Nursery diseases

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

Main field diseases

4. Brown Spot: Helminthosporium oryzae
5. Sheath Rot: Sarocladium oryzae
6. Sheath Blight: Rhizoctonia Solani
7. False Smut: Ustilaginoidea virens
8. Grain discolouration – fungal complex
9. Leaf streak-Xanthomonas oryzae pv. oryzicola

Nursery diseases

1. Blast :Pyricularia grisea (P.oryzae)

Occurrence

• 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%

		Symptoms 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
Infected leaf	Healthy leaf

Healthy leaf	Leaf	collar	nodal	neck

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
Management

• Avoid excess N - fertilizer application
• Apply nitrogen in three split doses.
• Removes weed hosts from bunds.
• Use of tolerant varieties (Penna, Pinakini, Tikkana, Sreeranga, Simphapuri, Palghuna, Swarnamukhi, Swathi, Prabhat, Co 47, IR - 64, , IR - 36, Jaya)
• Burning of straw and stubbles after harvest
• Dry seed treatment with Pseudomonas fluorescens talc formulation @10g/kg of seed.
• Stagnate water to a depth of 2.5cm over an area of 25m2 in the nursery. Sprinkle 2.5 kg of P. fluorescens (talc) and mix with stagnated water. Soak the root system of seedlings for 30 min and transplant.
• Spray P. fluorescens talc formulation @ 0.5% from 45 days after transplanting at 10 day intervals, three times.
• Seed treatment at 2.0 g/kg seed with Captan or Carbendazim or Thiram or Tricyclazole.
• Spraying of Tricyclazole at 1g/lit of water or Edifenphos at 1 ml/lit of water or Carbendazim at 1.0 gm/lit.
• 3 to 4 sprays each at nursery, tillering stage and panicle emergence stage may be required for complete control.

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.  

2. Bacterial Leaf Blight: Xanthomonas oryzae pv. oryzae

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

Management

• Secure disease free seed
• Grow nurseries preferably in isolated upland conditions
• Avoid clipping of seedlings during transplanting.
• Balanced fertilization, avoid excess N - application
• Skip N - application at booting (if disease is moderate)
• Drain the field (except at flowering stage of the crop)
• Destruction of wild collateral hosts
• Avoid flow of water from affected fields
• Grow tolerant varieties (IR 20, TKM 6).
• Spraying streptomycin sulphate and tetracycline combination 300g +copper oxychloride 1.25 kg/ha.

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

Symptoms 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

Management

• Set up light traps to monitoring and attract vectors
• Destruction of weed hosts on bunds
• Leaf yellowing can be minimized by spraying 2 % urea mixed with Mancozeb at 2.5 gm/lit.
• Instead of urea foliar fertilizer like multi-K (potassium nitrate) can be sprayed at 1 per cent which impart resistance also because of high potassium content.
• Grow tolerant varieties like Co 45, Co 48, Surekha, Vikramarya, Bharani, IR 36 
• In epidemic areas follow rotation with pulses or oil seeds.
• Green leaf hoppers as vectors are to be controlled effectively in time by spraying Monocrotophos at 1.6 to 2.2 ml/lit or Fenthion /Phosphomidan @1.0 ml/lit or Neem by applying Carbofuran 3 G @ 10 kg/acre.
• In nursery when virus infection is low, apply Carbofuran granules @ 1 kg a.i./ha to control vector population.
• During pre-tillering to mid-tillering when one affected hill/m is observed apply Carbofuran granules @ 1 kg a.i./ha or spray Monocrotophos @ 1.6 to 2.2ml/lit to control insect vector.

Main field diseases

4. Sheath Blight: Rhizoctonia solani

Symptom

• Initial lesions are water-soaked to greenish gray and later become grayish white with brown margin
• Lesions on leaf sheaths near waterline
• Presence of sclerotia
• Lesions may coalesce death of the whole leaf
• Partially filled or empty grains

Infected sheath	Healthy leaf	Infected leaves

Management

• Apply FYM 12.5 t/ha or green manure 6.25 t/ha to promote antagonistic microflora.
• Soil application of P. fluorescens @ 2.5 kg/ha mixed with 50 kg FYM after 30 days of transplanting.
• Foliar spraying of P. fluorescens @0.2% at boot leaf stage and 10 days later.
• Avoid flow of irrigation water from infected to healthy field.
• Carbendazim (1 g/lit), Propiconazole (1ml/lit) may be applied.
• Spraying of infected plants with fungicides, such as Benomyl and Iprodione, and antibiotics, such as Validamycin and Polyoxin, is effective against the disease
• Reduce Nitrogen dosage  and  skip top dressing

5. Sheath Rot: Sarocladium oryzae

Symptoms

• 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 Apply Ipomea or Prosophis leaf powder extract 5 % or NSKE 5% Spraying of Mancozeb at 2.5 g or Carbendazim at 1.0 g/lit or Benomyl 0.5 g/lit of water at flowering stage Destruction of the infected plant debris by burning.
Infected sheath	Advanced stage of infection

6. Brown Spot : Helminthosporium oryzae

Occurrence

• 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

Healthy field	Infected leaf	Advanced stage of infection

Occurrence

• 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

Management

• Use disease free seeds.
• Since seed soak / seed treatment with Captan or  Thiram at 2.0g /kg of seed
• Spray Mancozeb (2.0g/lit) or Edifenphos (1ml/lit) - 2 to 3 times at 10 - 15 day intervals.
• Spray preferably during early hours or afternoon at flowering and post - flowering stages.

7. 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

Management

• Use disease free seeds
• Destruction of straw and stubble
• At tillering and preflowering stages, spray Hexaconazole @ 1ml/lit or Chlorothalonil 2g/lit.

8. 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
Healthy grain	Infected grain

Management

• Spray the crop with Carbendazim + Mancozeb (1:1) @ 2g/lit. at boot leaf stage and 50 % flowering.
• Store grains at 13-14 % moisture.

9. Leaf streak -Xanthomonas oryzae pv. oryzicola

Symptoms

• 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.
  

Management Secure disease free seed Grow nurseries preferably in isolated upland conditions Avoid clipping of seedlings during transplanting. Balanced fertilization, avoid excess N - application Skip N - application at booting (if disease is moderate) Drain the field (except at flowering stage of the crop) Destruction of wild collateral hosts Avoid flow of water from affected fields Grow tolerant varieties (IR 20, TKM 6). Spraying streptomycin sulphate and tetracycline combination 300g +copper oxychloride 1.25 kg/ha.