Two main types of symptoms are conventionally distinguished on tomatoes leaf caused by potato ( virus Y Potato virus Y , PVY) :
- various coloring anomalies resulting in the presence on young leaves of initially discrete mottles, progressively evolving into a green mosaic (figure 1). Bands of dark green tissue located along the veins (vein banding), and diffuse chlorotic spots, are also observed. These symptoms are often due to strains of the PVY group ^O ;
- necrotic changes caused by necrogenic strains inducing leaf spots that reddish-brown quickly necrotize (Figures 2 to 6). Necrotic lesions are sometimes present on the petioles, and even the stem, in the form of more or less extensive dark streaks.

The nature and intensity of these symptoms may vary depending on the stage of development of the plants, the cultivar, the environmental conditions, but especially the nature of the strain involved.

As previously reported, mixed PVY-CMV infections are relatively frequent, especially during the summer period. They are the cause of symptoms that are sometimes more spectacular, both in the open field and in shelters.