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

- Alternaria tomatophila

- Botryosporium sp.

- Botrytis cinerea (figure 1)

- Didymella lycopersici
- Sclerotinia sclerotiorum

- Thanatephorus cucumeris

- Clavibacter michiganensis subsp. michiganensis (figure 2)

 

 

The fungi Botrytis cinerea , Sclerotinia sclerotiorum and Didymella lycopersici are responsible for more or less canker damage on tomato stems and exhibit roughly the same behavior on this plant. They sometimes cohabit on the same lesions. These are opportunistic parasitic microorganisms that often take advantage of special conditions to settle on plants and occasionally cause serious lesions:

- a prolonged period of rainy and humid weather, excessive irrigations;

- stagnant free water on the leaves, especially at the edge of the blade;

- Plants with numerous wounds linked, for example, to pruning and stripping wounds;

- the presence of senescent tissues, in particular the old low leaves in contact with the ground;

- very growing plants, with succulent tissues.
 

These opportunistic fungi readily colonize wounds and senescent tissues which constitute entry points or nutrient bases facilitating their penetration and development in plants. With significant enzymatic equipment, they degrade the invaded tissues fairly quickly. In general, they gradually encircle the stem and eventually reach the vessels. Wilting and drying out can then be observed.
 

These fungi are for the most part easily identifiable, in particular Botrytis cinerea and Scleroti nia sclerotiorum , thanks to the rather characteristic conservation organs or fruiting bodies that they produce quite quickly. To promote their appearance, we recommend that you place a few samples in an airtight box or plastic bag containing paper towels soaked in water. It will ensure the humidity essential for the formation of these structures.
 

Note that these pathogens produce other symptoms on the other aerial organs of the tomato, in particular on the leaves and fruits. We therefore advise you to consult the section Brown, beige spots more or less extensive .