plant pathology - agademy · khaira disease of paddy - zn deficiency 2. infectious diseases • a...

PLANT PATHOLOGY

Disease - When there is a harmful deviation from normal functioning of physiological process.

CLASSIFICATION OF PLANT DISEASE

1. Non-infectious diseases • Diseases with which no animate or virus pathogen is associated. • Cannot be transmitted. • No parasite is associated (Non-parasitic diseases).

Ex. Tip rot or Necrosis of mango - B deficiency. Black heart of potato - Oxygen deficiency. Khaira disease of paddy - Zn deficiency

2. Infectious diseases • A specific pathogen is responsible for the diseases. • diseases are infectious, contagious and transmittable

Koch's postulates are: 1. The pathogen must show constant association with the disease. 2. The pathogen must be isolated from the diseased host and grown in pure culture. 3. The pathogen from the artificial culture should be able to reproduce the disease when

inoculated on healthy plant of the same kind. The symptoms produced should be identical with those seen on the plant from which isolation was made.

4. The artificially produced disease should yield the same pathogen on reisolation.

Infectious diseases are often classified according to their occurrence in the following groups - Fungi, Bacteria, Virus, Viroids, Phytoplasma, Spiroplasma, Fastidious vascular bacteria, Nematode.

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FUNGI

Eukaryotic protist, achlorophyllus, nucleated, branched, unicellular or multicellular organisms that may reproduce by the division of vegetative cells, well defined asexual and sexual spores. Body of the fungus is called as 'Thallus'.

GENERAL SYMPTOMS OF FUNGAL DISEASES

1. Damping off • Rotting of seeds and radicle before seedling emergence – Pre-emergence • Rotting of emerged seedlings at ground level resulting in toppling down of seedlings –

Post-emergence • Eg. Damping-off of vegetable - Pythium aphanidermatum P. debaryanum P. ultimum

2. Club root • Modification of roots and rootlets into club shaped swellings due to hypertrophy and

hyperplasia • Eg. Club root of cabbage : Plasmodiophora brassicae

3. Root rot • Disintegration or decay of roots • Eg. Root rot of pulses Macrophomina phaseoina

4. Foot rot • Disintegration of basal part of the stem • Eg. Foot rot in pepper Phytophthora palmivora

4. Collar rot • Collar region of the seedlings rot • Eg. Collar rot of groundnut – Aspergillus niger A.pulveruilentus

5. Stem rot • Leads to rotting Disintegration of the tissues of the stem. • Eg. Stem rot of paddy – Sclerotium oryzae

6. Wilt • Loss of turgidity and dropping of leaves and shoots • Eg: Red gram wilt – Fusarium oxysporum f.sp. udum

7. White rust • White or creamy, shiny irregular pustules seen on the lower surface of the leaves. • Eg. White rust of amaranthus - Albugo bliti


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8. Downy mildew • Mildew growth seen on the lower surface of the leaf and corresponding upper surface are

chlorotic • Eg. Cumbu downy mildew – Sclerospora graminicola

9. Powdery mildew • Small irregular powdery patches are seen on the upper surface of the leaves. • Eg. Powdery mildew of blackgram – Erysiphe polygoni.

10. Leaf spot • Localised necrotic lesions on host leaves. • The spots vary in size, shape and colour

11. Leaf blight • Rapid browning and death of leaves giving a burnt appearance • Eg. Leaf blight of sorghum – Exerohilum tursicum

12. Blast • Spindle shaped spots with grey centre and brown margin appear on leaf (leaf blast) • Blackening of node of the plant (node blast) and neck of the panicle (neck blast) • Eg. Blast of paddy – Pyricularia grisea

13. Anthracnose • Black sunken lesion circular to angular are seen on leaves, cotyledons, stem, fruits, flowers

and pods of plants. • Acervuli the asexual fruiting body is produced in the sunken lesion. • Eg. Anthracrose of bean – Colletotrichum lindemuthianum.

14. Rust • Raised reddish brown (rusty) pustule appear on both surface of leaf, stem etc • Eg. Sunflower rust - Puccinia helianthi

15. Scab • Slightly raised or sunken lesion with cracks on petiole, pedicel, blossom, fruit, leaves and

gives a scabby appearance. • Eg. Scab of apple - Venturia inaequalis

16. Sooty Mould • Superficial dark black sooty growth found on leaf, stem and fruits. • Eg. Sooty mould in mango – Capnodium mangiferae

17. Gummosis • Exudation of gummy substances from infected bark and bark completely rots and dries due

to girdling • Eg. Gummosis of citrus – Phytophthora citrophthora


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18. Sugary disease or Ergot • Exudation of creamy, sticky honey dew like secretion from the infected floret (Sugar

disease). • Long, straight or curved cream to dark brown hard sclerotia replaces the grain in the ear

head (Ergot) • Eg. Pearl millet – Claviceps fusiformis

19. Smut • Seeds in the infected ear head or entire earhead is replaced by a gall (or) sori contain large

number of black colour, smut spores or spore bolls. • Eg. Loose smut of wheat – Ustilago nudo tortice

20. Fruit rot • Rotting of fruit. • The infected portion is converted with mouldy growth. • Eg. Fruit of citrus : Penicillium expansu

21. Die back • Drying of twigs from the tip downward • Eg. Die-back of mango Botrydiplodia theobromae.

22. Bunt • The infected grain are found to be full of sooty black powdery manes of bunt spores

decayed fishy odour. • Eg. Bunt of wheat Tilletia caries.

23. Wart • Wart like protuberances on tubers and stem • Eg. wart of potato Synchytrium endobioticum.

24. Soft rot • Maceration and disintegration of root, bulbs, tubers, fruits and fleshy leaves.

25. Gall • Enlarged sac like growth on stem, leaves, blossoms etc. • Eg. Stem gall in coriander (Protomyces macrosporus).

26. Leaf curl • Distortion, thickening and curling of leaf. • Eg. Leaf curl of peach – Taphrina deformans.


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27. Chlorosis • Loss of chlorophyll giving pale green appearance is the green plant parts.

28. Necrosis • Killing of plant tissue often result in development of brown to black colour.

29. Discolouration • Change in colour of the plant or one or more its pacts

BACTERIA

Bacteria are unicellular, microscopic, chlorophyll less, prokaryotic microorganism reproduce mainly by fission.

SYMPTOMS OF BACTERIAL DISEASES

Plant pathogenic bacteria are basically facultative saprophytes and they enter into the host plant mostly through wounds and natural openings. The important symptoms are

1. Leaf spot • Symptom include the appearance of water soaked, circular or irregular, necrotic spot on

leaves. Sometimes the spots are encircled with a yellow halo. • Dicot - spot is restricted by veins and become angular. • Monocots - spots usually appears as streaks or stripes.

Eg. Bacterial leaf spot in tomato : X. axonopodis. pv. vesicatoria, Angular leaf spot in cotton : X. a. pv. malvacearum Bacterial leaf streak in paddy : X. oryzae. pv. oryzicola

2. Leaf blight • Rapid and extensive necrosis of affected leaves resulting in scorched appearance.

(Eg) Bacterial blight in paddy : X. oryzae. pv. oryzae Bacterial blight in beans : X.c. pv. phaseoli.

3. Soft rot • Affected area is soft, watery, discoloured and somewhat depressed, or wrinkled or

blistered. • Eg. Soft rot of tomato, egg plant, crucifers, onion, carrot, celery, lettuce is caused by

Erwinia carotovora pv. carotovora.


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4. Canker • Formation of corky outgrowth on the surface of leaves, swigs and fruits as a result of

necrosis of host • Eg. Citrus canker : X. axonopodis. pv. citri, • Bacterial canker in mango : X. a. pv. mangiferae indica

5. Scab • The infected area becomes rough, corky, slightly raised with rusty surface and pitted due to

the abnormal proliferation of tissues in the epidermis. • It is only by epidermal infection and are not deep seated. • Eg. Potato scab: Streptomyces scabies

6. Galls and tumours • Development of elongated (or) irregular targe sized outgrowth on the affected plant part

due to the hypertrophy and hyperplasia of cell. • Hypertrophy - abnormal increase in size of individual cells • Hyperplasia - abnormal increase in number of cells • Eg. Crown gall in apple – Agrobacterium tumefaciens.

7. Wilt • Yellowing, dropping, wilting and death of the above ground parts of the plant. • Bacteria enter and multiply inside the xylem vessels of host plant. • The occlusion of vessels by bacterial cells and their polysaccharides interfere with

translocation of water and nutrients and Wilt symptom develops. • Eg. Bacterial wilt in solanaceous plants : Pseudomonas solanacearum • The wilted plants show brown to black colour discolouration in vascular bundle.


