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Questions and Answers
What is the primary purpose of using nitrogen fertilizers in soil?
What is the primary purpose of using nitrogen fertilizers in soil?
Which of the following is NOT a type of therapeutic measure for diseased plants?
Which of the following is NOT a type of therapeutic measure for diseased plants?
At what temperature is soil sterilized by steam in therapeutic measures?
At what temperature is soil sterilized by steam in therapeutic measures?
What is the purpose of hot water treatment in therapeutic measures?
What is the purpose of hot water treatment in therapeutic measures?
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What is the most effective temperature for refrigeration treatment to prevent post-harvest diseases?
What is the most effective temperature for refrigeration treatment to prevent post-harvest diseases?
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Which therapeutic measure uses physical agents such as temperature and radiations?
Which therapeutic measure uses physical agents such as temperature and radiations?
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What is a common method used to kill pathogens in post-harvest diseases of fruits and vegetables?
What is a common method used to kill pathogens in post-harvest diseases of fruits and vegetables?
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Which of the following statements about hot air treatment is true?
Which of the following statements about hot air treatment is true?
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What is the primary function of fungicides in plant disease management?
What is the primary function of fungicides in plant disease management?
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Which type of fungicide is applied to a host plant before pathogen exposure?
Which type of fungicide is applied to a host plant before pathogen exposure?
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Why are most fungicides considered effective only in areas where they are applied?
Why are most fungicides considered effective only in areas where they are applied?
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Topical fungicides are primarily used for which type of fungal infection?
Topical fungicides are primarily used for which type of fungal infection?
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What is the main difference between topical and systemic fungicides?
What is the main difference between topical and systemic fungicides?
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Which type of fungicides is typically used after a plant has been infected with a pathogen?
Which type of fungicides is typically used after a plant has been infected with a pathogen?
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Which type of fungicide is used to treat infected seeds?
Which type of fungicide is used to treat infected seeds?
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Fungicides can function as disinfectants for what types of areas?
Fungicides can function as disinfectants for what types of areas?
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What is the primary goal of treating plant diseases?
What is the primary goal of treating plant diseases?
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Which of the following is NOT one of the broad categories of plant disease control measures?
Which of the following is NOT one of the broad categories of plant disease control measures?
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How do prophylactic measures primarily function in plant disease control?
How do prophylactic measures primarily function in plant disease control?
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What is the purpose of plant quarantine?
What is the purpose of plant quarantine?
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Which regulatory method is included in the exclusion measures for plant disease control?
Which regulatory method is included in the exclusion measures for plant disease control?
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What does the term 'Eradication' refer to in the context of preventive measures?
What does the term 'Eradication' refer to in the context of preventive measures?
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What is a primary function of systemic fungicides in plants?
What is a primary function of systemic fungicides in plants?
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Which of the following best describes the role of plant quarantine stations?
Which of the following best describes the role of plant quarantine stations?
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Which of the following systemic fungicides is used against post-harvest diseases?
Which of the following systemic fungicides is used against post-harvest diseases?
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The legislation related to plant quarantine measures in India was first passed in which year?
The legislation related to plant quarantine measures in India was first passed in which year?
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How is the Bordeaux mixture prepared?
How is the Bordeaux mixture prepared?
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Which of the following systemic fungicides is primarily used to treat rust?
Which of the following systemic fungicides is primarily used to treat rust?
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What are Dithane R-24 primarily used for?
What are Dithane R-24 primarily used for?
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Which of the following is NOT classified as an inorganic fungicide?
Which of the following is NOT classified as an inorganic fungicide?
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Which of these systemic fungicides is categorized under Pyrimidines?
Which of these systemic fungicides is categorized under Pyrimidines?
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Which systemic fungicide is derived from antibiotics?
Which systemic fungicide is derived from antibiotics?
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What is the main characteristic of a variety introduced through plant introduction?
What is the main characteristic of a variety introduced through plant introduction?
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Which of the following best describes the selection method for breeding disease resistance?
Which of the following best describes the selection method for breeding disease resistance?
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What is the primary goal of hybridisation in disease resistance breeding?
What is the primary goal of hybridisation in disease resistance breeding?
