Rice blast is one of the most damaging diseases for rice cultivation in Bangladesh. Caused by the fungus Magnaporthe oryzae, this disease can drastically reduce crop yield if not identified and controlled early. In this article, we discuss the symptoms, causes, and effective ways to manage rice blast disease for Bangladeshi farmers.
What is Rice Blast Disease?
Rice blast is a fungal infection that affects all parts of the rice plant—leaves, stems, nodes, and even grains. It is common during wet and humid weather, especially in the monsoon and Aman seasons.
Symptoms of Rice Blast
- Leaf Symptoms: Spindle-shaped grayish lesions with brown borders on leaves.
- Node Symptoms: Black or brown discoloration near nodes causing weak stems.
- Neck Blast: Infection near the panicle neck causing grain abortion or poor filling.
- Yield Loss: Severely infected fields can lose up to 50–80% yield.
Causes and Contributing Factors
- High humidity and continuous rainfall (above 90% RH).
- Dense sowing without proper spacing.
- Excess nitrogen fertilizer usage.
- Planting susceptible rice varieties.
- Use of infected seeds or lack of crop rotation.
Effective Control Measures
- Resistant Varieties: Use blast-resistant varieties like BRRI dhan50, BRRI dhan51, and BRRI dhan74.
- Proper Fertilization: Avoid excess nitrogen. Apply balanced NPK fertilizers.
- Field Sanitation: Remove and destroy infected crop residues after harvest.
- Crop Rotation: Rotate with non-host crops like vegetables or pulses.
- Fungicide Use: Apply fungicides such as Tricyclazole or Carbendazim at early stages when symptoms appear.
- Spacing and Drainage: Maintain proper spacing and field drainage to reduce humidity.
When to Apply Fungicide
The best time to apply fungicide is at the booting stage (just before panicle emergence) or as soon as lesions appear on leaves. A second spray may be needed after 7–10 days depending on severity.
Conclusion
Rice blast is a major threat to rice farmers in Bangladesh, but with timely intervention and good management practices, the damage can be minimized. Awareness, early detection, and preventive actions are the keys to protecting your harvest.
Stay alert this season and keep your paddy field healthy!