documents/Tobacco_Diseases_Bangladesh.txt

COMMON TOBACCO (TAMAK) DISEASES IN BANGLADESH
Farmer's Guide: Symptoms, Prevention & Control

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1. BLACK SHANK
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Causal organism: Phytophthora nicotianae (fungus-like organism)

SYMPTOMS
- Black, water-soaked lesions appear at the base of the stem (shank), near soil level
- Infected stem tissue turns black and the pith inside becomes hollow with a diagnostic black, banded discoloration
- Plants wilt suddenly, often starting with the lower leaves, and can collapse and die
- In wet fields, entire patches of plants can die within days
- Roots may also rot, appearing black and mushy

PREVENTION & CONTROL
- Use resistant/tolerant tobacco varieties where available
- Ensure good field drainage; avoid waterlogging, since the pathogen spreads in standing water
- Rotate with non-host crops (avoid other Solanaceae like tomato, eggplant, chili) for at least 2-3 years
- Remove and destroy infected plants and debris immediately
- Avoid moving soil or water from infected fields to healthy ones (sanitize tools and boots)
- Apply a recommended fungicide (e.g., metalaxyl or mefenoxam-based) as a soil drench in severely affected fields

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2. FUSARIUM WILT
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Causal organism: Fusarium oxysporum f. sp. nicotianae (fungus)

SYMPTOMS
- Yellowing and wilting of leaves, often starting on one side of the plant
- Leaves droop and may show a one-sided (unilateral) yellowing pattern
- Brown streaking visible inside the stem when cut lengthwise
- Stunted growth and eventual plant death, especially in warm soil conditions
- Symptoms often worsen during hot, dry weather

PREVENTION & CONTROL
- Use resistant varieties where available
- Practice long crop rotation (3-4 years) with non-host crops
- Avoid excessive nitrogen fertilization
- Remove and destroy infected plants promptly
- Maintain balanced soil moisture; avoid drought stress, which worsens symptoms
- Improve soil health with organic matter to support beneficial soil microbes

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3. TOBACCO MOSAIC VIRUS (TMV)
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Causal organism: Tobacco mosaic virus

SYMPTOMS
- Light green to yellow mottled (mosaic) pattern on leaves
- Leaves may appear puckered, curled, or distorted with uneven surfaces
- Stunted plant growth and reduced leaf size
- Reduced leaf quality, which lowers market value
- Virus spreads easily through handling (hands, tools, contaminated tobacco products) and can survive in dried plant material

PREVENTION & CONTROL
- Use certified virus-free seed and healthy transplants
- Wash hands and disinfect tools between handling plants, especially after smoking or handling tobacco products
- Avoid working in fields when leaves are wet, as this increases spread
- Remove and destroy infected plants promptly
- Control weeds that may harbor the virus
- Avoid planting near old tobacco debris or previously infected fields

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4. FROGEYE LEAF SPOT
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Causal organism: Cercospora nicotianae (fungus)

SYMPTOMS
- Small, circular spots on leaves with a light tan to white center and a dark brown margin (resembling a frog's eye)
- Spots may merge under humid conditions, damaging large areas of the leaf
- Lower, older leaves are usually affected first
- Severe infection reduces leaf quality and market value

PREVENTION & CONTROL
- Use resistant varieties where available
- Avoid excess nitrogen fertilization
- Ensure proper plant spacing for good air circulation
- Remove and destroy infected lower leaves and crop debris after harvest
- Apply a recommended fungicide (e.g., copper-based or chlorothalonil) if disease appears early in humid weather
- Practice crop rotation with non-host crops

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5. BLUE MOLD
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Causal organism: Peronospora tabacina (fungus-like organism, downy mildew type)

SYMPTOMS
- Pale yellow to light green patches on the upper leaf surface
- A blue-grey, fuzzy/downy fungal growth appears on the underside of the leaves, especially in cool, humid, cloudy weather
- Affected leaf tissue eventually turns brown and dies
- In seedbeds/nurseries, young seedlings can be severely damaged or killed
- Spreads rapidly by wind-blown spores during cool, wet conditions

PREVENTION & CONTROL
- Use resistant varieties where available
- Avoid overcrowding seedlings in nurseries; ensure good ventilation
- Avoid overhead irrigation, especially late in the day; water early so leaves dry quickly
- Apply a recommended fungicide (e.g., metalaxyl or mancozeb-based) preventatively in nurseries and fields during high-risk (cool, cloudy, humid) weather
- Remove and destroy infected plants and debris promptly
- Monitor fields closely during cool, overcast weather

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6. BACTERIAL WILT
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Causal organism: Ralstonia solanacearum (bacterium)

SYMPTOMS
- Sudden wilting of the whole plant, often starting with upper leaves, while leaves remain green initially
- Cutting the stem near the base reveals brown, discolored vascular tissue; a milky bacterial ooze may appear from the cut stem
- Plants collapse and die quickly, especially in warm, wet soil
- Disease spreads through soil, water, and infected plant material

PREVENTION & CONTROL
- Use resistant varieties where available
- Practice crop rotation with non-host crops (avoid Solanaceae) for several years
- Ensure good field drainage; avoid waterlogging
- Remove and destroy infected plants and surrounding soil where possible
- Disinfect tools and avoid moving soil/water from infected to healthy fields
- Avoid mechanical injury to roots and stems during cultivation

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GENERAL TIPS FOR ALL TOBACCO DISEASES
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- Start with healthy, certified seed and disease-free transplants
- Practice crop rotation (3+ years) with non-Solanaceae crops
- Ensure good field drainage; avoid waterlogged conditions
- Avoid excess nitrogen fertilizer; maintain balanced fertilization
- Keep fields and field bunds free of weeds and volunteer plants
- Remove and destroy infected plants and crop debris promptly (do not compost infected material)
- Wash hands and disinfect tools regularly, especially when moving between fields
- Scout fields regularly, especially during humid, wet, or cool cloudy weather
- When applying any pesticide or fungicide, wear gloves and a mask, and follow label instructions
- Contact your nearest Department of Agricultural Extension (DAE) office or Bangladesh Agricultural Research Institute (BARI) for the latest recommended varieties and chemicals