and Zinc sulphate. 

Disinfestation of soil with Metam-sodium at 252 ml/10m 2 area to control 

nemtodes. 

17

DISEASES OF SAPOTA 

1. Phavophleospora leaf spot – Phavophleospora indica 

Symptoms 

Numerous, small, circular, pinkish to reddish brown, conspicuous spots with 

whitish center on mature leaves 

Spots coalesce and leaves drop prematurely 


Severe during Oct-Dec 

Fungus grows best at 25 0 C and 90% RH 

Susceptible varieties: Cricket ball, Kirthabarthi, Mimusops hexandra (root stock) 

Management 

Avoid susceptible varieties 

Spray zineb@0.2% or ziram@0.2% or COC@0.25% 

2. Pestalotiopsis leaf spot – Pestalotiopsis versicolor (Syn: Pestalotia versicolor, P. 

sapotae and P. podocarpi) 

Symptoms 

Small, reddish brown specks on leaf lamina 

Spots enlarge, become circular measuring 1 to 3 mm in diameter 

Fully developed spots show grayish centre and dark brown to reddish margin 

Minute black fruiting bodies (pycnidia) are seen in the center of spots 

Management 

Spray zineb@0.2% 

3. Flat limb – Botryodiplodia theobromae 

First reported from Maharashtra and Gujarat by Khurana and Singh in 1972 

Symptoms 

Branches of affected trees become flat and twisted 

Leaves become thin, small and yellow 

Cluster of leaves and flowers on affected twigs 

Flowers remain infertile 

If fruits are set, they are undersized, hard and fail to ripen 

Foliage and fruits fall prematurely 

Management 

Pruning of affected branches followed by Captan or Zineb (0.3%) spray 

18

DISEASES OF PAPAYA 

Powdery mildew – Oidium caricae 

Foot rot – Pythium aphanidermatum 

Rhizoctonia solani 

Mosaic – Papaya mosaic virus or Papaya ringspot virus 

Leaf curl – Tobacco leaf curl virus or Nicotiana virus 10 

Anthracnose – Colletotrichum papayae 

1. Powdery mildew: Oidium caricae 

Symptoms 

Diffuse mats of external, white mycelium develops on both the leaf surfaces 

Lesioned areas become chlorotic and sometimes surrounded by a dark margin 

Flower stalks and fruits are also affected 

Stems of young seedlings are affected when grown under reduced light conditions 

Severe attack leads to death of top portion of the seedlings 


P.I: Mycelium or cleistothecia in infected plant debris 

S.I: Wind borne conidia 


Maximum disease incidence during Sept – Nov with a peak in October 

Management 

Spray wettable Sulphur@0.3% at 10 days interval 

Spray systemic fungicides like Bayleton@0.1% or carbendazim@0.1% at monthly 

intervals 

2. Foot rot / stem rot: Pythium aphanidermatum, Rhizoctonia solani 

Symptoms 

Water soaked patches on the stem at the ground level 

Patches enlarge and girdle the base of the stem 

Diseased tissues turn brown or black and rot 

Terminal leaves turn yellow, droop and wilt 

Fruits shrivel and drop off 

Entire plant topples over and dies 

Internal tissues of bark appear dry and give honey comb appearance 

Roots deteriorate and may be destroyed 


P.I: Oospores (Pythium) or Sclerotia (Rhizoctonia) in soil 

S.I: Seedlings raised in infected soil carry the disease to field 


Appears from June to August 

Younger seedlings are more susceptible than older ones 

Severity increases with intensity of rainfall 

19

R. solani is severe in dry and hot weather (36 0 C) 

Management 

Seedlings should be raised in well drained nursery area 

Uproot the diseased seedlings and burn 

ST with captan@4g/kg seed or chlorothalonil@2g/kg seed (R. solani) 

Drench the base of stem with COC@0.25% or metalaxyl@0.1% or Bordeaux 

mixture@1.2% 

3. Mosaic: Papaya mosaic virus or Papaya ringspot virus or Carica virus1 

Economic importance 

Occurs in a severe from in central India. 

In India 1 st reported from Mumbai and Pune in 1947 

90-100% damage occurs in severe cases 

Symptoms 

Mottling and puckering of leaves, especially the young ones 

The lamina is reduced and malformed and are often modified into tendril like 

structures (shoestrings) 

Decline & marked reduction in growth of diseased plants (within 30-40 days) 

Older leaves fall down and a small tuft of younger leaves is left at the top with 

upright postion 

The stem, petiole and fruits develop elongated water soaked areas showing 

concentric or circular rings 

Fruits develop innumerable circular, water soaked lesions with spots in the center 

Fruit size is severely reduced with deformed shape 


P.I: Affected plant parts (Mechanical) 

S.I: Aphids (Myzus persicae) 

Other aphids: Aphis malvae, A. gossypii, A. medicaginis, Rhopalosiphum maidis, 

Microsiphum solonifolii 

Most of the cultivated species of Carica papaya are susceptible: C. candamarcensis 

and C. microcarpa 

Other hosts: Cucumis sativus, Cucurbita pepo, C. maxima, Citrullus vilgaris, Luffa 

acutangula, Lagenaria siceraria, Safflower and some ornamental plants. 

Management 

Disease free seedlings 

Rouging and destruction of diseased plants 

Vector control 

Carica cauliflora is resistant 

Weekly sprays with 1% groundnut oil 

20

4. Leaf curl: Tobacco leaf curl virus or Nicotiana virus 10 

Symptoms 

Severe curling, crinkling and distortion of leaves accompanied by vein clearing 

and reduction of leaf lamina 

Leaf margins are rolled downward and inward in the form of inverted cup 

Curled leaves have thickened veins 

Leaves become leathery, brittle and petioles are twisted 

Diseased plants fail to flower or bear any fruits 

In advanced stage, defoliation takes place and growth is arrested 


P.I: Infected plant parts 

S.I: Whitefly, Bamesia tabaci and grafting 

Virus also infects tobacco, tomato, sunhemp, chilli, Petunia, Zinnia, Datura 

stramonium, hollyhock, cape gooseberryetc. 

Management 

Disease free seedlings 

Rouging and destruction of diseased plants 

Vector control with monochrotophos@0.05% or Dimethoate@0.2% or 

metasystox@0.1% 

5. Anthracnose – Colletotrichum papayae (Syn: Gloeosporium papayae or 

Colletotrichum gloeosporioides) 

Symptoms 

Spots on fruits appear as brown superficial discolouration of the skin 

Spots develop into circular, slightly sunken areas and 1 to 3 cm in diameter 

Lesions coalesce and sparse mycelial growth appears on the margins of the spots 

Early fruit infection results in mummification and deformation 

Necrotic spots on leaves and stems 

Older parts are generally highly susceptible 


Excessive moisture 

Older leaves and mature fruits are more susceptible 


P.I: Incipient infection carried by fruits from the field 

S.I: Conidia by wind and rain splash 

Management 

Foliar spray, twice, with carbendazin@0.1% at 15 days interval or 

chlorothalonil@0.2% at 10 – 15 days interval. Last spray to be given 10 days 

before harvest 

Fumigation of fruits with benzylisothiocyanate and coating with groundnut oil 

controls post harvest spots and rots 

21

LECTURE 4 

DISEASES OF BANANA 

1) Yellow Sigatoka leaf spot - Mycosphaerella musicola (I.S: Cercospora musae) 

Black sigatoka – Mycosphaerella fijiensis 

First observed in Java in 1902 

Epidemic in 1913 in plains of Sigatoka in FIJI Island 

Wide spread in nature and occurs is many countries except in Egypt and Israel 

In India - states of Assam, Tamil Nadu, Karnataka & A.P 

Significant losses are caused by destruction of the foliage and reduction of the 

functional leaf surface of the plant 

Symptoms 

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

leaves 

Small spindle shaped spots on foliage with greyish centre and yellowish halo 

running parallel to veins. 

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 

If the fruit is nearing maturity at the time of heavy infection, the flesh ripens 

unevenly and individual bananas appear undersized and their flesh develops a buff 

pinkish colour, and store poorly. 


Survives on dry infected leaves on the field soil and primary infection takes place 

through ascospores in the infected plant debris. 

Secondary spread through wind borne conidia and ascospores 

Infection takes place through stomata on the lower surface of young leaves. 

Surface moisture is necessary for release of both conidia and ascospores. Hence the 

disease is severe in moist weather. 

Favourable conditions: High humidity, heavy dew and rainy weather with temp 

above 21 0 C. Soils with poor drainage and low fertility favour the disease incidence. 

Thick planting, presence of weeds and increased number of suckers in a mat promote 

disease development. 

22

Management 

Removal and destruction of affected leaves followed by spraying with BM (1%) + 

linseed oil (2%) 

Prevent water accumulation around the plant and go for periodical weeding. 

Spray zineb@0.25% or copper oxy chloride@0.3% suspended in mineral oil 

Spray chlorothalonil@0.2% or carbendazim or thiophanate methyl@0.1% or 

mancozeb@0.25% along with spreading agent. Wetting agent such as teepol or 

sandovit added at the rate of 1ml/lit of water. 

2) Panama wilt- Fusarium oxysporum f.sp. cubense 

First reported from Australia in 1876 

The popular variety Gros Michel, mostly grown for export quality fruits, was most 

susceptible and had to be replaced with Cavendish bananas which were resistant 

Severe on Rastali variety (Amrutapani), Gros Michel, Monthan Karpooravalli 

Symptoms 

Conspicuous symptoms ususlly appear on atleast 5 months old banana plants, 

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

Symptoms initially seen in older plants in a mat and on older leaves. 

The earliest symptoms are faint yellow streaks on the petiole of oldest, lower most 

leaves 

Affected leaves show progressive yellowing, break at the petiole and hang down 

along the pseudostem. 

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

severe cases. (Heart leaf alone remains upright) 

Varying degrees of longitudinal splitting along pseudostem are often observed 

Light yellow to dark brown vascular discolouration of pseudostem. Usually the 

discolouration appears first in the outer or oldest leaf sheath and extends upto 

the pseudostem 

The fungus grows and blocks the vascular system resulting in wilting of the plant. 

Affected plants give characteristic odour of rotten fish. 

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. Hoever the pathogen does not infect the 

fruits. 

Roots of diseased rhizomes are frequently blackened and decayed 

23


Soil conditions like texture and structure, fertility level, temperature, drainage, 

cultural operation will greatly influence the disease incidence and spread in the 

field. 

Survival and growth of fungus are generally greater in acidic or light textured soils 

than in clay or alkaline soils with high calcium content. Sturated poorly drained 

soils have greater incidence. 

Insect injuries and wounds and infestation of burrowing nematode, Radopholus 

similis, predispose the disease 


Survive as chlamydospores in soil or in infected rhizomes 

Spread as conidia through irrigation water or through root contact 

Management 

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 or crop rotation with rice. 

Application of lime (1-2 kg/pit) to the infected pits after chopping of the plants 

parts. 

Dipping of suckers in carbendazim (0.1%) solution before planting 

Soil drench with 0.1% carbendazim or 0.01% Vapam 

Growing resistant Cavendish varieties, viz., Basrai (Vamanakeli), Poovan 

(Karpura chakkarakeli), Moongil 

Dwarf varieties are generally resistant 

3) Moko disease / Bacterial wilt 

C.O: Ralstonia solanacearum (Pseudomonas or Burkholderia) 

First recorded in Guyana in 1840 in Moko plantain 

In India, first reported from West Bengal in 1968 

Symptoms 

Symptoms start on rapidly growing young plants 

The youngest three to four leaves turn pale green or yellow and collapse near the 

junction of lamina and petiole. 

Characteristic discoloration of vascular strands, wilting and blackening of suckers. 

Vascular discolouration (pale yellow to dark brown or bluish black) is concentrated 

near the centre of the pseudostem, becoming less apparent on the periphery 

Greyish brown bacterial ooze is seen when the pseudostem of affected plant is cut 

transversely 

A firm brown dry rot is found within fruits of infected plants (characteristic 

symptom) 

Death of whole plant occurs under severe infection. 

Pathogen: 

Moko disease is caused by race 2 of Ralstonia solanacearum which infects Musa and 

Heliconia. Cells of bacterium are rod shaped and motile by 1-4 flagella. They are 

Gram negative. 

