Leaf mosaic

There are two main causes for leaf mosaic or similar symptoms in tobacco:
a
 - many viruses, as pointed out in general sections, such as tomato spotted wilt virus (TSWV), cucumber mosaic virus (CMV ), alfalfa mosaic virus (AMV), tobacco mosaic virus (TMV), potato virus Y (PVY), tobacco ring spot virus (TRSV), and finally other viruses (TEV, TVMV, TLCV, PVX ...), specific fact sheets on these viruses are available in the Viruses section;
 
- but also genetic abnormalities such as variegation.

Figure 1	Figure 2	Figure 3	Figure 4

 
Warning:
Mosaic symptoms are not always easy to assess on virus-infected tobacco leaves especially on sunny days. In this case, we recommend you to observe the leaves by transparency and / or observe them in a shady place.
 
Quite often the symptoms, that may have different aspects and intensities, are called mosaic. The photos presented herewith should allow you to review some symptoms that are frequently associated with mosaic and often considered as such (figures. 1-4). When you are faced with these symptoms, you may rightly suspect the involvement of a virus. Yet you should be particularly cautious with regard to a precise diagnosis of the virus(es) concerned. In fact, many viruses cause a wide range of quite similar symptoms in the plants, which is confusing.
 
To help you in your diagnosis, the section of Abnormal leaf colour describes the main symptoms that you can observe in a tobacco field. We have also indicated to which viruses these symptoms are frequently associated, in this case in French epidemiological conditions.
 
Moreover, we recommend you to consult the comments on different viruses presented in the section of the Abnormal leaf shape, because the viruses also cause deformations in addition to abnormal leaf colour.