Geographic distribution, prevalence, and incidence of citrus black spot caused by Phyllosticta citricarpa in Tunisia

Citrus black spot (CBS), caused by Phyllosticta citricarpa, is an important disease of citrus, an economically important fruit crop worldwide and particularly in Tunisia. CBS was recently detected in Tunisia and this study revealed that it is widespread in the governorates of Nabeul and Sousse. The highest incidence of CBS was found in the Bouargoub region (73.7%), while the lowest was observed in Soliman (25.0%) in the Nabeul governorate. The surveys revealed that CBS affected mainly lemon (Citrus limon). The symptoms of CBS observed were hard spots on fruits, twigs, and leaves, as well as false melanose on fruits. Symptoms were observed in both mature and immature citrus fruits, but disease incidence was higher in mature (97.0%) than that in immature fruits (2.95%). In this study, morphological and molecular identifications confirmed the presence of P. citricarpa. This is the first time that the extent of CBS has been documented in a Mediterranean citrus area.