Abnormal leaf shape or size 

In tobacco, different parasitic or non-parasitic causes may provoke leaf distortion, or decrease of leaf size. These leaves may be curled up, twisted or curved, sometimes slender at the tip, or serrated on the edges. The same causes can also provoke a reduction in leaf width and bring about an elongated form.

Among the pests and non- parasitic diseases one may include:
- Peronospora hyoscyami f.sp. tabacina (systemic blue mould, figure 1);
- different viruses, such as tomato spotted wilt virus (TSWV), cucumber mosaic virus (CMV) (figures 2, 3 and 4), alfalfa mosaic virus (AMV) (figure 5), potato virus Y (PVY), tobacco mosaic virus (TMV), tobacco ring spot virus(TRSV), and other viruses (TLCV, BCTV, TRV, TStV ...) for which you can find more information on the fact sheets of Other parasitic tobacco viruses;
- Stolbur;
- Ditylenchus dipsaci, nematode which causes asymmetric leaf growth;
- bugs;
- polyphylla or ("Frenching");
- genetic abnormalities, nutritional disorders (boron deficiency ...) or various chemical injuries

Figure 1	Figure 2	Figure 3	Figure 4	Figure 5

•  Diagnostic tips :

It is rather difficult to distinguish the different symptoms considered as abnormal leaf shapes. In fact, a leaf can be both embossed and curled up, which gives it a particular shape. In addition, several  different diseases can sometimes induce similar leaf deformations. It is very difficult to identify their origin(s) only based  on these deformations. We have tried to assemble in the following subjects some of the major foliar causes inducing malformations.

You will need to refer regularly to other sections and fact sheets of pests to confirm your diagnosis.