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Rice blast


Rice blast: Magnaporthe grisea (Hebert) Barr

(Deuteromycotina: Moniliales: Moniliaceae)

Kannada Name: Benki Roga

            In southern states, blast incidence is primarily associated with dry periods and cooler nights that are prevalent during November - February.Depending on the site of symptom rice blast is referred as leaf blast, collar blast, node blast, neck or panicle blast. Amongst which, neck blast is the most destructive phase of the disease.

Period of occurrence: All stages of crop growth (seedling to maturity)

Extent of yield loss: 70-80% under extreme cases 100%

Alternate hosts: Grasses (Panicum repens, Digitaria marginata, Brachiaria mutica, Leersia hexandra and Dinebra retroflexa)

Favorable conditions for the pathogen:

  • Low night temperature (22 to 28°C)
  • High relative humidity (> 95%)
  • New deposit
  • Extended leaf wetness period (>10 hrs)
  • Cloudy and drizzling weather
  • Soil fertility (High N)
  • Degree of host susceptibility
  • Straw of the previously infected crop heaped nearby 

Mode of transmission/dissemination: Wind, Seed

Sources of inoculum: Seed, Grasses


Leaf blast - Elliptical spots with more or less pointed ends resembling a spindle. Initially appear as small grayish dots of pin-head size that finally enlarge into a spindle shaped spot with brown margin and gray centre. Usually, the disease starts from lower to upper leaves. Finally leads to  the death and drying up of the plant.

 Collar blast - Death of the entire leaf blade.

 Node blast - Black patches appear on the infected nodes and all parts above the infected node die similar to the damage done by rats.

Panicle blast or Neck blast - Improper grain filling, poor milling recovery and also chaffy ear heads similar to the damage of white ears by stem borer.

Preventive measures:

  • Use of resistant varieties like Gauthami, IR-36, IR-64, Parijatha, Rasi, Sasyashree, Salivahana, Simhapuri, Srinivas, Tikkana
  • Burn previously blast affected straw and stubbles
  • Use of disease free seeds
  • Use of balanced rates of nutrition based on soil test- split applications of nitrogen  (Excessive N use can promote excessive luxuriant crop growth which increases the relative humidity and leaf wetness of the crop canopy. This can lead to increased infection).

Biological control:

  • Seed treatment with Pseudomonas fluorescence (10g / 1 of water) for 30 min.
  • Seedling root dip treatment with Pseudomonas fluorescence (4g / 1 of water) for 20 min (   Videos-1,2,3,4, and 5 )
  • Foliar spray of Pseudomonas fluorescence (4g / 1 of water) at 20-25 days after transplanting.

Control measures:

Cultural practices -

  • Delay topdressing of N fertilizers when infection seen.
  • Remove collateral weed hosts from bunds and channels.
  • Use only disease free seedlings.
  • Avoid excess nitrogen.
  • Apply N in three split doses, 50% basal, 25% in tillering phase and 25%N in panicle initiation stage.
  • Use resistant variety

ii) Chemical control - 

Seed treatment:

            Seed dress with either Tricyclazole 75 WP or Carbendazim 50 WP  @ 2 g per kg of seed.  (For seed treatment, measured quantity of fungicide is thoroughly mixed with water. Seeds are then soaked in the fungicide solution for 12 hours. The soaked seeds are then put in a cloth bag and incubated for 2 to 3 days for proper germination. The fungicide treated sprouted seeds are then broadcasted in the nursery bed) (Video-seed treatment against blast).


Foliar spray:

Recommended Fungicides

Sl No.

Chemical Name

Trade Name

Dosage per l of water

Dosage for spray tank

10 l

12 l

16 l

Liquid/Spray formulations (EC, SL, WP, WG, WDG, SC)


Tricyclazole 75WP


0.6 g

6 g

7.2 g

9.6 g


Isoprothiolane 40EC


1.5 ml

15 ml

18 ml

24 ml


Ediphenphos 50EC


1.0 ml

10 ml

12 ml

16 ml


Isobenphos 48EC


2.0 g

20 g

24 g

32 g


Carbendazim 50WP

Bavistin, Jkstin, Derosal 

1.0 g

10 g

12 g

16 g


Thiophanale methyl 75WP


1.0 g

10 g

12 g

16 g


Propiconazole 25EC


1.0 ml

10 ml

12 ml

16 ml

 Collar blast

Nodal blast  

Neck blast

Photographs showing seedling root dip


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