Alternaria alternata

(brown spot disease)

In most of the countries where it occurs Alternaria Alternata (brown spot) affects the lower and mature tobacco leaves. This fungus induces well defined brown spots with thin concentric rings (figures 1 to 5). On these spots, similar to other nutritional bases, the fungus sporulates abundantly when the weather allows. The produced conidia induce secondary contamination on the upper, younger leaves. Spot development is possible during tobacco curing (see the section on Curing barn diseases).
 
One should note that the fungus strains isolated in France do not seem to be as aggressive as some American strains. In addition, many varieties grown in France are not very susceptible to this fungus. More certainly for these reasons this disease does not cause serious damage in tobacco production in France.

For further information, please, see the fact sheet of Alternaria alternata.