Robigalia Roundup LXXII

Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley is a mitosporic ascomycete (Coelomycetes), formerly known as Phoma tracheiphila. It is a tracheomycotic, necrotrophic pathogen that colonises xylem tissues and produces water‑dispersed conidia in pycnidia on infected citrus tissues.

The primary host is lemon, for which mal secco is considered the most serious fungal disease, causing major yield and tree losses. Other susceptible hosts include citron, bergamot, lime, sour orange, rough lemon, Volkamer lemon and alemow, while sweet orange and grapefruit are generally less affected.

Infections typically initiate through wounds, with the pathogen invading the vascular system and ascending in the xylem. Early foliar symptoms include vein‑limited chlorosis, sectorial yellowing, and leaf rolling and wilt, followed by twig and branch dieback and, in severe cases, whole‑canopy collapse. Internally, discoloured, reddish to brown streaking of xylem and necrosis of woody tissues reflect its necrotrophic, tracheomycotic habit, often leading to chronic decline or rapid “mal fulminante” collapse.

Plenodomus tracheiphilus is established throughout many citrus‑growing regions of the Mediterranean basin and the eastern Black Sea coast, with records from countries such as Italy, Greece, Turkey and Georgia. The pathogen is also present in parts of the Middle East and has recently been reported outside this core range, including detections in Canada, highlighting ongoing biosecurity relevance.

Management relies on integrated approaches: use of tolerant or resistant lemon cultivars and rootstocks, removal of infected trees, and pruning of symptomatic shoots and branches to reduce inoculum. Protective fungicide applications (often copper‑based, including novel super‑absorbent polymer–copper formulations), biological control agents such as Bacillus amyloliquefaciens, and strict nursery and quarantine measures are used to limit infection and spread under favourable conditions.

Keep reading for more on mal secco disease 👇

This week, we meet Francis Mirara, a Master’s graduate from CIHEAM (Centre International de Hautes Études Agronomiques Méditerranéennes) in Bari, Italy, and the University of Ghana.

Growing up in Kenyan farming communities, Francis witnessed fungal, bacterial, and viral pathogens devastate smallholder harvests, motivating him to pursue agricultural sciences with a focus on eco‑friendly disease management.

During his Master’s in Innovative Approaches and Technologies in Plant Pathology at CIHEAM Bari, he specialised in integrated pest management (IPM) for Mediterranean fruits and vegetables, developing skills in molecular pathogen detection, diagnostics, pathogen characterisation, and international biosecurity regulations related to quarantine threats.

He later completed an internship at Università degli Studi di Bari, assessing the resistance of various citrus genotypes to mal secco and Alternaria brown spot diseases in Italy’s Apulia region.

Francis is now working as a director at Mirara Crop Science where he promotes sustainable production through integrated field and laboratory trials of biological control agents for horticultural crops. By designing and evaluating biocontrol strategies, he aims to reduce reliance on synthetic fungicides and enhance crop health, yield stability, and ecological balance through microbiology, precision technology, and climate‑smart innovations tailored to real‑world farming conditions.

He is especially proud of his time at the University of Ghana’s West Africa Centre for Crop Improvement, where he pursued Seed Science and Technology with a specialisation in seed pathology. There, he pioneered the first research in Sub‑Saharan Africa on Bacillus amyloliquefaciens‑based, biologically encapsulated seed‑coating agents, showing that nano‑enhanced microbial delivery can match chemical fungicide efficacy while offering safer, eco‑friendly alternatives.

Francis is open to connecting on LinkedIn, and you can also find him on Instagram.

Have a job, scholarship, or event to advertise? List it in Robigalia. I’ll help promote your opportunity or event to a global network of over 10,000 plant pathologists for free.

See you next Monday!

P.S. Why Robigalia? The name originates from the Ancient Roman festival dedicated to crop protection. You can read all about the history here: