Bacterial leaf spot

It was first observed in the U.S.A. in 1912. At present it is prevalent in many countries. It is the most common of the bacterial diseases of chilli in India.

Bacterial leaf spot

Symptoms:

1. The leaves exhibit small, circular or irregular, dark brown or black greasy spots. As the spots enlarge in size, the centre becomes lighter surrounded by a dark band of tissue.
2. The spots coalesce to form irregular lesions. Severely affected leaves become chlorotic and fall off. Petioles and stems are also affected.
3. On the fruits, round, raised water soaked spots with a pale yellow border are produced.

Brown or Black greasy spots on leaves	Brown spots on fruits
Wart-like, dark brown spots on the fruit	Symptoms on the peduncle
Severe infection leads to defoliation

Causal organism: Xanthomonas campestris pv. vesicatoria

Disease cycle:

• Primary source of inoculum: Seed
• Secondary source of inoculum: Rain splash

Epidemiology:

• The bacterium needs a temperature of 22 to 34^oC with high humidity for maximum infection.
• Infection takes place at a wide range of temperatures from 15 to 35^oC but the optimum is 24 to 30^oC.
• Forty to fifty day old plants are most susceptible to this disease.