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Which of the following is NOT a method used to breed for disease resistance?
Which of the following is NOT a method used to breed for disease resistance?
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What is a unique characteristic of plants developed through grafting?
What is a unique characteristic of plants developed through grafting?
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Which wheat variety is resistant to black and yellow rust?
Which wheat variety is resistant to black and yellow rust?
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Which rice variety is recognized for its early maturing characteristic?
Which rice variety is recognized for its early maturing characteristic?
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What disease are varieties NP 15 and NO38 of arhar resistant to?
What disease are varieties NP 15 and NO38 of arhar resistant to?
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Study Notes
Plant Disease Control
- Plant disease control focuses on protecting plant populations rather than individual plants, with exceptions for trees, ornamentals, and some virus-infected plants.
- Control measures aim to minimize losses caused by diseases.
- Selecting the appropriate control measure requires understanding the relationship between the pathogen and the host plant.
- Plant disease control is categorized into three main approaches: prophylactic (preventive), therapeutic (curative), and immunization.
Prophylactic (Preventive) Measures
- These measures are applied to prevent healthy plants from coming into contact with pathogens.
- Prophylactic measures are divided into three categories: exclusion, eradication, and protection.
Exclusion
- Aims to keep pathogens away from susceptible host plants.
- Achieved through regulatory methods such as quarantine and inspections.
Plant Quarantine
- Legal restrictions on the movement of diseased plant material or pathogens.
- Implemented in agriculturally advanced countries.
- The Destructive Insects and Pests Act in India (1914) imposes restrictions on shipments of diseased plant materials and pathogens.
- Quarantine stations at major sea and air ports check the entry of plant materials carrying pathogens.
- Imported plant materials and seeds require a certificate from the Ministry of Agriculture confirming disease-free status.
- Cultures of fungi and bacteria are only allowed into India with authorization from the authorized Mycologist.
Eradication
- Eliminating pathogens from a specific area to prevent disease outbreaks.
- Methods include destruction of infected plants, removal of infected plant parts, and soil sterilization.
Protection
- Measures that protect healthy plants from pathogen contact.
- Methods include using disease-resistant varieties, practicing crop rotation, and utilizing appropriate cultural practices.
Therapeutic (Curative) Measures
- Applied to treat diseased plants and plant parts.
- Aim to relieve symptoms and repair damage.
- Two types of therapeutic measures are physical therapy and chemical therapy.
Physical Therapy
- Involves treating plants, plant parts, and soil with physical agents like temperature and radiation.
Soil Sterilization by Heat
- Soil is sterilized by steam under pressure or through benches where steam is passed through the soil.
- Soil is heated to 82°C or higher for 30 minutes to kill soil-borne pathogens.
- Used in seed beds and greenhouses.
Hot Water Treatment
- Seed-borne smut diseases are eliminated by immersing infected seeds in hot water at 54°C for 10 minutes.
- Effective for roots and rhizomes infected with pathogens like Verticillium.
Hot Air Treatment
- Removes excess moisture from plant organs, protecting them from fungal and bacterial attacks.
- Treats viral-infected dormant plant materials at temperatures ranging from 35°C to 54°C.
- Hastens healing of wounds and protects them from weak pathogens.
Refrigeration (Low Temperature Treatment)
- Common method for preventing post-harvest diseases in fruits and vegetables.
- Storage plants are kept under low temperatures to inhibit pathogen activity and prevent secondary infections.
- Effective temperature is slightly above freezing point.
Treatment of Radiations
- Pathogens causing post-harvest diseases are killed by ultraviolet radiations, X-rays, gamma rays, alpha particles, and beta particles.
Chemical Therapy
- Uses chemical substances called pesticides to protect plants.
- Pesticides are classified based on the target organism: fungicides, bactericides, insecticides, nematicides, rotenticides, acaricides, herbicides.
Fungicides
- Chemical substances that kill fungal spores and mycelium.
- Used as eradicants or to control disease after infection.
- Most fungicides are not absorbed or translocated by plants, so they are only effective where applied.
- Some fungicides are absorbed and translocated, making them eradicants.
