Diseases Of Paddy

By TamilNadu Agricultural University on 14 Dec 2018 | read
    05
Nursery DiseasesMain 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 leafImage title

Healthy leaf  Image title

LeafImage title

CollarImage title

Nodal Image title

NeckImage title

  • 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 PathogenLife Cycle of Pyricularia Oryzae

Conidia of Pyricularia Oryzae

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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 FertilizerImage title

Use Resistant variety

BPT 5204Image title

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 CarbendazimImage title

Thiram-Seed Treating FungicideImage title

Treat the Seeds with CaptanImage title

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


Pre-Tillering to Mid-Tillering

Light at 2 to 5 % disease severities - Apply 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 Carbendazim or Tricyclazole @ 0.1 %.


Flowering and after 

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


Bacterial Leaf Blight: Xanthomonas 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 LeafImage title

Infected LeafImage title


Identification of PathogenLife Cycle of Xanthomonas oryzae

Xanthomonas oryzaeImage title

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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 


 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 LeafImage title

Infected LeafImage title


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 


Main Field Diseases

Sheath Blight: Rhizoctonia solani

Symptom of Damage

Infected sheathImage title

Healthy leafImage title  

Infected leavesImage title

  • 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 PathogenLife Cycle of Rhizoctonia solani

Conidia of Rhizoctonia solani

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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 AmendmentsImage title

Deep Summer PloughingImage title

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 IprodioneImage title

Use Polyoxin AntibioticImage title

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


Sheath Rot: Sarocladium oryzae

Symptom of Damage

Irregular Spots on SheathsImage title

Discoloration of Leaf SheathImage title

Panicles remain within the SheathImage title

Rottening of Flag Leaf SheathImage title

  • 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 SpacingImage title

Apply Potash at Tillering StageImage title

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 BenomylImage title

Spray ChlorothalonilImage title

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

 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 fieldImage title 

Infected leafImage title

Advanced stage of infectionImage title


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 LeavesImage title

Spots on leaves with brown marginImage title

Dark Brown or Black Spots on Panicle

Glumes and GrainsImage title

Brown Spot on GrainsImage title


Identification of PathogenLife Cycle of Helminthosporium oryzae

Conidia of Helminthosporium oryzae

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


 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 grainImage title

Infected panicle Image title 

Infected grainImage title


Identification of Pathogen

Conidia of Ustilaginoidea virensImage title


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


Grain discoluration – fungal complex

Symptoms
  • Drechslera oryzae, Curvularia lunata, Sarocladium oryzae, Phoma sp., Microdochium sp., Nigrosporasp. and 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 grainsImage title

Black Spots Appear on

Grains with Prominent

Fungal DiscolourationImage title

Black Spots Appear on

GrainsImage title

Fungal Growth on GrainsImage title


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

Spray Mancozeb at Boot Leaf StageImage title


 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

LeavesImage title

Lesions turn brown to greyish and drying of leavesImage title


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 ExtractImage title

 

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