🍂 Crop Diseases & Management
Major crop diseases of Kharif, Rabi, and fruit crops — causal organisms, symptoms, management, IDM principles, fungicide classification for CUET Agriculture
Crop Diseases & Management
This lesson covers the major diseases of Indian crops organized by cropping season, along with the principles of disease management and fungicide classification. For CUET, you need to know the causal organism, key symptoms, management practices, and special facts about each disease.
Major Crop Diseases — Detailed Tables
Kharif (Rainy Season) Crop Diseases
The Kharif season (June-October) coincides with the monsoon. High humidity and warm temperatures favour fungal and viral diseases, making this the most disease-prone season.
| S.No. | Disease | Causal Organism | Symptoms | Management | Important Points |
|---|---|---|---|---|---|
| 1. | Green ear & Downy Mildew of Bajra | Sclerospora graminicola (Obligate fungus); Sexual spore: Oospore | i. Green ear — floral parts transform into leafy structures (inflorescence becomes green and leaf-like, resembling a cluster of leaves instead of grains). ii. Downy mildew — white cottony growth on lower leaf surface | Metalaxyl (Apron 35 SD) @ 6 gm/kg seed; Metalaxyl + Mancozeb (Ridomil MZ-72) @ 2 gm/litre | Discovered by E.J. Butler (1907). Green ear is pathognomonic (uniquely diagnostic) for this disease. |
| 2. | Ergot of Bajra/Sorghum | Claviceps fusiformis; Soil & seed borne; Survives as sclerotia in soil | i. Honeydew stage — sweet sticky fluid oozes from infected florets (attracts insects which spread disease). ii. Sclerotial stage — hard black bodies (sclerotia) replace grains | Early sowing; COC @ 0.25%; Resistant bajra variety: WCC-75 | Alkaloid produced: Ergotin/Ergotoxin; causes Ergotism disease in humans who consume contaminated grain (symptoms: burning sensation, gangrene of limbs) |
| 3. | Cotton Wilt | Fusarium oxysporum f.sp. vasinfectum; Soil borne: Conidia & Chlamydospores | Plugging of xylem vessels → wilting, browning/blackening of root. The vascular discoloration is visible when stem is cut lengthwise. | Soil solarization; Seed treatment with Carbendazim; Trichoderma biocontrol | Root turns black due to melanin pigment produced by the pathogen in the vascular tissue |
| 4. | Tikka/Leaf spot of Groundnut | Early: Cercospora arachidicola; Late: C. personata | Early leaf spot (appears 3-4 weeks after sowing): Yellow halo around brown spots. Late leaf spot (6-8 weeks): Round dark spots without halo — darker and more damaging | Seed treatment: Thiram/Captan @ 2.5 gm/kg seed; Foliar: Carbendazim @ 0.1% | Soil & seed borne disease. Two distinct Cercospora species cause early vs late spots. |
| 5. | Peanut Clump Virus | IPCV (Indian Peanut Clump Virus); Soil & seed borne | 30-35 DAS: Patches (clumps) of stunted plants appear in field; Bunchy growth; Mosaic pattern on leaves | Seed treatment with Carbendazim @ 0.1% | Unique vector: Fungi (Polymyxa graminis) — this is one of the rare cases where a fungus acts as virus vector |
| 6. | Cotton Angular Leaf Spot | Xanthomonas axonopodis pv. malvacearum; Soil & seed borne | i. Seedling blight ii. Angular leaf spot — water-soaked angular lesions limited by veins iii. Black arm — dark elongated lesions on stem iv. Boll rot | Hot water treatment (56°C for 10 min); Acid delinting: H₂SO₄ @ 1:10; Streptocycline spray | Bacterial disease — one of the few important bacterial diseases of cotton. Angular shape of spots (limited by leaf veins) is diagnostic. |
| 7. | Bhendi Yellow Vein Mosaic | Bhendi YVMV (ssDNA virus); Vector: Whitefly (Bemisia tabaci); Weed hosts: Croton, Malvestrum | Yellow vein pattern in all leaves — veins turn bright yellow creating a network pattern; overall stunted growth | Systemic acquired resistance: Salicylic acid @ 500 ppm; Dimethoate spray (to control whitefly vector) | Resistant variety: Arka Abhay. Managing the whitefly vector is key to controlling this viral disease. |
| 8. | Tomato Leaf Curl | Tomato Yellow Leaf Curl Virus (ssDNA); Vector: Whitefly (B. tabaci) | Leaves curl upward (cup-shaped); Yellowing; stunted plant growth | Dimethoate @ 1 ml/litre or Imidacloprid @ 3 ml/litre | Resistant varieties: Arka Samrat; Arka Rakshak. Both this and Bhendi YVMV are transmitted by the same whitefly vector. |
| 9. | Tomato Early Blight | Alternaria solani; Soil borne conidia | Yellow spots with concentric rings forming a target board pattern — this is the hallmark symptom of Alternaria; Severe leaf defoliation | Mancozeb OR COC @ 2.5 gm/litre | The concentric ring (target board) pattern in leaf spots is diagnostic for Alternaria diseases across many crops. |
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Crop Diseases & Management
This lesson covers the major diseases of Indian crops organized by cropping season, along with the principles of disease management and fungicide classification. For CUET, you need to know the causal organism, key symptoms, management practices, and special facts about each disease.
