Plant pathology

           PLANT PATHOLOGY

Plant pathology:Plant pathology is the scientific study of plant diseases, including their causes, mechanisms, and management.

SCOPE:

Key Areas:

• • Disease Diagnosis: Identifying and diagnosing plant diseases caused by pathogens, pests, or environmental factors.

  • Disease Etiology: Studying the causes and mechanisms of plant diseases.

  • Disease Management: Developing and implementing strategies to prevent, control, or mitigate plant diseases, including cultural practices, chemical control, biological control, and breeding for disease resistance.

  • Epidemiology: Investigating the spread and dynamics of plant diseases in populations, including the role of environmental factors, host plants, and pathogen populations.

  • Pathogen Biology: Studying the biology and ecology of plant pathogens, including their life cycles, genetics, and evolution.

History:

•   1675 - Dutch worker Anton von Leeuwenhoek -first microscope.

•   1729 - Italian botanist P. A. Micheli proposed fungi comes from spores; father of Mycology.

•   1821 - E. M. Fries published Systema Mycologicum for naming of fungi

•  1845 - Irish Potato famine due to Phytophthora infestans caused starvation of million and    immigration of 1.5 million people.

•  1858 - J. G. Kuhn published first textbook in Plant Pathology – The Diseases of Cultivated Crops, their Causes and their Control.

•  1861 -Anton de Bary (Germany) worked out the life cycle of potato late blight and first to prove experimentally Phytophthora infestans is the cause of potato late blight. He proved that fungi are causes but not the results of diseases.Father of Modern Plant Pathology.

•  1865 – Anton de Bary reported heteroecious nature of wheat stem rust.

•  1869 – England loses coffee production to coffee rust, forced to grow tea.

•  1877 – M. S. Woronin discovered and named the Club root of Cabbage pathogen as Plasmodiophora brassicae.

•  1878 – M. S. Woronin found out the life cycle of potato wart disease.

•  1878 -Downy mildew of grapevine was introduced into Europe from America. The disease almost ruined the wine industry.

•  1881 -H.M. Ward worked out the life cycle of coffee leaf rust. He is called as Father of Tropical Plant Pathology.

•    1882 -Robert Hartig published a textbook -Diseases of Trees."Father of Forest Pathology".

•  1885 -Pierre Marie Alexis Millardet  discovered Bordeaux mixture for the control of downy mildew of grapevine.

•   1887 -Burgundy mixture introduced by Mason of France.  

PLANT DISEASES:

     A  Plant disease is a condition that interferes with a plant’s normal growth, development, and function, often caused by pathogens or environmental factors.

CLASSIFICATION OF PLANT DISEASES:

1. Contact disease: These diseases are limited to a definite area of an organ or part(s) of a plant. e.g. leaf spots and anthracnoses caused by fungi.

2. Systemic diseases: In these diseases the pathogen spreads from a single infection point to infect all or most of the host tissues, e.g. Downy mildews caused by fungi and mosaics and leaf curls caused by viruses.

On the basis of parts of host affected:

· Foliage diseases – affecting aerial parts such leaves

· Stem diseases

· Root diseases

Type of perpetuation and spread:

a.Soil-borne diseases: The causal agents perpetuate and spread through soil. E.g. Damping off caused by fungi Pythium spp.

b.Seed-borne diseases: Seed or seed materials help in the perpetuation and spread of this disease.  disease-causing agents may be internally seed-borne or externally seed-bone. E.g. Loose smut of wheat caused by Ustilago nuda tritici (internally seed-borne).

c.Air-borne diseases: The causal agents are spread by wind (air). E.g. Early leaf spot and late leaf spot of groundnut caused by Cercospora arachidicola and Phaeoisariopsis personata respectively.

                          Extent of occurrence and geographic distribution:

a.Endemic diseases:

·Also known as endophytotic disease.

·When a disease is more or less constantly occurring year after year in a moderate to severe form in a locality

·e.g. Wart disease of potato caused by Synchytrium endobioticum is endemic to Darjeeling.

b. Epidemic or epiphytotic diseases:

·Epiphytotic refers to sudden outbreak of a disease periodically over a widespread area in a devastatingly severe form causing extensive losses or complete destruction.

·It may be present constantly in the locality but assumes severe form only on occasions. e.g. late blight of potato (Phytophthora infestans)

c.Sporadic diseases: It occur at irregular intervals over limited areas or locations. e.g. Fusarium wilt of cotton (Fusarium oxysporum f.sp. vaxinfectuon)

d. Pandemic diseases: A disease is said to be pandemic when it is prevalent throughout the country, continent or world involving mass mortality. e.g. Late blight of potato and wheat stem rust.

Robert Koch :

         Robert Koch (1843-1910) a German Bacteriologist

• • 1876: proved- animal disease, anthrax is incited by a bacterium, Bacillus anthracis.

  • 1882: announced plate method of isolating bacteria using gelatin  medium

  • He was awarded Nobel Prize in 1905

        'Koch's postulates

1. The microorganism must be found in all organisms suffering from the disease, but not in healthy organisms.

2. The microorganism must be isolated from the diseased organism and grown in a pure culture.

3. The cultured microorganism should cause the disease when introduced into a healthy organism.

4. The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent. 

SYMPTOMS AND SIGNS OF PLANT DISEASES:

Symptoms- External expression or the evidence of the abnormalities in the appearance of the diseased plants brought about by the pathogens after host-pathogen interaction.

Sign- When the pathogen itself becomes visible on the host surface in the form of its organs or structures. Eg. Sclerotia, mycelium etc.

Disease syndrome- A sum of variety of symptoms produced by the disease.

1.Symptoms of Plant Diseases Due to the Character and Appearance of Visible Pathogen, its Structures and Organs

Mildews: simplify – reduce words

       White, grey, brownish or purplish pathogen growth on the host surface.

• • Downy mildew -Downy growth mostly on  lower surface of leaves or other plant parts.

  •  Powdery mildew -Black minute fruiting bodies may also develop in the powdery mass.

Rust:

·Small pustules of the spores, usually breaking through the host epidermis.

·Pustule-small blister-like elevation of the epidermis

Smut:

·Smut -sooty or charcoal like powder.

·The affected parts of the plants show black or purplish black dusty areas.

White Blister:

·  White blister-like pustules appear on the leaves and other parts of cruciferous plants.

Blotch:

   Superficial growth giving the affected plant parts ie., fruits and leaves smoky (blotched) appearance, e.g. sooty blotch of apple.

Sclerotia:

·Sclerotium-compact, often hard mass of dormant fungus mycelium.

·Sclerotia-dark in color and are found mixed with the healthy grains

Exudation:

  Mass of bacterial cells ooze out on the surface of the affected organs where they may be seen as drop or smear in several bacterial diseases such as bacterial blight of paddy, gummosis of stone fruits and fire blight of apple and pear.

Mycelial growth:

  Appearance of white cottony, mycelial growth of the fungi like Dematophora necatrix

II. Symptoms Resulting from Internal Disorders in the Host Plants

Colour change

·Etiolation is yellowing due to the lack of light.

·Chlorosis is yellowing due to low temperature, lack of Iron.

·Albinism-leaves become devoid of any pigment and look bleached or white.

·Chromosis is change of colour to red, purple or orange.

Overgrowths or hypertrophy

·Hypertrophy is the abnormal increase in the size of the plant organs due to increase in the size of  the cells of a particular tissue.

·Overgrowths cause galls, curl, pockets or bladders, hairy root, witches’ broom.

Necrosis:

·Death of the cells, tissues and organs occurs as a result of parasitic activity.

·Symptoms include spots, streaks or stripes, canker, blight, damping off, burn

Wilt:

·Drying of the entire plant.

