The vessels and / or the pith of the tomato stem present various alterations linked in particular to pest attacks; Figures 1 to 6 show the nature of the symptoms that can be observed in such situations.

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

In the presence of such symptoms, you can make the following assumptions:

- Fusarium oxysporum f. sp. lycopersici (figure 3)

- Fusarium oxysporum f. sp. root-lycopersici

- Verticillium dahliae

- Clavibacter michiganensis subsp. michiganensis (figures 2 et 5)

- Pectobacterium carotovora subsp. carotovora

- Pseudomonas corrugata (figures 4 et 6)

- Lightning

Among the many diseases that attack the tomato, a number of them cause symptoms, particularly on the inside of the stem. Thus, very different alterations can be observed in this organ, on the marrow, the vessels and the tissues constituting the cortex. A panel of these symptoms is illustrated by (Figures 1 to 6), comparing with the interior of a healthy stem.
 

A certain number of the microorganisms responsible for these internal alterations of the stem have a predilection for the vessels (vascular microorganisms). This location is not without consequences for the plants: in order to act as a barrier, the latter secrete numerous gummy substances, partly at the origin of other equally characteristic symptoms, involving wilting, yellowing and drying out of the leaves, often sectoral or unilateral.
 

Note that the vessels, when colonized, turn yellow and brown more or less. Contiguous tissues like the cortex or the marrow can be affected. This is when symptoms may begin to appear on the outside of the stem:

- longitudinal yellowing on one side of the stem;

- browning or longitudinal necrotic damage on one side of the stem;

- browning of a large portion of the stem.
 

To identify these vascular diseases, it is necessary to observe the plants very carefully for the symptoms mentioned in the following pages. You will be able to note that these diseases cause, on tomato, quite comparable symptoms that we qualify as "generalists": wilting, yellowing, vascular browning
 

In order to avoid diagnostic confusion, it will be advisable to try to look for more specific symptoms and / or to have a plant analyzed by a specialized laboratory which will carry out vascular isolations on an artificial medium.
 

Note that certain diseases, parasitic or not, affecting the roots or the crown, can be at the origin of vascular browning located rather in the lower part of the stem and diffusing more or less high in the latter. If you are unable to identify one of the conditions detailed in this section, we advise you to refer to the chapters corresponding to these organs.