24

Disease cycle 

P.I: Through diseased plant suckers used for planting. 

S.I: Through irrigation water, implements and by insects. 

Management 

Grow resistant varieties like poovan and monthan. 

Adopt 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 diluted with water in 1:3 ratio. 

Crop rotation (3 years rotation with sugarcane or rice) & providing good drainage 

Allow fallow period or flooding during off-season 

Fumigation of infected site with Methyl Bromide or chloropicrin. 

Spray systemic insecticide to prevent transmission of disease to healthy plants. 

Biocontrol with Pseudomonas fluorescens 

4) Erwinia rhizome rot: Erwinia caratovora sub.sp. caratovora or Erwinia 

chrysanthemi 

Symptoms 

Affected plants show discolouration and soft rotting of rhizomes and suckers. The 

affected plants have scanty roots with dark brown lesions and necrotic tip. 

In many cases, the pseudostem tips over breaking across the rotted stems 

particularly at the ground level. 

Mature plants seldom show above ground symptoms until the disease is well 

advanced. Such plants may produce small sized fruits which may fail to emerge 

from the shoot tip. 

Infected plants can be pushed over easily and are very susceptible to wind damage. 

In severely infected soil newly planted rhizomes may rot and fail to sprout. 

When young plants are infected, a dark brown necrosis appears in the lamina of the 

older leaves. Later the plant becomes stunted and yellow. 

As the rhizome becomes infected, pockets of dark water soaked areas develop. 

Infection may result in the production of cavitieswhich resemble root borer tunnels. 

Disease cycle 

P.I: Through diseased plant suckers used for planting and infested soil. 

S.I: Through irrigation water, implements and by insects. 


Prevalence of high temperature during initial stages of crop growth. 

Growing susceptible varieties like, vamanakeli, basrai and tella chekkarakeli 

Management 

Avoid planting susceptible varieties during periods of high rainfall or in water 

logged soils in problematic areas 

Maintain proper soil aeration by intercultivation 

Ensure that only healthy suckers are planted 

Restrict ratoon to one or wo based on disease incidence 

Crop rotation with rice or sugarcane 

25

Remove and destroy infected plants along with roots 

Dip the suckers in copper oxy chloride (5g/lt) + monochrotophos (2.5ml/lt) 

solution. 

Drench the infected suckers with bleaching powder (25g/lt) solution 

5) Bunchy top / Curly top / cabbage top /strangles disease 

Bunchy top virus or Banana virus - 1 or Musa virus - 1 

First reported from Fiji in 1889 in Cavendish varieties 

Around 1940, introduced into India from Srilanka through cyclone 

Banana bunchy top virus is a ss DNA virus with single isometric particles 

Symptoms 

Prominent dark green streaks on the petioles and midrib along the leaf veins 

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

line (Morse code) 

Marginal chlorosis and curling of leaves 

Petioles fail to elongate 

Leaves are reduced in size, chlorotic, stand upright and become brittle and are 

crowded at the top (Bunchy top) and shoe dark green streaks with ‘J hook’ shape 

near the midrib. 

Flowers display mottled and streaked discolouration 

Plants show marked stunting 

Disease cycle 

P. I. Through infected plant suckers. 

S. I. By Banana aphid, Pentalonia nigronervosa 

Reservoir hosts: Cucumus sativus, C. melo, Catharanthus roseus, Gynura 

aurantiaca, Colocasia esculenta, Amomum subulatum and Elettaria cardamom 

Management 

Adaptation of strict quarantine measures 

Eradication of all infected suckers by spraying with kerosene or by injecting 

herbicide, 2, 4-D 

Use of only certified banana suckers for planting 

The new crop should be regularly inspected and the diseased plants destroyed as 

soon as noticed. 

Vector control with systemic insecticides, Viz., Phosphomidon @ 1ml/lt or Methyl 

demeton @ 2 ml/lt 

26

6) Banana Mosaic / Infectious chlorosis / Heart rot: Cucumber mosaic virus (ss 

RNA virus) 

Symptoms 

Typical mosaic-like or discontinuous linear streaking in bands extending from 

margin to midrib (Mosaic) 

Leaf size is reduced and leaves are malformed. 

Chlorosis of newly formed leaves (Infectious chlorosis) 

Rotting of heart leaf and leaf sheaths in severe cases (Heart rot) which progress 

into the pseudostem and plant dies. 

Diseased plants do not reach maturity 

Disease cycle 

P.I: Infected suckers 

S.I: Aphis gossypii, A. maydis 

Reservoir host: Cucumis sativus 

Management 

Use of disease free suckers for planting 

Dry heat treatment of suckers at 40 0 C for 1 day 

Avoid growing cucurbits as intercrop 

Vector control with Methyl demeton or dimethoate@ 0.2% at 3 – 4 weeks interval 

7) Banana bract mosaic: Banana bract mosaic virus (BBMV) 

Symptoms 

Symptom expression is clearly seen in Monthan and plantain group of banana 

The disease is characterized by development of black streak on petiole, yellow or 

pinkish colouration on pseudostem and mosaic like purple spindle shaped 

streaks on the bract. 

In severe cases, pink streaks continue on the lower surface of the midrib. 

Suckers exhibit unusual reddish brown streaks at emergence and separation of leaf 

sheath from central axis. 

Leaves cluster at the crown region and leaf sheath separates from the central axis. 

Clustering of leaves at the crown with a ‘travellers palm’ appearance, elongated 

peduncle and half filled hands are other characteristic symptoms. 

Disease cycle 

P.I: Infected suckers 

S.I: Aphids and planting material 

Among the Monthan group, Nendran and Robusta are severely damaged 

Management 

Use of disease free suckers for planting 

Dry heat treatment of suckers at 40 0 C for 1 day 

Avoid growing cucurbits as intercrop 

Vector control with Methyl demeton or dimethoate@ 0.2% at 3 – 4 weeks interval 

27

DISEASES OF POMEGRANATE 

1) Cercospora leaf spot – Cercospora punicae 

Symptoms 

Light zonate brown spots appear on the leaves and fruits. 

Black and elliptic spots appear on the twigs. 

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

Such infected twigs dry up. 

In severe cases the whole plant dies. 


P.I: Diseased plant debris 


Management 

Pruning and destruction of destruction of diseased twigs. 

Application of thiophanate- methyl 0.1% or chlorothalonil 0.2% or mancozeb 0.2% 

2) Anthracnose – Colletotrichum gloeosporioides 

Symptoms 

Small, regular to irregular dull violet or black spots on the leaves 

Spots surrounded by yellow margins 

Infected leaves turn yellow and drop off 

Small irregular lesions on the fruit 

Reduction in market value 


Severe during August-September 

High humidity and temp ranging from 20 to 27 o C 

28

Management 

Spray carbendazim@0.1% or Thiophanate-methyl @0.1% or mancozeb@0.2% at 

fortnightly intervals 

3) Bacterial leaf spot - Xanthomonas axonopodis pv. punicae 

Symptoms 

Small irregular water soaked spots appear on the leaves. 

Small, deep red spots of 2-5 mm dia. with indefinite margins on leaf blade 

Leaves distorted and malformed 

Severely infected young leaves shed 

The bacterium attacks stem, branches and fruits also. 

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

Girdling and cracking of nodes 

Branches break down 

Brown to black spots on the pericarp of fruit with L or Y shaped cracks 

Spots on fruits are raised with dark brown lesions of indefinite margins on the 

surface 


P.I: Infected cuttings 

S.I: Wind splashed rains 

The bacteria infect through wounds and stomatal openings. 

Management 

Clean cultivation and strict sanitation in orchard 

Spray B.M @1% along with antibiotic 

29

LECTURE 5 

DISEASES OF GRAPE 

1. Powdery mildew: Uncinula necator (I.S: Oidium tuckeri) 

Losses in yield of fruits may be upto 40-60%. In addition to loss of yield, infected 

berries tend to be higher in acid content than healthy fruits and are unsuitable for wine 

making. 

Symptoms 

The disease attacks the vines at any stage of their growth. All the aerial parts of the 

plant are attacked. Cluster and berry infections usually appear first. 

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

Early berry infection results in shedding of affected berries. 

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

of skin of the berries. Often infected berries develop a net-like pattern of scar 

tissues. 

Powdery growth mostly on the upper surface of the leaves. 

Malformation and discolouration of affected leaves. Leaf lesions appear late and 

doesn’t cause much damage 

Discolouration of stem to dark brown. 

Pathogen: The mycelium is ectophytic and produces bilobate or multilobate 

appressoria. The conidiophores are simple, multiseptate and erect bearing a chain of 

3-4 conidia. Under Indian conditions, perfect stage of the fungus is not found. When 

the mating types are present cleistothecia can form on all infected tissues during later 

part of the growing season. 


Through dormant mycelium and conidia present in the infected shoots and buds. 

Through air-borne conidia 


30

Cool dry weather 

Maximum temperature in the range of 27-31 0 C with R.H. upto 91% favour disease 

incidence (November and December). Increase of R.H. by 1% increased disease 

incidence by 2.4% and increase of temperature by 1 0 C decrease the disease by 

4.4%. 

Management 

Clean cultivation of vines or removal and destruction of all diseased parts 

Dustings of vines with 300 mesh Sulphur (1 st when new shoots are 2 weeks old, 2 nd 

prior to blossoming, 3 rd when the fruits are half ripe). 

Prophylactic spray with B.M. 1% or Lime sulphur at dormant stage delays 

development of disease by decreasing initial inoculum. 

Spray 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 1 st week of March 

Grow resistant varieties like Chholth Red, Chholth white, Skibba Red, Skibba 

White, etc. 

2. Downy mildew: Plasmopara viticola 

Economic importance 

Since 1875, this disease caused heavy losses in France to wine industry. 

It led to discovery of B.M. by Prof. Millardet in 1885. 

Symptoms 

Sym,ptoms appear on all aerial and tender parts of the vine. Symptoms are more 

pronounced on leaves, young shoots and immature beries. 

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

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

appears. 

Affected leaves become, yellow and brown and gets dried due to necrosis 

Premature defoliation. 

Dwarfing of tender shoots. 

Infected leaves, shoots and tendrils are covered by whitish growth of the fungus. 

White growth of fungus on berries which subsequently becomes leathery and 

shrivels. Infected berries turn hard, bluish green and then brown. 

Later infection of berries results in soft rot symptoms. Normally, the fully grown or 

maturing berries do not contact fresh infection as stomata turn non-functional. 

No cracking of the skin of the berries. 

Pathogen: P. viticola is a biotroph. The intercellular mycelium of the fungus is 

coenocytic, thin-walled, hyaline, and produce spherical or pear shaped haustoria. 

31

Sporangiophores arise from hyphae under high humid conditions. The branching of 

the sporangiophores is at right angles to the main axis and at regular intervals. From 

the apex of each branch 2-3 sterigmata arise and bear lemon shaped, papillate 

sporangia. Sporangial germination may be through zoospores or by germ tube based 

on humidity and temperature. 

Spread and survival 

Sporangia or zoospores by wind, rain etc. 

Oospores present in the infected leaves, shoots and berries. Also as dormant 

mycelium in infected twigs. 


Optimum temperature : 20-22°C 

Relative humidity : 80-100 per cent 

Management 

Collect and burn fallen leaves and twigs 

Sanitation of the orchard 

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

spacing 

Pruning (April- may & September and October) and burning of infected twigs 

Grow resistant varieties like Amber Queen, Cardinal, Champa, Champion, 

Dogridge and Red Sultana 

The disease can be effectively managed by giving 3-5 prophylactic sprays with 1% 

B.M or Fosetyl -Al (Aliette) 0.2% or metalaxyl + mancozeb 0.3 to 0.4% or 

Azoxystrobin or Dimethomorph 

Chemical -5 sprays with 1% B.M. 

1 – Immediately after pruning of vines 

2 - When new flush formed (3-4 weeks after pruning) 

3 – Before buds open 

4 - When bunches or berries have formed 

5 – During growth of shoots 

32

3. Anthracnose / Birds eye disease: Elsinoe ampelina (I.S: Gloeosporium 

ampelophagum or Sphaceloma ampelinum) 

It is especially serious on new sprouts during rainy season. Among various foliar 

diseases of grapevine in India, anthracnose has longest spell spread over the period 

from June to October 

Symptoms 

Visible on leaves, stem, tendrils and berries. 