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VIRUS

Virus

Virus particles consist of nucleic acid encapsidated within a protective protein coat called capsid. Capsid is made up of individual subunits called capsomeres. Mature virus particle is called virion. It is obligate in nature

Common symptoms

1. Reduction in growth • Reduced plant height • Almost all parts show reduction

2. Mosaic and related symptoms • Development of patternof dark green and light green areas giving mosaic effect • Seen on leaves and fruits • Eg. Tobacco mosaic virus, Cucumber mosaic virus

3. Chlorosis • Whole leaf become yellow due to loss of chlorophyll • Chlorosis confined to the vein – Vein clearing • Eg. Bhendi yellow vein virus

4. Ringspotting • One or more concentric rings of dead cells with normal green tissue between them • Eg. Tobacco ring spot virus, Papaya ring spot virus, Tomato spotted wilt virus

5. Necrosis • Death of tissue, organs or whole plant • Eg. Potato virus X, Potato virus Y

6. Abnormalities in growth of leaves • Texture of leave become thick and brittle • Veins become unusually thickened • Leaves become smaller, malformed and blistered • Shoe string – Leaves becomes thread like • Leaf rolling • Eg., Papaya ring spot virus, CMV on tomato

7. Enation or tumours • Outgrowth from upper or lower surface of leaves • Eg. Pea enation mosaic virus


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8. Symptoms on stem and Roots • Tumours are produced on the stem and roots of woody plants • Eg. Cocao swollen shoot virus – Swollen stem on cocao plant • Wound tumour virus – Tumours on roots of clover

9. Flower symptom • Color breaking on flowers • Reduced size, deformed shape and reduced flowering • Eg. Tulip color breaking virus

10. Abnormalities in Fruits, Seeds and Pollens • Color change on fruits, Mottling, ring spotting and necrotic symptoms, distorted

and mishappened • Eg. Cucumber mosaic virus on cucumber • Tomato spotted wilt virus on groundnut leads to reduced kernel size

Satellite Viruses

• Viruses which depend for their replication on HELPER VIRUSES • Eg., Tobacco necrosis satellite virus (sTNV), which has a small piece of ssRNA which

codes only for a capsid protein, and depends for its replication on the presence of TNV.

Diseases resembling virus diseases

Viroids • Viroids are circular, single stranded pathogenic RNAs of few hundred nucleotides long

(240 – 400nt) smallest of known agents of infectious diseases. • They do not code for any protein and are replicate independently of any associated

plant virus • They lack protein coat

Important diseases caused by viroids are, • Potato spindle tuber viroid (First viroid disease by Diener, 1971) • Citrus exocortis viroid • Coconut cadang cadang viroid • Tomato bunchy top

Phytoplasma • Lack true cell wall, bounded by single triple-layered membrane, gram negative, cells

containing cytoplasm, randomly distributed ribosomes and strands of nuclear material. • Exhibit pleomorphic shape • Reproduce by budding and binary fission • Lack flagella and do not produce pores • Resistant to penicillin and sensitive to tetracycline, chloramphenicol and erythromycin


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• Transmitted by leaf hoppers • Not culturable – Koch’s postulate not proved

Important phytoplasma diseases are, • Little leaf of brinjal (Vector: Hishimonus phycitis) • Gingelly phyllody (Vector: Orosius albicinctus) • Rice yellow dwarf • Grassy shoot of sugarcane • Coconut root wilt (Vector: Lace wing)

Spiroplasma • Gram positive, Pleomorphic cells, varying in shape and helical in form • Lack true cell wall bounded by triple layered membrane • Require sterol for its growth • Culturable on nutrient media and multiply by fission • Susceptible to tetracycline but not to penicillin

Important Spiroplasma diseases are, • Corn stunt (Vector: Dalbulus maidis, D. elimatus – Leafhopper) • Citrus stubborn (Vector: Circulifer tenellus)

Fastidious vascular bacteria • Previously called as rikettsia like organism (RLO) • Cause plant diseases and cannot be grown on artificial media • Limited only fastidious to xylem/phloem.

Important fastidious vascular bacterial diseases 1) Xylem inhabiting fastidious bacteria i) Gram positive

a) Sugarcane ratoon stunting (Clavibacter xyle subsp. Xyli). ii) Gram Negative - Xylella fastideosa

a) Pierce's disease of grapes b) Citrus variegation c) Peach phony disease d) Plum leaf scald e) Almond leaf scorch

2) Phloem inhabiting fastideous bacteria (Gram negative) a) Citrus greening b) Clover club leaf


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PHANEROGAMIC PARASITES DISEASES

1. Stem parasite Total parasite - Cuscuta Semiparasite - Loranthus

2. Root parasite Total parasite - Orabanche Semiparasite – Striga

EPIDEMIOLOGY

Edpidemiology or epiphytology is the study factors influencing the outbreak of an infectious disease

• Endemic – A disease which more or less present constantly from year to year in a particular area – Eg. Potato wart disease in Darjeeling area, Club root disease of cabbage is endemic in the Nilgiris district

• Sporadic – A disease when occurs at irregular intervals, locatio and in relatively few instances – Eg. Angular leaf spot of cucumber, Udubatta disease in rice

• Epidemic / Epipytotic – A disease which occurs in a severe form over a larger area for a limited period – Eg. Brown spot of rice, Powdery mildew disease in grapevine

• Pandemic – When a disease is prevalent through out the country, continent or world – Eg., Late blight of potato, coffee rust, Damping off disease in Tomato. An epidemic may cause widespread and mass destruction of crop in a short time or may

persist for long periods depending upon the three following factors responsible for the disease:

!

Pathogen Host


Environment

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Types of Epidemics Rapid Epidemic / Compound interest disease

Pathogen multiply at a higher rate with in a short period leads to rapid increase of disease Eg. Late blight of potato, Stem rust of wheat, Powdery mildew of wheat Slow epidemic / Simple interest disease

Infection take several years to become epidemic – Eg. Vascular wilts, Soil borne smuts Causes of epidemic

i. Inoculum potential ii. Unnatural culture iii. Introduction of a disease to a new area – Eg. TN1 rice variety from Japan – BLB

susceptible iv. Due to plant breeding – Eg. HB3 Cumbu – highly susceptible to downy mildew

v. Weather factors a. Temperature

Powdery mildew favoured in summer BLB – Temp around 25-30oC (not below this temp) Apple Scab – temp is near 20oC and blossom remain wet for 18hrs

b. Relative humidity Sorghum downy mildew – maximum sporulation @ 100% RH Late blight of potato – temp of 10oC & RH not less 75%

c. Rainfall Frequent drizzling favours cumbu ergot BLB – combination of rainy weather, strong wind & temp of 22-26oC Brown spot of rice – Heavy rainfall accompanied by temp of 25-30oC, cloud weather & low solar radiation

d. Dew Sorghum downy mildew - more sporulation @ leaves are wet for 4-5hr Blast – Dew for 6-8hrs favours disease

e. Light Heavy shade – increases brown spot of rice, Blister blight of tea More sporulation of cumbu downy mildew @ Increased light duration

Host Pathogen Environment

❖ Susceptibility of the host ❖ A g g r e g a t i o n a n d

distribution of susceptible hosts

❖ Introduction of new hosts ❖ I n t r o d u c t i o n o f n e w

collateral or alternate host

❖ Introduction of a new pathogen ❖ Presence of aggressive strain of

the pathogen ❖ High birth rate of the pathogen ❖ Low death rate of the pathogen

❖ Easy and rapid dispersal of the pathogen

❖ Adaptability of the pathogen

❖ Temperature ❖ M o i s t u r e a n d

humidity ❖ Rainfall ❖ Light and shade ❖ Wind


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vi. Soil factors a. Soil Moisture

Low moisture – favours potato scab, Root rot (Dry) High moisture – Damping off, Root rot (Wet)

b. Soil Temperature Verticillium wilt of cotton – low soil moisture (<20 oC) Fusarial wilt – hight soil moisture (>32 oC)

c. Soil pH Acid soil – Favours Club root of cabbage Alkaline soil – Fusarial wilt of cotton, Common scab of potato

DISEASE SURVEY AND ASSESSMENT Methods of Survey

i. Fixed plot survey Select two villages and fix two fields per village. Select 5 sampling plots per field of one acre away from bund. Sample plot size is 1sq. m. Select 20 plants or leaves per plot.

ii. Roving survey Select four villages and fix two fields in each village. Observe and score 100plants or leaves by walking across field in each field.

