Bacterial Diseases

6. Bacterial spot
The disease affects bell pepper/ chillies and tomato. Bacterial spot of capsicum was first reported from Florida, USA by Sherbakoff (1918), but in India, disease was observed for the first time at Poona during 1948.


  • On leaves, initially the lesions are water-soaked, circular or irregular that becomes necrotic with brown centers and thin chlorotic borders (Plate-7a).
  • These lesions are generally sunken on the upper surface of the leaves and slightly raised on the bottom.
  • In favourable environmental conditions, these spots coalesce and give a blighted appearance and such leaves turn yellow and fall down prematurely.
  • Lesions on the stem are narrow, elongated and raised.
  • Lesions on fruit initially begin as green spots, which enlarge and later become brown in colour (Plate-7b).
  • These spots are raised with a cracked, roughened wart like appearance.
  • During periods of high humidity, fruit around the lesions may start rotting.


  • The bacterium responsible for this disease is Xanthomonas campestris pv. vesicatoria (ex Doidge) Vauterin et al.
  • The bacterium is motile, strictly aerobic, Gram -ve, rod shaped with round ends, non-spore forming and possesses a single pollar flagellum (Monotrichous).
  • Bacteria occur singly but occasionally in pairs and rarely in short chains.
  • Its colonies on nutrient agar or on specific medium yeast dextrose agar (YDA) are lemon yellow, slightly convex, wet and shining.
Disease cycle and epidemiology:
  • The bacterium persists in infected seeds and plant debris.
  • Moderate temperatures along with high precipitation and relative humidity favour disease development.
  • Infection of the plants can take place at a wide range of temperature i.e. 15 to 35 o C.
  • The optimum temperature lies between 22 to 34o C and maximum disease develops in between July and September.
  • The bacterium is disseminated within a field by wind driven rain droplets, clipping of transplants and aerosols.
  • Since the disease development requires high precipitation and high relative humidity, fields should be well drained, free of low-lying areas to minimize water-logged conditions.
  • The field should be rotated with non-solanaceous crops and bell pepper/ chillies should not be rotated with tomato.
  • Use of disease free seeds also reduce the immediate availability of primary inoculum and ensures disease free transplants.
  • Sprinkler or overhead irrigation of the field should be limited to keep the disease under check.
  • Treat the seeds by dipping in Streptocycline (100 ppm) for 30 minutes. Spray the crop with Streptocycline (100 ppm) with the initiation of the disease.

7. Bacterial wilt

  • It is an important disease of this crop. Symptoms, pathogen, disease cycle and epidemiology and management are same as described in tomato.
Last modified: Friday, 2 March 2012, 6:19 AM