Lesions of limited size and poorly defined, concave and moist outline appear on the fruits initially. They are often located near the stem or in the stem area of the named fruit "shoulder" ( shoulder ) by the Anglo-Saxons (Figures 1 to 3). Subsequently, they gradually spread, and the subcuticular tissues located in their center soon turn brown and then blacken. Let us note that this fungus can colonize secondarily, like other species of Alternaria , the lesions caused by the physiological disease called apical necrosis of the tomato.
 

Ultimately, if the ambient humidity is high, the surface of the alterations becomes covered with a dense velvety texture, dark green to black, in particular at the level of small cracks that alter the epidermis. This mold is formed by the mycelium, conidiophores and the numerous conidia of Alternaria alternata . The spores of this fungus have relatively characteristic shapes; Figures 4 and 5 should allow you to easily identify them.

In some cases, small black globular structures form in the damaged tissue in place of previous molds (Figure 6). These symptoms are then caused by a Pleospora ( Pleospora herbarum ; syn .: Pleospora lycopersici ), teleomorph of a Stemphylium . These globular structures will in fact be perithecia containing several asci and ascospores.

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* Fungi, Ascomycota, Pezizomycotina, Dothideomycetes, Pleosporomycetidae, Pleosporales, Pleosporaceae