Pseudomonas cichorii

(black spot disease)

Pseudomonas cichorii bacterium causes black spot disease of tobacco, it is known to affect many cultured plants and weeds. It has been rarely reported on tobacco, except in Brazil in the region of Minas Gerais where it has caused important damage. It has been observed in France, mainly at the end of season on mature dark tobacco plants and during rainy periods.
 
This bacterium causes greasy spots which enlarge quickly and become necrotic on lower tobacco leaves. Their dark brown colour and size are particularly symptomatic (figures 1-5). At an early stage, diagnosis may be confused with that of Alternariosis but the latter one is very uncommon in dark tobacco.

For further information please see the fact sheet of Pseudomonas cichorii.