Young shoots and fruits are more susceptible than leaves. 

Circular, greyish black spots or red spots with yellow halo appear. 

Later the centre of the spot becomes grey, sunken and fall off 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 (Birds eye 

symptom). In warm and wet weather pinkish spore mass develop in the centre of 

the spots 

Mummification and shedding of berries. 

Etiology 

Anamorph – Gloeorporium ampelophagum, produce hyaline, single celled conidia. 

Teleomorph - Elsinoe ampelina, Produces hyaline 4 celled ascospores 


Survives as dormant mycelium in the infected stem-cankers 

Secondary spread is by means of conidia formed in the leaf and other plant parts 

which are easily disseminated by wind and splashed rain. Continuous drizzle of 

rain for 2-3 days encourages the disease. No infection can take place in the absence 

of rain. Wind associated with warm atmosphere (temp.) and heavy rains favour the 

disease spread. 


Warm wet weather 

Low lying and badly drained soils. 

Anab-e-shahi is susceptible. 

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%. 

33

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

Isabella. 

4. Alternaria leaf spot: Alternaria vitis 

Symptoms 

Appearance of patches mostly along the margin of leaves 

Individual spots appear rarely in the middle of the leaves 

In the initial stage, minute, yellow spots appear on the upper surface of leaves 

Later, spots enlarge and form brownish spots with concentric rings in them 

In severe cases of attack, leaves dry completely and defoliation occurs 


Survives as mycelium or conidia in infected plant debris 

Spreads through air borne conidia 


High humidity 

High rainfall and dew 

Heavy dosage of N2 fertilizers 

Management 

Destruction of crop debris 

Selection of disease free seed 

ST with mancozeb@2g/kg seed 

Foliar spray of mancozeb@0.25% 

5. Bacterial leaf spot: Pseudomonas viticola 

First reported from S.V. Ag. College, Tirupati (1969 – 70). 

Anab-e shahi & Thomson seed less varieties are highly susceptible 

Symptoms 

Symptoms appear on foliage and twigs 

Initially yellowish, circular, translucent spots develop along the midrib and veins 

of leaves 

Necrotic areas along midrib & veins is the characteristic symptom 

Leaves turn yellow, shriveled and shed pre-maturely 

Disease cycle 

P.I: Mainly from infected twigs. Bacterium survives in the soil on plant debris. 

S.I Through wind splashed rain. 

Management 

Prune out and destroy infected plant debris 

Spraying antibiotics like streptomycin 100 ppm along with copper fungicides 

34

6. Rust: Phakopsora vitis 

GLR is common throughout South-East Asia and other parts of the world. Cultivar 

Black prince is highly susceptible 

Symptoms 

The presence of clustered, small, yellow to orange, powdery spores on the 

underside of mature grapevine leaves. Small, dark spots also appear on the upper 

surface. 

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

defoliation occurs 

The disease eventually lead to weakening of the vine due to poor shoot growth 

Reduction in quantity and quality of fruit. 

Disease cycle 

P.I: Teliospores 

S.I: Uredospores 

GLR affects Vitis spp., including commercial and some ornamental grape varieties. 

It has also been found on native Ampelocissus species 

Management 

Spray zineb@0.2% or dust sulphur@25Kg/ha 

35

LECTURE 6 

DISEASES OF APPLE 

1) Scab – Venturia inaequalis 

First reported from Sweden (1819) 

First reported on Ambri variety in Kashmir valley (1935) 

Symptoms 

Scab infections usually noticed on leaves and fruits 

+Affected leaves become twisted or puckered and have black, circular spots on 

their upper surface. 

On the under surface of leaves, the spots are velvety and may coalesce to cover the 

whole leaf surface 

Severely affected leaves may turn yellow and drop 

Scab can also infect flower stems and cause flowers to drop 

Scabby spots on fruit begin as sooty, gray-black lesions and may have a white or 

red halo 

The lesions later become sunken and tan and may have spores around their 

margins 

Infected fruit become distorted and may crack, allowing entry of secondary 

organisms 

Severely affected young fruit may drop 


P.I: Ascospores formed from pseudothecia 


Management 

Clean cultivation 

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

Ambred 

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 

• 1 st spray - Silver tip stage - 0.2% captofol (or) 0.3% captan 

• IInd spray pink bud - 0.2% captan (or) 0.3% mancozeb 

• IIIrd spray at petal fall - 0.5% carbendazim 

• IVth spray - after 10 days - 0.2% captan 

• Vth spray - 15 days after - mancozeb 0.3% 

36

• Fruit set - 0.15% captafol 

2) 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 narrower 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 


P.I: Mycelium in diseased vegetative buds and fruits 


Management 

Sanitation of orchard 

Pre-bloom spray of lime sulphur (1:60) 

Spray dinocap@0.05% or Wettable S 

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

Yantarka Altaskya, Dolgoe (Crab apple cultivars) 

3) Fire blight of apple 

Symptoms 

All above ground tissues including blossoms, fruits, shoots, branches, and in the 

rootstock near the graft union on the lower trunk are affected 

Blossom clusters and young shoots: Blossom symptoms are first observed 1-2 

weeks after petal fall. The floral receptacle, ovary, and peduncles become water 

soaked and dull, grayish green in appearance. Later these tissues shrivel and turn 

brown to black. 

Shoot symptoms: Tips of shoots may wilt rapidly to form a "shepherd's crook”. 

Leaves on diseased shoots often show blackening along the midrib and veins, 

before becoming fully necrotic. 

Numerous diseased shoots give a tree burnt and blighted appearance 

37

Bark on younger branches becomes darkened and water-soaked. At advanced 

stages, cracks will develop in the bark, and the surface will be sunken slightly. 

Wood under the bark will show streaked discolorations. Similar symptoms can be 

observed in infected apple rootstocks 

Infected small immature fruit becomes water soaked, then turn brown, shrivel, 

turn black and cling to the tree for several months after infection 

Droplets of milky coloured, sticky ooze may appear on infected parts which 

usually turns brown on exposure to air 


The bacteria overwinter at the margins of the cankers and possibly in buds and 

apparently healthy woody tissue 

Insects such as bees, flies and ants spread the bacteria to the flowers 

Management 

During winter prune out and burn blighted twigs, branches and cankers, and even 

whole trees, at about 30cm below the point of visible infection 

Disinfect the tools after each cut with 10% sodium hypochlorite 

Insect control 

Resistant varieties 

Dormant sprays with copper sulphate or bordeaux mixture, however, bordeaux 

mixture or streptomycin are the only effective blossom sprays 

4) Crown gall – Agrobacterium tumefaciens 

38

Symptoms 

Small outgrowths on stem and roots 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 

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 K1026) (No gall) applied to fresh wounds. 

39

LECTURE 7 

DISEASES OF CHILLI 

1) Damping off – Pythium aphanidermatum, P. debaryanum, P. ultimum, Fusarium 

and Rhizoctonia 

Disease of nursery beds and young seedlings resulting in reduced seed germination 

and poor stand of seedlings. 

25-75% loss 

Symptoms 

Pre-emergence damping off: Seedlings disintegrate before they come out of soil 

surface. This is known as pre-emergence damping-off which results in poor field 

emergence / poor seed germination. 

Post-emergence damping off is characterised by development of disease after 

seedlings have emerged out of soil surface but before the stems are lignified. 

Lesion formation at collar region 

Infected areas appear brown and water soaked 

Plants shrivel and collapse as a result of softening of tissues 

Infected stems become hard, thin (Wire stem symptoms) and infected seedlings 

topple. Disease appear in patches both in nursery and field beds. 

Disease cycle 

P.I: Oospores in soil or plant debris 

S.I: Zoospores through irrigation water 


Heavy rainfall 

Excessive and frequent irrigation 

Poorly drained soil and close spacing 

High soil moisture with temp around 25-30 o C 

P. aphanidermatum, prefer temp above 20 0 C 

P. debaryanum, P. ultimum, prefer cool temp (

Severely infected leaves defoliate 

Infection of growing tips leads to necrosis of branches from tip backwards 

Necrotic tissues appear grayish white with black dot like acervuli in the center 

Shedding of flowers due to the infection at pedicel and tips of branches 

Fruit symptoms 

Ripe fruits are more liable for attack than the green ones 

Small, circular, yellowish to pinkish sunken spots appear on fruits 

Spots increase along fruit length attaining elliptical shape 

Severe infection result in the shrivelling and drying of fruits. 

Such fruits become white or greyish in colour and lose their pungency. 

On the surface of the lesions minute black dot like fruiting bodies called ‘acervuli’ 

develop in concentric rings and fruits appear straw coloured 

The affected fruits may fall off subsequently. The seeds produced in severely 

infected fruits are discoloured and covered with mycelial mat. 

Pathogen: The mycelium is septate and grows both inter and intracellularly in the 

host tissue. The asexual fruiting bodies, acervuli contain many rigid, brown coloured, 

1-5 septate setae. A large number of conidia are borne on conidiophores in each 

acervulus which are falcate, unicellular, hyaline having a normally truncated base. 

Disease cycle 

P.I: Infected seeds and diseased crop debris 

S.I: Conidia dispersed by rain splash and wind 


Temp, 28 0 C with RH more than 97% 

Humid weather with rainfall at frequent intervals 

Management 

Collect and destroy all infected plant parts 

Collect seeds only form fruits without infection 

Removal and destruction of Solanaceous weed hosts and infected plant debris 

Seed treatment with captan or Thiram 3-4g/kg 

Spray thrice with captan@1.5% or mancozeb@0.25%. just before flowering, at 

fruit formation stage and 15 days after second spray. 

Resistant varieties: G3, G4, B61, Lorai, etc. 

41

3) Choanephora blight /Wet Rot (Choanephora cucurbitarum) 

Symptoms: 

The pathogen attacks flowers, buds and tender young shoots. 

This disease produces a blossom blight as well as a fruit rot stage and occasionally 

a leaf blight. 

Blossoms exhibit a lack of turgidity as petals begin to wilt. 

Luxuriant growth of the pathogen is seen on infected portion which appears as 

black pin heads or Stiff whisker-like strands of the causal fungus, topped with 

black heads (sporangia) grow off the infected blossoms causing a blossom drop. 

Young fruit may become infected, soften and abort with the black fungal growth 

apparent on the fruit. 

Management: 

A dopt recommended spacing to maintain adequate air circulation. 

Select the seeds from healthy fruits and treat the seed with captan or 

thiram@3g/kg seed 

Spray Mancozeb@0.25% or Copper oxy chloride@0.3% 

Grow resistant varieties like Seoul hot, Liachi-2, AT-Good, etc. 

4) Mosaic complex 

Chilli mosaic virus, Potato Virus Y, Cucumber Mosaic Virus (CMV), Tobacco 

Mosaic Virus (TMV) and Tomato spotted wilt virus 

Symptoms: Symptoms vary with the infected virus 

TMV: 

• Backward bending of petiole 

• Raised blisters and mottled areas of light and dark green areas on the foliage 

• Leaves point towards ground. 

• Necrotic spots on stem. 

• Fruit ripens unevenly and is reduced in size 

CMV 

• Downward curling along with midrib 

• Most plants exhibit some degree of "shoestringing" (narrowing of the leaves) in 

addition to stunting, yellowing, and whitish spotting of the leaves. 

• Fruit may be small and distorted. 

PVY 

• Vein banding 

• Small, crinkled leaves. 

Spread 

Sap transmissible (TMV) 

Aphids: Myzus persicae, Aphis gossypii, A. craccivora 

42

Tomato Spotted Wilt Virus. The disease affects late-maturing pods, reducing yield. 

This virus occurs throughout temperate and subtropical regions and infects a diverse 

group of plant species from tomatoes and peppers to peanuts, lettuce, pineapple and 

many ornamentals. The virus is transmitted from diseased to healthy plants by thrips. 

The virus overwinters in perennial weeds. 