·Leaves and other green or succulent parts lose their turgidity, become flaccid and droop down.

Die-back or Wither Tip

·Drying of plant organs, especially stems or branches, from the tip Backwards.

·Die back symptom on Mango and citrus.

                                       DIAGNOSIS OF PLANT DISEASES

Diagnosis of plant diseases:

          Diagnosis – refers to the process of identifying the cause of abnormal symptoms or signs in plants.

·Serological methods – based on protein of the pathogen

·Molecular methods – based on the nucleic acid genome of the pathogen

I. Chemodiagnosis

       It is a technique of identification of plant pathogens (viruses) using certain chemicals.

Tetrazolium chloride test

·This method is specially followed for detection of Banana bunchy top virus and cassava mosaic viruses.

·This helps in selection of disease free planting materials.

ii. Iodine test

     To Identify rice tungro virus infection.

iii. Paraquat test

     The herbicide paraquat (1,1′-dimethyl4,4′-bipyridinium dichloride) has been used to enhance the detection of latent infection of species of Colletotrichum, Alternaria, Botrytis, Cercospora,Phomopsis and other fungi on healthy appearing plant material.

II. Serodiagnosis

     The study of relationship between an antigen and an antibody is called serology. All serological assays depends on the interaction between an antigen and an antiserum.

Serology : Study of relationship of antigen and antibody

Antigen : Protein that induces the production of specific proteinaceous antibodies in warm

blooded animals

Antiserum : The blood serum containing antibody

Antibody : A specific protein formed in the blood of warm blooded animals in response to the

injection of an antigen

Important Serological Methods

• Agglutination / Microprecipitin test

• Gel diffusion / Double diffusion test

• Enzyme Linked Immuno Sorbant Assay

• Dot Blot Immunoassay

• Western blotting

• Immunostrip / Lateral flow Assay

ELISA (Enzyme linked Immunosorbent Assay)

     The Enzyme Linked Immuno sorbent Assay (ELISA) is one of the most widely used serological test for detection of plant viruses, identification, quantification and comparison owing to its simplicity, sensitivity and adoptability.

Limitations of applications of Serology to Diagnosis

1. Measures virus protein, not infectious virus

2. Possible cross-reactions - chance of false positives

3. Positives are limited to viral antisera used

4. Plants may be infected with another virus

Polymerase Chain Reaction: The technique, which generates unlimited numbers of copies of specific DNA within a short time by a relatively simple enzymatic method. PCR was invented by Kary Mullis during 1985 to amplify specific DNA sequences.

PCR Applications

·Characterising the structure and expression of genes

·Identifying disease-causing genes and pathogens

·DNA fingerprinting in forensics, agriculture and archaeology

·PCR reaction components

DNA Template - Original DNA that contains the target sequence that will be copied and

amplified

DNA Polymerase - Taq Polymerase (Thermus aquaticus ) that synthesizes new strands of

DNA complementary

Primers – A short piece of single-stranded DNA that is complementary to the template. The

polymerase begins synthesizing new DNA from the end of the primer. Primers should be 10-24

nucleotides in length & GC content should be 40-60%. It should not be self-complementary or

complementary to any other primer in the reaction mixture.

Nucleotides:

 Single units of each of the bases A, T, G and C- dNTPs (deoxynucleotides).

These act as ‘building blocks’ for the new DNA strands.

Types of PCR

1. PCR based molecular markers (Conventional)

·RAPD – Random segments of genomic DNA

·RFLP - RFLP analysis the DNA sample is broken into pieces by restriction enzymes and the resulting restriction fragments are separate according to their lengths by electrophoresis.

2. Multiplex PCR

3. Reverse transcription –PCR (RT-PCR)

4. Nested PCR

5. Immunocapture PCR

6. Real-time – PCR

                                        Seed Health Testing Methods

1. Examination of dry seeds

·Detection of seed borne fungal pathogens which cause discoloration of the seed or change the shape and size of the seed.

·Suitable to detect the sclerotia, galls, smut balls, discolouration, malformation,resting hypha, fruiting bodies of fungi (oospores, smut spores, pycnidia, perithecia) and bacterial masses.

2. Seed washing technique

      Useful in testing surface-borne, contaminating fungi like smuts, bunts, downy mildews,

powdery mildews, rusts, etc.

Example:Flag smut of wheat (Urocystis agropyri)

3. Blotter method

      All kinds of cereals, vegetables, Crucifers, legumes, ornamental and forest seeds are tested by this method.

4.Freezing blotter method

     It is a modified blotter method, wherein the blotters are incubated at 20°C for 2 days, then at -20°C for a day and again at 20 °C for 5-7 days

5. Agar plate method

·Seeds are treated with 1% sodium hypochlorite solution (to prevent the

growth of saprophytic fungi for 5-10 minutes.

·Then, seeds are placed on potato dextrose agar medium or malt extract agar medium and incubated at 20±2 C for 7 days.

6. Grow on test /Seedling symptom test

· Applicable for those fungi which are capable of producing symptoms on the root and shoot of the young seedlings.

· Grow on test is normally used to determine virus seed transmission.

7.Indicator test

     Viruses can be detected by assaying the extracts of different parts of seeds and seedlings

raised from infected seeds on suitable indicator plants.

Disease pyramid also known disease triangle or disease tetrahedron.

The Four Components:

1. Host Plant: The susceptible plant species or variety.

2. Pathogen: The disease-causing agent, such as a fungus, bacterium, or virus.

3. Environment: The external conditions, like temperature, humidity, and light, that influence disease development.

4. Time: The duration of exposure and the timing of infection.overning epiphytotics

Role of weather factors in disease development

1. Effect of temperature

      Eg;Ralstonia are favored by a higher temperature.

The high temperature favours few diseases

·Powdery mildew of black gram, green gram , beans – severe in summer

·Dry root rot of pulses – severe when temperature is >30-350C
·Yellow mosaic of pulses- severe in summer due to more whitefly population 

         Bacterial leaf blight – severe when temperature is around 25-300C

2.Effect of soil moisture
      Common scab of potato (Streptomyces scabies) and onion white rot (Sclerotium cepivorum) are most severe under low moisture levels.

3.Effect of wind
      Fungi, bacteria and viruses that are spread either directly by wind or indirectly by insects which can travel long distances with the wind, e.g., uredospores of rusts and conidia of many fungi are transported to several kilometers by wind.

4.Effect of light
    Reduced light intensity which in turn increases the susceptibility of plants to non-obligate parasites

5.Effect of soil pH
        Growth of potato scab (Streptomyces scabies) pathogen more severe at a pH 5.2 to 8.0 or above.

6.Effect of host-plant nutrition
  Nutrition affects the rate of growth and the state of readiness of plants to defend themselves against pathogenic attack.eg:

·Phosphorus has been shown to reduce the severity of potato scab but to increase the severity of cucumber mosaic virus 

                                                                Survival and Dispersal of Plant Pathogens

I. Survival of Plant Pathogens
      Chief sources of survival of plant pathogens are:

      i. Infected living hosts
      ii.Infected or contaminated planting organs

      iii.Infected crop residues

      iv.Resting structures

      v.Soil

Infected living hosts

·Infected plants are the most important sources/reservoir of inoculum for plant diseases. Bacteria, fungal spores and spore producing structures such as pycnidia, acervuli etc. may survive the unfavorable season in the infected twigs and branches of perennial plants.

·For example Erwinia amylovora in apple.

a)Collateral hosts

b) alternate hosts  

c) wild hosts of the same family and

d) weed hosts. Fungal pathogens like Alternaria solani and A. brassicicola mostly attack members of Solanaceae and Brassicae family, respectively which are their collateral hosts.

Disease survey and surveillance

·Disease surveillance is an information-based activity involving the collection, analysis and interpretation of large volumes of survey data collected from different sources.

