Different viruses

Several viruses can cause small necrotic lesions on tobacco leaves. The potato virus Y (PVY) is probably the most common cause of such symptoms in France. Note that the nature of spots varies with genotypes of tobacco. They can be brown, surrounded by a yellow halo, resembling a bacteriosis (figure 1).

On some cultivars such as the basic "Virginia" infected by the virus, there may be tiny brown spots and rings which later turn greyish-beige (figure 2). These small lesions occasionally mingle with pollution spots ("weather fleck"), in this case the plants are particularly affected. One may wonder whether there was a synergy between this physiological disease and PVY which could explain the nature and severity of symptoms. A similar situation has already been reported for tobacco streak virus (TSV) associated with this type of physiological disorder.