November 29, 2017 Chief Editor

Diseases of Rice Fields

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 / Internode Blast

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

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.

Tags: ,