How to Control Blast in Paddy
BHUMI AGRO 02 Sep 2026

How to Control Blast in Paddy

The total amount of rice destroyed by blast disease every year is estimated to be enough to feed over 60 million people annually. Rice blast, a dreadful disease for farmers, is caused by Magnaporthe oryzae. It can move from a few leaf spots to a broken, empty panicle in a few weeks if it isn't caught or treated at the right stage. Source

What Causes Blast in Paddy? 

Rice blast is caused by the fungus Magnaporthe oryzae (also known by its older name, Pyricularia oryzae).

It reaches the crop through several pathways and then infects the plant. It can be favoured by warm, humid weather with prolonged leaf wetness, conditions which are quite common during the monsoon-season Kharif crop across most of India. 

Several pathways of infection include infected seeds, crop residue, air borne spores from nearby fields; spores can spread through wind and rain splash. 

Types of Blast in Paddy

Leaf blast 

Leaf blast

Damage: spindle-shaped lesions with grey or ash-coloured centre and brown margins. It reduces the plant's photosynthetic area and also stunts growth.

Attack: young leaves during tillering.

Nodal blast 

Nodal blast

Damage: blackens the stem nodes, which makes the stem brittle which makes snaps under plant weight.

Attack: Stem joints (nodes)

Neck blast 

Neck blast

Damage: neck of the panicle breaks, turns white or hangs down before grain fill, resulting in empty panicles.

Attack: Base of the seed panicle (seedhead)

Collar blast

Collar blast

Damage: rots the leaf joint and dries out the leaf, cutting off that leaf’s contribution to the plant entirely.

Attack: Junction between leaf blade and leaf sheath 

Glume Blast 

Glume Blast

Damage: directly infects the husk and produces brown spots and discoloured, shattered, or dried-up rice grains. 

Attack: panicle branches and grain hull

Different blast needs a different approach. So first understand what you are seeing.

How to Control

  • Use resistant varieties where available, particularly in fields and regions with a known history of repeated blast outbreaks. 

  • Avoid excess nitrogen application. Apply N in three splits: 50% basal, 25% at active tillering, 25% at panicle initiation. Excessive use of fertilizer can increase blast intensity.

  • Ensure adequate potassium. It directly strengthens the plant’s resistance to fungal penetration. Read our complete paddy fertilizer guide for exact NPK dosing recommendations.

  • Adjust planting time. Avoid late planting. Sow seeds early, when possible, after the onset of the rainy season.

  • Apply silicon fertilizers to reduce blast. It improves tolerance to drought, lodging and some insect pests.

  • Ensure water management. Avoid water stress and also avoid waterlogging. Maintain recommended standing water depth.

  • Apply systematic fungicides. Spray only after observing any infection or as a preventive in high-risk situations.
Stage Targeted Disease Chemical & Formulation Application Rate
Seed Treatment Preventative Tricyclazole 75% WP or Carbendazim 50% WP 2 g per kg of seed
Vegetative / Tillering Leaf Blast Tricyclazole 75% WP or Isoprothiolane 40% EC 0.6 g/L of water (120 g/acre) or 1.5 mL/L
Booting / Heading Neck & Panicle Blast Azoxystrobin 18.2% + Difenoconazole 11.4% SC – Defender 1 mL/L of water (150–200 mL/acre)
Early Emergence Biological / Antibiotic Kasugamycin 3% SL 2 mL/L of water

Common Mistakes to Avoid

  • Do not delay spraying until the neck blast system appears. Once the neck node rots, nutrient and water transport is permanently cut off.

  • Do not stop only after treating leaf blast. The flag-leaf-stage spray is still necessary as a preventive step.

  • Do not ignore the field history. Fields with a history of blast have more spores. So, a preventive spray is recommended.

  • Do not drain paddy fields during high-risk periods. Lack of proper moisture weakens plants and creates favourable conditions for fungal spores to germinate. 

  • Do not use a single fungicide class repeatedly. Magnaporthe oryzae can change quickly, which may lead to the development of fungicide-resistant strains 

Conclusion

If there’s one takeaway here, it’s that timing is everything. Blast moves fast, but a little prep goes a long way. Keep your crop healthy and properly nourished with shallow, continuous water. And always get out there with protection before you start to see the whiteheads, not afterwards. Keep it simple, and let your paddy do what it does best. 

If you want to read about other Paddy diseases. Read 7 Paddy Diseases: Causes, Symptoms, and Control



Frequently Asked Questions

Fungicides that combine a strobilurin (like Azoxystrobin) with a triazole (like Difenoconazole) give both preventive and curative control by attacking the fungus through two different mechanisms. This dual mode of action is more effective and more resistance-resistant than relying on a single active ingredient.

Neck blast must be controlled preventively, with a fungicide spray at the flag leaf stage, before the panicle emerges and becomes vulnerable. Once a broken or discolored panicle neck is visible, that panicle's yield cannot be recovered, the goal shifts to protecting the rest of the field from further spread.

Cultural practices like balanced nitrogen, adequate potassium and silicon, proper spacing, and good drainage meaningfully reduce blast pressure and can be sufficient in low-risk fields. However, in fields with a history of blast or during sustained humid, monsoon conditions, a preventive fungicide spray is typically still necessary for full control.

Excess nitrogen produces soft, lush plant tissue that the blast fungus penetrates far more easily than firmer, well-balanced growth. Adjusting nitrogen timing and ensuring adequate potassium and silicon, which strengthen cell walls, is one of the most effective non-chemical ways to reduce blast severity.

Yes, to a meaningful degree. Research shows Trichoderma harzianum seed treatment can reduce blast disease intensity while also improving germination, and Pseudomonas fluorescens has reduced blast incidence significantly in field trials by competing with the pathogen and triggering the plant's natural resistance response. Biological agents work best as a preventive layer or alternated with chemical fungicide, rather than as the sole treatment during an active, high-pressure outbreak.