Symptoms: The disease is most commonly recognized by the symptoms on the fruit. 

Both green and red fruit can be infected. Infected green pods display small, offcolored 

spots. Red fruit exhibit patches of yellow that never turns red. Other fruit 

symptoms include chlorotic and necrotic spotting, concentric ring patterns, and 

distortion. Foliage symptoms include general mosaic, chlorotic ring spots, and 

deformation. In some cultivars, the shoot terminals die and leaves defoliate. When 

new growth develops, it is severely distorted. Plants infected at an early age are 

stunted severely. 

Managemet 

Select healthy seed for planting 

Crop rotation with non-hosts 

Control perennial weed hosts. 

Rogue out and destroy infected plants in early stages of infection 

Gow disease tolerant varieties like Bhagyalakshmi, Bhaskar and LCA 305 

Soak the seed in Trisodium orthophosphate (Na3PO4) solution (150g/lt) for 30 min 

prior to sowing 

Growing barrier crops like sorghum or maize (2-3 rows) around chillies to reduce 

the disease incidence. 

Cover the seed bed with nylon net or paddy straw 

Spray seedlings in nursery with monochrotophos@1.5ml/lt or dimethoate@2ml/lt 

before transplantation in the main field. 

Apply carbofuran granules@10-12kg/acre in the main field or spray with 

monochrotophos@1.5ml/lt or dimethoate@2ml/lt 

5) Powdery mildew – Leveillula taurica 

Usually seen from December - February 

Symptoms 

White powdery coating appears mostly on the lower surface 

Sometimes the powdery coating can also be seen on the upper surface. 

Correspondingly on the upper surface yellow patches are seen 

Severe infection results in the drying and shedding of affected leaves. 

Powdery growth can also be seen on young fruits, and branches. 

Diseased fruits do not grow further and may drop down. 

Disease cycle 

P.I: Dormant mycelium in the infected crop debris. 



Cool dry weather favours conidial germination 

High RH favours disease development 

43

Management 

Spraying wettable S@0.3% or Dinocap or Carbendazim or Tridemorph 0.1%. 

6) Cercospora leaf spot – Cercospora capsici 

October - November and continues up to February 

Symptoms 

Circular spots with brown margins appear on leaves 

The spots enlarge and coalesce with others 

The central portion of the spot becomes white and the leaves turn yellow and 

defoliate 

Sometimes central portion of spot drops off 

Spots also appear on stems and twigs as dark brown, irregular lesions with whitish 

centers 

In severe cases die-back of twigs occur 

Disease cycle 

P.I: Dormant mycelium in infected plant debris, infected seeds and volunteer 

plants 

S.I: Wind borne conidia. 

Management 

ST with carbendazim@2g/kg seed 

Spray carbendazim@0.1% or Difolaton@0.3% at 15 days interval 

7) Bacterial leaf spot: Xanthomoas campestris pv. vesicatoria 

Symptoms 

Leaves, fruits and stems are affected 

Lesions on leaf begin as circular, water soaked spots 

Spots become necrotic with brown center with chlorotic borders 

Enlarged spots may develop straw coloured centres 

Lesions are slightly raised on lower leaf surface 

Severely spotted leaves turn yellow and drop 

Raised brown lesions appear on fruits 

Narrow elongated lesions or streaks may develop on stems 


The bacterium is seed borne 

Spread by rain splash 

Management 

Seeds should be collected from healthy fruits, 

Seed treatment with copper oxychloride 2g/kg seed. 

Spray twice with Agrimycin (100 ppm) or plantomycin (200ppm) along with 3g 

COC per litre of water at 15 days interval 

44

1) Little leaf – Phytoplasma 

LECTURE 8 

DISEASES OF BRINJAL 

Symptoms 

Small or little leaves. 

The petioles are so short that the leaves appear to be sticking to the stem. 

Affected plants have narrow, soft, smooth and yellow shorter leaves. 

Newly formed leaves are much shorter. 

Internodes of the stem are also shortened. 

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

giving the plant a bushy appearance. 

Mostly there is no flowering but if flowers are formed they remain green. 

Fruiting is rare, if any fruit is formed, it becomes hard, tough and fails to mature. 

Young fruit turns necrotic, get mummified and cling to the plant 

Pathogen: the disease is caused by phytoplasma having ovoid to spherical body 

which is concentrated in the phloem sieve tubes. 

Spread 

The pathogen perenneates in weed hosts 

Jassid - Hishimonas phycitis. The disease is also transmitted by Emposca 

devastans, however, it is a less efficient vector. 

The varieties pusa purple long and selection T are highly susceptible 

Collateral hosts: Datura fastuosa, D. stramonium, Vinca rosea, Argemone 

mexicana, chilli, tomato and tobacco 

Management 

Tolerant variety: Pusa Purple Round, Pusa purple cluster and Arka sheel 

Destruction of affected plants 

Eradication of solanaceous weed hosts 

Spray methyl demeton, 2 ml/l or Malathion 3 ml/l or soil application of phorate 

granules. 

Seed dip in teracyclines (10-50ppm) 

2) Bacterial wilt – Ralstonia solanacearum 

Symptoms 

Sudden wilting and death of infected plants is the characteristic symptom. The 

petiole of older leaves droop down and the leaves show epinasty symptoms 

accompanied by yellowing and stunting of whole plant. 

45

Typical browning of vascular tissues of roots and stems can be seen 

From cross sections of infected plants whitish bacterial exudate comes out. 

Pathogen: the bacterium is Gram negative motile rod having rounded ends with 1-4 

polar flagella. Race 1 of R. solanacearum affects solanaceous plants such as tomato, 

egg plant and many other non-solanaceous plants also. 


The bacterium isboth soil and seed borne in nature and overwinters in infected 

plant parts, in wild host plants and weeds. 

Spread through irrigation water or infested soil and agricultural implements. 


Relatively high soil moisture and soil temperature favour the disease development. 

Management 

Grow resistant varieties like Pant Samrat, Arka Nidhi, Arkas Kashav, Arka 

Neelakantha, Surya and BB 1, 44 & 49. 

Crop rotation with non solanaceous hosts 

Green manuring with Brassica species (Biofumigation) 

Soil solarization with a transparent polyethylene sheet (125 µm thick) for 8-10 

weeks during March-June 

Biological control with Pseudomonas fluorescens, P. glumae, P. cepacia, Bacillus 

sp. & Erwinia sp. 

3) Phomopsis fruit rot or blight – Phomopsis vexans (P.S: Diaporthe vexans) 

The disease is severe in tropical and sub-tropical areas of the world. In India, it was 

reported in 1935 in Gujarat. The pathogen attacks foliage and fruits, but the latter 

phase is more destructive. 

Symptoms 

The plants are attacked at all stages of growth, producing damping-off symptoms 

in nurseries and collar rot on young plants 

On leaves, circular to irregular, clearly defined grayish brown spots having light 

centers appear. The diseased leaves become yellowish in colour nd may drop off. 

Several black pycnidia can be seen on older spots. 

The lesions on stem are dark brown, round to oval and have grayish centers where 

pycnidia develop. At the base of the stem, the fungus causes characteristic 

constrictions leading to canker development and toppling of plants. 

On fruits, small pale sunken spots appear which on enlargement cover entire fruit 

surface. These spots become watery leading to soft rot phase of the disease. A large 

number of dot like pycnidia also develop on such spots. 

The infection of fruit through calyx leads to development of dry rot and fruits 

appear black and mummified. 

Pathogen: The mycelium of the pathogen is septate and hyaline becoming dark with 

age. Pycnidia are submerged and later becoming erumpent with a prominent ostiole. 

Conidia are produced on simple to branched conidiophores and are of 2 types: Alpha 

conidia, which are sub cylindrical and beta conidia, which are filiform and curved. 

Role of beta-conidia in the epidemiology of the disease is not very clear. The perfect 

46

stage produces perithecia in which asci with 8 hyaline, bicelled, ellipsoid-fusoid 

ascospores are produced which are usually contricted at septum. 


P.I: Pathogen is seed borne and also survives in plant debris as mycelium and 

pycnidia. 

S.I: Conidia dispersed through rain splashes, irrigation water, agricultural tools and 

insects. 


High relative humidity coupled with higher temperatures favour disease 

development. Maximum disease development takes place at about 26 0 C under wet 

weather conditions with 55% R.H. 

Management 

Removal and destruction of diseased crop debris 

Practicing crop rotation and summer ploughings helps in reducing initial inoculum. 

Use of disease free seed 

Hot water treatment of seed at 50 0 C for 30 minutes 

Seed treatment with thiophanate methyl at 1g/kg seed 

Spray twice with thiophanate methyl or carbendazim@0.1% at 20 days interval. 

DISEASES OF BHENDI 

1) Yellow vein mosaic: Bhendi Yellow vein mosaic virus or bhendi vein clearing 

virus 

Symptoms 

Yellowing of the entire network of veins in the leaf blade (vein clearing) is the 

characteristic symptom. In severe infections the younger leaves turn yellow, 

become reduced in size and the plant is highly stunted. 

In a field, most of the plants may be diseased and the infection may start at any 

stage of plant growth. 

47

Infection restricts flowering and fruits are not formed, if formed, turns smaller, 

harder and rough. Loss in fruit yield ranges from 50-100% based on disease 

incidence 

Disease cycle 

P.I: Infected plant parts 

S.I: The virus is transmitted by the whitefly, Bemisia tabaci. 

Management 

Tolerant varieties: Parbhani Kranti, Pusa savani, Janardhan, Haritha, Arka 

Anamika and Arka Abhay 

The disease spread can be restricted by spraying Monocrotophos, 1.5 ml/l. 

2) Cercospora leaf spot: Cercospora malayensis, C. abelmoschi 

C. malayensis causes brown, irregular spots and C. abelmoschi causes sooty 

black, angular spots on lower surface of leaves 

Both the leaf spots cause severe defoliation and are common during humid season. 

Disease cycle 

P.I: The fungi survive through conidia and stromata on crop refuse in soil. 

S.I: Air borne conidia 

Management 

Spray mancozeb or zineb@0.2% or carbendazim@0.1% for disease control a 

month after sowing and repeat at fortnightly intervals based on disease incidence. 

3) Powdery mildew: Erysiphe cichoracearum 

Symptoms 

Grayish powdery growth occurs on the under as well as on the upper surface of the 

leaf causing severe reduction in fruit yield. 

Management 

Dust finely ground sulphur at 30 kg/ha or spray wettable sulphur@0.3% or 

Dinocap@0.1% , three to four times at 15 days intervals. 

48

LECTURE 9 

DISEASES OF POTATO 

1) Late blight – Phytophthora infestans 

Usually infection starts in 6 weeks old plants 

First reported from Andes mountains of South America 

In India, the disease was first reported in Darjeeling district in India (1880) 

Symptoms 

Initially starts from leaf tips or margins and spread inward 

Small faded green patches on upper surface of leaf which turn into brown spots 

Downy growth of the pathogen on subsequent lower surface 

Progressive defoliation and collapse of plants under favourable conditions 

Water soaked stripes on stem which becomes 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 

P.I: Infected potato tubers or oospores 

Collateral host: Tomato (Lycopersicon esculentum), Pepper and egg plant. 

S.I: Conidia dispersed by wind or water 


Cool moist conditions 

RH: >90% and with suitable temperature (12-24 0 C) 

Dutch rules 

Night temperature below the dew point for 4 hours or more 

Night temperature not below 10°C 

Cloudiness on the next day. 

Rainfall at least 0.1mm on the following day 

Management 

Regulatory measures 

Select healthy tubers for planting 

Delayed harvesting 

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

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

Kufri Sherpa, etc. 