Uses:

· prevalence of disease in a crop in a particular area
·damages caused by a disease and assess the economic loss of the disease
·to give suitable forecasting to the farmers about the outbreak of the disease

Methods of Survey

i. Fixed plot survey

·Select two villages and fix two fields per village
·Select five sampling plots per field of one acre and it should be three metres away from the bunds
·The size of the sample plot should be 1 sq. m.

Select 50 or 100 plants or leaves per plot and observe for the disease intensity using the
standard disease score chart having 0-9 grades
·Work out the Per cent Disease Index (PDI) or per cent disease incidence using the standard formula

Roving survey

·Select four villages and in each village, fix two fields
·Observe and score 100 plants or leaves in each field by walking across, starting from South West corner to North East corner
·Work out the PDI or per cent disease incidence using the standard formula
Disease surveillance reports
i.White Report
It contains the disease/pest surveillance detail in a particular block/division/district for a week.

ii. Yellow Card
It should be sent when the disease/pest occurrence attained half the level of Economic Threshold Level (ETL).

iii. Red Card
It should be sent when the disease/pest occurrence exceeded the Economic Threshold Level.

Blister blight of tea – No. of spores in air in tea plantation and duration of surface wetness

-The duration of sunshine is negatively correlated

Rice blast – Minimum night temperature (20 to 260C), RH (>90%)

Wheat stem rust – Air borne primary inoculum and its deposition

           . Eradication - Role of cultural practices in plant disease management- Different methods of Eradication of Plant Diseases

Cultural Methods of Plant Disease Management

1. Host eradication

·When a plant pathogen enters into new area despite quarantine, a plant disease epidemic occurs.

·To prevent such epidemics, all the host plants infected by pathogen may have to be removed and burned.

·This type of eradication of pathogen was done in Florida and other southern states for control of bacterial canker of citrus in 1915.

2. Crop rotation

·The field is tilled and left fallow for a year or part of year.

·During fallowing, pathogen debris and inoculum are destroyed by microorganism with little or no replacement.

3. Sanitation

·Sanitation consists of all activities aimed at eliminating or reducing the amount of inoculum present in a plant, field or a warehouse and at preventing the spread of the pathogen to other healthy plants and plant products.

4. Creating conditions unfavourable to the pathogen

·Stored product should be aerated properly to hasten the drying of their surface and inhibit germination and infection by any fungal or bacterial pathogens present on them.

·e.g. Phytophthora causing root rot

5. Polyethylene traps and mulches

·If reflectant aluminum or black, whitish-grey or colored polyethylene sheets are used as mulches between the plants or rows in the field, incoming aphids, thrips and possibly other insect vectors are repelled and misled away from the field.

6. Use of pathogen free propagating material

  When a pathogen is excluded from the propagating material of the host, it is often possible to grow the host free of that pathogen for the rest of its life. Examples are woody plants affected by non-vectored viruses. All types of pathogen can be carried in or on propagating material.

  Eradication of Plant Diseases

      Eradication is the process of reducing, inactivating, eliminating or destroying inocula at the source, or from an individual plant in which it is already established.

The practices include :physical, chemical and biological measures.

i. Eradication by physical method
                            ·Seed treatment with captan or thiram @2g/kg seeds for brown spot of Rice
                                            (Helminthsoporium oryzae)
                            ·Luthras solar treatment for loose smut of wheat by soaking seeds in cold water for 4 h and spread in hot sun for 4 h
ii. Eradication by chemical method:
                            ·Seed treatment with vitavax@6g/ kg seeds for wheat loose smut and Apron @6g/ kg seeds for downy mildew
iii.Eradication of collateral hosts:.

·   Removal of Barberry plant will eradicate wheat stem rust pathogen   Puccinia graminis tritici on wheat
iv. Eradication of affected plant parts by tree surgery
·   Removal of affected plant parts reduces the source of primary inoculum. Affected branches on apple trees removes Fire blight bacterium (Erwiniaamylovora) v. Crop rotations:

·Wheat and potato to be rotated to eradicate Clubroot of cabbage (Plasmodiophorabrassicae ) .

   · Crop rotation with sugarcane or paddy is effective in the control of ‘Panama wilt’ of banana (Fusariumoxysporumf.sp. cubense)

vi.Fallowing :

·Fallowing starves the pathogen and helps in reduction of the inoculum by elimination of

the host.

vii.Field sanitations

·Destruction of infected leaf debris and rouging of infected plants

viii.Summer ploughing :

·Deep ploughing during summer periods buries/ exposes the sclerotia / chlamydospores

of the fungi to hot sun

ix.Adjustment of harvesting time:

·Harvesting of groundnut should not coincide with the rainy days and it helps to avoid infection by Aspergillus flavus.

x. Closer spacing

·Avoid closer spacing in tea reduces blister blight of tea

xi. Barrier cropping

·Barrier cropping with 3 rows of maize or sorghum around blackgram or greengram is

effective in reducing the vector population and incidence of yellow mosaic

xii. Yellow sticky traps

·Sticky, yellow polythene sheets in field attract the aphids and stick to sticky polythene.

xiiii. Avoiding ratoons

·Ratooning is a general practice in sugarcane where the incidence of grassy shoot disease and red rot are very high.

Zineb-Hexathane 75%wp can be applied--Early and late blight of potato and tomatoes, downy mildews and rust diseases of cereals:

Maneb-Indofil M – 22--Broad spectrum against foliar fungal pathogens:

Mancozeb-Indofil M – 45--Broad spectrum / foliar pathogens:

Nabam-Indofil A – 40--Leaf spot diseases:

Vapam-VPM, Vapam--Soil borne pathogens:

Dialkyl dithiocarbomates

Ziram--Ziram, Cuman, Milbam--Anthracnoses

Ferbam--Coromat, Febam, Ferberk--Antracnoses

Thiram--Thiram,TMTD--Seed treatment

Phytotoxicity :Sulphur fungicides are phytotoxic to cucurbits and apple, when they are applied during warm seasons.

Mode of action of Sulphur fungicides:

              Three theories are proposed to explain the mode of action of sulphur fungicides.

1. Oxidised Sulphur Theory :

          S oxidised to form SO2 responsible for fungicidal activity

2. Hydrogen Sulphide Theory :

         H2S responsible for fungicidal activity
3. Direct Action Theory :

         H+ acceptor to disturb the hydrogenation in cells of fungi.

Special methods of fungicide application

  The special methods of fungicide application are swabbing (painting), acid delinting, pseudo stem injection, capsule application/corm injection, paring and pralinage, trunk injection and root feeding.

1. Swabbing (Painting)

  This method is normally practiced in ornamental / fruit trees after pruning. The fungicidal solution / paste is prepared at desired concentration and painted on the cut ends to prevent the entry of pathogens / saprophytes. Swabbing is also done after removing the diseased portion of the plant.

2. Acid - delinting

  This is especially followed in cotton to kill the seed-borne fungi and bacteria. The seeds are treated with concentrated sulphuric acid @ 100 ml / kg of seed for 2-3 minutes with continuous stirring. The seeds are then washed 2 or 3 times thoroughly with cold water to remove the acid and shade dried. After drying, they are treated with fungicide, captan or thiram @ 4 g/kg before sowing.

3. Pseudostem Injection

  This method is adopted for managing the aphid vector (Pentalonia nigronervosa) of Banana bunchy top virus in banana. The banana injector is used for injecting the insecticide.`

4. Capsule application

  It is an effective method used to manage Panama disease or Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense. Capsule applicator is used for this purpose.

5. Corm Injection

  It is also an effective method used to manage Panama disease or Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense. It is similar to that of capsule application. Capsule applicator is used for this purpose

6. Paring and Pralinage

  This method is adopted to manage Fusarium wilt and burrowing nematode (Radopholus similis) of banana.

