Didymella lycopersici , a fungus capable of affecting in particular peppers and eggplants, can be rife on tomatoes, especially in open fields in amateur gardens and in a few intensive farms, particularly in Brittany. Note that it can also be present under shelter. If it is not frequent on this crop, it can occasionally be damaging if the agro-cultural and climatic conditions present are favorable to it. Once installed in a plot, it is difficult to eliminate.

The Stem is the organ of choice for this fungus. He is able to infect her through the numerous stripping wounds. It also affects its lower part, causing brownish to black moist lesions on the cortex that progressively encircles the foot of diseased plants (figure 1), which explains why this symptom is called "tomato black foot. »( Didymella foot rot ). In addition, its attacks at this location of the stem could be explained by penetration via the cotyledonary scars. Let us add that the underlying vascular tissues also take on a brownish tint (figure 2).

At this point, lower leaves may turn yellow, wither and necrost, and the plants may die. Globular structures, brownish to black, form in the injured tissues: these are often the pycnidia of the anamorph of this fungus (Figures 3 and 4). They should not be confused with the dark brown glandular trichomes present on the stems of the tomato.

Note that D. lycopersici causes other symptoms on the Leaves and Fruits of the tomato.

For additional information on this fungus, you can consult the sheet Didymella lycopersici fact .