Resistant sources: Solanum demissum and S. phureja 

49

Prophylactic measures 

Metalaxyl (0.1%) or Mancozeb (0.25%) or chlorothalonil (0.2%) or 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 

2) Common scab – Streptomyces scabies 

Important in Punjab and Himachal Pradesh 

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 characterized by lesions with depressions beneath the tuber 

surface 

• Raised scab appears as cushion like warty lesions 


P.I: Soil and infected tubers 

S.I: Soil, water, wind blown soil and infected tubers 

Pathogen enters through unsuberized lenticels or wounds 

Epidemiology 

Soil pH (5.2-8.0) 

Soil temperature of 20-22 0 C 

Low soil moisture 

Management 

Use of disease free tubers 

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

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 

3) Wart – Synchytrium endobioticum 

Losses seen in temperate regions 

In India, the disease is restricted to Darjeeling 

Symptoms 

Host cells at the point of infection are hypertrophied 

White granular swellings form on the eyes of tubers 

White tumour like outgrowths, called as warts, develop on stems and tubers 

As the crop matures, warts become black and rot 

50

Infected auxillary bud or the leaf is transformed into cock’s comb like greenish 

yellow outgrowth 

Disease cycle 

P.I: Resting sporangia in soil 

S.I: Zoospores dispersed by water 


High soil moisture 

Optimum temperature of 21 0 C (12 to 28°C) 

Slightly acidic to neutral pH 

Management 

Strict quarantine measures 

Grow resistant varieties such as kufri Jyoti, kufri Jeevan and kufri Muthu 

4) Black leg (Soft rot) – Erwinia caratovora subsp. caratovora 

Introduced into India through seed stocks from Italy 

Symptoms 

Disease occurs in two phases – Blackleg of shoots and soft rot of tubers 

Blackleg 

Plants are stunted with a stiff, erect growth habit. 

Foliage becomes chlorotic and the leaflets tend to roll upward at the margins. 

Stems of infected plants exhibit an inky black decay. 

The base of the stem is often completely rotted. 

Plants may wilt. 

In relatively dry soil, only the pith may show blackening 

Soft rot symptoms 

Soft rot include rotted tissues that are wet, cream to tan in color, and soft. 

Rot begins on the tuber surface and progresses inward. 

Infected tissues are sharply delineated from healthy tissue by dark brown or black 

margins. 

51

Shallow necrotic spots on the tubers result from infections through lenticels 

Rotting tissue is usually odorless in the early stages of decay, but develops a foul 

odor as secondary organisms invade infected tissue. 

Soft rot also infects wounded stems and roots 


Survive in diseased and contaminated tubers 

Spread through contaminated soil, tubers and maggot flies 


High humidity (94 – 100%) 

Temperature (21 – 29 0 C) 

Late blight and Fusarium tuber rot infections predispose soft rot 

Management 

Remove all debris from warehouses and disinfect the walls with formaldehyde or 

copper sulphate 

Avoid wounding of plants and storage organs 

Products to be stored should be dry, and the humidity and temperatures of 

warehouses should be kept low 

Crop rotation with cereals 

Crop should be planted in well drained areas and at sufficient distances to allow 

adequate ventilation 

Insect control 

Dip cut seed pieces of potato in a solution of Streptocycline 100ppm and CuSo4 

40ppm for 30 min 

5) Brown rot – Ralstonia solanacearum 

First bacterial disease reported in India 

First recorded in 1891 from Pune district of Maharashtra 

Also referred as bacterial wilt or ring disease or bangle blight 

Occurs in Deccan and Central plateau, Assam, West Bengal, Orissa, hills of Uttar 

Pradesh and Nilgiris 

Symptoms 

Wilting, stunting and yellowing of foliage followed by collapse of entire plant 

Browning of xylem in vascular bundles 

Stems, petioles of the lower leaves and roots become brown and on cutting of 

infected materials slimy mass of bacteria oozes out 

Brown ring is formed in the tubers due to discolouration of vascular bundles (ring 

disease) 

Formation of pockets or cavities around vascular bundles in the pith and cortex 

When pressed slimy bacterial ooze emerge. 

The tubers may rot at harvest or during storage. 


Survive in infected soil and seed tubers 

Spread through wind blown soil and water 

Infection occurs through wounds 

52


High soil temperature (25-35 0 C) 

Soil moisture >50% 

Management 

Crop rotation with maize or soybean for 3 yrs 

Use disease free tubers for sowing 

Deep summer ploughing 

Treat seed tubers with 0.02% streptocycline for 30 min giving 4mm deep sharp cut 

Disinfestation of cutting knives with sodium hypochlorite (10%) or mercuric 

chloride 

6) Viral diseases 

a) Mild mosaic/Interveinal mosaic – (Potato virus X) PV X 

Symptoms 

Often referred as latent potato mosaic 

Light yellow mottling with slight crinkling on potato plants 

Interveinal necrosis of top foliage 

Stunting of diseases plants 

Leaves may appear slightly rugose where strains of PV Y combines 

Spread 

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

cutting knives, farm implements. 

Root clubbing of healthy and diseased plants in field 

Management 

Disease free seed tubers for planting 

Rouging of diseased plants 

b) Severe mosaic – Potato virus Y (PV Y) 

Also called potato leaf drop streak 

Symptoms 

Chlorotic streaks on leaves which become necrotic 

Necrosis of leaf veins and leaf drop streak 

Interveinal necrosis and stem/petiole necrosis 

Plant remain stunted in growth 

Rugosity and twisting of the leaves occurs in combination with PV X and PV A 

53


Infected tubers 

Spread by aphids, Myzus persicae and Aphis gossypii 

Management 


Rouging of diseased plants 

Aphid control 

c) Leaf roll – Potato leaf roll virus 

Symptoms 

Upward rolling of leaves, which have a stiff leathery texture 

Plants stunted and have a stiff upright growth 

Phloem necrosis of tubers in some varieties 

Spread 

Infected seed tubers or by aphids 

Management 


Aphid control 

7) Potato spindle tuber – Viroid 

Symptoms 

Plants appear erect, spindly and dwarfed 

Leaves small, erect and leaflets dark green 

Tubers elongated with tapering ends 

Tuber eyes are numerous and more conspicuous 

Spread 

Infected seed tubers 

Mechanically spread by knives used to cut seed tubers 

54

Also transmitted by pollen and seed and contaminated mouth parts of 

grasshoppers, flea beetles and bugs 

Management 

Use of PSTVd free potato seed tubers 

Disinfestation of cutting knives 

55

1) Early blight – Alternaria solani 

LECTURE 10 

DISEASES OF TOMATO 

Symptoms 

Small, isolated, scattered pale brown spots on the leaf 

Fully developed spots are irregular, brown to dark brown in colour, and with 

concentric rings inside the spot 

Spots coalesce to form large patches resulting in the leaf blight 

Lowest leaves are attacked first and the disease progresses upwards 

In severe attacks the entire plant may be defoliated 

Zonate lesions may also develop on stems and petioles, which break at the point of 

infection 

Brown spots are also seen on calyx 

Slightly dark, sunken, round to irregular lesions on fruit at the calyx end 

Disease cycle 

P.I: Mycelium or conidia in infected plant debris 

S.I: Conidia dispersed by wind, water or rain splashes 

Epidemiology 

Dry warm weather alternating with the intermittent rains 

Reduction in plant vigour and senescence 

Management 

Maintain proper vigour of the plant 


Removal and burning of diseased crop debris 

Mancozeb@0.25% or chlorothalonil@0.2% or Zineb@ 0.25% spray at weekly 

intervals 

2) Stemphylium leaf spot – Stemphylium lycopersici 

Symptoms 

Small brownish black specks on the underside of leaves 

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 the plant 

56

Disease cycle 

P.I: Mycelium or conidia in infected plant debris 



Warm, moist weather 

Management 

Rouging and burning of infected plant debris 

Foliar application of mancozeb@0.25% 

3) Septoria leaf spot – Septoria lycopersici 

Symptoms 

Less vigorous plant are usually affected 

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 

Stems and flowers are sometimes attacked 

Fruits are rarely attacked 

Disease cycle 

P.I: Infected plant debris or seed or Solanaceous weeds 

S.I: Rain splash, wind-blown water, insects and on hands and clothing's of tomato 

pickers 


High humidity or persistent dew at 25 0 C 

Moist weather with intermittent showers 

Management 

Crop rotation with non hosts 

Destroy infected crop debris 

ST with Mancozeb or zineb@2g/kg seed 

Spray zineb@0.2% or mancozeb@0.2% at 10 d interval 

Tomato line PI 422397 is resistant 

4) Tomato spotted wilt – Tomato Spotted Wilt Virus (TSWV) 

Symptoms 

Symptoms vary among hosts and in a single host species 

Stunting is a common symptom of TSWV infection 

Chlorotic or necrotic rings form on the leaves of many infected hosts 

Pale red or yellow areas with concentric circular marking in the normal red 

skin of ripe tomato are formed 

Discoloration of seed 

Thickening of veins and bronzing of young leaves 

Growing tips may die-back and terminal branches may be streaked 

Affected plants may have a one sided growth habit or may be entirely stunted and 

have drooping leaves, suggesting a wilt 

57

Mode of spread and Survival 

Thrips, Frankliniella schultzii, Scirtothrips dorsalis. 

Adult thrips transmit the disease, only when the larvae acquire the virus from 

infected plants. 

Collateral hosts: Acanthospermum hispidum, Aster sp., Boerhaavia diffusa, 

Chrysanthemum sp., Cleome gynandra, cowpea, Dahlia variabilis, egg plant, 

French bean, Gerbera sp., groundnut, Lagasca mollis, lettuce, marigold, pea, 

pepper, pineapple, potato, Trianthema portulacastrum, water melon and Zinnia 

elegans. 

Management 

Removal and destruction of infected plants & weed hosts 

Vector control with dimethoate or methyl demeton at 10 days interval 

Growing Crotolaria juncea as a barrier crop reduces vector migration 

Spraying of sorghum or coconut leaf extract 

5) Tomato Mosaic – Tomato mosaic virus 

Symptoms 

The virus causes a light and dark green mosaic mottle with raised dark green area 

and distorted crinkled younger leaves. 

The plants are stunted and leaves may be distorted to a fan leaf or tendril like 

The symptoms vary depending on the strain of the virus. Some strains cause 

yellowing or leaf mottling which may also affect the fruit. 

Some other strains produce streak symptoms consisting of longitudinal necrotic 

streaks on stem or petioles. Such diseased plants are killed 

Necrotic sunken lesions also appear on fruits and sometimes internal necrosis or 

browning of mature fruit occurs. 


The virus is seed borne and is sap transmissible 

The virus is spread easily by man and implements in cultural operations or by 

animals and by leaf contact. Infection is through roots 

Collateral hosts: Capsicum annuum, C. frutescens, Chenopodium armanticolor, C. 

murale, C. quinoa, Cucumis melo, C. sativus, Cucurbita pepo, Datura metel, 

Lycopersicon pimpinellifolium, Nicotiana benthamiana, N. clevelandii, N. 

glutinosa, N. megalosiphon, N. rustica, N.tabacum, Petunia hybrida, Physalis 

floridana, P. peruviana, Vigna ungiculata, brinjal, cowpea, French bean and night 

shade 

58

Management 

All collateral hosts in the vicinity should be destroyed before planting new crop 

Rouge out and destroy diseased plants 

Virus free seed should be obtained and used for sowing 

Soak the seeds in 10% Tri-sodium orthophosphate for 15 to 20 minutes prior to 

sowing 

Heat treatment for 2-4 days at 70 0 C 

Cross protection of tomato seedlings by inoculating with mild strains 

Field workers should avoid using tobacco products while working in the field 

6) Bacterial fruit canker: Clavibacter michiganense subsp. michiganense 

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 

Light coloured streaks on stems and petioles at the joints 

Cracks develop in streaks and form cankers 

Slimy bacterial ooze through the cracks in humid weather 

Small, shallow, water soaked, white spots on fruits 

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

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

Vascular discolouration 

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

cankers 


Survive in or on seeds and on plant debris in soil 

Spreads through the seed and Solanaceous weeds such as Solanum nigrum 

Epidemiology 

Soil temperature of 28 0 C and humid weather 

Management 

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

eradicates the bacterium from the seed. 

Hot water treatment of seed at 52 0 C 

Three year crop rotation 

Protective sprays with COC and streptomycin sulphate 

Soil solarization 

59

7) Root knot nematode – Meloidogyne sp. 

Root knot is the most important group of phytonematodes and was first recorded in 

green house vegetables in England in the year 1855. Of the four predominant species 

of Meloidogyne, M. incognita and M. javanica are commonly found in the tropics, 

whereas M. arenaria is more common in the sub-tropics. M. hapla is common in the 

temperate region and can occasionally found in the cooler uplands of tropics. 

