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Agricultural crops :: Cereals :: Paddy

Nursery Diseases Main field diseases

Blast - Pyricularia grisea (P. oryzae)
Bacterial Leaf Blight - Xanthomonas oryzae pv.oryzae
Rice tungro disease - Rice tungro virus (RTSV, RTBV)

Brown Spot - Helminthosporium oryzae
Sheath Rot - Sarocladium oryzae
Sheath Blight - Rhizoctonia Solani
False Smut - Ustilaginoidea virens
Grain discolouration - fungal complex
Leaf streak - Xanthomonas oryzae pv. oryzicola

Blast :Pyricularia grisea (P.oryzae)

Occurance
  • Earliest known plant disease
  • Also known as rotten neck or rice fever.
  • Reported from 80 rice-growing countries. First recorded in India during 1918.
  • Expected grain loss : 70 to 80%

Symptom of damage

Infected leaf

Healthy leaf  
Leaf
Collar
Nodal 
Neck
  • Disease can infect paddy at all growth stages and all aerial parts of plant (Leaf, neck and node).
  • Among the three leaves and neck infections are more severe.
  • Small specks originate on leaves - subsequently enlarge into spindle shaped spots(0.5 to 1.5cm length, 0.3 to 0.5cm width) with ashy center.
  • Several spots coalesce -> big irregular patches

Blast

Leaf Blast :

  • Severe cases of infection - entire crop give a blasted or burnt appearance- hence the name "BLAST"
  • Severe cases - lodging of crop (after ear emergence)

Neck Blast

  • Neck region of panicle develops a black color and shrivels completely / partially grain set inhibited, panicle breaks at the neck and hangs

Nodal Blast: Nodes become black and break up


Identification of Pathogen Life Cycle of Pyricularia Oryzae
Conidia of Pyricularia Oryzae

Management
Cultural method
  • 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 CO 47.

Avoid Excees Use of Nitrogen Fertilizer Use Resistant variety
BPT 5204
Chemical Method
  • Spray after observing initial infection of the disease,
  • Carbendazim 50WP @ 500g/ha (or)
  • Tricyclozole 75 WP @ 500g/ha (or)
  • Metominostrobin 20 SC @ 500ml/ha (or) 47
  • Azoxystrobin 25 SC @ 500 ml/ha

Spray Carbendazim Spray Edifenphos Thiram-Seed Treating Fungicide Treat the Seeds with Captan
Biological control
Seed Treatment with TNAU Pf 1liquid formulation @ 10 ml/kg of seeds
Seedling root dipping with TNAU Pf 1liquid formulation (500 ml for one hectare seedlings)
Soil application with TNAU Pf 1liquid formulation (500ml/ha)
Foliar spray with TNAU Pf 1liquid formulation @ 5ml/lit

Nursery stage
Light infection - Spray Carbendazim or Edifenphos @ 0.1 %.

Pre-Tillering to Mid-Tillering
Light at 2 to 5 % disease severities - Apply Edifenphos or Carbendazim @ 0.1 %. Delay top dressing of N fertilizers when infection is seen. Panicle
initiation to booting

At 2 to 5% leaf area damage spray Edifenphos or Carbendazim or Tricyclazole @ 0.1 %.

Flowering and after 
At 5 % leaf area damage or 1 to 2 % neck infection spray Edifenphos or Carbendazim or Tricyclazole @ 1 g /lit of water.  

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Bacterial Leaf BlightXanthomonas oryzae pv. oryzae

Symptom of Damage
  • Seedling wilt or kresek
  • Water-soaked to yellowish stripes on leaf blades or starting at leaf tips then later increase in lengthand width with a wavy margin
  • Appearance of bacterial ooze that looks like a milky or opaque dewdrop on young lesions early in the morning
  • Lessions turn yellow to white as the disease advances
  • If the cuts end of leaf is kept in water it becomes turbid because of bacterial ooze

Healthy Leaf

Infected Leaf


Identification of Pathogen Life Cycle of Xanthomonas oryzae
Xanthomonas oryzae

Management
Biological Method
  • Spray fresh cowdung extract 20% twice (starting from initial appearance of the disease and another at fortnightly interval)
  • Neem oil 60 EC 3% (or) NSKE 5% is recommended for the control of sheath rot, sheath blight, grain discolouration and bacterial blight