7. Root Feeding

  Root feeding is normally adopted for the management of basal stem rot disease (Ganoderma lucidum) of coconut. The root region is exposed two feet away from the trunk by removing the top soil.

Common name/Trade name/Disease

i. Inorganic mercurials

Mercuric chloride/Merfusan, Mersil--Seed Treatment

Mercurous chloride/Cyclosan, M-C Turf fungicide for Club root

ii. Organo mercurialsMethoxy ethyl mercury chloride

Agallol, Areton, Ceresan wet, Emisan--Seed Treatment

Systemic fungicides

       A systemic fungicide is defined as fungitoxic compound that controls a fungal pathogen remote from the point of application, and that can be detected and identified.

Common Name/Trade Name/Diseases controlled

• Benomyl--Pre and post harvest spray for post harvest diseases; blast, scab, powdery mildews, Verticillium and Rhizoctonia

• Carbendazim--Bavistin, Tagstin--Leaf spots and rusts; Fusarium and Cercospora

• Thiabendazole--Thiabendazole--Botyti ,Cercospora, Ceratocystis, Septoria, Colletotrichum, Fusarium, Rhizoctonia

Mode of action of systemic fungicides

· Inhibits sterol biosynthesis

· Inhibits mitosis and cell division

· Inhibits the production of lipids and membrane synthesis

Fungicide                                                                      Reaction site                                                            Biosynthesis

Metalaxyl                                                                Nucleic acid synthesis                                        Inhibition of ribosomal RNA

Carbendazim, Thiobendazole,Benomyl                 Nucleic acid functions                                               Cell wall breakage

Tridemorph, Dodemorph                                        Sterol biosynthesis                                    Inhibitiors’ of cell cytoplasm

Ediphenphos, IBP                                              Cell wall synthesis                                         Chitin incorporation through membrane transport

Foestyl Al.                                                             Respiration - mitochondria                  Electron transport chain poisoning

Thiophane methyl,Thiophanate                               Nuclear functions                                         Mitosis and microtubule fubctioning

Bitertanol, Triademefon                                           Sterol biosynthesis                                           C- 14 methylation inhibition

Systemic induced resistance (SIR) chemicals

  The SIR chemical is nothing but the chemical which has the ability to induce host plant

resistance upon its application on plant.

· Messenger – United States

· Bion, Actigard – Europe

· Agri-fos – Australia and US

· Oryzemate – Japan

ANTIBIOTICS
  Antibiotic is defined as a chemical substance produced by one microorganism which can inhibit or even kill other microorganism at low concentration. In general, the antibiotics are classified into two groups viz., antibacterial antibiotics (effective against bacteria) and antifungal antibiotics (effective against fungi).

Mode of action of antibiotics
Antibacterial antibitics
            ·Streptomycin act as uncoupling agent and inhibit electron transport. Sterptomycin also inhibits protein synthesis
            ·Tetracyclin known to inhibit protein synthesis, amino acids and ribosomal protein Antifungal antibitics
            ·Aureofungin causes disruption of cell wall
            ·Griseofulvin inhibits chitin and protein synthesis in fungi
            ·Cyclohexamide inhibits protein and nucleic acid synthesis and incorporation of some amino acids in fungi

Toxicity levels of fungicide
   Toxicity levels of the fungicidal formulations are based on the LD50 values. LD50 means the concentration of the chemical at which 50 per cent of the test animals dead, which is expressed as mg/kg body weight of the test animal. The toxicity levels of the chemicals are

Red Triangle:Extremely toxic

Yellow Triangle:Highly toxic

Blue Triangle:Moderately toxic

Green Triangle:Slightly toxic

Disease resistance

· It is the ability of the plant to resist / retard / reduce the attack of a pathogen / disease
· Most simple, practical, effective and economical
· It ensure protection against disease and also save time, energy & money
· It is only method for virus / phytoplasma diseases

             IPM module for soil borne , Airborne , Seed borne and vector borne plant  diseases

The major components are listed below for respective diseases. Each and every method has to be discussed with examples.

IPM module for soil borne diseases

·Selection of geographical location / season
·Crop Rotation-different crop are planted sequentially on the same land over a period of time.

·Summer ploughing-tilled during summer months

·Soil solarization

·Soil fumigation

·Use of resistant variety

·Soil mulching

·Seed treatment – Biocontrol agents / chemicals

·Raised bed nursery

·Roguing out of infected palnts

·Nutrient management

·Soil application of neem cake / organic amendments

·Soil application of biocontrol agents / chemicals

·Irrigation management – Frequency and method

·Isolation trenches

IPM module for air borne diseases

• Selection of geographical area / season

• Crop rotation        

• Summer ploughing

• Hygiene- Removal of infected branches / fallen leaves and fruits

• Prophylactic spray

• Follow chemical spray schedule

IPM module for seed borne diseases

· Selection of seed Seed inspection and seed certification

· Physical methods – All physical agents viz., Solar (Luthras’), UV, heat forms, aerated

steam therapy

· Mechanical methods – Sieving / soaking in brine solution

· Seed treatment – Biocontrol agents / chemicals

IPM module for vector borne diseases

· Resistant varieties

· Virus free seed / planting materials

· Meristem tip culture

· Roguing – Hand / 2,4 D injection for banana

· Vector management – Traps like yellow sticky traps, pheromones, ttrap crops, predators

and parasitoids, etc

·Use of systemic insecticides for vector control

                                 DISEASE CAUSING MICROORGANISMS

Types of Plant Pathogens

1.Fungi and Fungal-like Organisms (FLOs)

·         Fungi and FLOs cause the most plant disease.

·         These organisms cannot make their own food, lack chlorophyll, have filamentous growth, and may or may not reproduce by spores.

2.Bacteria

·         Bacteria are single-celled microscopic organisms with cell walls that reproduce by binary fission (one cell splits into two).

·         It occur through natural openings or wounds in the plant. Bacteria overwinter primarily in soil and in or on plant material that does not decompose, but some survive inside insect vectors

3.Phytoplasmas:Phytoplasmasare microscopic, bacteria-like organisms that lack cell walls and thus appear filamentous

4.Viruses and Viroids

·         Viruses are intracellular (live inside the cell) nucleic acid particles with a protein coat that infect other living organisms and replicate in the hosts they infect.

·         Viroids are virus-like particles but lack a protein coat. Viruses and viroids are primarily transmitted by vectors including insects, nematodes, and fungi, which introduce the virus or viroid during feeding.

5.Nematodes

·         Nematodes are microscopic worm-like animals.

·         The majority of nematodes are soil dwelling animals and move with soil. However, there are some nematodes that are transmitted through insects and infect above ground plant parts.

6.Parasitic Higher Plants

·         Parasitic high plants are plants that contain chlorophyll but cannot produce their own food.

·         They parasitize other plants to obtain nutrients and water. Examples include mistletoe and dodder.

Inoculation

·         This describes the introduction of the plant pathogen to the host.

·         Different pathogen groups employ different inoculation methods and are equipped with various specialized mechanisms that aid in the inoculation process.

·         Ex:Some fungal pathogens release spores into the air and the spores are then spread with the aid of air currents.

Penetration

·         Wound sites and natural plant openings, such as stomata and hydathodes, facilitate the entrance of some plant pathogens; others have evolved unique mechanisms for direct penetration.

·         Fungi and nematodes are able to actively penetrate host tissues and cells if environmental conditions, such as moisture and temperature, are favorable for the penetration process.

Infection

·         This occurs when the pathogen invades the plant tissue and establishes a parasitic relationship between itself and the plant.

·         Viruses, bacteria, and phytoplasmas are not able to actively penetrate or enter plant host tissues.

