Bacterial leaf spot: Xanthomonas campestris pv. vesicatoria

Symptoms

• 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.
• The spot coalesce to form irregular lesions. Severely affected leaves become chlorotic and fall off.
• Petioles and stems are also affected. Stem infection leads to formation of cankerous growth and wilting of branches.
• On the fruits round, raised water soaked spots with a pale yellow border and produced.
• The spots turn brown developing a depression in the centre wherein shining droplets of Bacterial cozen may be observed.   

Management

• Spray mancozeb @ 2 g/l or copper oxychloride @ 2.5 g/l .
• Seed treatment with 0.1% mercuric chloride solution for 2 to 5 minutes is effective.
• Seedlings may be sprayed with Bordeaux mixture 1. Per cent or copper oxychloride 0.25%.
• Spraying with streptomycin should not be done after fruits begin to form.
• Field sanitation is important. Also seeds must be obtained from disease free plants.