Disease surveillance reports i. White card – Contains disease / pest surveillance detail in a particulr block/ division /

district for a week. ii. Yellow card – When the disease / pest occurrence attained half the level of ETL iii. Red card - When the disease / pest occurrence exceeded ETL

Disease assessment 1. Assessment in terms of percentage

Applicable for disease which cause complete death of plants (Eg. Damping off, Root rot, wilt, etc.), systemic diseases (eg. Virus, Phytoplasma, etc.,) and in diseases leading to total destruction of infected organs (eg., Smut, greenear, etc.,)

Percent disesase incidence = (No. of plants infected / No. of plant observed) x 10

2. Assessment using disease grades Applicable for the foliar diseases like downy mildew, powdery mildew, leaf spot, leaf blight, canker, rust, etc. Sum of all numerical ratings 100

Total number of leaves graded Maximum grade


x PDI =

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GENERAL PRINCIPLES OF DISEASE MANAGEMENT Controls must be based on knowledge of the specific diseases, pathogen life cycle, time and method of infection, plant parts affected method of causal agent dissemination and organic considerations. Six fundamental principles of disease management are

1. Exclusion 2. Eradication 3. Protection – chemicals 4. Resistance – resistant varieties 5. Therapy 6. Avoidance of insect vectors and weed hosts.

Exclusion • Plant disease legislation • Inspection of plant product • Elimination of pathogen from planting material

Eradication • Direct removal of pathogen • Elimination by actual practices • Destruction of pathogen

Avoidence • Choice of geographic area • Selection of field • Time of sowing • Disease escape

o IR-50 susceptible host to blast – sown during summer escaped from blast. • Selection of seed and planting materials • Modification of cultural practices

o Closer spacing increase – Powdery mildew, sigatoka disease o Less shade –increase – tea blister blight and coffee rust o Mixed cropping of pulse and Cumbu reduce yellow mosaic incidence.

Exclusion • Exclusion is to prevent the spread of disease when avoidance failed • It can be achieved by

▪ Seed certification ▪ Crop inspection ▪ Plant quarantine

Plant quarantine • Quarantine - 40 • Legal registration on the movement of plants and plant materials between countries

and between states within the country in order to prevent the establishment and introduction of diseases.

Regulations • First quarantine law – France, 1960 – prevent spread of barberry plants • First quarantine act – USA, 1912


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• Destructive insects and pests act, 1914 – India. • Quarantine offices in India – Mumbai, Cochin, Chennai, Calcutta, Vizagapattinam. • Airports – Amritsar, Mumbai, Chennai, Calcutta, New Delhi. • NBPGR – National Bureau of Plant Genetic Resources involved in import / export

of plant materials.

CLASSIFICATION OF QUARANTINE • Exclusive – Prohibition of importation of plant materials. • Regulatory – import permitted if accompanies “Phytosanitary certificate” Also

DOMESTIC: Restricts spread of a disease with in a country from one place to another with in state or between states.

• In TN Madras Agricultural pests and diseases Act, 1919 - Control of sandal spike, Cardamom mosaic, Orabanche, Wheat stem rust, blister blight.

• In INDIA DIP Act 1914 – Prevent spread of BBTV from Assam, Kerala, Orissa, Tamil Nadu and

west Bengal. – Prevent spread of potato cyst nematode from TN.

INTERNATIONAL (Foreign) • Coffee leaf rust – Hemilieavastatrix (Srilanka)- 1940 • Late blight of potato – Phytophthorainfestans(Srilanka)- 1883 • Banana bunchy top virus- (Srilanka)-1940 • Paddy blast- (Srilanka)-1918 • Cardamom suckers – prohibited from Anamalais to avoid Katte mosaic virus

Embargo Total prohibition on import or export of transport of plant material in a country.

Categorization of quarantine restrictions: • Unrestricted • Restricted – require phytosanitary certificate • Post entry quarantine • Prohibited – require phytosanitary certificate and import permit

Eradication Aims at killing of pathogen that have already gained entry in to the country. Eradication from seeds and seed materials Mechanical

▪ 20% brine solution Physical

▪ Steam at 52 – 540 c for 20 mins – ex. BLB and Blast ▪ Sugarcane grassy shoot – hot water treatment 500 c for 2 – 2.30 hrs ▪ Hot air @ 500 c for 8 hrs ▪ Aerated steam theraphy at 500 c for 1 hr


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▪ Moist hot air treatment – 54 0 c for 2 hrs ▪ Luthra solar treatment – loose smut of wheat.

Chemical Biological

Eradication of infected / diseased plants i. Sanitation ii.Surgery and rouging iii.Eradication of alternate host / collateral host iv.Crop rotation

Successful for a. Pathogens live in soil for short time b. Having short host range c. Annual diseases

Eg. Cotton wilt – Paddy Redgram wilt – Paddy Potato brown rot – Wheat Club root – Wheat and Potato Green ear of cumbu – Pulses / Cotton

v.Mixed cropping vi.Modifying soil reaction

a. Application of lime –Reduces club root of cabbage & Brown rot of potato b. Application of Gypsum – Reduces Potato scab & wilt of cotton

vii.Cultural practices viii.Eradications of pathogens in soil

Protection – Accomplished by the application of chemicals to the plats i. Protection from air borne disease ii. Protection from seed borne disease iii. Protection from soil borne disease

a. Physical method - Soil solarisation – Irrigate field upto 10 cm depth and cover the soil with

polythene sheet after 2 days of and leave it undisturbed for 4-6 weeks. - Steaming - Direct flaming – Burning plant residues to manage disease caused

Pythiumspp. and Red rot. - Hot water

b. Chemical method c. Biological method

Immunization – Process of developing resistance in plants to diseases - Best way is planting resistant variety - Immune plants never affected by the pathogens

Resistance – Ability of the plant to reduce or retard the attack of pathogen Methods of developing resistance variety

i. Introduction


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ii. Pureline selection iii. Crossing and hybridization iv. Mutation – X ray, UV, Gamma & chemical mutagens

Important resistant varieties

Paddy: Blast – ADT 36, 37, 39, 40, 43, Co 37, Co 43, Co 44, Co 45, Co 47, IR 64, Ponmani, IR 20, ASD 16 Brown spot – Co 20, Co 44, Bala, Bhavani BLB – IR 20, Zenith, IR 28, 29, 30 RTV – IR 20, 28, 29, 30, IR 50 and Co 45

Sorghum: Downy Mildew – QLSCO 25, CO 26, CO 21 Wheat: Stem and Yellow rust – Lerma Roja, Safed Lerma, Sonalika, Choti Lerma

Yellow rust – Hira Brown rust – Pratap Yellow and Orange rust – VP 262 Loose smut – Kalyani 277, PV 18, WG 307, C 302

Bengalgram: Wilt – ICCC 32, 42, ICC 12223, 11322, 12408, H 82-2, bdn 1, 2 Redgram: Wilt – NP 41, 51 and 80

Sterility Mosaic – VR 3, DA 11, 12, 13, Bahar, BSR 1, Co (RG) 7 Yellow Mosaic – Co 6, Vamban 2, APK 1

Groundnut: Leaf spot and Rust – ALR 1, ALR 3 Bud necrosis – Co 3 (Moderately resistant)

Black gram: Yellow Mosaic – VBN 1, VBN 3 Sugarcane: Red rot – COC 99061, Co 86249, COC 22, Co(Si)6 – Resistant

COC 8001, Co 8201 – Moderately resistant Smut – Co 7704 - resistant

COC 85061, COC 8201 – Moderately resistant Tobacco: Tobacco mosaic virus – TMVRR 2, RR 29, RR3 Potato: Late blight – Kufri Jyothi, Kufri Malar, Kufri Thangam Bhendi: Yellow mosaic – Parbhani kranti Coffee rust: Cauvery Cotton: Bacterial leaf blight – MCU 10, Paiyur 1

FUNGICIDES AND ANTIBIOTICS

❖ Fungicide is a chemical capable of killing fungi ❖ Fungistat - chemicals do not kill but simply arrest the growth of the fungus ❖ Antisporulant - chemicals that inhibit the spore production without affecting the

vegetative growth


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Fungicides grouping: Mode of action

1. Protectant - effective only if applied prior to fungal infection eg., Zineb, Sulphur 2. Therapeutant - Capable of eradicating a fungus after it has caused infection and there by

curing the plant eg. Carboxin, Oxycarboxin antibiotics like Aureofungin 3. Eradicant - eradicate the dormant or active pathogen from the host. eg. Organic

mercurials, lime sulphur, dodine etc.

Based on general use 1. Seed protectants: Eg. Captan, thiram, organomercuries carbendazim, carboxin etc. 2. Soil fungicides (preplant): Eg. Bordeaux mixture, copper oxy chloride, Chloropicrin,

Formaldehyde Vapam, etc., 3. Soil fungicides (for growing plant): Eg. Bordeaux mixture, copper oxychloride, Capton,

PCNB, thiram etc. 4. Foliage and blossom protectant: Eg. Capton, ferbam, zineb, mancozeb, chlorothalonil

etc. 5. Fruit protectants: Eg. Captan, maneb, carbendazim, mancozeb etc. Eradicants: Eg.