Major Crop Diseases — Detailed Tables
Kharif (Rainy Season) Crop Diseases
The Kharif season (June-October) coincides with the monsoon. High humidity and warm temperatures favour fungal and viral diseases, making this the most disease-prone season.
| S.No. | Disease | Causal Organism | Symptoms | Management | Important Points |
|---|---|---|---|---|---|
| 1. | Green ear & Downy Mildew of Bajra | Sclerospora graminicola (Obligate fungus); Sexual spore: Oospore | i. Green ear — floral parts transform into leafy structures (inflorescence becomes green and leaf-like, resembling a cluster of leaves instead of grains). ii. Downy mildew — white cottony growth on lower leaf surface | Metalaxyl (Apron 35 SD) @ 6 gm/kg seed; Metalaxyl + Mancozeb (Ridomil MZ-72) @ 2 gm/litre | Discovered by E.J. Butler (1907). Green ear is pathognomonic (uniquely diagnostic) for this disease. |
| 2. | Ergot of Bajra/Sorghum | Claviceps fusiformis; Soil & seed borne; Survives as sclerotia in soil | i. Honeydew stage — sweet sticky fluid oozes from infected florets (attracts insects which spread disease). ii. Sclerotial stage — hard black bodies (sclerotia) replace grains | Early sowing; COC @ 0.25%; Resistant bajra variety: WCC-75 | Alkaloid produced: Ergotin/Ergotoxin; causes Ergotism disease in humans who consume contaminated grain (symptoms: burning sensation, gangrene of limbs) |
| 3. | Cotton Wilt | Fusarium oxysporum f.sp. vasinfectum; Soil borne: Conidia & Chlamydospores | Plugging of xylem vessels → wilting, browning/blackening of root. The vascular discoloration is visible when stem is cut lengthwise. | Soil solarization; Seed treatment with Carbendazim; Trichoderma biocontrol | Root turns black due to melanin pigment produced by the pathogen in the vascular tissue |
| 4. | Tikka/Leaf spot of Groundnut | Early: Cercospora arachidicola; Late: C. personata | Early leaf spot (appears 3-4 weeks after sowing): Yellow halo around brown spots. Late leaf spot (6-8 weeks): Round dark spots without halo — darker and more damaging | Seed treatment: Thiram/Captan @ 2.5 gm/kg seed; Foliar: Carbendazim @ 0.1% | Soil & seed borne disease. Two distinct Cercospora species cause early vs late spots. |
| 5. | Peanut Clump Virus | IPCV (Indian Peanut Clump Virus); Soil & seed borne | 30-35 DAS: Patches (clumps) of stunted plants appear in field; Bunchy growth; Mosaic pattern on leaves | Seed treatment with Carbendazim @ 0.1% | Unique vector: Fungi (Polymyxa graminis) — this is one of the rare cases where a fungus acts as virus vector |
| 6. | Cotton Angular Leaf Spot | Xanthomonas axonopodis pv. malvacearum; Soil & seed borne | i. Seedling blight ii. Angular leaf spot — water-soaked angular lesions limited by veins iii. Black arm — dark elongated lesions on stem iv. Boll rot | Hot water treatment (56°C for 10 min); Acid delinting: H₂SO₄ @ 1:10; Streptocycline spray | Bacterial disease — one of the few important bacterial diseases of cotton. Angular shape of spots (limited by leaf veins) is diagnostic. |
| 7. | Bhendi Yellow Vein Mosaic | Bhendi YVMV (ssDNA virus); Vector: Whitefly (Bemisia tabaci); Weed hosts: Croton, Malvestrum | Yellow vein pattern in all leaves — veins turn bright yellow creating a network pattern; overall stunted growth | Systemic acquired resistance: Salicylic acid @ 500 ppm; Dimethoate spray (to control whitefly vector) | Resistant variety: Arka Abhay. Managing the whitefly vector is key to controlling this viral disease. |
