Blast disease, caused by the fungus Magnaporthe oryzae, is a major concern for paddy crops worldwide. It can infect all parts of the rice plant, leading to significant yield losses, sometimes reaching up to 70%. Early detection and identification are crucial for effective management. Globally, blast disease is responsible for 10-30% annual yield losses in paddy crops. In severe outbreaks, losses can reach 50% or even 100% for susceptible varieties under conducive conditions.
- Type of Infestation: Disease
- Common Name: Blast
- Causal Organism: Magnaporthe oryzae
- Affected Parts Of the plant: Leaves, Stems, Panicles
Environmental Favorable Factors for Blast Disease in Paddy:
- Temperature: Optimal temperatures for blast disease range from 25°C to 30°C (77°F to 86°F). Warmer temperatures accelerate fungal growth and increase the number of disease cycles per season.
- Humidity: This is critical for spore germination, infection, and fungal growth. Humid environments above 80% relative humidity, especially for extended periods, create optimal conditions for disease development.
Symptoms of Blast in Paddy:
Leaves:
- Lesions: These are the most common symptom, appearing as spindle-shaped or oval spots with grey or white centers and brown or reddish-brown borders.
- Blighting: In severe cases, the lesions can cause the entire leaf to turn brown and die, giving the crop a blighted appearance.
Leaf collars:
- Collar rot: This symptom manifests as brown discoloration around the junction of the leaf blade and sheath
- Black lesions: Black lesions develop on the stem nodes, eventually causing the stem to break at the infected point.
- Greyish-brown discolorations: The branches of the panicle become discolored and may break.
- Blanking: Infected spikelets fail to develop grains, resulting in empty spaces on the panicle.
Measures to control Blast Disease in Paddy:
| Products | Technical Names | Dosages |
| Hexa 5 Plus | Hexaconazole 5 % SC | 500ml/acre |
| Dr Zole | Azoxystrobin 11.00 % Tebuconazole 18.30 % SC | 300ml/acre |
| Prodizole | Propiconazole 13.9 % + Difenoconazole 13.9 % | 200mlacre |
| Azozole | Azoxystrobin 18.2 % + difenoconazole 11.4 % SC | 300ml/acre |
Frequently Asked Questions Related Blast Disease in Paddy
Q. What is nodal blast in rice?
A. Nodal blast infects the stem nodes, causing blackening and weakening of the nodes, leading to stem breakage.
Q. What is neck blast in rice?
A. Neck blast affects the neck of the rice panicle, causing black lesions and broken panicles, leading to grain loss.
Q. What is leaf blast in rice?
A. Leaf blast causes spindle-shaped lesions on rice leaves with grey centres and brown borders, leading to leaf blight.
Q. How can you control rice blast?
A. Apply fungicides at the late boot stage and near full heading, combined with water management and balanced nitrogen use for best results.
Q. How can I control blast Disease in paddy?
A. Adjust planting time, split nitrogen fertiliser applications, and flood the field regularly to manage blast in paddy.
