Bacterial blight of paddy

bacterial blight of peddy

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 i nto the host through wounds and stomata. High doses of nitrate, silicate and magnesium in the soil.

10. 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.)

11. 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.

12. 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.

13. Reference https://WWW.forestryimages.org Plant pathology, by B.P.PANDEY.

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