Causal Agent: 

Bacteria (Xanthomonas spp.)

Characteristic Symptoms:
Leaf lesions are angular to irregular, dark brown and water-soaked spots.
Affected leaves may turn yellow and fall off.
Under high humidity conditions, numerous lesions coalesce giving the plant a blighted appearance.
On immature tomato fruit, small black specks are formed which may enlarge to become brown, slightly sunken, scabby spots and are sometimes surrounded by a green halo.
Conditions for Disease Development:
The pathogen is seed-borne and is capable of overwintering on plant debris in the soil and on volunteer host plants in abandoned fields.
Bacteria invade the plant through stomata on the leaf surfaces and through wounds on the leaves and fruit caused by abrasion from sand particles and/or wind
Temperatures between 24-30°C and prolonged periods of high relative humidity favour infection and disease development.
The bacteria is spread by windblown rain, overhead irrigation, drainage of infested water, by mechanical means (handling of infected seedlings, on contaminated tools) and by workers (on hands, clothing).
Management and Control:
Use pathogen-free seeds or seedlings as the disease is difficult to control once introduced in the field.
Avoid working in affected areas when leaves are wet to minimize spread. Disinfect tools (10% chlorox) after working in infested area.
Avoid overhead irrigation.  Rain shelters in seedbeds may help reduce rain splash and disease severity.
Practice 2-3 years rotation with non-host crops.
Apply copper or copper+mancozeb sprays on dry seedlings prior to transplanting and continue at 5 days interval.
AVRDC Publication 05-638. 2005; Sun, et. Al. 2002. Bacterial Spot of Tomato and Pepper

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