Citrus products are economically important in Tunisia and constitute a significant part of agricultural exports. In March and April 2019, symptoms resembling citrus black spot were observed on citrus fruit in Nabeul Gouvernorat.
From June to September 2019, phytopathologists at Université de Sousse carried out an intensive survey in 339 orchards located in this region. Symptoms were observed in 69 orchards of lemon and orange trees located in the areas of Bou Argoub, Beni Khalled, Menzel Bouzelfa, Soliman, Grombalia, Takelsa, Korba, Nabeul and Hammem Ghezaz. Diseased fruits showed freckle spots or hard spots bearing pycnidia, whereas no symptom was observed on leaves.
Morphological and DNA analysis followed by pathogenicity test have confirmed that the causal agent was Phyllosticta citricarpa.
"To our knowledge, this is the first report of Phyllosticta citricarpa causing citrus black spot on citrus in Tunisia - the scientists say - The disease may have a severe impact on citrus production in Tunisia by reducing yield and affecting the quality of Citrus limon and C. sinensis. Surveys are ongoing and management strategies have been developed to control and limit the spread of the disease in Tunisia."
Source: Boughalleb-M’Hamdi N., Fathallah A., Benfradj N., Ben Mahmoud S., Bel Hadj Ali A., Medhioub L., Jaouadi I., Huber J., Jeandel C., Ioos R., 'First report of citrus black spot disease caused by Phyllosticta citricarpa on Citrus limon and C. sinensis in Tunisia', 2020, New Disease Reports, Vol. 41, 8.