Bacterial blight of cotton

This ppt have all details about bacterial blight of cotton

1. Presentation on Bacterial b light of Cotton Presented by Anand Choudhary

2. About Disease First reported in Alabama state of U.S.A. in 1891. In India the disease was first reported in Tamil Nadu in 1918. Annual losses vary from 5-25%.

3. About Pathogen Pathogen – X anthomonas axonopodis pathovar malvacearum Gram – ve bacteria Motile rod shaped Non spore forming bacterium with a single polar flagellum

4. Symptoms Angular leaf spots on the leaves Venial blight Black arm lesions on the stem Boll rot and gummosis Spots on cotyledons are circular, dark green and greasy

5. 1. Seedling blight – the earliest symptoms of the disease is seen in the cotyledon of germinating seeds. Minute water-soaked spots appear on the under surface of the cotyledons and ultimately collapse and die .

6. Often the disease spreads along the edge of vein, hence called vein blight or black vein . 2 . Blackarm S ymptoms – lesions on stem, petioles, and fruiting branches are dark brown to stooty black. Affected stem show crackes and gummosis and are easily broken by wind or there may be girdling and death of affected organs. These are called black arm

7. 3. Angular leaf spot - On the leaves, scattered small dark-green, water-soaked, areolate spots, form measuring 1–2 mm on the lower surface, which appear translucent against transmitted light. The spots increase in diameter to 5 mm, become angular (due to leaf veination ), brown and later turn dark brown to blackish, becoming visible on the upper surface

8. 4. Boll rot – water soaked lession on the surface. Young infested bolls fall down prematurely.  The pathogen also infects the seed and causes reduction in size and viability of the seeds.

9. Inoculum Sources X. axonopodis   survives in infested crop debris or seeds. Although infections may be seed borne , acid- delinting cotton seed has been instrumental in minimizing the spread of bacterial blight through contaminated seed. Volunteer seedlings may also be a source of primary inoculums for bacterial blight.

10.     Epidemiology  Optimum soil temperature of 28 O C , high atmospheric temperature of 30- 40 O C Relative humidity of 85 per cent Early sowing, Relayed    thinning, Poor tillage, Late irrigation and potassium deficiency in soil. Rain followed by bright sunshine during the months of October and November are highly favourable.

11. Disease Cycle The bacterium survives on infected, dried plant debris in soil for several years. The bacterium is also seed-borne and remains in the form of slimy mass on the fuzz of seed coat. The bacterium also attacks other hosts like  Thumbergia thespesioides , Eriodendron anfructuosum   and  Jatropha curcus .   The primary infection starts mainly from the seed-borne bacterium. The secondary spread of the bacteria may be through wind, wind blown rain splash, irrigation water, insects and other implements.

12. Management Delint the cotton seeds with concentrated sulphuric acid at 100ml /kg of seed. Treat the delinted seeds with carboxin or oxycarboxin at 2 g/kg or soak the seeds in 1000 ppm   Streptomycin sulphate  overnight . Remove and destory the infected plant debris. Rogue out the volunteer cotton plants and weed hosts . Follow crop rotation with non-host crop

13. Early thinning and early earthing up with potash. Grow resistant varieties like Sujatha , 1412 and CRH 71. Spray with  Streptomycin sulphate   + Ttetracycline  mixture 100g along with  Copper oxychloride  at 1.25 Kg/ha Grow resistant varieties like Sujatha , 1412 and CRH 71 .

14. Thanks for your time