Organomercurials, lime sulphur, etc. 6. Tree wound dressers: Eg. Boreaux paste, chaubattia paste, etc. 7. Antibiotics: Eg. Actidione, Griseofulvin, Streptomycin, Streptocycline, etc.,

Based on chemical Nature 1. Mercurial fungicides 2. Copper fungicides 3. Sulphur fungicides 4. Quinones 5. Heterocyclic nitrogenous compounds 6. Aromatic compounds 7. Non – aromatic compounds 8. Organotin compounds 9. Organophosphorus compounds 10. Nickel compounds 11. Miscellaneous fungicides 12. Systemic fungicides 13. Antibiotics

1. Mercurial fungicides


Mercurial fungicides

Inorganic Eg. Mercuric chloride

Mercuous chloride

Organic Eg. Ethyl mercury chloride, Phenyl

mercury acetate, methoxy ethyl mercuric chloride, etc.

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2. Copper fungicides

3. Sulphur fungicides Inorganic – WP, Dust (Kosam, Thiovit) Organic – (Carbamate fungicides)

Monoalkyl dithiocarbamates – Zineb, Maneb, Mancozeb, Nabam, Vapam Dialkyl dithiocarbamates – Thiram, Ziram, Ferbam

4. Quinone fungicides Chloranil – Spergon Dichlone – Phygon, Phygon XL

5. Heterocyclic nitrogen compounds Captan, Folpet, Captafol, Vincozolin (rolinan), Iprodione

6. Aromatic compounds Quintozene (PCNB) – Brassicol, Terraclor (Soil treatment) Dinocap – Karathane, Arathane 7. Non-Aromatic compounds - Dodine 8. Organotin compounds (Triphenyl tin) Fentin hydroxide, Fentin acetate, Fentin chloride

Common Name Trade name

1. Copper Sulphate Preparations

1. Bordeaux mixture • It is prepared by mixing copper sulphate and lime in water (to get 1% mixture, mix 1 kg of CuSO4 and 1 kg of lime in 100 litres of water)

• CuSO4+Ca (OH) 2 ----------> Cu (OH) 2 + CaSO4 • Phytotoxic to apple, pear, peaches and high yielding

varieties of Rice, Maize

2. Bordeaux paste It is prepared by mixing 1 kg of CuSO4 and 1 kg of lime in 10 litres of water.

3. Burgundy mixture It is prepared by mixing 1 kg of CuSO4 and 1 kg of Sodium Carbonate in 100 litres of water,

4. Cheshnut compound It is prepared by mixing 2 parts of copper sulphate and 11 parts of Ammonium Carbonate

II. Copper carbonate preparation

Chaubattia Paste This is prepared by mixing 800 g of copper carbonate and 800 g of Red lead in 1 litre of linseed oil or lanolin.

III. Cuprous oxide Preparation

Fungimar, Perenox, Copper Sandoz, Copper 4% dust, Perecot, Cuproxd, Kirt i copper.

IV. Copper oxychloride Preparation

Blitox, Fytolan, Blue copper 50, Cupravit, Cuprax


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9. Organophosphorus compounds - Ediphenphos 10. Nickel compounds Nickel chloride – For Tea blister blight 11. Miscellaneous fungicides

Chinomethionate – Morestan (Acaricidal) 12. Systemic fungicides

i. Acetamides: e.g., cymoxanil ii. Acylalanines: e.g., Metalaxyl, Furalaxyl, Benalaxyl iii. Pyrimidines and purines: e.g., Dimethirimol, Ethirimol iv. Triazoles: e.g., R.H-24, Tricyclozole, Fluotrimazole, Triadimefon, v. Phenol derivatives: e.g., Chloroneb

13. Antibiotics Chemical substance produced by one microorganism which in low concentration can

inhibit or even kill other microorganisms. Antibacterial antibiotics

Streptomycin, Tetracycline Antifungal antibiotics 1. Aureofungin

o Produced from Streptoverticillium o Given as soil drenching and foliar spray. o As a truck application/root feeding, 2 g of aureofungin-sol+1g of copper sulphate in 100 ml

of water effectively reduce Basal stem end rot of coconut. o Trade name: Aurefungin-Sol.

2. Griseofulvin o Produced by Penicillium griseofulvum. o Tradename: Griseofulvin, Fulvicin and Grisovin. o Highly toxic to powdery mildew of beans and roses, downy mildew of cucumber. o Control Alternaria solani in tomato Sclerotinia rot in apple and Botrytis rot in lettuce.

3. Cycloheximide o Produced by different species of Streptomyces, o Trade Name: Actidione, Actidione PM, Actidione RZ and Actispray.

4. Blasticdin o Product of Streptomyces griseochromogenes o Specifically used against blast disease of rice caused by Pyricularia oryzae. o Trade Name: Bla-s.

5. Antimycin o Produced by several species of Streptomyces, o Effectively used against early blight of tomato, rice blast and seeding blight of oats. o Trade Name: Antimycin.

6. Kasugamycin o Obtained from Streptomyces kasugaensis. o very specific antibiotic against rice blast disease.


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o Trade Name: Kasumin.

DISEASES OF FIELD CROPS

RICE 1. Rice blast or rotten neck - Pyricularia grisea (Perfect stage: Magnaparthae grisea) Symptoms 1. Leaf blast/ leaf infection

• Initially formation of reddish brown specks on the leaf blade. • Later specks enlarge to form spindle shaped lesions with reddish brown margin and grey

centre. • Later the lesion coalesces and leads to drying of entire leaf.

2. Nodal blast/nodal infection • Black discoloration on the nodal region.

3. Neck blast/rotten neck • Initially black discoloration on the neck region. • Weakening of the tissue in the neck region - ear heads are broken and hang down.

4. Grain blast • Black irregular lesion on the grain is seen.

Management: • Non-systemic: Ediphenphos. • Systemic: Iprobenphos, Tricyclazole (neck blast), Tridemorph.

2. Brown spot of rice / Sesamum leaf spot - Helminthosporium oryzae / Cochliobolus miyabeanus.

Symptoms • Coleoptile infection - brown circular spots on first emerged leaf which leads to seedling

blight. • Leaf sheath & leaf infection - circular brown leaf spot on the leaf sheath as well as on the

leaf surface. • Neck infection - reddish brown lesion on the neck region but there is no rotting of the neck

portion. • Nodal infection - reddish brown lesion on the nodal region. • Grain infection - reddish brown discoloration on the grain surface.

Management • Systemic: Tridemorph. • Non-systemic: Mancozeb.

3. Sheath blight of rice: Rhizoctonia solani / Thanatephorus cucumeris Symptoms

• Sheath blight: Greenish grey lesion initially seen on the sheath portion which later turns to dark brown margin and whitish grey centre.

Management


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• Systemic: Carboxin, Oxycarboxin, Iprobenphos

4. Sheath rot of rice: Sarocladium oryzae Symptoms

• Sheath infection: reddish brown lesion on the sheath enclosing the young panicle. This • Leads to ear head chocking. • Grain discoloration (black).

Management • Systemic: Tridemorph – 0.1% • Non systemic: Mancozeb - 0.25%.

5. Foot rot/bakanae/foolish rice: Fusarium moniliforme / Gibberella fujikuroi Symptoms

• Compared with healthy plants, infected plants are pale yellow, thin and lanky • Taller than the healthy plant and mature early. • Adventitious roots are seen in the 2nd and 3rd adventitious roots.

Management • Systemic: Tridemorph - 0.1%.

6. False smut / Lakshmi disease - Ustilaginoidea virens / Claviceps oryzae sativa. Symptoms

• At flowering stage, individual ovaries of the spikelets/grains are converted into orange yellow spore mass. Later stage it turns to greenish grey.

Management • Thiophanate methyl (Topsin M) 0.1%, Mancozeb 0.25%.

7. Bacterial leaf blight: Xanthomonas oryzae pv. oryzae Symptoms

• Kresek / wilting: wilting of entire plant within 30 days after transplanting. • Leaf blight: water soaked lesion at the tip of the leaf. • Later it leads to drying of the leaf from tip to bottom with wavy margin.

Management: • Seed treatment and foliar spray with Streptomycin sulphate - 200ppm. • Copper hydroxide – Kocide

8. Bacterial leaf streak: Xanthomonas oryzae pv.oryzicola Symptom

• Initially water soaked streaks are formed. Later it turns to reddish brown streaks. Management

• Seed treatment and foliar spray with Streptomycin sulphate - 200ppm.

9. Rice tungro disease: Rice tungro bacilliform virus / Rice tungro spherical virus. Vector: Nephotetix virescens/ Nephotetix impecticeps. Symptoms


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• Reduced tillering and stunting of the plant. Orange yellow discoloration of leaves. Management

• Foliar spray with systemic insecticide and 2% urea.

