Different viruses

Among the symptoms caused by the viruses, a number of them appear in the form of various spots or lesions. The most common virus causing brown, occasionally necrotic spots are potato virus Y ( PVY) (figure 1), and more rarely tomato spotted wilt virus (TSWV) (figure 2).
 
Two other viruses, seldom observed in tobacco, also cause necrotic spots: tobacco streak virus (TSV) virus and tobacco necrosis virus (TNV). For further information about these viruses we recommend you consult the fact sheet of Other parasitic viruses of tobacco.
 
With regard to other viral symptoms which can accompany these spots, we also recommend you consult all the fact sheets of Leaf mosaic and the section of Different viruses in Abnormal leaf shape.