Brown Spot of Rice

Brown Spot of Rice:

Helminthosporium oryzae

Mode of transmission/ dissemination: wind, infected seeds.

Period of occurrence:

Disease is a Fungal disease. The fungus attacks the crop from Seedling in nursery to milk stage in the main field.

Symptoms occurs: 

• Spots vary in shape and size and appear on the coleoptiles of the leaves, leaf sheath, and glumes.Stems and grains of adult plants may also be affected.

Why and where it occurs:

• Temperature of 25-30°C
• Relative humidity (>90%)
• Heavy and late north-east monsoon
• Cloudy days
• High doses of Nitrogen

Symptoms:

• The disease appears first as minute brown dots,with greyish centers when fully developed.later becoming cylindrical or oval to circular up to 1 cm in length.(resemble sesame seed).

Fig: Brown Spot of Paddy

• Circular to oval leaf spot,brown in color,darker center and lighter margin with light yellowish halo spots develop on leaf blade in leaf sheath and plumes.

• Spots are not evenly distributed and do not join together .

• Infection also occurs on panicle, neck with brown color appearance

• Seeds also infected (black or brown spots on glumes spots are covered by olivaceous velvety growth)The seeds are sometimes wrinkled and discolored image.

Management:

• Preventive measures:

• Seed treatment with Pseudomonas fluorescens @ 10g/kg of seed

• seed soak / seed treatment with Captan or Thiram at 2.0g /kg of seed.

• Seed treatment with tricyclazole.

• Treat seeds with hot water (53−54°C) for 10−12 minutes before planting, to control primary infection at the seedling stage.

• Use of resistant varieties – Rasi, IR 36, Jagannath, ADT 44,PY 4, CORH 1,CO 44, CAUVERY, BHAVANI, TPS 4.

• To manage nutritional imbalance by use of Nitrogen,Potash and Phosphate.

• Avoid water stress.

• Clean and Weed free cultivation.

• Cultural methods:

• Use disease free seeds.


• Removal of alternate & collateral hosts.


• Avoid excessive use of nitrogenous fertilizer.


• for soils that are low in silicon, apply calcium silicate slag before planting.

• Chemical methods:

             If the disease observed in the field than spray one of the following Fungicide.

                  ---Spray at later tillering and panicle stage.

• Spray Mancozeb 75% Wp @ 2.5 Gm / Lit Of Water. (Dithane M45, Uthane, Manjet, Indofil M45) 

• Spray Carbendazim 12% + Mancozeb 63% (75% Wp) @ 2 Gm / Lit Of Water. (Saaf,Companion) Spray at onset of infestation.

• Tricyclazole 18% + Mancozeb 62% ( 80% Wp) @ 2 Gm / Lit Of Water. (Marger)

• Spray Tebuconazole 50% + Trifloxystrobin 25% (75% Wg) @ 1.5 Gm / 2 Lit. Of Water. (Netivo)

• Spray Hexaconazole 4% + Zineb 68% (72% Wp) @ 2 Gm / Lit. Of Water. (Avtaar)

• Iprodione 25% +Carbendazim 25%(50% WP) @ 1.5 GM/ Lit. of Water.(Quintal)

• Azoxystrobin 18.2% + difenoconazole 11.4% SC @ 1.5 ML/ Lit. of Water.

• Also we can spray 2% of Urea (20 gm/lit.water) .