Wilted and dry leaves

Various parasitic or non-parastic diseases cause wilting and drying of tobacco leaves, preceded or accompanied by yellowing. Among the parasitic causes there are different soilborne pests responsible for root and collar abnormalities and lesions and internal stem lesions. For more information, you should see the corresponding fact sheets on: Root and collar abnormalities, and Internal alterations of stem.
 
- In addition to pathogenic micro-organisms various viruses such as potato virus Y, (PVY), cucumber mosaic virus (CMV), or tomato spotted wilt virus(TSWV) can also cause wilting.
 
Note that also bugs can cause that kind of symptoms.
 
- The non-parasitic causes can also be considered, such as various chemical injuries, nutritional disorders, waterlogging (drowning). Drought spots, sunburn (sunscald) and lightning injuries are associated with dry and wilted tobacco leaves.

•  Analyse and understand wilting: 

In many cases, when plants have one or more wilted and/or dry leaves, tobacco farmers and technicians faced with these symptoms tend to focus only on the leaves. Every now and then, as shown in the following examples, they are right, but usually the cause for wilting must be sought elsewhere. It is most commonly found on the roots, the collar or outside or inside of the stem (figures 1 to 4).

Figure 1	Figure 2	Figure 3	Figure 4

Indeed, various changes occurring in these organs disrupt absorption functions (roots) and transport (collar, stem) of water and nutrients. This leads to lack of water in plants that will more or less rapidly wilt (temporarily or irreversibly) and partially or completely dry up.
 
The apparition of wilting and speed of development depend mainly on three parameters:
- plant development stage;
- type and severity of the lesion and its origin. At an early stage, when the damage is not too important, wilting may be reversible, because at night the leaves evaporate less and become turgescent;
- weather conditions; high temperatures, windy periods, increase evapotranspiration of the plants and thus promote its early apparition. Conversely, under conditions of low evapotranspiration during a cold, wet spring, for example, plants will not wilt, in spite of previously reported problems (collar canker, root rot ...) ; but when they do, it will often be too late to intervene.

In some cases, wilting may have a particular location on leaves and plants. It is characteristic of one or more diseases; which you will see later, especially when having a close look at Vascular diseases.
 
The foliage is a good indicator of plant water status. Wilting or drying of one or more leaves, should be considered as sign of disturbance. The causes should be sought carefully by examining all the organs possibly involved.
 
This fact sheets describes the main causes of wilting, drying or comparable symptoms on tobacco, which do not normally induce symptoms on other organs of this plant.