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Rice tungro disease : Rice tungro virus (RTSV, RTBV)

Symptom of Damage
  • Plants affected by tungro exhibit stunting and reduced tillering. Their leaves become yellow or orange-yellow, may also have rust-colored spots.
  • Discoloration begins from leaf tip and extends down to the blade or the lower leaf portion
  • Delayed flowering, - panicles small and not completely exerted
  • Most panicles sterile or partially filled grains

Healthy Leaf

Infected Leaf


Management

Physical Method

  • Light traps are to be set up to attract and control the leaf hopper vectors as well as to monitor the population.
  • In the early morning, the population of leafhopper alighting near the light trap should be killed by spraying/dusting the insecticides. This should be practiced every day.
  • Spray Two rounds of any one of the following insecticides
  • Thiamethoxam 25 WDG 100g/ha
  • Imidacloprid 17.8 SL 100ml/ha
    at 15 and 30 days after transplanting. The vegetation on the bunds should also be sprayed with the insecticides.
  • Special detection technique
    PCR detection facilities available at the Department of Plant Pathology, TNAU, Coimbatore-3 can be used

Top

Main Field Diseases

Sheath Blight: Rhizoctonia solani

Symptom of Damage

Infected sheath

Healthy leaf  

Infected leaves

  • Plants affected by tungro exhibit stunting and reduced tillering. Their leaves become yellow or orange-yellow, may also have rust-colored spots.
  • Discoloration begins from leaf tip and extends down to the blade or the lower leaf portion
  • Delayed flowering, - panicles small and not completely exerted
  • Most panicles sterile or partially filled grains

Identification of Pathogen Life Cycle of Rhizoctonia solani
Conidia of Rhizoctonia solani

Management
Cultural Method
  • Apply Neem cake at 150 kg/ha
    Botanical
  • Foliar spray with Neem oil at 3% (15 lit /ha) starting from disease appearance
Apply Organic Amendments Deep Summer Ploughing
Chemicial Method
  • Carbendazim 50 WP @ 500g/ha
  • Azoxystrobin @ 500ml/ha
  • Hexaconazole 75% WG @ 100mg/ lit 1st spray at the time of disease appearance and 2nd spray 15 days later
Spray Iprodione Use Polyoxin Antibiotic
Biological control
  • Seed Treatment with TNAU Pf 1liquid formulation @ 10 ml/kg of seeds
  • Seedling root dipping with TNAU Pf 1liquid formulation (500 ml for one hectare seedlings)
  • Soil application with TNAU Pf 1liquid formulation (500ml/ha)
  • Foliar spray with TNAU Pf 1liquid formulation @ 5ml/lit

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Sheath Rot: Sarocladium oryzae

Symptom of Damage
Irregular Spots on Sheaths Discoloration of Leaf Sheath Panicles remain within the Sheath Rottening of Flag Leaf Sheath
  • Irregular spots or lesions, with dark reddish brown margins and gray center
  • Discoloration in the flag leaf sheath
  • Lesions enlarge and often coalesce and may cover the entire leaf sheath
  • Severe infection causes entire or parts of  young panicles to remain within the sheath
  • Unemerged panicles rot and florets turn red-brown to dark brown
  • Whitish powdery growth inside the affected sheaths and young panicles
  • Infected panicles sterile, shrivelled, or with partially filled grain.

Management
Cultural Method
  • Apply Gypsum @ 500 kg/ha at two equal splits once basally and another at active tillering stage.
  • Botanicals
  • Neem oil 3%
  • Ipomoea leaf powder extract (25 kg/ha)
  • Prosopis leaf powder extract (25 kg/ha). First spray at boot leaf stage and second 15 days later


Provide Optimum Plant Spacing Apply Potash at Tillering Stage
Chemical Method
  • Spray any one of the following:
  • Carbendazim @ 500g/ha
  • Metominostrobin @ 500 ml/ha
  • Hexaconazole 75% WG @ 100 mg/ lit 1st spray at the time of disease appearance and 2nd spray 15 days later
Spray Benomyl Spray Chlorothalonil
Biological control
  • Seed Treatment with TNAU Pf 1liquid formulation @ 10 ml/kg of seeds
  • Seedling root dipping with TNAU Pf 1liquid formulation (500 ml for one hectare seedlings)
  • Soil application with TNAU Pf 1liquid formulation (500ml/ha)
  • Foliar spray with TNAU Pf 1liquid formulation @ 5ml/lit

