Stunted plant growth

   

The pests, or parasitic diseases have various effects on plants, in particular on their growth. The disorder can occur at any time of plant ?development. It can occur at an early stage, which is the case for example of a viral infection. Growth of plants infected by a virus is sometimes immediately and completely stopped, and thus plants remain stunted (figure 1). This is the case in particular with TLCV (tobacco leaf curl virus), TStV (tobacco stunt virus) and TYDV (tobacco yellow dwarf virus). 
 
Similar situations also occur in fields heavily contaminated by a soilborne fungus or nematodes. The seedlings which  face the inoculum in the soil soon after transplanting suffer from root damage that disrupt their development. See the topics related to Root and Collar abnormalities and lesions.

Sometimes, the plants seem to be perfectly normal, then suddenly the apical bud stops growing. This is the case particularly with a boron deficiency (figure 2).
 
Slow growth or cessation of vegetation may occur later when the plants have reached a certain size (figures 3 and 4). In this case, we can observe:
 - a slowdown in apex development, newly formed leaves are smaller in size and have shorter internodes in the affected stem parts than healthy stems;
- An almost complete cessation of growth, the leaves are smaller, grey/bronze green and tend to curl.

Figure 1	Figure 2	Figure 3	Figure 4	Figure 5	Figure 6

 
As you understand from these few examples, the diseases described in this section on abnormal leaf shape change both the shape of tobacco leaves, and the general growth of plants, and thus often give the tobacco plants or their apex (temporarily or permanently) particular appearances which contrast with the surrounding healthy plants (figures 5 and 6). These appearances are sometimes very specific to one or similar to several diseases. It is therefore necessary to be very careful. They reflect the malfunctions of the plants and their cause(s) must be sought in different sub-headings and the following fact sheets.

If you cannot identify the pest problem that affects your crop by consulting the above mentioned symptoms, remember that several parasitic and non-parasitic diseases covered in other sections of this web site can sometimes cause growth cessation and stunting of plants. They also induce more characteristic symptoms, which should be investigated and analysed.
 

• A very uncommon condition, referred to as tobacco stunting, has been reported only in Kentucky, USA, on Burley tobacco. This essentially results in a significantly slower plant growth, which causes stunted plants. No symptoms are observed in the roots. In affected plots the yields are low and the quality poor. The development of two mycorrhizal fungi in the tobacco roots, Glomus macrocarpus Tul. & Tul. and Glomus microcarpus (Tul. & Tul.) Gerd. & Tul., disrupts the root growth and consequently that of the plants. This condition may exist in other production areas and other types of tobacco, but it is not easy to identify.