10. Rice yellow dwarf: Phytoplasma Vector: Nephotetix virescens/ Nephotetix impecticeps. Symptoms

• Excessive tillering and stunting of the plant. Yellow discoloration on leaves. Management

• Foliar spray with systemic insecticide and 2% urea.

Other important diseases: 1. Udbatta disease: Ephelis oryzae (Sexual stage: Balansia oryzae-sativa). 2. Narrow brown leaf spot :Cercospora janseana (Sexual stage : Sphaerulina oryzina) 3. Stackburn disease :Trichoconis padwickii (Syn : Alternaria padwickii) 4. Bunt or Kernel Smut or black smut : Tilletia barclayana 5. Stem rot :Sclerotium oryzae (Sexual stage : Magnaporthe salvinii) 6. Grassy stunt disease: Grassy stunt virus 7. Ragged stunt disease: Ragged stunt virus

WHEAT 1. Black stem rust: Puccinia graminis f.sp. tritici

• Seen only on the stem. Initially linear, elongated reddish brown raised pustules. Later it turns to black raised linear pustules.

2. Brown / orange leaf rust: Puccinia graminis fsp.recondida • Mostly seen on the leaves. Reddish brown/orange raised pustules scattered on the leaf

surface. Later the orange pustules turn to black lesion.

3. Leaf yellow stripe rust: Puccinia graminis fsp.striformis • Mostly seen on the leaves. Yellow, linear and elongated raised stripes on the leaf surface.

Later it turns to black elongated stripes. Management

• Foliar spray with Carboxin or Oxycarboxin 0.1%

4. Loose smut of wheat: Ustilago nuda fsp.tritici/ Ustilago tritici Symptoms

• Individual spikelets are converted into smut sorus (black kernals). • These are easily blown off by wind leaving the rachis alone.

Management • Luthra’s solar treatment – soak the seeds in cold water for 4 hours from 8 to 12 noon.

Decent the water and dry the seeds in sunlight for four hours (12pm to 4pm) by spreading over the threshing floor.

• Foliar spray with Mancozeb 0.25%.


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5. Tundu disease / Yellow ear rot / Ear cockle disease: Clavibacter tritici associated with nematode: Anguina tritici.

Symptoms • Exudation of yellow, slimy liquid from individual spikelets. Oozing is deposited on the

stalk of the ear head, stem as well as surface of the leaves. After drying, tissues are malformed and twisted of leaves. Presence of nematode galls is seen on individual grains.

• Tundu disease / Yellow ear rot – Action of both bacteria and nematode • Ear cockle disease – Nematode alone

Management: • Soak the seeds in brine solution -10%, remove the floating infected grains and wash the

good seed with running tap water. • Seed treatment with streptomycin sulphate – 200ppm.

Other important diseases: • Flag smut : Urocystis tritici • Rough spored bunt or Stinking smut : Tilletia caries • Smooth spored bunt: Tilletia foetida • Karnal bunt: Neovassia indica • Foor rot: Pythium graminicolum and P. arrhenomanes • Powdery mildew: Erysiphe graminis var. tritici

SORGHUM 1. Downy mildew: Peronosclerospora sorghi Symptom:

• Downy mildew: White downy growth on the lower surface of the leaf. Yellow discoloration on the corresponding upper surface.

• Leaf shredding: formation of chlorotic streaks along the veins due to oospore formation. Shredding of the leaves along the veins at the final stage of the crop growth.

Management: • Foliar spray with Metalaxyl - 0.4%.

2. Charcoal rot: Rhizoctonia solani / Macrophomina phaseolina Symptom:

• Seen only at the flowering phase when crop is subjected to moisture stress. Lodging of the plants. When we split open the base of the culm internal portion is fibrous and hallow with black vegetative structures namely the sclerotia and pycnidia.

Management: Frequent irrigation at the time of flowering phase.

3. Rust disease: Puccini sorghi Symptom:

• Reddish brown raised pustules on the leaf surfaces. • Later the reddish brown pustules turn to black pustules.

Management: • Foliar spray with carboxin or oxycarboxin 0.1%


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4. Ergot/ sugary diseases: Claviceps purpurea • Symptoms: • Mostly seen when the flowering phase coincides with the winter season. • Characteristic honey dew secretion from individual spikelets. • Each spikelets is converted into black ergot/sclerotia.

Management: • Foliar spray with Mancozeb 0.25% (consumption purpose), Thiophanate methyl 0.1%

(seed purpose).

9. Other important diseases: 1. Anthracnose or Red leaf spot: Colletotrichum graminicolum. 2. Leaf blight: Helminthosporium turcicum 3. Twisted top/Bokah boeing: Fusarium moniliforme 4. Phanerogamic parasite/Witch weed: Striga asiatica/Striga densiflora.

Symptom: yellowing of the entire plant. Stunted growth. Management: application of the 2,4 D

5. Leaf spot: Cercospora sorghi

Diseases / casual

organism

5. Grain smut / Kernel smut /

Covered smut / Short smut:

Sphacelotheca sorghi

6.Loose smut / Loose kernel smut:

Sphacelotheca cruenta

7.Long smut : Tolyposporium

ehrenbergii

8.Head smut : Sphacelotheca

reiliana

SymptomA l m o s t a l l t h e individual grains are smutted. Sorus is small. Externally seed borne disease.

A l m o s t a l l t h e individual grains a r e s m u t t e d . Externa l ly seed borne disease.

Only 2% of grains are smutted. Air borne disease.

Entire head is converted into a s i n g l e s m u t sorus. Soil borne disease.

ManagementS e e d t r e a t m e n t with captan/ thiram – 4g/kg of the seed.

Seed treatment with captan/ thiram – 4g/kg of the seed.

Foliar spray with mancozeb 0.25%

Seed treatment w i t h c a p t a n / thiram – 4g/kg of the seed.


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PULSES

REDGRAM 1. Wilt: Fusarium oxysporum fsp.udum. Symptom:

• Yellowing and drooping of the plants. • Partial wilting or entire wilting of the plant is seen. • Pink discoloration in the vascular region is the characteristic symptom.

Management: • Spot soil drenching with copper oxychloride @0.25%.

2. Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola Symptoms:

• Yellowing of the plant. • Drying and wilting of the whole plant. • Typical bark shedding is seen.

Management: • Frequent irrigation at the time of flowering phase.

3. Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris Symptoms:

• Reddish brown lesion at the collar region. This leads to girdling of the basal stem. • External symptom is yellowing of the plant.

Management: • Spot soil drenching with copper oxychloride @0.25%.

4. Powdery mildew: Leveillula taurica Symptom:

• White powdery growth on the lower surface of the leaf. • On the corresponding upper surface yellow discoloration of the leaves is seen.

Management: • Foliar spray with Wettable powder-0.25%, dinocap – 0.05%, tridemorph- 0.1%.

5. Sterility mosaic: Pigeon pea sterility mosaic virus. Vector: Aceria cajani Symptom:

• Reduction of leaf size and proliferation of auxillary buds. • Sterility of the plant is also observed.

Management: • Spraying of dicofol-0.1%, inorganic sulphur.

6. Yellow mosaic: Pigeon pea yellow mosaic virus. Symptom: plants become stunted and on the leaves alternate patches of yellow and green discoloration is observed.


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Management: • Destruction of the infected plants and foliar spray with systemic insecticide.

COWPEA, LAB LAB, PEAS 1. Anthracnose: Colletotrichum lindemuthianum

Symptoms: • On the pods initially water soaked lesion appear. • Later it turns to brown and enlarge into circular spots. • Spots are depressed at the centre with reddish brown margin and black centre.

Management: • Foliar spray with Tridemorph-0.1%, copper oxy chloride -0.25%, mancozeb

-0.25%

2. Downy mildew of peas: Pernospora pisi 3. Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola 4. Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris 5. Aphid borne mosaic: Cowpea aphid-borne mosaic virus Symptom:

• Mosaic mottling of the leaves with alternate dark green and light patches. • Stunting of the plant.


OILSEEDS GROUNDNUT

1. Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola. 2. Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

3. Crown rot: Aspergillus flavus Symptom:

• Pre emergence: Rotting of the seeds before the emergence of the seedling. • Post emergence: Rotting at the collar region of the seedling. • Crown rot: On the well-established plant, rotting at the basal portion and spreads

upward and leads to death of the entire plant. Management:

• Shallow sowing of the seeds and adopt wider spacing. • Spot soil drenching with copperoxychloride.

4. Tikka disease: Cercospora arachidicola (early leaf spot) & Cercospora personata (late leaf spot)

Symptom: • Early leaf spot: seen within 3-4 weeks of sowing. On the leaves irregular to circular

reddish brown/ black lesions surrounded by “yellow halo”. • Late leaf spot: seen within 5-7 weeks of sowing. Mostly on the leaf margin, enlarged

black lesion without yellow halo.


