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Shri Shivaji Education Society, Amravati’s�JIJAMATA MAHAVIDYALAY, BULDANA�Department of Botany� � Programme: B. Sc. Botany�(B.Sc. Part I) Semester I �Code of the Course/Subject : BOT(1S)/Botany ��Title of the Course/Subject: DIVERSITY OF MICROBES, PHYCOLOGY, MYCOLOGY AND PHYTOPATHOLOGY � �UNIT-VI : Phytopathology ��Topic: 6.2 Symptoms, Pathogen biology and disease management of Bacterial diseases- ��6.2.1- Citrus canker �6.2.2- Angular leaf spot of cotton � �Name of Teacher�Dr. Rahul W. Ukey (Assistant Professor)�

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6.2.1- Citrus Canker

Host: Citrus aurantifolia

Causal Organism: Phytomonas citri (=Xanthomonas citri)

Object : Study the symptoms of citrus canker.

Work procedure:

Study the diseased parts of the plant such as leaves, twigs, fruits.

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Symptoms

1. Citrus canker is produced by a bacterium Phytomonas citri (=Xanthomonas citri) on citrus (Citrus aurantifolia; vern. kagzi nimboo; fam. Rutaceae).

2. Bacterium causing this disease is a short bacillus (rod-shaped), monotrichous and strictly aerobic.

3. It produces corky outgrowth (cankers) on any aerial part of the plant. Mostly leaves, twigs, young branches and fruits are infected.

4. Canker on the leaves appears first on the underside. In the beginning it appears as convex protuberance of dark green colour but later, spots become white-greyish and finally rupture.

5. The spongy and rough formations remain scattered irregularly or several coalesce to form irregular scabby mass.

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6.2.2- Angular leaf spot of Cotton

Causal organism: Xanthomonas auxonopodis pv. malvacearum

Symptoms: Small water-soaked spots appear on the under surface of

cotyledons, which may dry and wither. Such spots also appear on the leaves.

  • They become angular bound by veinlets and turn brown to black in colour.
  • Several small spots may coalesce. The infected petiole may collapse.
  • Elongated, sunken and dark brown to black lesions appear on stern, petioles and branches. The young stems may be girdled and tilled in the black arm phase.
  • Sunken black lesions may be seen on the bolls. Young boll may fall off. The attacked stern becomes weak. Bacterial slime is exuded on the brown lesions. Discoloration of lint may take place.

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Control measures:

1. Field sanitation

2. Seed Treatment:

  1. Externally seed borne infection can be eradicated by delinting the seed with. Conc. H2SO4 for 5 minutes, wash with lime solution to neutralize the effect and finally washing with running water to remove the residue and drying seeds.

b) Internally seed borne infection can be eradicated by soaking seeds overnight in 100 ppm streptomycin sulphate or agrimycin.

3) Deshi cotton (Gossypium arborum) is tolerant comparatively.

4) Secondary spread of the disease can be controlled by spraying the crop with streptomycin sulphate 100 ppm + Copper oxychloride (0.25%) at an interval of 15 days.

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Thank You