Crops
Main symptoms
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. Note that Alternaria alternata can secondarily colonize the end of the fruit (figure 4), like other species Alternaria , and in particular the lesions caused by the physiological disease called apical necrosis of 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.
In some cases, small black globular structures form in the damaged tissue in place of the previous molds (Figure 5). 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.
In some cases, small black globular structures form in the damaged tissue in place of the previous molds (Figure 5). 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.
More pictures of symptoms!
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5