This document summarizes bacterial blight, a common rice disease caused by the bacterium Xanthomonas oryzae. It first appears as water-soaked leaf spots and streaks, which can coalesce and spread to grains. The disease spreads via seeds, infected plant debris, and rain splash. Management strategies include seed treatment, multiple fungicide applications, chlorinated irrigation water, burning debris, isolation of nurseries, and growing resistant varieties.

1. Bacterial Blight of
Paddy

2. CONTENTS
• Introduction
• Symptoms
• Causal organism
• Disease cycle
• Disease control

3. Introduction
Host plant:- Rice
Causal organism:-Xanthomonas oryzae

4. • Bacterial blight is a very common and
widespread disease of paddy in Asia.
• The disease was first reported from
Japan in 1881.
• In India, the disease was first reported in
1951 from Bombay.

5. SYMPTOMS
• It is a foliar disease
which appears in early
or late august and
causes maximum
damage during the
heading stage.
• It first appears as
water-soaked ,
translucent spots on
the leaf blade and leaf
sheath.

6. • The spots gradually increase to form
elongated yellow to straw colored streaks
which may coalesce to form white blotches
the streaks usually develop form the tip
towards the base.
• In severally infected fields, infection may
reach the grains.
• The glumes become discolored and water
soaked spots developed on them.

7. CAUSAL ORGANISM
 The pathogen
responsible for
bacterial blight of
paddy is Xanthomonas
oryzae.
 It is an aerobic, rod
shaped, non
capsulated, non-spore
forming, gram negative
bacterium.

8.  0.5-0.8 x 1-2 µ in size. It is motile with a
single polar flagellum.
 The bacterium produces waxy yellow
colored colonies on agar medium and is
incapable to reduce nitrates.
 The optimum temperature for its growth is
28°-30° C and its thermal death point is
53°C.

9. Disease cycle
• It is principally a vesicular disease.
• Seeds and disease stubbles are mainly the
primary sources of infection.
• The secondary infection spreads due to
wind-borne rain splashes and gains entry
into the host through wounds and stomata.
• High doses of nitrate, silicate and
magnesium in the soil.

11. Disease control
The following measures can be adopted to
control the disease incidence:
• One if the good measures is to treat seeds
with 0.025 percent water solution of agrimycin
plus 0.05 percent wettable ceresan for 12
hours and then transfer them to hot water at
52°-54° C for 3 minutes.
• Initial infection can be checked by dipping
seeds for 8 hours in o.1 percent ceresan wet
plus streptomycin (0.3 gm in 2.5 gallons of
water.)

12. • Spraying agrimycin plus copper oxychloride
for 5 times at 12 day intervals prevent
secondary spread.
• Chlorination of irrigation water also helps in
reducing infection.
• Burning of infected straw and stubble to
destroy the bacteria present is also a good
measure.

13. • By sowing of nursery beds in disease free
isolated areas to prevent the inflow of
primary inoculums into fields.
• Pruning of top portions of the host should
be avoid.
• By cultivating resistant varieties such as
sathi, N-22, IR-20, IR-22, W-529, W 348 and
Ratna.

14. Reference
1. https://WWW.forestryimages.org
2. Plant pathology, by
B.P.PANDEY.