Symptoms 

Formation of galls on host root system is the primary symptom 

Roots branch profusely starting from the gall tissue causing a ‘beard root’ 

symptom 

In severely infected plants the root system is reduced and the rootlets are almost 

completely absent. The roots are seriously hampered in their function of uptake 

and transport of water and nutrients 

Plants wilt during the hot part of day, especially under dry conditions and are often 

stunted. 

Seedlings infected in nursery do not normally survive transplanting and those 

surviving have reduced flowering and fruit production 


Juveniles and eggs survive periods of moisture stress in a state of anhydrobiosis 

Irrigation water and soil adhering to animal feet and implements help in 

dissemination of juveniles and eggs of nematodes 

Management 

Crop rotation with graminaceous hosts 

Inclusion of non-preferred hosts like mustard, sesame, maize, wheat, etc., in the 

cropping system 

Intercropping of marigold with tomato reduces nematode population 

Nursery should be raised in nematode free sites or fumigated beds 

Deep ploughing of infested fields during summer. Three summer ploughings at 10 

days interval reduces juvenile population 

Flooding the field for prolonged periods 

Use of biocontrol agents like Paecilomyces lilacinus (egg parasite) 

Nursery bed treatment with metham sodium (Vapam)@25ml/m 2 or 

Carbofuran@0.39g a.i/m 2 

Bare root dip treatment in EC formulation of systemic pesticides like Dimethoate 

or Phenemiphos for 6-8 hours before transplantation 

Grow resistant varieties like Hissar Lalit and PNR-7 

Integration of three summer ploughings or use of treated nursery with spot 

application of carbofuran @1 kg a.i/ha at transplanting stage have been found 

successful to manage nematode population in tomato. 

60

LECTURE 11 

DISEASES OF CRUCIFERS 

1) Club root of crucifers or Finger and toe disease: Plasmodiophora brassicae 

Fairly severe in hilly regions on cabbage, cauliflower and other crucifers. Fields once 

infested with the club root pathogen remain so indefinitely and become unfit for 

cultivation of crucifers. 

Symptoms 

Infected plants have pale green to yellowish leaves initially. Later, infected plants 

show wilting in the middle of hot, sunny days, recovering during the night 

Stunting of above ground parts and reduction in size of heads 

Characteristic symptoms become apparent in advanced stage of root infection as 

spindlelike, spherical, knobby, or club-shaped swellings. 

The swellings may be few, or they coalesce and cover the entire root system 

Disease cycle 

P.I: Soil borne resting spores, which survive for longer periods in soil (10yrs.) 

Collateral hosts: Broccoli, Brussels sprout, cabbage, cauliflower, Chinese cabbage, 

mustard, raddish, turnip 

S.I: Resting spores or zoospores carried through irrigation water or by root contact 


It occur at a temp range of 12-27 0 C (25 0 C) 

High soil moisture 

Neutral to acidic soils 5-7.0 pH 

Management 

Use of seedlings from disease free fields 

Plant cabbage and other susceptible cruciferous crops in well drained fields that 

have a pH slightly above neutral (usually about pH 7.2) 

Crop rotation does not work since pathogen persists long in soil. 

Add hydrated lime to soil to increase pH to 7.2 ( 6weeks before planting @ 

2.5T/ha) 

Avoid excess irrigation 

Treat the soil of seed bed areas with chloropicrin, methyl bromide or vapam two 

weeks before planting. Drenching soil with a solution of Brassicol 

(Pentachloronitrobenzene) 

61

2) Downy Mildew – Peronospora parasitica 

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

Symptoms 

Small purplish brown spots on under surface of leaves 

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

the under surface. 

The spots coalesce and the leaves shrivel and dries up prematurely 

In cabbage, these spots expose the heads to soft rot 

Cauliflower curds look brownish at the top 

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

downy growth of fungus 

Disease cycle 

P.I: Oospores in infected plant parts or in soil 

S.I: Wind borne sporangia 

Management 

Destruction of infected plant debris 

Avoidance of thick sowing and excessive moist conditions 

Spray metalaxyl@0.25% or COC@ 0.3% or Mancozeb@ 0.2% at 10 days interval 

3) Powdery mildew – Erysiphe polygoni 

Symptoms 

Seen on cabbage & cauliflower 

Symptoms 

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

Finally the mildew may cover the entire surface. 

Disease cycle 

P.I: Mycelium in infected plant debris 

S.I: Wind borne conidia. 

Management: Application of Dinocap@0.2% 

4) Alternaria leaf spot: Alternaria brassicola, A.brassicae, A.raphani 

Common on cabbage, cauliflower and mustard. 

Symptoms 

Spots are small, dark coloured 

They enlarge, soon become circular & 1mm. in diameter 

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

Spots develop concentric rings 

Finally the spots coalesce leading to blighting of leaves. 

62

The fungus is seed borne and cause shriveling of seeds and poor germination 

Linear spots also appear on petioles, stems, pods & seeds 

Disease cycle 

P.I: Mycelium persisting in the seed or as spores on seed or from debris 

S.I: Wind or insect borne conidia 

Management 

Hot water treatment at 50 0 c for 30min 

Seed treatment with agrosan 

Foliar spray with Mancozeb@0.2% or COC@ 0.3% twice 

5) Black rot – Xanthomonas campestris pv. campestris 

Serious on cabbage, cauliflower, knol-khol, mustard, raddish 

Symptoms 

1 st appear near the leaf margins as chlorotic or yellow (angular) areas 

The yellow area extends to veins & mid rib forming characteristic ‘v’ shaped 

chlorotic spots 

Veins and veinlets turn brown and finally black 

The vascular blackening extend beyond affected veins to midrib, petiole and stem 

In advanced stages, infection may reach the roots system and blackening of 

vascular bundles occur 

Bacterial ooze can also be seen on affected parts 

If the infection is early, the plants wilt and die 

If the infection is late plant succumb to soft rot &die 

Disease cycle 

Bacterium is internally seed and soil borne. It also survives on plant debris 

Collateral host: Centella asiatica 

Bacteria enter through stomata of cotyledons. 

Also enters through hydathodes on leaf margin and also through wounds 

S.I: Bacterium through irrigation water or wind splashed rain and also by 

mechanical means 

Management 

ST with Hg Cl2 solution for 30 min or Agrimycin or Aureomycin 0.01% 

Hot water treatment at 50 0 c for 30min, for killing seed borne inoculum followed 

by a 30min dip in streptocycline 100ppm 

Spray Agrimycin-100 or Streptocycline-50ppm at transplanting, curd formation 

and pod formation 

Crop rotation for 2-3 yrs with non cruciferous crop 

Drenching seed bed with 5% formalin or any antibiotic solution in nursery beds 

R.V: Cabbage: Cabaret, Defender, Gladiator, Pusa Muktha 

Cauliflower: Pusa ice, Pusa snow ball-K-I-F, Sel-12 

63

6) White rust – Albugo candida (Syn: Cystopus candidus) 

Symptoms 

White, shiny raised blisters (pustules) on the lower surfaces of leaves, stems & 

flowers. 

Pustules coalesce to form irregular patches 

The epidermis ruptures exposing white spore mass which gives the pustule a 

powdery appearance 

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

and hyperplasia 

Plants malformed beyond recognition 

Disease cycle 

P.I: Oospores in soil and Perennial weeds hosts 

S.I: Sporangia & Oospores carried by wind 

Management 

Sanitary measures 

Crop rotation 

Destruction of weeds 

Spray 0.8% B.M or any copper fungicide 

64

DISEASES OF CUCURBITS 

1) Downy mildew – Pseudoperonospora cubensis 

Host range: Musk melon, Sponge gourd and Bitter gourd etc. 

Symptoms 

Yellow, angular spots appear on upper surface of leaves 

The corresponding lower surface of these spots shows a purplish downy growth in 

moist weather 

The spots turn necrotic with age 

The diseased leaves become yellow and fall down 

Diseased plants get stunted and die 

Fruits produced may not mature and have a poor taste 

Disease cycle 

P.I: Collateral hosts or fungus surviving in plant debris 

S.I: Wind borne sporangia or splashing rain water 

Management 

Destruction of cucurbitaceous weeds around field 

Spray metalaxyl@0.2% or chlorothalonil@0.2% 

Spray zineb@0.3% at 10 days interval 

2) Powdery mildew: Erysiphe cichoracearum, Sphaerotheca fuligena 

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

Bitter gourd is less effected 

Symptoms 

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

parts 

The superficial growth ultimately covers the entire leaf area 

The diseased areas turn brown and dry. This leads to premature defoliation and 

death 

Fruits remain undeveloped and are deformed 

65

Disease cycle 

P.I: Collateral hosts or through Cleistothecia 


Management 

Spray Calixin 0.1% or Karathane @0.2% 

3) Cucumber Mosaic: Cucumber mosaic virus 

Host range: Cucumber, Pumpkin, gourds, Cowpea, tomato, chilli, etc. 

Symptoms 

Leaves curl downwards and become mottled, distorted, wrinkled and reduced in 

size 

Stunting and rosetting of young leaves 

Fruits are often misshapen, mottled, warty and reduced in size 

Fruits may be bumpy or deformed in late infections 


Survive on weeds, ornamentals or other crops 

Transmitted by aphids (Aphis craccivora, Myzus persicae) and spotted and striped 

cucumber beetles 

Collateral hosts: Banana, clover, corn, passion fruit, safflower, spinach, sugarbeet, 

wild cucumber, Commelina communis, C. diffusa, C. nudiflora, Solanum 

elaegnifolium, Phytolacca sp., periwinkle, Gladiolus sp., Impatiens sp. and Phlox. 

Management 

Rogue out infected plants 

Eliminate perennial weed hosts 

Vector control by spraying monochrotophos or phosphamidon, 1.5 ml per liter of 

water 

4) Cercospora leaf spot: C. citrullina, C. melonis, C. lagenarium 

Common on watermelon, muskmelon 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 large blotches 

The leaf may dry and die presenting the leaf a scorched appearance 

Stems and fruits are also attacked 

66

Disease cycle 

P.I: Collateral hosts or plant debris 


Management 

Maintain good soil drianage and good aeration between vines 

2 - 3 protective sprays with zineb@0.2% 

67

LECTURE 12 

DISEASES OF BETELVINE 

1) Wilt – (Phytophthora, Sclerotium and Fusarium) 

Symptoms 

Sclerotium 

Collar region is usually infected 

White mycelial growth over the infected area of stem on which small mustard seed 

like sclerotia appear 

Shredding of infected bark 

Vine wilts and totally dries off 

Phytophthora parasitica 

The disease is characterized by darkening of basal stem. Soon the wine wilts 

accompanied by yellowing of leaves and drooping of vines, starting from tip 

downwards. 

Infection from soil level spread upwards reaching 2 nd or 3 rd internode. 

