Main Symptoms

Alternaria Alternata affects the lower, mature tobacco leaves on which it first induces small wet spots (figures 1 to 5). These evolve rapidly and become brown and circular, often containing discrete concentric rings and surrounded by a halo of chlorotic tissue. In humid conditions, it is not uncommon to observe a black, velvet-like conidial layer on the surface of spots. Lesions can appear on stems and petioles (figure 6).

Note that spots can depreciate the quality of cured tobacco leaves (figure 7).

Some of the information on the worldwide distribution of the disease is obtained from surveys conducted by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). The reliability of the information is not confirmed in all countries.