| 8. | Tomato Leaf Curl | Tomato Yellow Leaf Curl Virus (ssDNA); Vector: Whitefly (B. tabaci) | Leaves curl upward (cup-shaped); Yellowing; stunted plant growth | Dimethoate @ 1 ml/litre or Imidacloprid @ 3 ml/litre | Resistant varieties: Arka Samrat; Arka Rakshak. Both this and Bhendi YVMV are transmitted by the same whitefly vector. |
| 9. | Tomato Early Blight | Alternaria solani; Soil borne conidia | Yellow spots with concentric rings forming a target board pattern — this is the hallmark symptom of Alternaria; Severe leaf defoliation | Mancozeb OR COC @ 2.5 gm/litre | The concentric ring (target board) pattern in leaf spots is diagnostic for Alternaria diseases across many crops. |
TIP
Whitefly (Bemisia tabaci) is the vector for both Bhendi YVMV and Tomato leaf curl virus. Controlling whitefly populations (through insecticides like Imidacloprid or Dimethoate) is the primary strategy for managing these viral diseases, since there is no direct cure for plant viruses.
Rabi (Winter) Crop Diseases
The Rabi season (October-March) is cooler and drier. Rust diseases of wheat are the most important Rabi diseases in India.
| S.No. | Disease | Causal Organism | Symptoms | Management | Important Points |
|---|---|---|---|---|---|
| 1. | Brown/Leaf Rust of Wheat | Puccinia recondita; Heteroecious rust (requires two different hosts to complete life cycle); Wheat: Uredial & Telial stages; Thalictrum: Aecidial & Pycnidial stages | Orange-brown uredium pustules scattered on leaves | Oxycarboxin (Plantavax) | Caused famine-like conditions in India during 1972-73 |
| 2. | Yellow/Stripe Rust of Wheat | Puccinia striiformis; Heteroecious rust | Yellow uredium pustules arranged in stripes (linear rows) on leaves — the striped pattern is diagnostic | Oxycarboxin (Plantavax) | Higher damage than brown rust in India due to cooler hilly regions being major wheat areas |
| 3. | Black/Stem Rust of Wheat | Puccinia graminis tritici; Heteroecious rust; Hosts: Wheat AND Barberry (Mahonia) | Uredium pustules as dark spots on stem (not just leaves) | Oxycarboxin (Plantavax) | Has the longest disease cycle and highest damage potential among all three wheat rusts. The alternate host is barberry. |
| 4. | Loose Smut of Wheat | Ustilago nuda var. tritici; Internally seed borne — mycelium inside the embryo | Grains completely replaced by black powder (teliospores) that is exposed and easily blown away by wind | Hot water treatment: 54-56°C for 10 minutes; Solar heat treatment: Luhra & Suttur method; Carboxin/Vitavax | Because the pathogen is inside the seed, surface seed treatments are ineffective — systemic fungicides or hot water treatment are needed. |
| 5. | Covered Smut of Barley | Ustilago hordei; External seed borne | Grains covered by a silvery membrane containing black powder (teliospores) — the membrane keeps spores intact until harvest | Carboxin (Vitavax) | Unlike loose smut, the membrane covering retains spores, so they are released during threshing and contaminate healthy seeds. |
| 6. | White Rust of Mustard | Albugo candida; Obligate parasite; Sexual spore: Oospore | i. Localized: White pustules (blisters) on lower leaf surface ii. Systemic: Hypertrophy (swelling) of flowers, staghead formation — inflorescence becomes swollen and deformed | Metalaxyl (Apron 35 SD) @ 6 gm/kg seed; Metalaxyl + Mancozeb (Ridomil MZ-72) @ 2 gm/litre | Staghead is the most dramatic and easily recognizable symptom — the entire inflorescence swells into a club-like structure. |