Roots of affected plants are discoloured, rotted, starting from smaller roots and 

spreading to the stem 

Management 

Destruction of dead vines 

Long crop rotation with non hosts 

Deep summer ploughing 

Green manuring before planting 

Application of Trichoderma viride, 2kg mixed in 50 kg of FYM 

Drench the soil with 1% BM 

2) Anthracnose/Leaf spot/Marginal blight: Colletotrichum capsici 

Symptoms 

Light to dark brown irregular spots on leaves surrounded by diffuse chlorotic halo 

Marginal leaf tissue becomes black, necrotic and gradually spreads towards the 

centre 

Circular, black lesions may girdle the stem culminating in death of the vine 

Management 

Spray 1% BM or COC@0.3% at 15 days interval 

68

1) Purple blotch – Alternaria porri 

LECTURE 13 

DISEASES OF ONION 

Symptoms 

Minute whitish dots on the leaves with irregular chlorotic areas on tip portions 

Circular to oblong, concentric velvety rings appear in the chlorotic area 

Sometimes yellow halo is seen around lesions 

Spots coalesce and leaves die from tip backwards 

Diseased leaves break at point of infection & hang down 

Infection also seen on outer scales of bulb, seed stalk and neck 

Severely infected crop dries up 

Bulbs become dry and papery 


P.I: Plant debris and seed bulb 



Warm humid weather with rains or heavy dew 

Management 

Select disease free bulbs for planting 

ST with thiram @3g/kg seed 

Spray mancozeb@0.2% or chlorothalonil@0.2% 

2) Smudge – Colletotrichum circinans 

Symptoms 

Chiefly a disease of scales of bulb. Red scaled onions are usually resistant to the 

smudge due to the presence of protocatacheuic acid and catechol 

Damping off in seed bed under wet and warm conditions 

Disease appears at all stages and also during storage and transportation 

Sub-cuticular, dark green to almost black smudge appear on the bulb, neck or 

green leaves that are clinging to bulb after digging 

Circular lesions with concentric rings of dark stromata and mycelium appear on 

leaves 

Small, sunken and yellow lesions on inner scales 

Pinkish mass of fungal growth on lesions under humid conditions 

69


P.I: Soil and on infected onions as stromata 



Wet soils with a temperature of 26 0 C 

Management 

Resistant varieties: Nasik red, Pusa Ratna, Pusa Red 

Protection of bulbs from rains after harvest 

Dry bulbs properly before storage by hot air at 37 – 48 0 C 

Spray zineb or captan @0.2% before harvest of crop 

3) Smut – Urocystis cepulae 

Symptoms 

Fungus attacks cotyledons of young plants soon after their emergence causing 

dark, elongated eruptive spots 

On older leaves, the lesions may extend from base to the tip and appear as blisters 

Lesions develop into thickened areas of several mm in size 

Lesions burst open releasing masses of black smut spores 

Severely affected plants killed within 3-4 weeks of emergence 

Surviving plants are stunted with stout, brittle, distorted leaves bearing lesions 

throughout their length 

Numerous blisters appear on leaves and bulb scales of mature plants which rupture 

to expose masses of black powdery spores 


P.I: Spore balls in infected soil 

S.I: Wind blown soil and surface drianage water, onion bulbs and onion transplants 


Optimum temperature of 10-20 0 C 

Plant is susceptible for 2-3 weeks from the DOS 

Management 

ST with thiram@3 g/Kg seed 

Crop rotation and use of disease free seedlings 

Cultivar, Hardy white bunching is resistant 

Spray with captan or ferbam @0.2% along with a sticker 

70

DISEASES OF BEANS 

1) Anthracnose – Colletotrichum lindemuthianum 

Symptoms 

All the above ground parts are affected at any stage of crop growth. However, the 

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. When the infection is severe, the affected plants wither off. 

Black, sunken, circular spots of varying sizes appear on pods with bright red, 

yellow or orange margins 

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

pathogen. The border of these spots appear raised 


P.I: Through seed and collateral hosts 

S. I: Conidia by splashing rain water or air borne conidia 

Host range: All vegetable beans and cowpea, mungbean, blackgram etc. 

Management 

Use healthy seed for planting 

Seed treatment with Carbendazim@2g/kg seed 

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

@2Kg/ha at 7-10 days interval 

2) Rust 

On Beans: Uromyces phaseoli typica 

On cowpea and others: U. phaseoli vignae 

On dry bean: Uromyces appendiculatus 

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

Symptoms 

The symptoms mostly appear on leaves, though often they are found on petiole and 

stem of some hosts 

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 and appear in groups 

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

black. 

Diseased leaves may wither or fall off under severe infection 

Pathogen 

Uredospores are echinulate, oval and yellowish brown in colour and the teliospores 

are dark brown coloured, elliptical and ovate, pedicillate, smooth walled, single celled 

with warty papillae at the top. 

71


P.I: Survives through teliospores in cooler regions and on collateral hosts 

S.I: Wind borne Uredospores 

Host range: French beans, green gram, black gram and cowpea 

Management 

Adjust sowing dates to avoid severe infection of plants in the field 

Protect the crop with mancozeb or zineb @ 2 kg/ha or wettable sulphur @0.3% 

3) Yellow mosaic: Bean Yellow Mosaic Virus, Mungbean yellow virus or Phaseolus 

virus-2 (ss DNA virus) 

Symptoms 

Bright yellow patches appear on leaves. Yellow areas alternate with dark green 

areas of the leaf blade. 

Younger leaves show more severe mottling and chlorosis. 

Leaves completely turn yellow and gradually becomes necrotic 

Plants are stunted and flower and pod set is reduced 

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

undersized seeds 


P.I: Collateral hosts 

S.I: Whitefly, Bemisia tabaci 

Not transmitted by sap, seed and pollen 

Host range: French bean, Soybean, Red gram, Xanthium strumarum, Eclipta alba, 

etc. 

Management 

Remove collateral hosts and destroy 

Use resistant varieties 

Spray metasystox@0.1% for vector control 

4) Common bean mosaic virus/ Green mosaic – Bean common mosaic virus (ss 

RNA) 

Symptoms 

Affects only beans (Phaeolus vulgaris & other Phaseolus species) 

Symptoms vary according to the variety of bean affected, time of infection and 

environmental conditions 

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

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

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

Diseased plants produce fewer pods which are smaller in size 

Seeds become smaller, malformed and aborted 


Seed, sap, graft and aphid transmissible. Infected seeds are primary means of 

spread. 

72

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

persicae and Brevicoryne brassicae transmit the virus in a non-persistent manner 

Management 


Vector control with insecticides 

73

LECTURE 14 

DISEASES OF COCONUT 

1) Ganoderma basal stem rot– Ganoderma lucidum, G. applanatum 

Most serious and destructive disease of coconut. Present in the districts of 

Srikakulum, Visakhapatnam, Vizianagaram, East and West Godavari districts. 

A recurring loss of Rs. 10 lakhs occur every year in A.P. alone. The disease is 

severe in lighter soils and on young palms. 

Symptoms 

The fungus infects the roots and spreads upwards killing the entire root system 

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

months 

Younger leaves remain green for sometime 

Tree become barren due to suppression of inflorescence 

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

The cortical tissues disintegrate and stem turn brown. 

Extensive rotting of roots and peeling of stem tissues 

In advanced cases the fungus produces the fruiting structures (brackets) along the 

sides of the basal trunk 

Diseased tree dies in about two years 

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. 

Disease cycle 

P.I: The fungus is soil borne (Basidiospores) 

Wide host range: Mango, jack, citrus, Arecanut, coffee and tea 

S.I: Through irrigation water and by root contact (Mostly from March-August) 

Management 

Preventive measures 

Dig isolation trenches of about 50cm wide and 1m deep, 2-3 m away from diseased 

palm to prevent spread of fungus 

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

Trichoderma viride 

74

Incorporate green manure crops like sunhemp and Sesbania for moisture retention 

and multiplication of antagonistic fungi 

Avoid deep ploughing or digging which are likely to injure roots 

Arrange separate irrigation to each tree to prevent spread of fungus 

Apply FYM (200 kg) and neem cake (5-10 kg) to each tree during June – July 

months 

Also apply 2 kg superphosphate and 3 kg MOP in two splits, one in July and other 

in November 

Apply 40 liters of 1% BM in basin of each tree, yearly once, during August – 

September 

Curative measures 

Destroy infected palms 

Root feeding with tridemorph (6ml in 25 ml of water), 3-4 times an year, in early 

stages of infection 

Control bark eating caterpiller 

2) Bud rot - Phytophthora palmivora 

First reported by butler in 1906 

Coconut and toddy palm (Borassus flabellifer) suffer badly 

Also infects Palmyrah & Arecanut. 

Datepalm is immune to the disease 

Bud rot affects the palms at various stages of growth. 

As the name indicates, the ultimate effect is rotting of terminal bud due to infection 

in or near the bud. 

Symptoms 

Severe on young palms 

Yellowish green discoloration 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 

The leaves and sheath in the central spindle fall off leaving an outer whorl of green 

leaves 

The withered central shoot can be pulled out very easily from the crown 

The central crown may rot and in few months the tree may wilt 

Young nuts fail to mature and fall 

Disease cycle 

P.I: Through dormant mycelium oospores or chlamydospores carried over summer 

months on the host debris. With the onset of monsoon rains, the fungus becomes 

active producing cottony mycelium that infects tender host tissue. 

S.I: Through sporangia with numerous zoospores which spread rapidly in the rain 

water or sporangia spread through wind and insects also 


High R.H., Temperatures of 18-20 0 C, presence of insect wounds and heavy 

rainfall aggravates the disease 

75

Management 

Cutting and burning of badly infected palms. 

If the disease is detected early remove the infected portions and protect with 

Bordeaux paste (Tree surgery) 

Spray copper fungicides (B.M@1% or COC@0.3%) after on set of monsoon to 

prevent infection 

Keep a mixture of CuSO4 + NaCl (1: 3-5) parts in a cloth bag in the crown or 

above bud 

3) Stem bleeding – Ceratocystis paradoxa 

Syn: Ceratostomella paradoxa, Ophiostoma paradoxa 

Symptoms 

Characterized by reddish brown ooze from the cracks near the base of the trunk (2- 

3 cm above soil line). 

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

Infection can occur any where on the trunk. 

The tissues, except vascular bundles, below infected patch show yellowish brown 

discolouration and decay 

Large cavities are formed in diseased stem from which yellowish to whitish fluid 

oozes out 

Growth of affected palms is arrested and yield reduced 

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. 

Disease cycle 

P.I: Perithecia and chlamydospores in cracks and cavities of infected stem 

S.I: Conidia dispersed by irrigation water, insects, wind 


Heavy rainfall followed by drought 

Cracks and insect wounds on stem 

Physiological imbalances 

Poor fertilization and poor maintenance of orchard 

Damage by Diocalandra and Xyleborus beetles 

Management 

Avoid any mechanical injury to the stem 

76

Provide proper drainage during rainy season 

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

paste 

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

coal and sawdust 

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

Along with 50kg of organic manure, apply 5 kg neem cake containing the 

antagonistic fungi, Trichoderma to the basin during September 

Coconut stem boring insects should be controlled by applying Carbaryl 50% WP 

on the trunk at 3g per liter 

4) Tatipaka disease – Phytoplasma 

The disease was first observed during the year 1952 in the village ‘Tatipaka’ of East 

Godavari District. Since then reported from in and around of ‘Razole’ of East 

Godavari district. 

Symptoms 

Plants between 25 – 60 years are most susceptible 

Development of abnormally large crown with dark green inner leaves and higher 

yield 

The palms continues 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 improper unfolding of leaflets 

Leaves turn pale and bend abnormally 

Leaves shed pre-maturely 

Affected tree produces smaller bunches with atrophied barren nuts 

Nuts get atrophied become spongy and round and contain no kernel (Copra). 

Severely damaged palms are barren with sickly crowns and slight tapering trunk 

Such trees never recover but die in few years 

Management 

Remove and destroy affected trees 

Avoid using nuts from infected tree for raising seedlings 

Avoid transport of nursery seedlings from infected areas 

5) Grey blight – Pestalotiopsis palmarum 

Symptoms 

Disease symptoms develop in mature leaves of outer whorl 

77

Minute yellow spots surrounded by a grayish margin appear on leaflets. Gradually, 

the centre of the spots turns grayish white with dark brown margins and a yellow 

halo. 

Spots coalesce into irregular necrotic patches 

Complete drying and shrivelling of leaf blade occur giving a blighted or burnt 

appearance. 

Large number of globose or ovoid black acervuli appears on the upper surface of 

affected leaves. 

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. 

Disease cycle 

P.I: Conidia in plant debris 

S.I: Conidia carried by wind splashed rain water 

Management 

Remove older affected leaves and burn 

Apply heavy disease of potash and improve drainage condition of soil 

Spray foliage with BM@1% COC or captan @0.2% 

1) Bunch rot: Marasmius palmivora 

DISEASES OF OILPALM 

Symptoms: 

Strands of mycelium are seen spreading over the bunch surface in initial stages 

Mycelium is profuse at the back of the bunch. 

Mycelium grows over the fruit surface and penetrates the mesocarp and leads to 

wet rot. 

Disease spreads rapidly within 2 to 3 months after initiation of monsoon rains. 

Management: 

Crown cleaning by removing aborted and dried bunches and inflorescences. 