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Management: • Foliar spray with chlorothalonil -0.25%.

5. Rust disease: Puccinia arachidis

6. Rosetting: Groundnut rosette virus Vector: Aphis craccivora Symptom:

• Mosaic mottling of the leaves with alternate dark green and light patches. • Stunting of the plant. • Bushy appearance due to the proliferation of the auxillary buds.


7. Bud necrosis: Tomato spotted wilt virus Vector: Thrips tabaci Symptom:

• Necrotic symptom on the terminal portion of the leaf. • Stunting of the plant. • Bushy appearance due to the proliferation of the auxillary buds.


SESAME

1. Sesamum phyllody: Phytoplasma Vector: Orosius albicinctus

Symptom: • Formation of the phylloid flowers. • All the floral parts are converted into green leaf like structure.

Management: • Foliar spray with tetracycline – 100ppm. • Foliar spray with systemic insecticides from two-leaf stage.

SUNFLOWER 1. Head rot: Rhizopus nigricans Symptom:

• Irregular water soaked lesion is seen on the backside of the head portion. • Lesion turns to black and spread to entire head and leads to rotting of the head.

Management: • Foliar spray with mancozeb -0.25%, calixin -0.1%

2. Sunflower necrosis: Tobacco streak virus Vector: Thrips tabacci Symptom:

• Stunting of the plant. • Necrotic lesion is seen on the veins, petioles and the stem.


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• Malformation of the flower. Management:

• Destruction of the infected plants and foliar spray with systemic insecticide.

CASTOR 1. Seedling blight: Phytophthora parasitica Symptom:

• Irregular water soaked lesion on the leaves. • Later it turns to black color and it spreads to petiole and stem.

Management: • Foliar spray with fosetyl aluminium -0.1%

COCONUT 1.Basal stem end rot: Ganoderma lucidum Symptom:

• Reddish brown oozing from the base of the stem and spreads upward. • Drooping of the lower fronds. • Oozing is through the cracks. • Formation of sexual fruiting body – basidiocarp.

Management: Curative:

• Isolation trench : apply sufficient amount of sulphur dust inside the trench. • Soil drenching : Bordeaux mixture – 1% @40 litres/ tree. • Trunk injection: Calixin @ 3ml/ trunk, 4 injections @ 4 month interval. • Root feeding : Calixin @ 3ml + 100ml water.

2.Kerala wilt: Phytoplasma Symptom:

• Production of the small fronds. • Fronds became pale yellow in color. • Ribbing and flaccidity of the fronds. • No decay of roots and rootlets.

Management: • Remove the plant and burn it.

3.Stem bleeding of coconut: Ceratocystis paradoxa Symptom:

• Reddish brown oozing through the cracks @ any parts of the trunks. External symptom only.

Management: • Scrap the bleeding patches and sterilize the scrapped portion with fire. • Swab the Bordeaux paste 10% on the sterilized surface.

4.Cracking and malformation: Botrydiploidia theobromae Symptom:


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• Malformation of the coconut • Splitting of the exocarp. Hardiness of the coconut. • Nut fall is commonly seen.

Management: • Crown clearing: Removal of infected plant parts. • Trunk injection – Calixin - 3ml

5.Bud rot of coconut: Phytophthora palmivora Symptom:

• Pale yellow discoloration of the heartleaf. Withering of the heartleaf. • Infected leaves can be easily pulled out. • At the base of the fronds reddish brown rotting is seen.

Management: • Foliar spray and trunk injection with fosetyl aluminium – 0.1%

6.Grey blight : Pestalotia palmarum Symptom:

• Irregular/ circular shaped lesions with brown margin and grey centre. Management:

• Foliar spray with copper oxychloride. • Trunk injection with calixin.

7.Lethal yellowing: Phytoplasma Symptom:

• Stunting and yellowing of the plant. • Reduction of leaf size.


SUGARCANE 1. Damping off: Pythium aphanidermatum Symptom:

• Pre emergence: before the emergence of the seedling. Death of the sets occurs inside the soil itself.

• Post emergence: after the establishment of the seedling. Reddish brown lesion at the collar region of the seedlings is seen.

Management: • Spot soil drenching with copperoxychloride -0.25%.

2. Redroot of sugarcane: Colletotrichum falcatum Symptom: • Shrinkage of the cane. • Yellowing and drying of leaves in patches. • Reddish brown discoloration interrupted with white patches of fungal growth.


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• On the leaves reddening of midrib is also seen. Management:

• Set treatment with carbendazim -0.1% • Foliar spray with tridemorph – 0.1%

3. Wilt: Cephalosporium sacchari Symptom:

• Stunting, yellowing of crown leaves. • Midrib of the leaves turn yellow white leaf lamina remains green. • Reddening of internal tissues without any white patches. • Infected canes emit foul smell.

Management: • Set treatment with carbendazim -0.1% • Foliar spray with tridemorph – 0.1%

4. Set rot/ pineapple disease: Ceratocystis paradoxa Symptom:

• Reddening of internal tissues without any white patches. • Infected cane emits pineapple odour. • Internodes become hollow and black in color.

Management: • Set treatment with carbendazim -0.1% • Soil drenching with coc-0.25%

5. Whip smut: Ustilago scitaminea Symptom:

• Severe infection is seen in ratoon crop. • Central shoot is converted into single whip like smut spores.

Management: • Foliar spray with carboxin/oxycrboxin -0.1%

6. Rust: Puccinia melanocephala 7. Eyespot: Helminthosporium sacchari 8. Ratoon stunting disease: Clavibacter xyli pv. xyli 9. Sugarcane mosaic: Sugarcane mosaic virus Vector:Melanaphis sacchari 10. Grassy shoot disease: Phytoplasma Vector: Aphis sacchari

COTTON 1. Wilt diseases: Fusarium oxysporum fsp. Vasinfectum

2. Verticillium wilt: Verticilium dahliae Symptom:

• Infected stem and roots show dark brown discoloration if we split open the stem.


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• On the leaves tiger stripe symptom is seen. Veins turn brown and interveinal areas become chlorotic.

• Cupping of leaf and tissues b/w the veins dry in patches. Management:

• Spot soil drenching with copperoxychloride -0.25%

3. Black arm of cotton: Xanthomonas axonopodis pv.malvacearum Symptom:

• Seedling blight: Watersoaked lesions on the cotyledon leaves. • Angular leaf spot: On mature plants, water soaked spots on the leaves restricted in b/w

the vein and veinlets. • Vein blight: Angular spots in leaf lamina extend to the vein and veinlets. The vein and

veinlets become black and blighted. • Black arm: Blackening extends from veins to the sympodial branches leaving the plant

as bare resembles like black arm. • Boll rot: On the boll depressed, circular, reddish brown lesion is seen.

Management: • Spot soil drenching with copperoxychloride -0.25%. • Foliar spray with streptomycin sulphate- 200pm.

4. Areolate mildew/ grey mildew: Ramularia areola Symptom:

• Frosty white to grey mildew patches appear on the under surface of the leaf. Management:

• Foliar spray with calixin-0.1%.

5. Leaf blight: Alternaria macrospora 6. Leaf spot: Cercospora gossypina 7. Rust disease: Phakopsora gossyii 8. Anthracnose: Colletotrichum capsici 9. Stenosis: Phytoplasma Vector: Unknown.

Symptom: • Rosetting of plant and reduction of leaf size.


TOBACCO 1. Damping off: Pythium aphanidermatum

2. Black shank: Phytophthora parasitica var nicotianae Symptom:

• Black lesion is seen at the collar region which spreads both upward and downward. • Later it leads to girdling symptom.

Management: • Foliar spray with fosetyl aluminium -0.1%

3. Frog eye spot: Cercospora nicotianae


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Symptom: • Reddish brown spots with grey centre and look similar to that of frog’s eye.

Management: • Foliar spray with mancozeb -0.25%

4. Powdery mildew : Erysiphe cichoracearum var. nicotianae

5. Wild fire: Pseudomonas tabaci Symptom:

• Symptom is seen on the leaves, stem and twigs. • Initially water soaked lesions is seen on the above said parts, which later turns to

drying of the leaves. • This gives a wild fire like appearance.

Management: • Foliar spray with streptomycin sulphate – 200ppm

6. Tobacco mosaic: Tobacco Mosaic Virus (TMV) Symptom:

• Stunting of the plant. • Reduction of the leaf size. • Mosaic mottling with alternate patches of green and yello colour. • Malformation of the leaf.