| 7. | Brinjal Little Leaf | PLOs/MLOs (Phytoplasma); Vector: Leafhopper (Hishimonas phycities) | Leaves remain abnormally small (little leaf); phyllody — floral parts converted to leaf-like structures | Spray Malathion @ 1 ml/litre of water (to control leafhopper vector) | This is a Phytoplasma disease, not fungal or bacterial. Control focuses on the leafhopper vector since phytoplasma cannot be directly targeted with fungicides. |
| 8. | Wilt of Cumin | Fusarium oxysporum f.sp. cumini; Facultative/Saprophytic — survives in soil for years | Xylem vessel plugging → stem wilting and necrosis; plants wilt and die rapidly | Soil solarization; Trichoderma @ 4 gm/kg seed; Soil application @ 4 kg/ha | Fusarium wilts are managed best through biocontrol (Trichoderma) + resistant varieties + soil solarization rather than chemical sprays alone. |
| 9. | Powdery Mildew of Cumin | Erysiphe polygoni; Dormant mycelium overwinters | White powdery growth on leaves (सफेद वृद्धि) — the white powder consists of fungal mycelium and conidia | Sulphur dust; Karathane; Tridemorph | Powdery mildew thrives in dry conditions with moderate temperatures (unlike downy mildew which needs humidity). Sulphur is the oldest and most reliable treatment. |
Understanding the Three Wheat Rusts
All three wheat rusts are caused by different species of *Puccinia* and are **heteroecious** (need two different host species to complete their life cycle). Here's how to distinguish them:- Brown/Leaf Rust (P. recondita): Orange-brown pustules scattered randomly on leaves. Most common rust.
- Yellow/Stripe Rust (P. striiformis): Yellow pustules in parallel stripes on leaves. Favours cooler temperatures.
- Black/Stem Rust (P. graminis tritici): Dark pustules on stems. Most destructive potential. Alternate host: barberry (Mahonia).
All three are managed with Oxycarboxin (Plantavax) — a systemic fungicide specific for rust diseases.
Fruit Crop Diseases
| S.No. | Disease | Causal Organism | Symptoms | Management | Important Points |
|---|---|---|---|---|---|
| 1. | Citrus Canker | Xanthomonas axonopodis pv. citri; Bacterial; Vector: Citrus leaf miner (Phyllocnistis citrella) creates wounds for bacterial entry | Water-soaked raised lesions (cankers) on leaves, branches, and fruits with a characteristic corky, crater-like appearance | Streptocycline (antibiotic spray) | First found by Fawcett & Jenkins (1933) in Kagzi lime, Dehradun. A quarantine disease in many countries. |
| 2. | Guava Wilt | Fusarium oxysporum f.sp. psidii; Soil borne disease | Progressive branch drying, withering; overall decline and death of tree over weeks to months | Lime or gypsum in soil (to raise pH); Carbendazim @ 1 gm/litre drench around root zone | First reported from Allahabad (1938). A serious threat to guava orchards across North India. |
| 3. | Powdery Mildew of Ber | Oidium erysiphoides | Whitish powdery growth on small developing fruits and leaves; fruits fail to develop, drop prematurely | Sulphur dust @ 25 kg/ha; Dinocap @ 0.1% | First reported 1946 by Mehta from Kanpur. Attacks during fruit development stage causing heavy crop loss. |
Principles of Plant Disease Management (पादप रोग प्रबन्धन के सिद्धान्त)
Effective disease management is based on six fundamental principles. Each principle targets a different aspect of the disease triangle — either the host, the pathogen, or the environment.
-
Avoidance (परिवर्जन) — Avoid conditions favourable for disease development. This includes adjusting sowing dates (e.g., early sowing to escape peak disease pressure), choosing proper plant spacing for air circulation, and selecting disease-free planting sites.