Spraying of Carbendazim 0.1% or Bordeaux mixture 1%. 

2) Spear rot: Phytoplasma disease 

Spear rot is an endemic disease in Kerala state. 

Symptoms: 

Disease is characterized by chlorosis of young whorl of leaves followed by 

necrosis. 

Rotting of spear leaves 

Reduction is leaf size 

78

As the disease advances the trunk gradually tapers. 

Emergence of inflorescence is arrested leading to loss in productivity. 

Spread: 

The disease is infectious, vector borne and lethal. 

Management: 

Avoid obtaining seedlings from infected areas to healthy areas. 

Tetracycline injection 500ppm to trunk reduces the disease. 

Rougueing of affected plants. 

Planting of barrier trees to isolate the infection source of other palms. 

3) Curvularia leaf spot - Curvularia lunata, C. geniculata 

Symptoms 

Small circular translucent yellow spots appear on both the leaf surfaces 

Lesions turn dark brown with sunken centre and yellowish orange halo 

A narrow rim of raised tissue with oily appearance is produced around the lesions 

Persistence of primary lesions within the dead tissue is a diagnostic feature for 

distinction from other leaf spots. 

Management 

Prophylactic spray with Thiram @ 2g/lt 

79

LECTURE 15 

DISEASES OF TEA 

1) Blister blight of tea – Exobasidium vexans 

Symptoms 

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

red shiny blisters 

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

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

Leaves become curled and distorted 

First flush of 2-3 young leaves are attacked 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 35°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 210g COC + 210g 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 

DISEASES OF COFFEE 

1) Coffee rust/Oriental leaf disease – Hemileia vastatrix 

Severe epidemics in Srilanka in 1868 

Symptoms 

The fungus confines itself to the leaf blade, rarely occurs on the berries 

Small, pale yellow spots on the upper surfaces of the leaves usually around the 

margins 

Later masses of orange uredospores appear on the under surfaces 

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 redorange 

in color 

80

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 and host tissue becomes dark 

brown, then black and dries up 

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

leaves 

The damage to the plant is severe when it affects the young flush, causing 

defoliation and considerable reduction in yield 

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. 


P.I: Survive as mycelium or uredospores in infected leaves 

S.I: Uredospores dispersed by wind and water 

Pycnial and aecial stages are not known 


Uredospores germinate only in free moisture 

Thick canopy of shade prevents the ready spread of the spores and thus secondary 

spread of the disease 

Rainy weather and heavy dew 

Severe from July to Dec 

Management 

Spray the bushes once with BM@0.5% or COC@0.25% and subsequently 2-3 

times during monsoon 

Spray Triadimefon@0.05% 

Collect diseased leaves and destroy 

81

DISEASES OF TURMERIC 

1) Rhizome rot – Pythium aphanidermatum, P. graminicolum 

The disease is common in Andhra Pradesh, Karnataka, Kerala and Tamil Nadu. 

Symptoms 

The disease occurs in patches. Infected plants show progressive drying up of the 

leave, which first proceeds along the margins and later the entire leaf dries up 

The root system is adversely affected. It gets reduced leaving few decaying brown 

roots. Infection gradually spreads to rhizomes which begin to rot and become soft. 

The bright orange colour of the rhizome is changed into different shades of brown. 

Disease cycle 

P.I: The fungi survive in soil and infected rhizomes as oospores 

S.I: Spreads through irrigation water as zoospores 

Management 

Crop rotation with non-hosts 

Grow turmeric in light soils with good drainage 

Use disease free rhizomes for planting 

Rhizomes should be dipped in Metalaxyl@2.5g/l or Bordeaux mixture@1% 

solution for 40 minutes 

Drench the soil at root region with captan@2 g or COC@2.5 g or metalaxyl@1 g 

per liter in the initial stages of the disease 

Turmeric varieties, PCT-13 and PCT-14 are resistant to this disease. 

2) Leaf spot – Colletotrichum capsici 

Symptoms 

Fungus attacks only leaves and usually infection is confined to leaf blades and 

occasionally extend to leaf sheaths 

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 4-5cm and breadth of 2-3cm 

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

halo 

Central portion of the spot becomes thin and papery 

Several spots coalesce to form irregular necrotic patches 

82

Disease cycle 

P.I: Infected plant debris 


Management 

Remove and destroy infected plant debris 

Treat rhizomes with COC@0.25% solution 

Spray Carbendazim@0.1% or Mancozeb@0.25%. during Aug-Dec along with 

sandovit@0.5 ml/lt 

Avoid excess shading 

Tolerant varieties: TS-2, TS-4, TS-9, TS-88 

3) Leaf blotch – Taphrina maculans 

Symptoms 

Appearance of large number of spots on both surfaces of leaf 

Spots first appear as pale yellow discolouration which gradually turn to reddish 

brown 

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

patches 


Infected plant debris 

Collateral hosts: Curcuma amada, C. angustifolia 


Temperature of 21-23 0 C with 80% R.H. 

Management 

Collect and destroy diseased leaves 

Spray Mancozeb@0.25% or COC@0.25% at 20 days interval 

Resistant varieties: China (Curcuma domestica) and Jaweli (C. amada) 

83

1) Rhizome rot/soft rot – Pythium sp. 

DISEASES OF ZINGER 

Symptoms 

Rhizome rot of zinger is common in all zinger growing areas. When infection takes 

place through contaminated seed, sprouts fail to grow resulting in pre-emergence 

damping off. 

If the disease strikes after sprouting it manifests itself on the leaves, which turn 

pale green in colour. 

Yellowing is noticed on the top leaves, gradually spreading downwards of the leaf 

blade and leaf sheath along the margin. 

Yellowing is followed by withering and drying of the dead area gradually 

extending to leaf sheath. Dead leaves ultimately drop off and hang down along the 

stem till the entire shoot becomes dry. 

On stem, a translucent brown lesion develop at collar region and later becomes 

water soaked and soft, extends to whole shoots and can be easily pulled out from 

this point. 

Soft rot extends from the collar region to rhizomes which first become discoloured 

and gradually decompose, forming a watery mass of putrifying tissues enclosed by 

tough ring of rhizome. 

The fibrovascular strands are rarely affected. Roots arising from affected rhizome 

undergo rotting and softening. Rotting is also noticed in rhizomes collected from 

infected crop during storage. 

Disease cycle 

P.I: Survive in soil and infected rhizomes as oospores 

S.I: Spreads through irrigation water as zoospores 


Mimegralla flies play a role in the spread of the pathogen 

Management 

Crop rotation for 3-5 years with non-host crops 

Avoid water stagnation 

Collect the seed from disease free plots 

Rhizome treatment with Metalaxyl@0.2% 

Drench the field with COC@0.3% or Metalaxyl@0.2% 

Control the Mimegralla insects by 0.05% methyl parathion 

2) Leaf spot – Phyllosticta zingiberi 

Symptoms 

In A.P., the disease is common during monsoon months. 

Initially disease appears as small, yellowish oval to elongated spots on the leaves 

measuring 0.5 to 1 mm. 

The spots enlarge; turn to white and papery at the centre with dark brown margin 

surrounded by a yellow halo. 

Spots are usually isolated but under humid conditions they coalesce with one 

another developing towards margin forming a big lesion 

84

Black minute pycnidia develop in the white papery centre of the spots which is 

conspicuous in the later stages of the disease. 


Infected plant debris 

Conidia spread by splashing rain 

Management 

Growing zinger in partial shade reduces the disease incidence 

Spray Mancozeb@0.25% or COC@0.25% during monsoon 

85

LECTURE 16 

DISEASES OF MULBERRY 

1) 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 


Mycelium or cleistothecia in infected plant debris 

Wind borne conidia 

Management 

Remove and destroy infected plant debris 

Spray wettable sulphur@0.2% or Dinocap@0.1% 

Waiting period of 15 days after spray may be allowed before harvesting the leaves 

DISEASES OF ROSE 

1) Powdery mildew – Sphaerotheca pannosa var. rosae 

Symptoms 

The infected leaves show grayish powdery fungal growth 

Rolling of leaf margins with the onset of sprouting season 

Affected leaves become curled and distorted 

Badly infected flower buds fail to open 

Infected floral parts become discoloured, dwarfed and dried 


P.I: Mycelium in dormant buds and shoots or as cleistothecia 


Management 

Collect and destroy infected plant debris 

Four sprays with wettable S@0.3% or carbendazim@0.1% or Dinocap@0.1% at 

10 days interval 

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

2) Black spot – Diplocarpan rosae (Anamorph: Marssonina rosae) 

Symptoms 

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 

86

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

pustules 


Pycnidia or ascospores in infected plant debris 

Wind borne conidia 

Management 

Affected parts should be collected and destroyed 

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

the sprouting of the plants till new foliage appears. 

Shade and extensive irrigation should be avoided. 

Resistant varieties: Bebe bune, coronado ,Grand opera, sphinx. 

Radiance - escape infection due to waxy surface 

3) Die-back – Diplodia rosarum 

Symptoms 

Infection starts from the pruned surface of the twigs. 

The infected portion become 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 


Pycnidia present in dead twigs 

Conidia through irrigation water 

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. 

87

1) Rust – Uromyces hobsonii 

DISEASES OF JASMINE 

Symptoms 

Leaves, stems and inflorescence are affected 

Blisters or tumors and other abnormalities may be produced on the infected plant 

parts 

Infected portions become hypertrophied 

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

surface 

Chlorosis & defoliation of leaves under severe conditions 

Yellow or orange coloured cankers on stems and twigs 

Splitting of bark of affected branches and subsequent death of branches 

Infected flower buds are swollen and deformed 

Flower production is highly reduced 

Disease cycle 

P.I: Teliospores in infected plant 

S.I: Wind borne aeciospores 

Pathogen 

Autoecious rust (Demicyclic rust/ Opsis rust) 

Uredial stage is absent 

Pustules are initially yellow (aeciospores) and later turn dark (teliospores) 


Rust initiates in June- July and persists till March 

Management 

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

Spray Oxy-carboxin (plantavax) or Mancozeb @0.2% 

Dust sulphur (20-25kg/ha) or spray tridemorph (0.05%) or triadimefon (Bayleton) 

@ 0.05% 

2) Cercospora leaf spot – Cercospora jasminicola 

Symptoms 

Conspicuous, circular to irregular, reddish brown spots with a darker border and 

whitish centers appear on both the leaf surfaces and other aerial parts of the plant 

Severe infection results in defoliation and die back symptoms 

Flowering is adversely affected 

Management 

Spray carbendazim@0.1% or COC@0.3% 

Monthly sprays of Benomyl or thiophanate methyl @0.1% 

Collect and burn diseased plant debris 

Pari Mullai is moderately resistant 

88

1) Blotch – Septoria chrysanthemella 

DISEASES OF CHRYSANTHEMUM 

Symptoms 

Blackish brown circular to irregular spots on leaves which later form large patches 

covering major portion of the leaf 

Patches are surrounded by chlorotic halo 

Later the centers turn greyish and the leaves remain small and curl 

Dead leaves hang on stem for some time 

Dead leaves hang on stem for some time 


P.I: Infected plant debris in soil 


Management 

Collect and burn diseased plant material 

Spray carbendazim@0.1% 

Tolerant varieties: Alpana, Sarad and flirt 

2) Chrysanthemum stunt - Viroid 

Symptoms 

Small plants with paler plants and flowers 

Some flowers appear bleached and are inferior in quality 

Flowers from diseased plants open 7 t0 10 days earlier than healthy ones 

Axillary buds grow prematurely and produce number of branches and stolons and 

plants are stunted in appearance 

White specks and yellow blotches appear on leaves of some varieties 

Cuttings from diseased plants root poorly 


P.I: Viroid survives in infected plants 

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

taking cuttings and cutting the flowers 

Management 

Use certified Viroid free stocks 

Remove and destroy infected plants 

89

3) Fusarium 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 

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

conditions 


P.I: Soil borne fungus or through cuttings 

S.I: Conidia dispersed through irrigation water 

Management 

Cuttings should be obtained from disease free plants 

Long crop rotation 

1) Wilt – Fusarium solani 

DISEASES OF CROSSANDRA 

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 

90

PATH 372 Diseases of Horticultural Crops

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