diagnostic field guide for bacterial and viral diseases of paddy next

DIAGNOSTIC FIELD GUIDE FOR DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES BACTERIAL AND VIRAL DISEASES OF PADDYOF PADDY

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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDYDIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY

Major Bacterial & viral Diseases

Bacterial Leaf Blight Bacterial Leaf Streak

Tungro Virus Disease

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Local name: Bacteria janita pata dhwasa Causal Organism: Xanthomonas oryzae pv. oryzae (Ishiyama) Swings et al.

Bacterial Leaf Blight Disease symptoms on paddy

Bacterial Leaf Blight

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High relative humidity (83-93%) and moderate temperature (26-300C) favour the disease development.

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Epidemiology:Epidemiology:

The disease usually occurs during the early stage of planting from maximum tillering to panicle initiation.

Older plants are more resistant to the disease.

The disease is transmitted through seeds

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Infection occur through wounds and stomata.


Epidemiology:Epidemiology:

Infected seeds present in the water or those surviving in the debris left after harvest, are also sources of inoculums in the next planting season.

The disease also disperse and spread by wind and rain water.

High dose of nitrogenous fertilizer, excessive shade and close planting favour the disease.

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Diagnostic Symptoms:Diagnostic Symptoms:The disease symptoms appear in two phases are leaf blight and wilt or Kresek.

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In susceptible rice varieties lesions may cover entire leaf lamina and even the leaf sheath.

First lesion start as water soaked looking stripes along the margins progressing from top to downwards of the leaf blades.

The margin of the blighted areas is typically wavy in nature

Under wet weather bacterial pathogen exudates and form turbit droplet on the affected portion, after wards bacterial exudates dries up and turn to white encrustation

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The leaves turn straw yellow, the leaf blight phase generally appears 4 to 6 weeks after transplanting and severe at booting to flowering stage.


Diagnostic Symptoms:Diagnostic Symptoms:

Severe infection causes partially filled or chaffy gains and unemerged panicles get rottened.

The diseased leaves roll, droop and wither away.

Systemic infection or Kresek or wilt phase is most destructive, generally causes from early infection.

Fresh cut out end of the infected leaves show bacterial oozing in clean water.

Sever incidence is noticed from August to November.

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Local name: Dora dag rogCausal organism: Xanthomonas oryzae pv. oryzicola (Fang et al.) Swings

et al.

Bacterial Leaf Streak Disease symptoms on paddy

Bacterial Leaf Streak

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High relative humidity (83-93%) and moderate temperature (26 -300C) favour the disease development.


Epidemiology:

Older plants are more resistant to the disease.

The disease usually occurs during the early stage of planting from maximum tillering to panicle initiation.

The disease is transmitted through seeds.

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Infection occur through wounds and stomata.


Epidemiology:

The disease also disperse and spread by wind and rain water.

Infected seeds present in the water or those surviving in the debris left after harvest, are also sources of inoculums in the next planting season.

High dose of nitrogenous fertilizer, excessive shade and close planting favour the disease.

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Initially, small, dark-green and water-soaked streaks appear on inter veins from tillering to booting stage.

Diagnostic Symptoms:


Very small yellow beads instead of bacterial exudates during dry season.

Streaks later enlarge and coalesce to become yellowish gray and translucent patches and cover the entire leaf lamina.

Numerous small yellow beads of bacterial exudates on surface of lesions on humid conditions.

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Lesions turn brown to grayish white then dry when disease is severe.



At late stages the leaves die and then bleached to grayish white.

Yellow halo symptom appears around the lesions on susceptible cultivars.

Leaves turn brown to grayish white then dry.

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Local Name: Tungro virus rogCausal Organism: Rice Tungro VirusVector: Green leaf hopper (Nepltotettix impicticeps, N. virescens,

N. nigropictus)

Rice Tungro Disease symptoms

Tungro Virus Disease

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High nitrogen fertilization had marked influence on development of disease.


Epidemiology:

The wild species of rice, weed host like Leersia hexandra, Cynenden dactylon, Eleusing indica and Echinochloa

colonum are also sucoptible to this disease.

The tungro virus is mainly transmitted by green jassid (Niphotottis Virescens Dist.). It is also transmitted by N. Nigropictus and Racilia dorsalis to same extend.

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September to November and March to April the insect vector population is more and active, thus disease is more prevalent in the field.


Epidemiology:

In Tripura green jassid population is low during the months of January, February, March and December, moderate during

the month of April, May, June, August and November, maximum during the month of September and October. So the incidence of disease is also observe to be well correlated with the high population of leaf happer vectors during these months.

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The characteristic symptoms appear in the field as stunted growth with reduced tillering.



The infected leaves often dry up quickly. In-the field, disease symptoms initially seen in localized spot in yellowing at patches of round nature.

The young leaves turn from normal green to pale green or yellowish green and show mottled appearance alongwith slight twisting.

The older leaves turn orange -yellow and interveinal chlorosis is observed starting from the margin of the leaf blade.

Root development of infected plant is also poor.

If infection starts at early stage of crop, panicle fail to emerge or bearing chaffy and shriveled grains.

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In field the symptoms of tungro are after confused with the symptoms of nitrogen deficiency or cold injury. So to identify the disease in the field one should observe the following points very carefully:-



In case of cold injury and nitrogen deficient field, yellow colouration of plants will be fairly uniform, but virus infected symptoms usually appear in isolated patches.

As the disease if mostly transmitted by green jassid (Niphotottis Virescens) presence of this vector

has to be established in the standing rice crop.

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