How to Identify and Treat Rice Blast Disease (Pyricularia oryzae) in Paddy Fields

Published by ICAR Agronomy Panel • Category: Cereal Pathology • 6 min read

Rice Blast, caused by the fungal pathogen Pyricularia oryzae (teleomorph Magnaporthe oryzae), is recognized as one of the most destructive diseases affecting paddy cultivation globally. Under favorable conditions—high relative humidity (above 85%), prolonged leaf wetness, and cool night temperatures (20°C–24°C)—rice blast can wipe out up to 80% of paddy grain yield within 10 to 14 days.

1. Diagnostic Visual Symptoms

Rice blast attacks paddy crops at all stages of growth, producing distinct pathology symptoms across leaves, stem nodes, and panicle necks:

Leaf Blast: Eye-shaped or spindle-like diamond lesions with gray or whitish centers and reddish-brown borders. As lesions enlarge, neighboring spots coalesce, causing entire leaf blades to dry and look burnt.
Nodal Blast: Stem nodes turn dark brown or black, becoming brittle and breaking easily under wind pressure (plant lodging).
Neck & Panicle Blast: The neck of the panicle turns dark brown and rots, resulting in unfilled, chaffy, white grains (often called "white heads").

2. ICAR & CIBRC Approved Fungicide Spray Dosages

🧪 Certified Chemical Spray Options (per Liter of Water):

Tricyclazole 75% WP (Baan / Beam / Sivic): 0.6 grams per Liter of water. Apply at early tillering and panicle initiation. PHI: 21 Days.
Isoprothiolane 40% EC (Fuji-One): 1.5 ml per Liter of water. PHI: 21 Days.
Syngenta Amistar Top (Azoxystrobin 18.2% + Difenoconazole 11.4% SC): 1.0 ml per Liter of water. PHI: 14 Days.

3. Organic Remedies & Preventive Agronomy

Biocontrol Drench: Spray Pseudomonas fluorescens (10g per Liter of water) or Trichoderma viride at 15-day intervals starting from seedbed nursery stage.
Balanced Nitrogen Management: Avoid excessive urea application. Split nitrogen doses into 3 equal applications (basal, tillering, and panicle initiation).
Seed Treatment: Treat seeds with Carbendazim 50% WP @ 2g/kg seed before sowing.

Disclaimer: Always consult your local Agricultural Extension Officer (AEO) or Krishi Vigyan Kendra (KVK) scientist before spraying high-concentration agro-chemicals.