- Applied in different forms to various plant parts (foliage, seeds, tubers, bulbs, wounds, stored fruits and vegetables).
- Also used as disinfectants for soil and warehouses.
Types of Fungicides
- Protectants: Applied to the host plant before pathogen attack to kill the pathogen before it penetrates.
- Eradicants (Therapeutic): Applied after host infection to kill the pathogen after invasion.
Topical Fungicides
- Chemical substances applied to infected plant parts.
- Destroy pathogens in situ, confined to a specific spot or organ.
- Effective against powdery mildews, which are exoparasites on the host surface.
- Used for seeds infected with fungi and bacteria, killing the pathogen in situ.
- This type of chemotherapy is called topical chemotherapy.
Systemic Fungicides
- Provide immediate external protection to the host plant against fungal pathogens.
- Absorbed by roots or foliage leaves and translocated upward through xylem capillaries.
- Provide internal protection without harming the host.
- Act as both protective and eradicants.
- Chase pathogens throughout the host plant.
- Equally distributed within the plant, killing the pathogen through direct toxic action.
Common Systemic Fungicides
- Oxanthiins: Carboxin (Vitavax) for damping off diseases and smuts, Oxycarboxin (Plantvax) for rust.
- Benzimidazoles: Benomyl (Benlate) for powdery mildews, Cercospora leaf spots, smuts of wheat, apple scab, blast of rice, fruit rots, and Thiabendazole for post-harvest diseases caused by fungi imperfecti.
- Pyrimidines: Triarimol, ethirimel, and dimethirimol for powdery mildews.
- Dithane R-24 (Indar): Used against leaf rust of wheat.
- Antibiotics: Streptomycin, tetracyclines, and cycloheximide are used as systemic fungicides.
General Classification of Fungicides
- Fungicides are classified into two main groups: inorganic and organic fungicides.
Inorganic Fungicides
- Earliest fungicides used to control crop diseases.
- Main types include copper fungicides.
Copper Fungicides
- Bordeaux mixture: Most common fungicide, discovered in 1885.
- Prepared by mixing copper sulfate, lime (calcium hydroxide) and water.
- Effective against leaf spots, blights, anthracnose, downy mildews, and cankers.
- Fixed (insoluble) copper: Contains basic copper sulfate (Basicop), basic copper chloride, copper oxides, or cupric hydroxide.
- Used as dust or sprays and are less effective than Bordeaux mixture but effective against the same diseases.
Immunization Measures
- This approach involves developing disease resistance in plants.
- Achieved through breeding methods like plant introduction, selection, hybridization, mutation, polyploidy, budding, and scion grafting.
- These methods aim to introduce disease resistance genes into susceptible varieties, creating new resistant cultivars.
Plant Introduction
- Introducing a variety from its center of origin to a new environment with different disease pressures.
- Aims to introduce disease-resistant varieties to areas where the disease is prevalent.
Selection
- Selecting plants exhibiting disease resistance and growing them alongside susceptible plants.
- Plants are then infected with pathogens to test for resistance.
- Resistant plants are selected and tested across seasons and different locations to confirm consistent resistance.
Hybridization
- Cross-breeding a susceptible variety with a disease-resistant variety.
- F1 hybrids are tested for disease resistance.
- Resistant hybrids are selected for further investigation.
Grafting
- Used for asexually propagated plants where sexual reproduction is not possible.
- A graft of a disease-resistant plant is made onto a susceptible plant to create a new variety.
Examples of Resistant Varieties
- Wheat: Sonara 64, K 65, Lerma Rojo 64A, Sharbati Sonara, Kalyan Sona, Sonalika, Chhoti Lerma (S331), Safed Lerma, Hira, Lal Bahadur
- Rice: IR-8, IR-20, Jaya, Padma (dwarf), Hansa (early maturing), Pankaj, Kavery
- Arhar (Cajanus cajan): NP 15 and NO38 are resistant to wilt disease.
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Description
This quiz covers essential concepts of plant disease control, including preventive, therapeutic, and immunization measures. It delves into methods such as exclusion, eradication, and protection, offering a comprehensive understanding of how to maintain healthy plant populations. Test your knowledge on pathogen-host relationships and disease management strategies.
