Main symptoms

In the field, where attacks are most destructive, lettuce appears stunted and sometimes severely necrotic. The leaves are narrower, slightly curled or twisted (Figure 1). The young leaves occasionally show necrotic changes, more or less limited and located near or not the veins (figure 2). We can also observe rings. Chlorotic spots are visible on certain leaf stages (figure 3). Fine necrosis sometimes appears, giving the blade a slightly "tanned" appearance. The severity of the symptoms is all the greater the earlier the stage of infection. We can also see nerve lightening, a more or less marked mosaic (figure 4), necrotic spots ...

Under shelter, we find quite similar symptoms. The young leaves appear tan at first, their veins thin out and, eventually, a fairly marked marbling settles on the blade. A multitude of tiny necrotic changes sometimes cover the latter.