7. Leaf curl : Tobacco leaf curl virus 8. Phanerogamic parasite/ broom rape: Orobanche cernua var. desertorum 9. Anthracnose: Colletotrichum tabacum


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DISEASES OF FRUITS BANANA

1. Panama disease – Fusarium oxysporumf.sp. cubense

- Symptoms appears only after 6 months of transplanting - Spliting of pseudostem @ the base near soil level - Cross section of the corm shows – vascular discolouration (Reddish brown streak around

the periphery of center of the corm - If we split open the infected rootlets – pinkish discolouration is seen due to nematode -

Management - Pairing &prolinage before plant for elimation of nematode damage - Sprinkle wthcarbofuran @20g/corm on surface before planting - Corm injection – with 2% carbendazim – 3ml / corm @ 6th and 7th month - Capsule application with carbendazim

2. Sigatoka disease – Mycosphaerella musicola Symptoms

- Spindle shaped lesions characterized by dark brown margin & grayish centre - It is surrounded by yellow halo and later they coalesce and cause drying

Management - Foliar spray – Chlorothalonil – 0.25%

3. Anthracnose – Colletotrichum musae Symptoms

- Initially circular reddish brown spots on surface fruit surface turns to irregular black lesion with acervuli leads to rotting of fruits

4. Cigar end rot – Verticillium theobromae Symptoms

- Tip of fruit are turned to ash colored with malformation end resembles like burnt cigar

5. Moko disease – Burkholderia solanacearum Symptoms

- Cavendish group of banana highly susceptible - Seen @ all stages of crop - Side suckers & main plants show wilting

Race I (Rasthali wilt) Race II (Monthan Wilt)

Drooping of lower leaves when they are still green (like skirting around the tree) and later they dried off

Orange yellow discoloration of lower leaves without drooping


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- Yellow streaks is seen in the centre of the corm with bacterial oozing - If we cut immature fruit – Blackening of the pulp is seen

6. Tip over disease / Erwinia rot – Erwinia caratovora Symptoms

- In both nursery and main field drying and wilting of plants is seen - At the base of the pseudostem rotting is seen - By giving slight pressure pseudostem will fall leaving corm inside

7. Bunchy top disease – Banana bunchy top virus (Vector: Pentalonianigronervosa) Symptoms

- Stunting of plants, bunching of terminal leaves gives resette appearance - Dark green streaks on petiole, midrib and leaf lamina - Green leaf like structure is seen at the tip of bract

8. Bract mosaic / Kokkan disease – Banana bract mosaic virus 9. Banana streak sisease – Banana streak virus Vector: Aphis gossypii

10. Minor disease a. Freckle – Phyllostictina musarum b. Crown rot – Botrydiplodia theobromae

MANGO 1. Malformation – Fusarium moniliforme var. subglutinans

Symptoms – Vegetative malformation – Bunchy top symptom Floral malformation – produce huge number of flowers gives bushy appearance

2. Powdery mildew – Oidium mangiferae Symptoms – White podery growth on leaves, Tender shoots, floral parts, Fruits

3. Anthracnose – Gloeosporium gloeosporioides Symptoms – Leaf spot – Circular, Reddish brown spot on leaf surface

Die back – Dieing of twigs from tip to downwards Floral blight – blackening of floral axis Fruit – Irregular black lesion o fruit leads to rotting

4. Die back – Botrydiplodia theobromae 5. Sooty mould – Capnodium ramosum 6. Grey blight – Pestalotiopsis mangiferae 7. Red rust – Cephaleuros virescens 8. Bacterial canker – Xanthomonas campestris pv. mangiferae-indica 9. Giant mistletoe – Dendropthe sp. 10. Bacterial leaf spot – Pseudomonas mangiferae-indicae


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CITRUS 1. Gummosis, leaf fall and fruit rot – Phytophthora spp. 2. Diplodia gummosis – Diplodia natalensis 3. Ganoderma root rot – Ganoderma lucidum 4. Anthracnose – Colletotrichum gloeosporioides 5. Citrus canker – Xanthomonas axonopodis pv. citri Symptoms

On leaves: Small yellowish spots on leaves – spots swell and raised above the surface as brown corky outgrowth of spongy eruption – spots surrounded by yellow halo. On twigs: irregular raised cankers on the surface resulting in drying On fruits: round to irregular raised cankerous growth on the surface.

6. Cirus greening – Candidatus liberobacter (Fastidious phloem limiting bacteria) Symptoms

- Reduced foliage with severe die back of twigs - Fruits fails to ripen and remain green imparts unpleasant flavour to juice

7. Tristeza – Citrus tristeza virus Symptoms

- Vein flecking seen on leaves - Severe stem pitting is seen - Die back of entire tree

8. Exocortis – Citrus exocortis viroid

9. Fruit rots i. Blue & Green mould – Penicillium spp ii. Alternaria rot – Alternaria citri iii. Soft rot – Aspergillus niger iv. Sour rot – Geotrichumcandidum

10. Red rust – Cephaleurosvirescens

GRAPEVINE 1. Powdery mildew – Uncinulanecator Symptoms

- Occurs on all stages of crops - White powdery growth on the upper surface of leaves, tender shoots, tendrils, floral parts

and immature fruits - Infected leaves dried and fall off

2. Downy mildew – Plasmopara viticola Symptoms

- Occurs on all stages of crops


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- White downy growth on lower surface of leaves and corresponding to upper surface yellow discoloration is seen

- Infection on fruits shows downy growth and fruit splitting is also seen - Infected leaf dried off and stick to plant itself

3. Anthracnose (Bird’s eye spot) – Elsinoe ampelina Symptoms

- Fruits – Depressed, circular, brown spot on fruit surface resembling bird’s eye with grey centre

- Laves – Dark brown spot with grey centre surrounded by yellow halo - Stem – Black elliptical sunken lesions on young shoots cause girdling & death

4. Fruit rot i. Grey mould – Botrytis cinerea ii. Blue mould – Penicillium digitatum iii. Soft rot – Phomopsis viticola iv. Stalk end rot – Aspergillus niger v. Penicillium rot – Penicillium canescens vi. Rhizopus rot – Rhizopus nigricans

5. Fan leaf – Grapevine fan leaf virus (Vector: Xiphinema index) 6. Leaf roll – Grapevine leaf roll associated virus (Vector: Mealy bug)

GUAVA 1. Wilt – Fusarium oxysporum f.sp. psidii

2. Fruit canker / Scab / Grey blight – Pestalotiopsis psidii Symptoms

- Infected green fruits has small, brown colord, unbroken, circular scabby raised lesions

3. Anthracnose – Gloeosporium psidii 4. Red rust – Cephaleuros virescens 5. Fruit rot – Phomopsis psidii

SAPOTA 1. Leaf spot – Phavophloeospora indica 2. Sooty mould – Capnodium sp. 3. Flat limb – Botryodiplodia theobromae

PAPAYA 1. Stem rot / Foot rot – Pythium aphanidermatum and Rhizoctonia solani Symptoms

- On mature plants, show complete decay of basal portion of the stem - Fruits shriveled and drop off


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2. Powdery mildew – Oidium caricae 3. Anthracnose – Colletotrichum papaya 4. Leaf spots – Cercospora papaya

5. Ring spot – Papaya ring spot virus Symptoms

- Leaves – Circular, chlorotic ring spot is seen - Severely infected leaves become linear & thread like showing shoe string / Rat tail

symptom - Fruits – Chloroticringspot is seen on fruit surface with concentric rings - On petiole & stem of the plant having linear oil streaks

6. Damping off – Pythium spp.

APPLE 1. Apple scab – Venturia inaequalis

- Symptoms – Scattered, rough, Circular, brown spots appear on leaves and they may be slightly raised

- On fruits – Small, rough, black, circular lesions on their skin and they enlarge and then depress leading to shrinkage

2. Powdery mildew – Podosphaera leucotricha Symptoms

- All parts of tree are affected. Small grayish or white patches of fungal growth appear. - Affected leaves become crinkled, curled and the entire surface of leaf is covered with

fungus. - On fruits causes depression andaffected fruits harden and develop cracks.

3. Fire blight – Erwinia amylovora Symptoms

- Infected flowers, leaves and twigs become water soaked, shrivel, turn brown to blackish and fall or remain hanging in the tree.

- Infected fruits mummified and finally turn black and clinging to tree

4. Crown gall – Agrobacterium tumefaciens Symptoms

- Hard and corky galls appear on the stem and roots at the crown region and infected plants are stunted and chlorotic.

VEGETABLES TOMATO

1. Damping off – Pythium aphanidermatum • Seedlings are affected. • Brown discolouration at the lower portion of stem.


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• Seedlings become weak and collapse.

2. Early blight – Alternaria solani • Symptoms are observed on leaves, stem and fruits. • Brown, necrotic and irregular with concentric zones on leaf • On stem brown discoloration leads to girdling.