-
Exclusion (बहिष्कारण) — Prevent the pathogen from entering a new area through quarantine measures. National and international quarantine laws restrict movement of infected plant material.
- Domestic plant quarantine examples: Wart of potato, Bunchy top of banana, Golden nematode of potato
-
Eradication (उन्मूलन) — Remove the pathogen from an already infested field. Methods include rouging (removing infected plants), destroying crop residues, deep ploughing, and soil fumigation.
-
Protection (रक्षण/बचाव) — Shield the host from infection before it occurs. This includes preventive seed treatment, timely fungicide sprays, and use of resistant varieties.
-
Resistance (प्रतिरोधकता) — Develop and deploy Host Plant Resistance (HPR) — breeding crop varieties that carry genes for disease resistance. This is the most economical and environmentally friendly approach.
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Therapy (उपचार) — Treat already infected plants through chemotherapy (applying systemic fungicides/antibiotics), heat therapy (using hot water or hot air to eliminate pathogens from planting material), pruning of infected parts, or even tree surgery.
IMPORTANT
Remember the mnemonic: A-E-E-P-R-T (Avoidance, Exclusion, Eradication, Protection, Resistance, Therapy) — these six principles of disease management are frequently asked in CUET.
Integrated Disease Management (IDM) (समन्वित पादप रोग प्रबन्धर)
IDM is the modern, holistic approach that combines multiple methods rather than relying on any single technique. The goal is effective disease control while minimizing environmental harm and cost.
| Method | Examples |
|---|---|
| Legal/Regulatory | Plant quarantine laws; enforcement by NBPGR (National Bureau of Plant Genetic Resources), New Delhi |
| Cultural | Deep summer ploughing (exposes pathogens to heat), Crop rotation (breaks disease cycle), Seed treatment, Resistant varieties, Integrated nutrient & weed management |
| Physical | Hot air/water treatment, Solar heat treatment, Soil solarization (covering moist soil with transparent polyethylene in summer), Refrigeration (for post-harvest storage) |
| Biological | Botanicals: Neem, onion, garlic extracts; Beneficial fungi: Trichoderma viridae (best biocontrol agent for soil-borne fungi); Beneficial bacteria: Pseudomonas fluorescens |
| Biotechnology | Transgenic/genetically modified crops carrying resistance genes (e.g., Bt cotton, virus-resistant papaya) |
| Chemical | Fungicides — both contact and systemic (see classification below) |
Fungicide Classification (कवकनाशी वर्गीकरण)
Fungicides are chemical compounds used to kill or inhibit fungi. They are broadly classified as contact (non-systemic — remain on the plant surface) and systemic (absorbed and transported within the plant).
A. Contact Fungicides (Non-Systemic)
These fungicides remain on the plant surface where they are applied. They form a protective barrier that prevents fungal spore germination. They must be applied before infection occurs (preventive action) and need reapplication after rain.
I. Copper Fungicides (कॉपर युक्त)
Copper-based fungicides are among the oldest and most reliable. Copper ions are toxic to fungal spores.
| Type | Examples |
|---|---|
| Copper fungicide | Bordeaux mixture (CuSO₄ + Ca(OH)₂ + Water) — the world's first fungicide; Bordeaux paste; Burgundy/Soda mixture (CuSO₄ + Na₂CO₃ + Water); Chestnut compound |
| Copper carbonate | Chaubattia paste — widely used in fruit orchards for wound dressing |
| Cuprous oxide | Cuprox oxide |
| Copper oxychloride (COC) | Blitox, Fytolan — commonly used in field sprays |
II. Sulphur Fungicides (सल्फर युक्त)
Sulphur is particularly effective against powdery mildew diseases. It disrupts fungal cellular respiration.