Incubation

     Once inside the plant, pathogens may undergo an incubation period and remain latent for a period of time before initiating disease.

Reproduction

Plant pathogens can reproduce sexually and asexually.

Survival

Plant pathogens have can survive prolonged periods of unfavorable weather conditions. Ex: brown spot produce spores that are dark in coloration which reduces the amount of UV light penetrating and preventing cell death.

 1. Wheat                                                  

Disease Name  /////   Pathogen Name

                                                                                                       Major Diseases

        Black Rust / Stem Rust

        Puccinia graminis f. sp. Tritici

      1.Brick red colored elliptical blisters or pustules on stem,leaf,and leaf sheath

       2.At last pustules turns black

        Brown rust / orange rust / leaf rust

       Puccinia triticina (formerly P. recondita)

       1.Small circular to oval shaped,orange to brown cocored pustules on upper and lower surface of leaves

       Yellow rust / stripe rust

       Puccinia striiformis f. sp. Tritici

       Yellow coloured pustules between venis on leaf.

        Loose Smut

       Ustilago nuda tritici

       1.Seen in ear head stage.

       2.Spikelets are affected and transformed into a mass of black powdery spores.

        Powdery Mildew

        Blumaria graminis var. tritici

        Greyish white powdery growth appear on the upper surface of leaves

       Flag Smut

       Urocystis agropyri

       1.Greyish black linear sori occur on the leaf blade and leaf sheath

       2.Infected plants stunted in growth and bear twisted leaves.

       Rough bunt / Common bunt / stinking bunt / hill bunt

       Tilletia caries / T. laevis

       Infected plants produce smutted grains that emit a fishy stink smell.

       Karnal bunt / partial bunt

       Tilletia indica (Syn: Neovossia indica)

       1.Few grains are smutted

       2.Grains are converted into black powdery masses.

       Ergot

       Claviceps purpurea

       Creamy droplets of a sticky liquid exuding from young florets of infected heads

       Fusarium head blight / scab

       Fusarium graminearum (Gibberella zeae)

       1.Premature bleaching of one or more spikelets or entire immature  wheat ear head

       2.Bleached spikelets are sterile.

       Tundu / Yellow Ear Rot

       Rathayibacter tritici

       1.Formation of yellow slime on the inflorescence.

       2.It dries to form sticky yellow layers and cause curling of spikes

       2. Chickpea, Lentil, Sunflower and Mustard

       Disease Name //  Pathogen Name

       Wilt

       Fusarium oxysporum fsp cicero

       1.Seedlings are yellowing and drying of leaves, drooping of petioles and rachis, withering of plants.

       2.In adult plants drooping of leaves is observed initially in upper part of plant, and soon observed in entire plant.

       Ascochyta blight 

       Ascochyta rabiei

       On leaf, the lesions are round or elongated, bearing irregularly depressed brown spot and surrounded by a brownish red               margin.

       Rust

       Uromyces ciceris – arietini

        Infection appears as small oval, brown, powdery lesions on both the surface, especially more on lower surface or leaf.

       Dry root rot

       Rhizoctonia bataticola

       1.The infected plants show drooping of leaves and death occurs in patches.

       2.The bark of the lower stem and roots shreds

       Wet root rot

       Rhizoctonia Solani

       The infected seedling slowly turn yellow and petioles and leaflets show drooping symptoms

       Collar rot

       Sclerotium rolfsii

      1.Drying plants whose foliage turns slightly yellow before death, scattered in the field is an indication of the disease.                     Seedlings become chlorotic.

       2.Infected parts turn brown white.

       Stunt disease

       Chlorotic stunt virus

       1.Affected plants are stunted and bushy with short internodes.

       2.The leaflets are smaller with yellow, orange or brown discoloration. Stem also shows brown discoloration. The plants dry         prematurely.

       Lentil

       Fusarium Wilt

        Fusarium oxysporum f.sp. lentis

       1.the drooping and wilting of the uppermost leaflets and discolouration the vascular system.

       2.Plants become completely yellow and die.

       Ascochyta blight

        Ascochvta lentis

       1.lesions on leaves, petioles, stems and pods.

        2.The irregularly shaped lesions on leaves, petioles and stem are tan and darker brown on pods and seeds.

       Rust

       Uromyces viciae – fabae

       formation of yellowish-white pycnia and aecial cups on the lower surface of leaflets and on pods, singly or in small groups         in a circular form.

       Sunflower

       Root rot or charcoal rot

       Rhizoctonia bataticola

        The infected plants show drooping of leaves and death occurs in patches

       Leaf blight

       Alternaria helianthin

      1.The pathogen produces brown spots on the leaves, but the spots can also be seen on the stem, sepals and petals.

       2.The spots later enlarge in size with concentric rings and become irregular in shape.

       Downy Mildew

       Plasmopara halstedii

       1.yellowing of the first pair of true leaves.

       2.Affected plants bear abnormally thick, downward curled leaves showing prominent yellow and green mottling.

       3.The stem becomes brittle.

       Rust

       Puccinia helianthin

       1.Small, reddish brown pustules (uredia) covered with rusty dust appear on the lower surface of bottom leaves.

       2.In severe infection, when numerous pustules appear on leaves, they become yellow and dry.

       Head rot / Capitulum rot

       Rhizopus sp.

       1.The affected heads show water soaked lesions on the lower surface, which later turn brown

        2.The discoloration may extend to stalk from head.

       Powdery mildew

       Golovinomyces cichoracearum

       1.White powdery growth on the leaves White to grey mildew on the upper surface of older leaves.

        2.As plant matures black pin head sized are visible in white mildew areas

       Basal rot

       Sclerotium rolfsii

       1.The infected plants can be identified by their sickly appearance.

       2.Dark brown lesions appear on the base of the stem near ground level, leading to withering Large numbers of sclerotia are          seen.

       Necrosis - Tobacco streak virus (TSV)

       Tobacco streak virus

       Early infection either kills the plant or causes severe stunting with malformed head filled with chaffy

       Mustard

       Alternaria blight

       Alternaria brassicola and Alternaria brassicae

       1.The disease attacks on the lower leaves as small circular brown necrotic spots which slowly increase in size.

       2.Many concentric spots coalesce to cover large patches showing blightening and defoliation in severe cases.

       White rust

       Albugo candida (Cystopus candidus)

       white creamy yellow raised pustules appear on the leaves which later coalesce to form patches

       Downy Mildew

       Peronospora brassicae

       1.Light green or slightly chlorotic lesions that become yellow or necrotic after sporulation.

       2.Lesions are angular and variable in size

       Powdery mildew

       Erysiphe cruciferarum

       1.Symptoms appear as dirty white, circular, floury patches on either sides of the leaves.

       2.The whole leaf may be covered with powdery mass

       Club root

       Plasmodiophora brassicae

       1.Affected plants remain stunted.

       2.Leaves turn pale green or yellow followed by wilting and under severe conditions the plants die.

       Sclerotinia stem rot

       Sclerotinia sclerotiarum

       1.Elongated water soaked lesions appear on stem near to the crown region, covered with cottony mycelial growth later on.

       2.Premature ripening and shredding of stem, wilting and drying.

       Bacterial blight / black rot

       Xanthomonas campestris pv. Campestris

       1.The leaf tissue turns yellow and chlorosis reach towards the centre of the leaf and form V shaped area

       2.Dark coloured streaks are formed on the stem from the ground level and gradually these streaks enlarge and girdle the                stem.

       3.Stem become hollow due to internal rotting

        Parasitic weed – Broomrape

       Orobanche aegyptiaca L. (Orobanchaceae)

       Broomrape is an annual total root parasites lacking chlorophyll, upto 1 m tall.