3. Wilt – Fusarium oxysporium f. sp. lycopersici • Affected plants exhibits yellowing of lower leaves • Internal stem portion exhibits, vascular browning.

4. Leaf curl - Tobacco leaf curl virus (Vector – Whitefly – Bemissia tabaci)

5. Spotted wilt – Tomato spotted wilt virus - Thrips • Necrotic irregular spots are visible on the surface of leaf with green centre. • Leaf exhibits bronzing. • On fruit, pale yellow patches are scattered on the surface.

6. Septoria leaf spot - Septoria lycopersici

BHENDI 1. Yellow vein mosaic - Yellow Vein Mosaic Virus

• Main and lateral veins are bleached. • Interveinal portion exhibits green color later bleached off.

CUCURBITS 1. Anthracnose – Colletotrichum lagenarium 2. Downy mildew – Pseudoperonospora cubensis.

• White patch of downy growth on undersurface of leaf. • Upper surface correspondingly shows yellow patches. • Leads to drying of leaves.

3. Powdery mildew - Erysiphe cichoracearum • Whites powdery growth on the upper surface of leaf. • Leaf exhibit drying.

4. Cercospora leaf spot - Cercospora citrunella 5. Mosaic - Cucumis virus 1 (Vector: Aphids)

CHILLIES 1. Damping off – Pythium aphanidermatum 2. Die back and fruit rot - Colletotrichum capsici

• Symptoms are seen on stem and fruit – stem shows die back symptoms. • Water soaked spots are seen on mature fruits - Affected portion turns white. • Acervuli are formed on the spots and seen as black dots in large numbers.

CRUCIFERS


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1. Club root of cabbage – Plasmodiophora brassicae Symptom

• External symptom: Yellowing, wilting and stunting of the plant. • Internal symptom: Club like swelling of root and rootlets due to hypertrophy and

hyperplasia. Management

• Lime application at the rate of 2.5t/ha. • Soil drenching with pentachloronitrobenzene.

2. Black leaf spot – Alternaria brassicae 3. White rust – Albugo candida 4. Downy mildew - Peronospora parasitica

TURMERIC 1. Leaf spot - Colletotrichum capsici Symptom: Elongated irregular lesions with brown margin and grey centre with acervulli.

2. Leaf blotch – Taphrina maculans Symptom: Irregular reddish brown lesions formed in between the vein and veinlets.

3. Rhizome rot – Pythium graminicolum Symptom: Rotting of the rhizome under the soil. Finally leads to the death of the plant.

POTATO 1. Early blight - Alternaria solani 2. Late blight - Phytophtor ainfestans Symptom

• Irregular black lesions seen on the leaf tip and margin. • Later spreads to whole parts of the plant and leads to death of the plant and rotting

of the tuber. Management:

• Fosetyl aluminium – 0.1% 3. Common scab - Streptomyces scabies Symptom: Scabby out growth on the surface of the tubers

4. Black scurf - Rhizoctoniasolani Symptom

• Brown, sunken, circular or elongated lesions on the lower portion of sproutsand girdling of infected stem

• Black irregular sclerotic are found in skin of tubers with brown discoloration.

5. Brown rot – Pseudomonas solanacearum Symptom:

• Sudden wilting of the crop. • Vascular browning is seen on the infected tube.


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• It is also associated with bacterial ooze out.

6. Mosaic – PVY, Vein banding virus

COFFEE 1. Rust – Hemilia vastatrix Symptom Orange or yellow raised pustules seen on the lower surface of the leaf. Management

Carboxin, Oxycarboxxin, Bordeaux mixture (0.5%) 2. Anthracnose - Colletotrichum coffeeanum 3. Brown eyespot – Cercospora coffeeanum 4. Sooty mould – Capnodium sp.

TEA Blister blight – Exobasidium vexans Symptoms

• Depression on the upper surface of leaf • Bulging on lower surface covered with myceial growth • On stem – Blisters are seen showing craking symptoms

Management • Foliar spray – COC – 0.25% + Nickel Chloride – 0.1%

POST HARVEST DISEASES OF STORAGE GRAINS Losses

Fruit & vegetables – 20-30% Food grains – 9.3% Post Harvest disease occurs in transit and storage are mainly due to the activity of fungi,

bacteria and of non-parasitic origin.

Effects of storage fungi on grains 1. Decrease the germination 2. Reduce the quality of grains 3. Cause discoloration of seeds 4. Produce toxins in stored grains 5. Cause biochemical changes and damage seeds 6. Cause heating and affect quality

Aflatoxin produced by Aspergillus flavus in groundnut, which is highly toxic. Heating favours growth of storage fungi. At higher temperature (45oC) grains get killed.

A. A. flavus & A. glaucus - 45oC B. Mucor - 30oC C. Fusarium - 35oC D. Alternaria - 25oC

Fungus require Moisture content of about Aspergillus flavus – 17.5 – 18%


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Aspergillus candidus – 15 – 15.2% A. restrictus – 13.2 – 13.5%

Management • Harvest and store the crops at optimum moisture content 12-13% and temperature

12-15oC • Fumigate the storage godowns • Provide proper ventilation to storage godowns

Disease of vegetables and fruits Infection may occurs before harvesting, during post harvest handling or storage. Ripened fruits are infected easily, while green fruits show resistance. Reasons are,

1. Nutritional requirement of fungus is not met out b the fungus 2. Higher enzyme potential is needed to invade green fruits 3. Phenolics and some other toxins present in the green fruits 4. Energy requirement of fungus is met out in ripening stage of fruit only.

Causal organism Biotic factors Soft rot producing bacteria, Fungus due to predisposing factors such as humidity, temperature, presence of bruises or lesions on fruits and vegetables

Abiotic factors When fruits and vegetables stored in poor ventilated conditions such s High level of CO2, Low O2 post harvest disease may happen.

Black heart of apple and Potato – caused by lack of oxygen (High temp, poor ventilation)

Crop Fungus Damage

Paddy Trichoconis pudwickii Black discoloration of grains

Drechlera oryzae Alternaria alternata Fusarium moniliforme Aspergillus niger, A. flavus Penici l l ium chrysogenum, Mucor, Rhizopus sp

Brittleness of grain

Wheat Anguina tritici (Nematode) Produce galls in seeds

Sorghum Fusarium moniliforme Grains converted in to smuts

Groundnut Aspergillus flavus, A. candidud, A. repens, A. restrictus

Kernals infected were contains aflatoxin


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Mode of entry Post harvest pathogens are weak pathogens - enter through injuries or natural openings.

Post harvest disease management 1. Chemicals : Benomyl, Imazalil, TBZ (Thiobendazole), Prochloraz, Sodium

hypochlorite 2. Heat treatment 3. Irradiation 4. Low temperature storage

Fruits / Vegetables Disease Causal organism

Apple and Pear Blue mould Pencillium expansum

Green mould Penicillium digitatum

Black mould Aspergillus niger

Soft rot Rhizopus arrihius

Bitter rot Gloeosporium fructigenum

Banana Anthracnose Colletotrichum musae

Cigar end rot Verticillium theobromae

Mango Anthracnose Gloeosporium gloeosporioides

Cirus Green mould Penicillium digitatum

Stem end rot Diplodia, Alternaria

Internal browning / Pitting Low temperature (4OC)

Grapes Blue mould Penicillium italicum

Tomato Alternaria rot Alternaria sp.

Soft rot Erwnia caratovora

Phoma rot Phoma destructive

Cabbage Black rot Xanthomonas campestris

Potato Soft rot Erwinia caratovora

Gangrene Phoma exigua var. foveata

Silver scurf Helminthosporium solani

Sweet potato Black rot Ceratocystis fimbriata

Rhizopus sof rot Rhizopus stolonifer


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5. Maintenance of host resistance

BIOLOGICAL CONTROL Biological control - reduction of inoculum density or disease producing activities of a Pathogen by introduction of one or more antagonists. Biological control is nothing but control of plant diseases using living microorganisms. The four main mechanisms involved in the biocontrol are

(i) Parasitism - antagonist parasite the other organism, (ii) Antibiosis - antagonist may secrete harmful metabolites (iii) Competition - antagonist may compete with the pathogens for nutrients or space (iv) Lysis - may cause death of the parasite by producing enzymes

Fungal biocontrol agents • Trichoderma viride • Chaetomium globosum (Gliocladium virens) • Trichoderma harzianum • T. hamatum • Paecilomyces lilacinus (Verticillium leccani) • Pochonia chlamydosporia • Laetisaria arvalis

Bacterial bioconrol agents • Pseudomonas fluorescens • Bacillus subtilis • B. thuringiensis • Streptomyces griseoviridis • Agrobacterium radiobacter • Pasteuria penetrans (for RKN)


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plant pathology - agademy · khaira disease of paddy - zn deficiency 2. infectious diseases • a...

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