| Type | Examples |
|---|---|
| Inorganic sulphur | Sulphur dust (Gandhak dhuli) — dusted directly on crops |
| Organic sulphur | Thiram (seed treatment), Zineb, Mancozeb (most widely used contact fungicide), Vapam (dual action: soil fungicide + nematicide) |
III. Mercury Fungicide (पारद कवकनाशी)
- Agallol, Areton — now largely banned or restricted due to environmental toxicity and health hazards of mercury
IV. Heterocyclic N-Compound
- Captan (कैप्टन) — widely used as seed treatment fungicide; broad-spectrum protection
B. Systemic Fungicides (सर्वांगी कवकनाशी)
Systemic fungicides are absorbed by the plant and translocated (moved) through the vascular system, providing protection from within. They can act both preventively and curatively (even after infection has started). This is their major advantage over contact fungicides.
| Group | Active Ingredient | Trade Name | Target Disease |
|---|---|---|---|
| Oxathin group | Carboxin | Vitavax | Smut (कण्डवा) — standard treatment for smut diseases |
| Oxycarboxin | Plantavax | Rust (रोली) — the go-to fungicide for all wheat rusts | |
| Benzimidazole group | Benomyl | — | Broad-spectrum |
| Carbendazim | Bavistin | Wilt, blight, leaf spot — most commonly used systemic fungicide in India | |
| Morpholins group | Tridemorph | Calixin | Powdery mildew |
| Others | Metalaxyl | Apron 35 SD | Downy mildew, late blight — specific for Oomycete diseases |
| Metalaxyl + Mancozeb | Ridomil MZ-72 | Downy mildew — combination of systemic + contact for broader protection |
TIP
Quick memory aid for fungicide-disease matching:
- Vitavax (Carboxin) → Smut
- Plantavax (Oxycarboxin) → Rust
- Bavistin (Carbendazim) → Wilt/Blight (most versatile)
- Apron/Ridomil (Metalaxyl) → Downy mildew
C. Antibiotics (प्रतिजैविकी)
Antibiotics are compounds produced by microorganisms that kill or inhibit other microorganisms. In plant pathology, they are used primarily against bacterial diseases.
| Target | Antibiotic |
|---|---|
| Anti-bacterial | Streptomycin (most widely used against bacterial plant diseases), Tetracycline |
| Anti-fungal | Aureofungin, Blasticidin |
Nutrient Deficiency Diseases (पोषक तत्वों की कमी)
Not all plant "diseases" are caused by pathogens. Nutritional deficiencies can mimic disease symptoms and cause significant yield loss. These are abiotic disorders — they are not infectious and cannot spread from plant to plant.
| Crop | Disease | Deficient Nutrient |
|---|---|---|
| Rice (धान) | Khaira disease (खैरा रोग) | Zinc (Zn) — most common micronutrient deficiency in Indian rice |
| Rice (धान) | Akiochi | H₂S toxicity — occurs in waterlogged, poorly drained soils |
| Cauliflower (फूलगोभी) | Whiptail (ह्विपटेल रोग) | Molybdenum (Mo) — leaves become narrow, strap-like (whip-shaped) |
| Tomato (टमाटर) | Blossom end rot (ब्लॉसम एण्ड रोट) | Calcium (Ca) — dark, sunken area at the blossom end of fruit |
| Maize (मक्का) | White bud disease (सफेद कलिका रोग) | Zinc (Zn) — newly emerging leaves are white/pale |
IMPORTANT
The two most frequently tested nutrient deficiency diseases: Khaira disease of rice = Zinc deficiency and Whiptail of cauliflower = Molybdenum deficiency. Both are abiotic — no pathogen involved.
Diseases by Season
This season-wise summary helps in quickly recalling which diseases to expect during which cropping period.