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Brown Spot : Helminthosporium oryzae
Occurance
Also called as sesame leaf spot or Helminthosporiose or fungal blight

Mostly seen in West Bengal, Orissa, A.P and Tamil Nadu

Occurance
  • Occur in nursery as well as main field
  • Causes blight of seedlings
  • Leaf spotting is very common
  • Isolated brown, round to oval (resemble sesame seed)
  • Spots measures 0.5 to 2.0mm in breadth - coalesce to form large patches.
  • Seed also infected (black or brown spots on glumes spots are covered by olivaceous velvety growth)
  • Infection also occurs on panicle neck with brown colour appearance
  • 50% yield reduction in severe cases
Healthy field 
Infected leaf
Advanced stage of infection

Occurance
  • Also called as sesame leaf spot or Helminthosporiose or fungal blight
  • Mostly seen in West Bengal, Orissa, A.P and Tamil Nadu

Symptoms
  • Occur in nursery as well as main field
  • Causes blight of seedlings
  • Leaf spotting is very common
  • Isolated brown, round to oval (resemble sesame seed)
  • Spots measures 0.5 to 2.0mm in breadth - coalesce to form large patches.
  • Seed also infected (black or brown spots on glumes spots are covered by olivaceous velvety growth)
  • Infection also occurs on panicle neck with brown colour appearance
  • 50% yield reduction in severe cases
Circular or Oval Spots on Leaves Spots on leaves with brown margin

Dark Brown or Black Spots on Panicle

Glumes and Grains

Brown Spot on Grains

Identification of Pathogen Life Cycle of Helminthosporium oryzae
Conidia of Helminthosporium oryzae

Management
Spray any one of the following:
  • Metominostrobin @ 500ml/ha

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False Smut: Ustilaginoidea virens

Symptoms
  • Only few grains in a panicle are usually infected and the rest are normal
  • Individual rice grain transformed into a mass of yellow fruiting bodies
  • Growth of velvety spores that enclose floral parts
  • Immature spores slightly flattened, smooth, yellow, and covered by a membrane
  • Growth of spores result to broken membrane
  • Mature spores orange and turn yellowish green or greenish black
Healthy grain
Infected panicle  
Infected grain

Identification of Pathogen
Conidia of Ustilaginoidea virens

Management
  • Two sprayings of Propiconazole 25 EC @ 500ml/ha (or) Copper hydroxide 77 WP @ 1.25 kg/ha at boot leaf and 50% flowering stages

Top

Grain discoluration – fungal complex

Symptoms
  • Drechslera oryzae, Curvularia lunata, Sarocladium oryzae, Phoma sp., Microdochium sp., Nigrosporaspand Fusarium sp.,
  • Grains are infected either after milk stage or after harvest or during storage
  • Infection may be internal or external causing discoluration of the glumes or kernels
  • Dark brown or black spots appear on grains
  • Under humid condition prominent fungal growth
Discolouration of grains Black Spots Appear on
Grains with Prominent
Fungal Discolouration
Black Spots Appear on
Grains
Fungal Growth on Grains

Management
Chemical Method
  • Spray - Carbendazim + Thiram + Mancozeb (1:1:1) 0.2% at 50% flowering stage.
Spray Mancozeb at Boot Leaf Stage

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Leaf streak -Xanthomonas oryzae pv. oryzicola

Symptom
  • Initially, small, dark-green, water-soaked translucent streaks on veins from tillering to booting stage
  • Lesions turn brown and bacteria ooze out under humid weather.
Brown to Greyish
Longitudinal Streaks on
Leaves
Lesions turn brown to greyish and drying of leaves

Management
Biological method
  • Spray fresh cowdung water extract 20%
  • Copper hydroxide 77 WP@1.25 kg/ha is also recommended
 
Spray Cowdung or Mint or
Lemongrass Extract

Updated on May, 2014


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