Of more limited distribution in the world, Didymella lycopersici is the fungus known to be responsible for stem cankers ( Didymella stem rot ) in glasshouses, located on the neck and and pruning wounds. In fact, it can attack all the organs of the plant, especially in the open field and after heavy rains or irrigation. It is also rampant under cover, in greenhouses where it is very difficult to eliminate it. It can manifest itself in France on all types of culture.
 

D. lycopersici causes moist cankers on stems, dark brown, which often start from leaf stripping and disbudding wounds (Figures 1 and 2). These lesions gradually spread and eventually encircle the stem and / or the petioles, thus disrupting the sap currents. Ultimately, it is not surprising to see yellowing, wilting and drying out of leaflets and plant parts downstream of the lesions . On the latter, tiny more or less brown globular structures (pycnidia) dot the altered tissues (Figures 3 to 5). Note that they are more easily distinguished with a magnifying glass than with the naked eye. These fungal structures produce hyaline bicellular conidia, quite characteristic of the genus Didymella (figure 6).
 

It should be noted that lesions are also visible on the Crown and on the Leaflets and Fruits , although less frequent on these last two organs. In addition, they are frequently darker than those caused by Botrytis cinerea and Sclerotinia sclerotiorum .

For more information on this fungus, we invite you to consult the sheet Didymella lycopersici .