ANGULAR LEAF SPOT OF COTTON K R.pptx

ANGULAR LEAF SPOT OF COTTON K R.pptx

1. ANGULAR LEAF SPOT OF COTTON K R MICRO NOTES 1

2. INTRODUCTION Angular Leaf Spot also called ,Bacterial Blight, is a disease caused by the bacterium, Xanthomonas axonopodis pv . Malvacearum . Bacterial Blight was first described in Alabama state of United States in 1891 and continues to be a major disease of cotton throughout the world. In india the disease was first reported in Tamil nadu in 1918. In India, losses of 5-20% were common in crops. K R MICRO NOTES 2

3. causitive organism Scientific classification Kingdom : Bacteria Phylum : Proteobacteria Class : Gammaproteobacteria Order : Xanthomonadales Family : Xanthomonadaceae Genus : Xonthomonas Species : axonopodis K R MICRO NOTES 3

4. Xanthomonas axonopodis pathovar Malvacearum A Gram negative Motile rod-shaped Non spore-forming bacterium with a single polar flagellum. The bacterium is aerobic, capsule forming and produces yellow colonies in culture medium. K R MICRO NOTES 4

5. xanthomonas axonopodis pv . Malvacearum colony characteristics K R MICRO NOTES 5

6. EPIDEMOLOGY MODE OF SURVIVAL AND SPREAD Primary infection : seed borne Secondary infection : wind, water and other physical and biological agents; also an several collateral hosts. The bacterium enters through natural openings or insect caused wounds. K R MICRO NOTES 6

7. FAVOURABLE CONDITIONS Optimum soil temperature of 28°C. High atmospheric temperature of 30-40°C. Relative humidity of 85%. Early sowing, delayed 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 . K R MICRO NOTES 7

8. 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 . K R MICRO NOTES 8

9. symptoms Water soaked circular or irregular lesions on cotyledons which spread to petiole and stem and finally withering and death of seedling known as seedling blight . Small, dark green, water soaked areas develop on lower surface of leaves, enlarge gradually and become angular when restricted by veins and veinlets and spots are visible on both the surface of the leaves ( Angular leaf spot ). K R MICRO NOTES 9

10. K R MICRO NOTES 10

11. symptoms The infection of veins and veinlets shows blackening with crinkled and twisted leaves and bacterial oozing ( Vein necrosis or vein blighting). Black lesions on stem and branches, pre-mature drooping of the leaves resulting in die-back known as black arm. It also affects the bolls causing boll rot. K R MICRO NOTES 11

12. disease managnement Delint the cotton seeds with concentrated sulphuric acid at 100 ml/kg. Treat the delinted seeds with carboxin or oxycarboxin at 2g/kg or soak the seeds in 1000ppm Streptomycin sulphate overnight. Remove and destroy the infected plant debris. Rogue out the volunteer cotton plants and weed hosts. Follow crop rotation with non host crops. Early thinning and early earthing up with potash. Grow resistant varieties like Sujatha, 1412, CRH71, HG-9, BJA 592, G-7and HS-6. Suvin is tolerant. Spray with Streptomycin sulphate and Tetracycline mixture 100g along with copper oxychloride at 1.25kg/ha. K R MICRO NOTES 12

13. references Plant pathology by P.D Sharma Agriculture microbiology by G.Rangaswami , DJ Bagyaraj www.cottoninc.com https://content.ces.ncsu.edu/bacterial-blight-angular-leaf-spot-of-cotton www.slideshare.com K R MICRO NOTES 13