       2.  DISEASES OF COTTON AND SUGARCANE

        Disease Name // Pathogen Name

       Cotton

       Fusarial wilt

        Fusarium oxysporum f.sp vasinfectum

        1.Wilting & drying of the seedling occur. Infection at later stages includes loss of turgidity, yellowing, drooping and                   wilting, starting from older leaves.

        2.Browning or blackening of vascular tissues occur on the stem and spreads upwardsand downwards.

        Verticilium wilt

        Verticillium dahlia

       1.Bronzing of veins followed by interveinal chlorosis, yellowing and scorching of leaves.

       2.It exhibits drying of leaf margins and areas between veins known as Tiger stripe symptom.

        Rootrot

       Rhizoctonia  bataticola

       1.Germinating seedling shows black lesions on hypocotyls, girdling of stem and death of seedling

       2.Affected basal stem becomes dark with bark shredding and scloretial bodies in the shredded bark

       Anthracnose

       Colletotrichum capsica

       1.Small reddish circular spots on the cotyledons of the seedlings

       2.Collar region shows lesions leading to wilting and drying. In matured plants stem splitting and shredding of bark

       Grey or Areolate mildew

       Ramularia areola

       1.Irregular to angular pale translucent lesions on lower surface, bound by veinlets and grey powdery growth

       2.Light green specks on upper surface

        Boll rot

        Fusariumm oniliforme;  Aspergillus  flavus

       1.Brown or black dots covering entire bolls

       2.Rotting may be internal or external

       3.Bolls do not open and fall prematurely

       Leaf blight

       Alternaria  macrospora

       1.Initially, produces small, brown irregular to round spots with a central necrotic lesions which on coalesce form large                 blighted areas

       2.The affected leaves brittle and fall off. Symptoms are also in stems, bracts and bolls in severe cases

       Bacterial blight

       Xanthomonas campestris pv.  Malvacearum

       Water soaked, circular or irregular lesions on cotyledons which spread to petiole and stem and finally withering and death          of seedling known as Seedling blight

       Stenosis (or) Small leaf

       Candidatus Phytoplasma

       1.Affected plants stunted, produces smaller leaves in clusters due to profuse vegetative growth

       2.Leaves disfigured and flower with abortive ovary.Premature dropping of flower buds and bolls

       Cotton leaf curl

       Cotton Leaf curl virus

       Leaves of infected cotton curl upward and bear leaf-like enations on the underside with vein thickening.

       Sugarcane

       Red rot

       Colletotrichum falcatum

       1.Drooping, withering, and finally yellowing of the 3rd or 4th upper leaves in the crown followed by wilting of the entire            crown.

       2.Dark-reddish zones having tendency to elongate rapidly turning blood-red enclosed by dark margins.

      Sett rot or Pineapple disease

       Ceratocystis  paradoxa

       1.Affected tissues are reddish colour later turns black

       2.Internal cavities formed due to rotting of internal tissues

       3.Affected setts produce sweet pine apple odour

       Rust

       Puccinia  erianthi

       Minute, elongated, yellow spots (uredia) appear on lower surface of young le Later the pustules appear on upper surface              also.The pustules turn brown on maturity

       Pokkah Boeng

       Fusarium moniliformae

       Appearance of chlorotic patches towards the base of the young leaveS

       Grassy shoot

       Candidatus Phytoplasma

       1.Clumps stunted, thin with short internodes having aerial roots

       2.Leaves pale yellow to chlorotic thin and narrow

       Phanerogamic parasite

       Striga  euphrasioides

       1.Partial root parasite, growing up from the roots to form a leafy shoots.

        2.The parasite cans synthesis carbohydrates through the green chlorophyll pigments

4. Mango and Sapota Spots are greenish grey in colour and velvety in texture with feathery margin

       Disease Name // Pathogen Name

       Mango

       Malformation

       Fusarium moniliforme var. subglutinans

       1.Excessive vegetative growth

       2.Formation of bunch of thickened small shootlets

       3.Bunchy top appearance.

       Powdery mildew

       Oidium mangiferae

      1.Powdery growth covers the stalks of panicle,flowers,tender fruits and leaves.

       Anthracnose

       Gloeosporium gloeosporiodes

       1.Black or dark colored circular spots on leaves with shot holes.

       2.Die back symptoms on young twigs and inflorescence

       Die back

       Lasiodiplodia theobromae

       1.Dying of twigs from tip downwards.

       2.Leaves turn brown and upward rolling.

       Sooty mould

       Capnodium mangiferae

       1.Black encrustation formed on flowers, leaves, stem and fruit

       2.Photosynthetic activity of plant is reduced

       Grey blight

       Pestalotiopsis mangiferae

      1.Black dots appear at the centre of the ashy grey spots represent the acervuli.

       Red rust

       Cephaleuros virescens

       1.Spots are greenish grey in colour

       2.Later they turn reddish brown.

        Bacterial leaf spot

       Xanthomonas axonopodis pv. Mangiferae

       Leaf lesions consist of black, raised, angular areas, restricted by the veins and frequently surrounded by a yellow margin.

       Giant mistletoe

        Partial stem parasite – Loranthus (Dendrophthoe spp.)

       1.The flowering plant parasitizes slender branches of the host tree by means of bulged haustoria.

       2.The severely attacked trees are weakened and their productivity is lowered

       Sapota

       Flat limb

       Botryo Diplodia theobromae

       1.Branches of the affected trees become flat and twisted with severe bunching of leave

       2.The affected branches bear small, dry, hard and shrivelled fruits

       Sooty mould

       Capnodium mangiferae

       1.Black encrustation formed on flowers, leaves, stem and fruit.

       2.Photosynthetic activity is reduced which results in reduced fruit set and fruit fall

       Leaf spot

       Phaeophleospora indica

       1.Small circular pink to dark brown spots with whitish centre appear on leaves at the time of maturity

       2.Premature leaf fall resulting in yield reduction

       Grey blight

       Pestalotiopsis versicolor

       1.Numerous small reddish brown pecks on lamina

       2.Greyish centre with reddish margin

5. Citrus and Grapevine

         Disease Name // Pathogen Name

         Citrus

         Foot rot / Gummosis / Leaf fall

         Phytophthora palmivora

         1.Sap oozing from small cracks in the infected bark,giving the tree a bleeding

         2.Exudation of gum from the bark of the trunk

         Scab / Verucosis

         Elsinoefaw cettii

         1.Sour orange,rough lemon and tangerine are highly susceptible

         2.Light brown,raised circular scabs appear on young stems or green twigs

          Anthracnose / Dieback

         Gloeosporium gloeosporioides

         1.Branches wither from tip to downwards

         2.Initially reddish brown spots develop on fruits

         Powdery mildew

         Acremonium (Oidium) tingitaninum

         1.White powdery patches on upper surface of young leaves

         2.Yellowing,crinkling and defoliation of leaf

         Sooty mould

         Capnodium citri

         Black encrustation formed on flowers,leaves,stem and fruit

         Canker

         Xanthomonas axonopodis pv. citri

         Circular brown colour corky cankerous growth with yellow halo on both surface of the leaves

         Citrus Greening / Huang Long Bing (HLB)

         Candidatus Liberibacter asiaticus

         1.Stunting of leaves,twig die back,green fruits with a yellow patches on the rind

         2.Chlorosis of leaves resemble to Zn deficiency

         Tristeza / Quick decline

         Citrus tristeza virus

         1.Stunting of trees,stem pitting,root decay,dieback of twigs

         Giant mistletoe

         Loranthus (Dendrophthoe spp.)

         Flowering plant parasitizes slender branches of the host tree by mens of bulged haustoria.