Kharif/Rainy Season Diseases
- Bajra: Green ear, Downy mildew (मुदुरोमिल आसिता)
- Rice: Bacterial leaf blight (जीवाणु पत्ती अंगमारी)
- Rice: Blast disease (ब्लास्ट रोग)
- Bajra: Ergot disease (अर्गट रोग)
- Groundnut: Tikka disease
- Sorghum: Grain mould
Rabi/Winter Season Diseases
- Mustard: White rust (सफेद रोली)
- Wheat: Rusts (all three — brown, yellow, black)
- Chickpea: Wilt (Fusarium)
Summer/Zaid Season
- Tomato: Sun scald
Key Points for CUET
- Carbendazim (Bavistin) = Most commonly used systemic fungicide
- Streptomycin = Anti-bacterial antibiotic for plant diseases
- Trichoderma = Best biocontrol agent against soil-borne fungal pathogens
- Khaira disease of rice = Zinc deficiency; Whiptail of cauliflower = Mo deficiency
- Bordeaux mixture = CuSO₄ + Lime + Water (first fungicide, 1885)
- Vitavax (Carboxin) = Systemic fungicide for smut diseases
- Plantavax (Oxycarboxin) = Systemic fungicide for rust diseases
- Ridomil MZ-72 = Metalaxyl + Mancozeb for downy mildew
- IDM combines legal, cultural, physical, biological, biotechnological, and chemical methods
- Six principles of disease management: Avoidance, Exclusion, Eradication, Protection, Resistance, Therapy
Image Generation Prompts
Image Generation Prompt: Polycyclic Disease Cycle Diagram
Create a detailed circular disease cycle diagram showing a polycyclic fungal disease (using wheat rust / Puccinia graminis as example) on a cream background. Show the complete cycle as a large circle with stages connected by arrows: (1) PRIMARY INOCULUM — overwintering teliospores in crop debris/soil, shown as dark structures; (2) BASIDIOSPORES — produced from teliospores, wind-dispersed (show wind arrows); (3) INFECTION of alternate host (Berberis/barberry) — show pycnial and aecial stages on barberry leaf; (4) AECIOSPORES released — wind-dispersed to wheat; (5) INFECTION of wheat — urediniospores penetrating through stomata (show magnified cross-section of leaf with fungal hyphae entering stoma); (6) UREDIAL STAGE — orange-brown pustules on wheat leaf surface releasing urediniospores; (7) SECONDARY SPREAD — multiple arrows showing urediniospores re-infecting wheat plants (labeled "polycyclic — multiple cycles per season, compound interest disease"); (8) TELIAL STAGE — dark teliospores form as crop matures, completing cycle. Include environmental conditions (temperature 15-25°C, humidity >80%, leaf wetness) noted at infection stages. Center label: "Wheat Stem Rust — Puccinia graminis tritici — Heteroecious, Macrocyclic Rust." Title: "Disease Cycle of a Polycyclic Pathogen." Style: detailed scientific diagram with life cycle arrows, educational textbook quality.
Summary Cheat Sheet
| Concept / Topic | Key Details / Explanation |
|---|---|
| Kharif — Green ear & DM of Bajra | Sclerospora graminicola; floral parts → leafy structures; discovered by E.J. Butler (1907); Rx: Metalaxyl (Apron 35 SD) @ 6 gm/kg seed |
| Kharif — Ergot of Bajra | Claviceps fusiformis; honeydew stage → sclerotial stage; produces ergotin/ergotoxin → causes ergotism in humans; resistant variety: WCC-75 |
| Kharif — Cotton Wilt | Fusarium oxysporum f.sp. vasinfectum; xylem plugging → wilting; root turns black (melanin); Rx: Carbendazim seed treatment, Trichoderma |
| Kharif — Tikka of Groundnut | Early: Cercospora arachidicola (yellow halo); Late: C. personata (no halo, darker); Rx: Thiram/Captan @ 2.5 gm/kg seed |
| Kharif — Peanut Clump Virus | IPCV; unique vector: fungus (Polymyxa graminis); stunted clumps, mosaic pattern |
| Kharif — Cotton Angular Leaf Spot | Xanthomonas (bacterial); angular lesions limited by veins + black arm; Rx: hot water (56 deg C/10 min), Streptocycline |
| Kharif — Bhendi YVMV | ssDNA virus; vector: Whitefly (Bemisia tabaci); yellow vein network; resistant variety: Arka Abhay |
| Kharif — Tomato Leaf Curl | ssDNA virus; vector: Whitefly; upward leaf curling; resistant: Arka Samrat, Arka Rakshak; Rx: Imidacloprid @ 3 ml/L |
