Transcript diagnostic field guide for bacterial and viral diseases of paddy

DIAGNOSTIC FIELD GUIDE FOR
BACTERIAL AND VIRAL DISEASES
OF PADDY
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DIAGNOSTIC 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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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Bacterial Leaf Blight
Local name: Bacteria janita pata dhwasa
Causal Organism: Xanthomonas oryzae pv. oryzae (Ishiyama) Swings et al.
Bacterial Leaf Blight Disease symptoms on paddy
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Epidemiology:
High relative humidity (83-93%) and moderate temperature (26-300C)
favour the disease development.
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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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Epidemiology:
Infection occur through wounds and stomata.
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 FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Diagnostic Symptoms:
The disease symptoms appear in two phases are leaf blight
and wilt or Kresek.
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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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Diagnostic Symptoms:
The leaves turn straw yellow, the leaf blight phase generally
appears 4 to 6 weeks after transplanting and severe at booting
to flowering stage.
Severe infection causes partially filled or chaffy gains and
unemerged panicles get rottened.
Systemic infection or Kresek or wilt phase is most
destructive, generally causes from early infection.
The diseased leaves roll, droop and wither away.
Sever incidence is noticed from August to November.
Fresh cut out end of the infected leaves show bacterial oozing
in clean water.
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Bacterial Leaf Streak
Local name: Dora dag rog
Causal organism: Xanthomonas oryzae pv. oryzicola (Fang et al.) Swings
et al.
Bacterial Leaf Streak Disease symptoms on paddy
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Epidemiology:
High relative humidity (83-93%) and moderate
-300C) favour the disease
development.
temperature (26
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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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Epidemiology:
Infection occur through wounds and stomata.
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 FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Diagnostic Symptoms:
Initially, small, dark-green and water-soaked streaks appear on inter
veins from tillering to booting stage.
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.
Very small yellow beads instead of bacterial exudates during
dry season.
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Diagnostic Symptoms:
Lesions turn brown to grayish white then dry when disease is
severe.
Yellow halo symptom appears around the lesions on susceptible
cultivars.
Leaves turn brown to grayish white then dry.
At late stages the leaves die and then bleached to grayish white.
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Tungro Virus Disease
Local Name: Tungro virus rog
Causal Organism: Rice Tungro Virus
Vector: Green leaf hopper (Nepltotettix impicticeps, N. virescens,
N. nigropictus)
Rice Tungro Disease symptoms
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Epidemiology:
High nitrogen fertilization had marked influence on development of
disease.
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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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Epidemiology:
September to November and March to April the insect vector
population is more and active, thus disease is more prevalent in the
field.
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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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Diagnostic Symptoms:
The characteristic symptoms appear in the field as stunted growth with
reduced tillering.
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.
The infected leaves often dry up quickly. In-the field, disease
symptoms initially seen in localized spot in yellowing at
patches of round nature.
If infection starts at early stage of crop, panicle fail to emerge or bearing
chaffy and shriveled grains.
Root development of infected plant is also poor.
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DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL DISEASES OF PADDY
Diagnostic Symptoms:
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:As the disease if mostly transmitted by green jassid
(Niphotottis Virescens) presence of this vector has to
be established in the standing rice crop.
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.
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