         Grapevine

         Downy mildew

         Plasmopara viticola

         1.Pale yellow oily spotson upper surface and downy growth on the lower surface of leaves

         2.Affected berries leathery and wrinkled

         Powdery mildew

         Erysiphe (Uncinula) necator

         1.White powdery patches on upper surface of leaf

         2.Stem turns grey and finally dark

         Anthracnose / Birds Eye Spot

         Elsinoe ampelina                             

         1.Small,circular or irregular dark brown spots with shot hole

         2.Red spots on berry

         Rust

         Phakopsoraeu vitis

         Yellowish to brownish rusty pustules appear on lower surface of leaves

         Fan Leaf

         Grapevine Fan Leaf NEPO virus (GFLV)

          1.Vines becomes stunted

2.Bunches are reduced in number

6. Jack Fruit, Pine Apple, Ber, Apple, Peach, Plum, Strawberry

Disease Name // Pathogen Name

Jack Fruit

Pink disease

Pellicularia salmonicolor

1.Young branches affected, pinkish outgrowth seen on surface

2.Leaf crinkle and shedds twigs get dried

Rhizopus fruit rot

Rhizopus atrocarpi

1.Fruits are mummified and dropped down

2.Young fruit rots begins in the stalk and covered by mycelium

Pine Apple

Heart rot

Phytophthora parasitica / P. cinnamomi

1.Fruits exhibits spongy texture

2.When plant pulled out the roots appear dark and in the process of decaying

 Ber

Powdery mildew

Oidium erysiphoides f.sp. zizyphi

1.White floury patches in young leaves and spread to developing fruits

2.Infected fruit become malformed and may shed off.

Black leaf spot

Isariopsis indica var. zizyphi

Brownish discolouration on lower and upper surface of the leaves

Anthracnose

Colletotrichum gloeosporioides

1.Spots appear on upper surface of the leaves

2.It coalesced to form large patches on infected leaves.

  Rust

Phakopsora zizyphi - vulgaris

1.Autocious rust

2.Reddish brown,Irregular small pustules on lower surface of leaves

 Apple

Scab

Venturia inaequalis

1.Leaf blade curved dwarfed distorted

2.Fruit show small rough black lesions

Powdery mildew

Podosphaera leucotricha

1.White powdery growth on upper surface of leaves

2.Fruit buds are also affected and deformed

Soft rot

Penicillium expansum

1.Skin become wrinkled, bluish green sporulating growth appears

Bitter rot

Glomerella cingulata

1.Faint, light brown discolouration beneath the skin

2.Pink masses of spores are found arranged in defined rings

Fire blight

Erwinia amylovora

1.Shepherd’s crook symptoms

2.Oozing in the affected area

 Peach

Peach leaf curl

Taphrina deformans

1.Leaves started turning yellowish or reddish and fall off prematurely

2.Infected portion develops pink or reddish bronze colour

Powdery mildew

Sphaerothe capannosa

White powdery mass on leaf appear, fruits may turn pinkish and finally dark brown in colour.

 Plum

Pocket plumor Bladder plum gall

Taphrinapruni

1.Galls appear on developing fruit form elongated,flattened,hollow

2.Inedible fruits shrivelled and most fall

 Strawberry

Leaf Spot

Mycosphaerella fragariae

1.Circular, deep purple upper leaf surface

2.The spots center turns greyish to white on older leaves,light brown on young leaves

Leaf Scorch

Diplocarpon earliana

1.Numerous small irregular purplish on upper surface of the leaves

2.Center of the blotches become brownish

Leaf Blight

Phomopsis obscurans

1.Circular, reddish purplish spot on leaflets

2.Spots enlarged to V shaped lesions with alight brown inner zones

Angular leaf spot

Xanthomonas fragariae 

1.On leaves angular shing water soaked spots appear surrounded by smallest veins,spots coalesced more frequently along the primary and secondary veins

7. Cucurbits

         Disease Name // Pathogen Name

         Fusarium wilt of watermelon

         Fusariumoxysporumf.sp. niveum

         Root rot

         Pythium aphanidermatum,Phytophthorasp.

         Anthracnose

         Colletotrichum lagenarium

         Downy mildew

         Pseudoperonospora cubensis

         Powdery mildew

         Golovinomycescichoracearum

         Bacterial wilt

         Erwiniatracheiphila

         Cucumber mosaic

         Cucumber mosaic virus

8. Potato, Peas, Beet Root, Radish

         Disease Name //  Pathogen Name

         Potato

         Black scurf and stem canker

         Rhizoctonia solani

         1.Dark brown lesion on corticle and vascular tissues

         2.Xylem vessels affected resulting in stem rot and wilting

         Wart / Black wart

         Synchytrium endobioticum

         1.Small white, soft ,pulpy wart on the eyes

         2.Wart later turns black

         Early blight

         Alternaria solani

         1.Brown spots with or without concentric rings

         2.Spots enlarge to form necrotic areas

         Late blight

         Phytophthora infestans

         1.Brownish to purplish ,black water soaked lesions on upper surface

         2.White mildew growth lower surface

         Soft rot

         Pecto bacterium carotovorum pv. carotovorum

         1.Water soaked area around lenticels

         2.Affected tissue become slimy and emit sulphurous odour

         Common scab

         Streptomyces scabies

         1.Rough corky lesions may range from small and raised to deeply pitted scab can be as deep as one half inch into the tuber

         Mild mosaic / mosaic / Latent mosaic

         Potato virus X

         1.Plants bushy and pale

         2.Interveinal mottling with slight dwarfing

         Severe mosaic / Vein banding

         Potato Virus Y

        1.Leaf crinkle, roll upward , form cup like structure

         2.Mottling of interveinal and veinal areas

         Leaf roll

         Potato leaf roll virus

         1.Necrosis of phloem

         2.Leaflets brittle, become yellow and brown

         Peas

         Wilt

         Fusarium oxysporum f.sp. pisi

        1.Brown to black discoloration of xylem

         Anthracnose

         Colletotrichum pisi

         1.On leaf and stem brown irregular spots

         2.Seeds become discolored and shriveled

         Rust

         Uromyces fabae

         Pustules which are powdery and orange brown in appearance

         Powdery mildew

         Erysiphe polygoni

         1.Powdery patches on upper surface of leaves

         2.It delay the maturity

Beet Root

         Leaf Spot

         Cercospora beticola

         1.Small circular spots with brownish to purplish color.

         2.Spots dry up giving a shot hole

         Downy Mildew

         Perenospora schachtti

         1.White powdery growth on lower surface of leaves

         2.Inflorescence appears as witches broom.

         Bacterial blight

         Pseudomonas syringae pv. aptata

         1.Irregular to circular shaped spots with tan to dark brown centers

         2.Spot may join together and dried area falls of with a ragged appearance

         Mosaic

         Spinach mosaic virus, Sugarbeet mosaic virus (BtMV)

         1.Stunted and may lose some leaves

         2.Ring spots on centre

         Curly-top

         Beet curly top virus (BCTV)

         1.Leaves become thick and leathery

         2.Internal symptoms consists of death of food conducting vessels

         Beet Yellows

         Beet Western Yellows Virus (BWYV)

         1.Yellow spots on young leaves.

         2.Foliage becomes red or yellow and often dies

         Radish

         Alternaria Blight 

          Alternaria raphani

         1.Affects leaves,stem and pod

         2.Lesions appear later on the stems and seed pods

         White Rust 

         Albugo candida

         1.Attack leaves and flowering shoots

         2.Flowering shoots get deformed

         Downy mildew 

         Peronospora parasitica 

         1.Purplish brown spots on under surface of leaves

         2.Upper surface of leaves tan to yellow

         3.Downy growth on under surface of these lesions

         Black rot

         Xanthomonas campestris pv. compestris

         1.Cotyledons affected at margins show blackening and it die

         2.Infected tissues turn yellow and chlorosis occurs.