| Kharif — Tomato Early Blight | Alternaria solani; concentric rings (target board pattern); Rx: Mancozeb or COC @ 2.5 gm/L |
| Rabi — Brown/Leaf Rust of Wheat | Puccinia recondita; orange-brown pustules scattered on leaves; heteroecious (alternate host: Thalictrum); famine 1972-73; Rx: Plantavax |
| Rabi — Yellow/Stripe Rust of Wheat | Puccinia striiformis; yellow pustules in stripes/linear rows; higher damage in cooler hilly regions; Rx: Plantavax |
| Rabi — Black/Stem Rust of Wheat | Puccinia graminis tritici; dark pustules on stem; longest cycle, highest damage potential; alternate host: barberry (Mahonia); Rx: Plantavax |
| Rabi — Loose Smut of Wheat | Ustilago nuda var. tritici; internally seed borne (mycelium in embryo); grains → black powder; Rx: hot water 54-56 deg C/10 min, Vitavax (Carboxin) |
| Rabi — Covered Smut of Barley | Ustilago hordei; externally seed borne; silvery membrane covers black spores; Rx: Vitavax |
| Rabi — White Rust of Mustard | Albugo candida; white pustules on leaves + staghead formation (swollen inflorescence); Rx: Metalaxyl (Apron 35 SD) |
| Rabi — Brinjal Little Leaf | Phytoplasma (not fungal/bacterial); small leaves + phyllody; vector: leafhopper; Rx: Malathion (vector control) |
| Rabi — Wilt of Cumin | Fusarium oxysporum f.sp. cumini; xylem plugging; Rx: Trichoderma @ 4 gm/kg seed |
| Rabi — Powdery Mildew of Cumin | Erysiphe polygoni; white powdery growth; thrives in dry conditions; Rx: Sulphur dust, Karathane, Tridemorph |
| Fruit — Citrus Canker | Xanthomonas (bacterial); water-soaked corky cankers; vector: citrus leaf miner; first found Fawcett & Jenkins (1933), Kagzi lime, Dehradun; Rx: Streptocycline |
| Fruit — Guava Wilt | Fusarium oxysporum f.sp. psidii; branch drying → tree death; first reported Allahabad (1938); Rx: Carbendazim drench |
| Fruit — PM of Ber | Oidium erysiphoides; white powdery growth on fruits; first reported 1946, Mehta, Kanpur; Rx: Sulphur dust, Dinocap @ 0.1% |
| 6 Principles of Disease Mgmt | A-E-E-P-R-T: Avoidance, Exclusion, Eradication, Protection, Resistance, Therapy |
| Avoidance | Adjust sowing dates, spacing, site selection to avoid favourable disease conditions |
| Exclusion | Quarantine measures; enforced by NBPGR, New Delhi; e.g., Wart of potato, Bunchy top of banana |
| IDM | Combines legal, cultural, physical, biological, biotechnological, chemical methods |
| Trichoderma viridae | Best biocontrol agent against soil-borne fungi |
| Pseudomonas fluorescens | Beneficial bacterium used in biological control |
| Contact fungicides — Copper | Bordeaux mixture (first fungicide), COC (Blitox/Fytolan), Chaubattia paste |
| Contact fungicides — Sulphur | Sulphur dust, Thiram, Zineb, Mancozeb (most widely used contact), Vapam (also nematicide) |
| Contact fungicides — Others | Captan (seed treatment); Mercury-based (Agallol — now banned) |
| Systemic — Vitavax (Carboxin) | Target: Smut diseases |
| Systemic — Plantavax (Oxycarboxin) | Target: Rust diseases |
| Systemic — Bavistin (Carbendazim) | Most commonly used systemic fungicide; target: Wilt, Blight, Leaf spot |
| Systemic — Apron/Ridomil (Metalaxyl) | Target: Downy mildew, Late blight (Oomycete diseases) |
| Antibiotics | Streptomycin (anti-bacterial, most used), Tetracycline; Aureofungin (anti-fungal) |
| Khaira disease of Rice | Zinc (Zn) deficiency — most common micronutrient deficiency in Indian rice |
| Whiptail of Cauliflower | Molybdenum (Mo) deficiency — leaves become narrow, whip-shaped |
| Blossom End Rot of Tomato | Calcium (Ca) deficiency — dark sunken area at blossom end |
| White Bud disease of Maize | Zinc (Zn) deficiency — newly emerging leaves white/pale |
| Akiochi of Rice | H₂S toxicity — in waterlogged, poorly drained soils |
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