bacterial leaf blight of rice

1. BACTERIAL LEAF BLIGHT OF RICE

3. BACTERIAL LEAF BLIGHT OF RICE
• Pathogen : Xanthomonas campestris p var
oryzae
Class : Schizomycetes
Order: Pseudomonadales
Family : Pseudomonadaceae

4. • History :
It was 1st reported in Japan during 1884 & in
India during the year 1951 in Maharashtra.
Later on,in 1962 the disease broke out in the
form of epidemics in Bihar and other parts of
North India. Now this disease is found to be
prevalent in all parts of country.

5. Symptoms
Leaf blight
kreseck
yellowing

6. Symptoms
• The disease appears early in August and
becomes quite distinct when the ears
developed.
• The symptoms of the disease may vary
depending upon growth stage of the crop.
There are 3 types of symptoms
Leaf blight
Kreseck /wilt
Yellow leaf

7. • Leaf blight : this symptoms will appear 4-6
weeks after transplanting.
Appearance of small circular water soaked spot
on the margins of the leaf & this spots also
extends to leaf sheath, also later this spots turn
yellow & becomes necrotic & results in drying of
leaf.

8. • Under humid conditions creamy white color
bacterial oozes comes out from the young
lessions in the morning hours.

9. • Yellowing stage : Here individual leaf becomes
yellow later wilting & dies.

10. • Kreseck / wilt : this is the most destructive
stage & Kreseck degenerations / wilting.
Young plants are more susceptible which
shows sudden wilting.
The bacteria multiplies in vascular bundels ,
exudation of bacterial ooze at the cut end
portion of leaf.

11. Etiology
• The bacteria is rod-shaped measuring
0.5 to 0.8 * 1 to 2 µ. They occur singly or in
pairs. They are Gram –ve , aerobic and with a
single polar flagellum. They are non-sporing
and do not form chains.

12. Infection
• Infection takes place through wounds. The
nitrogenous fertilization of the crop increases
the incidence of the disease. If the seedlings
are infected, the disease intensifies, after
transplanting.

13. Predisposing factors
Rainy weather, dull windy days and a suitable
temperature of 22 ̊c to 26 ̊c, clipping of tip of
leaves of seedling during transplanting , excess
application of nitrogenous fertilizer favor the
incidence of the disease.

14. • PSI : bacterial cells present on seeds, stubbles
& in soil. Here collateral host like Leessia
hexandra, Cyprus rotundus plays a major role.
• SSI : bacterial cells spread through irrigation
water and rain from one field to another.

15. Management
• Removal, collection and burning of diseased
plant parts straw left over in the field after
harvest
• Burning of choffy grains near the threshing
yard
• Irrigation canal, paddy field should be kept
free from weed , avoid movement of irrigation
water from field to field

16. • Selection of healthy seeds for sowing.
• Avoid clipping of tip of the leaves
• Judicious use of nitrogenous fertilizer
• Growing of resistant varieties Swarna, Ajay,
IR20
• Spraying of the crop with streptocyclin @
0.6 g/litre.