         Radish mosaic

          Radish enation mosaic virus, radish mosaic como virus

          1.Small,circular to irregular chlorotic lesions in between and adjacent to the veins

                                                                 Management of the Plant diseases

Fungal diseases:Leaf spot, leaf blight,rust, anthracnose(Foliar diseases causedby fungi),Smut, bunt, ergot, graindiscolouration, false smut(Earhead diseases causedby fungi),Wilt, root rot, collar rot,sclerotium rot, stem rot(Soil borne fungal diseases),Downy mildew,Powdery mildew

• Seed treatment with thiram at 2g/kg of seed

• Judicious applicationof fertilizers

• Foliar spray with chlorothalonil @ 2g/lit or carbendazim @ 1 g/lit (or) mancozeb 1000g/ha (or) propiconazole 500ml/ha

• Seed treatment with thiram at 2g/kg of seed,use of certified seeds

• Adjust sowing time to ensure flowering not coincided with rainy season,

•  Judicious application of fertilizers

• Spray of mancozeb at0.2% or carbendazim +mancozeb at 0.2% or propiconazole 500ml/ha

       In case of mould in sorghum, Spray mancozeb 1 kg/ha (or) captan 1 kg + aureofungin sol100g/ha in case of intermittent              rain during earhead emergence.

•        Soil application of Trichoderma viride at 1 kg/ac (or) Pseudomonas fluorescens at 1kg/ac

•        Avoid monoculturing

•        Follow crop rotation

•        Proper disposal of affected plant parts

•        Seed treatment with thiram at 2g/kg of seed,use of certified seeds

•        Proper leveling and drainage

•        Avoid water stagnation

•        Proper irrigation

•        Spot drench with Copper oxy chloride at 0.3% and repeated second time at 15 days interval if necessary

•        Treat seeds with metalaxyl 6 g/kg

•        Proper disposal of affected plant parts

•        Spray metalaxyl+mancozeb 500 g or mancozeb 1.0 kg/ha on 20 DAS

•  

•        Seed treatment with thiram at 2g/kg of seed,use of certified seeds

•        Spray of wettable sulphur at 0.2% or carbendazim ay 0.1%

        Bacterial diseases:BLB in paddy and cotton,Bacterial leaf streak in paddy, wild fire in tobacco, bacterial blight in            safflower

        Viral diseases:Sterility mosaic in redgram, RTV in paddy, grassy shoot in paddy, yellow mosaic, leaf crinkle in                 blackgram, bud necrosis in groundnut

• Seed treatment with thiram at 2g/kg of seed,use of certified seeds or acid delinted seeds in case of cotton

• Judicious application of fertilizers

• Spray of copper oxy chloride at 1200 g/ha or

• Spray of copper oxy chloride at 1200 g/ha + strephtomycin sulphate + tetracycline 120g/ac

        Erwinia rot in sugarbeet

• Spot drench with copper oxy chloride at 1200 g/ha or copper oxy chloride at 1200 g/ha + strephtomycin sulphate+ tetracycline 120g/ac

• Avoid water stagnation

• Seed treatment with imidachlorprid at 5g/kg of seeds(use of certified seeds)

• Use of resistant variety

• Field maintained with free of weeds

• Removal of alternate or collateral hosts

• Spray of imidachlorprid at 0.5 ml/litre of water to controlvector

• Setting of yellow sticky trap at 5/ac

• Border crop with millets

                                                          MUSHROOM CULTIVATION

·Mushroom farming:Most fruitful ,lucrative industry.

·Mushroom are delicious in taste it is rich in proteins, fibers, potassium, copper, and other vital minerals. Mushrooms comes from a family of fungi,they have 90 percent of water in them and low amount of calories and fats.

Different types of Mushrooms in India:

1.       Button mushrooms

·Most popular mushroom,also called as white mushroom or baby mushroom

·These mushrooms can be consumed raw or cooked, and are frequently added to salads, soups, and as toppings for pizza.

Processs in mushroom cultivation:

Compost:On neat concrete platforms these mushrooms are raised.

a)Natural compost

·Some natural ingredients are wheat straw, horse manure, gypsum.

·Moisten the prepared compost with a water sprayer.

b)Synthetic Compost

· A mixture of urea, gypsum, wheat straw, bran, and either ammonium nitrate or ammonium sulfate is required. To begin, trim the straw to a length of 8 to 20 cm.

· Then cover the compost with a fine layer of cut straws and mist it with water. Finally, thoroughly combine the bran, calcium nitrate, urea, gypsum, and other ingredients.

Spawning

·Crucial stage in mushroom cultivation, particularly for button mushrooms. It entails planting mycelium in the beds. two methods for spawning: the first is to distribute compost on the tray bed, and the second is to mix mycelium with compost before spreading it on the tray.

· After sprinkling the tray with water and spawning, you must cover it with newspaper to keep the moisture there.

2. Paddy straw Mushroom

Growing paddy straw mushrooms requires the least amount of investment and is therefore the most lucrative business. Straw mushrooms are fungi that grow on paddy straw.

Bed preparation

  Prepare a solid foundation made of earth and bricks that can support the entire weight. Spread spawn on the straw edges and arrange eight bunches of straws with four on each side. Repeat these actions now continuously.

Harvest:

·Usually, 10 to 15 days after spawning, mushrooms start to grow. For the following 10 days, they keep growing.

·It is ready to be harvested as soon as the volva erupts and the mushroom inside is revealed.

3. Oyster Mushrooms

·It the easiest to produce and very pleasant to eat.

·Unlike button mushrooms, this kind of fungus does not need special growing conditions.

·Recommended by doctors to people with diabetes and high blood pressure because they contain less fat.

·For six to eight months out of the year, oyster mushrooms can grow at a moderate temperature of 20 to 300 C and a humidity of 55 to 70 percent.

Casing

The tray must now be covered with a heavy layer of dirt during mushroom cultivation. This soil can be created by mixing garden soil and decomposing cow manure.

Harvesting

·The cap should be gently torn off during harvest. To do this, hold it gently between your forefingers, press it into the ground, and then twist it off.

·Afterward, cut off the base of the stalk where mycelial threads and dirt granules adhere.

·The cost of mushroom cultivation in India costs around 1,00,000 lakh rupees to 1,50,000 lakhs rupees

Biotic and abiotic stresses of mushroom 

INSECT PESTS:

a) Flies:

i) Phorid fly: Megaselia halterata  and M. tamilnodolensis

ii) Sciarid fly: Lycoriella malli

Beetles: Black beetle: Sacphisoma nigrofaceatum

Brown beetle : S. pictummotschulsky – golden lines seen on the body of the insect. Both feed on young buds and grown up mushrooms by scrapping the tissues. They mainly transmit the bacterial blotch disease from one bed to other.

Spring tails : Tiny insects with stout antennae feed on the mycelium and buds. Lepidocyrtus cyaneus and Isotoma simplex.

WEEDS, MOULDS AND DISEASES:

b) Green moulds:

      Penicillium and Aspergillus spp. may also cause mouldy growth on the beds. The infection lead to development of green color patches in the beds , which spreads quickly and entire bed is covered fully with green growth

ABIOTIC DISORDERS:

 a) Stroma

     Stroma prevents free air exchange in the beds leading to oxygen demand to the rowing pin heads and hence putrifying smell occurs in the beds which ultimately invites pests mainly flies.

b) Rose comb

     Large swellings or humps appear on the mushroom cap. Gills appear over the cap and stipe.

 c) Scales or crocodile skin formation

     Scale like out growths occurs on the pileus and stipe. Mushrooms become small with less weight. Low levels of RH and increased temperature with dry air in the cropping room increases scaling.