Title: DIAGNOSTIC FIELD GUIDE FOR
1DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
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2DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
Major Bacterial viral Diseases
Bacterial Leaf Streak
Bacterial Leaf Blight
Tungro Virus Disease
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3DIAGNOSTIC 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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4DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
- High relative humidity (83-93) and moderate
temperature (26-300C) favour the disease
development. -
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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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5DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
- Infection occur through wounds and stomata.
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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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6Diagnostic Symptoms
DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
- 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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7Diagnostic Symptoms
DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
- The leaves turn straw yellow, the leaf blight
phase generally appears 4 to 6 weeks after
transplanting and severe at booting to flowering
stage. -
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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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8DIAGNOSTIC 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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9DIAGNOSTIC 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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10DIAGNOSTIC 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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11DIAGNOSTIC 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. -
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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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12DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
Diagnostic Symptoms
- Lesions turn brown to grayish white then dry
when disease is severe. -
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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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13DIAGNOSTIC 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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14DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
Epidemiology
- High nitrogen fertilization had marked influence
on development of disease. -
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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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15DIAGNOSTIC 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. -
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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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16DIAGNOSTIC FIELD GUIDE FOR BACTERIAL AND VIRAL
DISEASES OF PADDY
Diagnostic Symptoms
- The characteristic symptoms appear in the field
as stunted growth with reduced tillering. -
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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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17DIAGNOSTIC 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- -
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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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