The European Commission requested the EFSA Panel on Plant Health to perform a pest categorisation of Phoma tracheiphila, the fungal pathogen responsible for “mal secco” disease of citrus. This pathogen is listed in Annex IIAII of Directive 2000/29/EC. Recently, the pathogen has been reclassified as Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley, based on molecular phylogenetic analysis. Plenodomus tracheiphilus is a single taxonomic entity, and sensitive and specific methods are available for its differentiation from other related Plenodomus species. The main host is lemon (Citrus limon L.), but the pathogen has also been reported on other species of the genera Citrus, Fortunella, Poncirus and Severinia and on their hybrids. Host plants are widely grown in the southern EU Member States (MSs) and climatic conditions are conducive to disease development in both orchards and nurseries. The pathogen is present in part of the risk assessment area, being mainly reported on lemon grown in Italy, Greece, Cyprus and France, where it has a serious impact on the citrus industry. There are no obvious ecological/climatic factors limiting the potential establishment and spread of the pathogen in the, so far, non-infested citrus-producing EU MSs (i.e. Spain, Portugal, Malta and Croatia). Short-distance spread of the pathogen occurs via water splash and wind-driven rain, whereas movement of infected host plants for planting, particularly asymptomatic plants, is considered to be responsible for the introduction of the pathogen into new areas. Cultural practices and copper-based fungicide sprays may reduce inoculum sources and prevent new infections but they cannot eliminate the pathogen. P. tracheiphilus fulfils all of the pest categorisation criteria for having the potential to be a quarantine pest and a regulated non-quarantine pest, as those are defined in the International Standards for Phytosanitary Measures No 11 and 21, respectively.