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Diseases of Rice

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Nursery disease
Blast (Pyricularia Oryzae Cavara)

Symptoms

  • Disease can infect paddy at all growth stages and all aerial parts of plant (Leaf, neck and node).
  • Among the three leaf 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 to form big irregular patches
  • Unde severe leads to
  • lodging of crop (after ear emergence)

Neck Blast

  • Neck region develops a black color and shriveled completely / Partially grain set inhibited, panicle breaks at the neck and hangs.

Internode Blast

Control

  • Use of tolerant varieties (Penna, Pinakini, Tikkana, Sreeranga, Simphapuri, Palghuna, Swarnamukhi, Swathi, Prabhat, IR - 64, Jaya, IR - 36, MTU 9992, MTU 1005, MTU 7414).
  • Burning of straw and stubbles after harvest.

Bacterial Leaf Blight

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.
  • Green water-soaked layer along the cut portion or leaf tip of leaves as early symptom.

Control

  • Secure disease free seed
  • Grow nurseries preferably in isolated upland conditions
  • Drain the field (except at flowering stage of the crop)
  • Destruction of wild collateral hosts
  • Avoid flow of water from affected fields
  • Grow tolerant varities (Swarna, Ajaya, Deepti, Badva mashuri, MTU-9992).

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

Control

  • Destruction of the infected plant debris by burning.

Brown Spot ( Helminthosporium oryzae)
Symptoms

  • Occur in nursery as well as main crop
  • 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 - coalasee to form large pathces.
  • Seed also infected (black or brown spots on glumes) (spots are covered by olivaceous velvety growth)
  • Infection also occur on panicle neck with brown colour appearance
  • 50% yield reduction in severe cases

Control

  • The fungus is seed transmitted, a hot water seed treatment (53-54°C) for 10-12 minutes.

False Smut (Ustilaginoidea viridis)

Symptoms

  • 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
  • only few grains in a panicle are usually infected and the rest are normal

Control

  • Destruction of straw and stubble.

Tungro Virus (Rice Tungro Virus)

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 exserted.
  • most panicles sterile or partially filled grains.

Control

  • Grow tolerant varieties like MTU 9992, MTU 1002, MTU 1003, MTU 1005, Surekha, Vikramarya, Bharani, IR 36 etc.,
  • In epidemic areas follow rotation with pulses or oil seeds.

Leaf streak (Xanthomonas oryzae pv. oryzicola)

  • Initially, small, dark-green and water-soaked streaks on interveins from tillering to booting stage.

Control

  • Proper, planting spacing, the use of resistant varieties, and hot water treated seeds.

 


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