First Report of Elsinoë Fawcettii in Citrus in the Azores Islands, Portugal

In July 2021, during an official survey on São Miguel Island (Azores, Portugal), citrus plants (Citrus deliciosa, C. limon and C. reticulata) showing scab symptoms were sampled. Citrus fruit and leaves were collected in three small orchards (1260–5500 m2) in the counties of Lagoa, Ponta Delgada and São Vicente Ferreira. Affected leaves were wrinkled and deformed, with creamy-yellowish pustules on both surfaces, often coalescing along the leaf blade (Figure 1). Fruits displayed raised, warty and deeply fissured crusts, forming patches or extensive roughened areas, with no symptoms in the pulp (Figure 2). Fungal isolation followed Barreto's method (Fan et al. 2017). Scab lesions were surface disinfected with 96% ethanol and air-dried. The epidermis was tangentially peeled and fragments of inner infected tissue were plated on 50% potato dextrose agar with 100 ppm streptomycin. Cultures incubated at 25 ±1°C under a 12 h photoperiod yielded slow-growing colonies with dense pseudostromatic structures, initially reddish and shiny, later becoming felt-like (Figure 3). Isolates were deposited in the Instituto Nacional de Investigação Agrária e Veterinária fungal collection under accession numbers MEAN1339–1344. Species identification was performed by DNA barcoding, using both fungal isolates and diseased tissues. DNA was extracted using the NucleoSpin Plant II Mini Kit (Macherey- Nagel, Germany). Amplification targeted the nuclear large subunit ribosomal DNA (LSU) with primers LR0R/LR5 and the second largest subunit of RNA polymerase II (RPB2) with primers RPB2-5F2/fRPB2-7cR (Fan et al. 2017). LSU sequences confirmed the genus Elsinoë (GenBank Accession Nos. PX591464, PX591465 and PX591886), while RPB2 sequences identified E. fawcettii with 100% identity (PX619318, PX619319 and PX645129). Duplex real-time PCR targeting E. fawcettii and E. australis (Ahmed et al. 2019) using the Maxima Probe qPCR master mix (ThermoFisher Scientific, USA) supported the results. A serial dilution of recombinant plasmid solution (2×106 copies/µL) was used as a positive control and to determine the analytical sensitivity, with the limit of detection being 190 copies. Elsinoë fawcettii, the causal agent of citrus scab (formerly sour orange scab), is a quarantine pest in the European Union (EU); listed in the European and Mediterranean Plant Protection Organization (EPPO) A1 list and Annex IIA of EU Regulation 2019/2072. It is a major pathogen in various citrus cultivars, particularly damaging young growth and nursery plants. Severely infected fruits became scarred and distorted and consequently unmarketable (Chung 2011). The fungus is primarily distributed in humid tropical regions, with limited occurrence in north temperate zones. Georgia has been the only European country with confirmed records (EPPO 2025). This is the first report of E. fawcettii in the Azores and in Portugal, where the official status is ‘present, under eradication, only in some parts of the Member State concerned’. Phytosanitary measures include destruction of infected material, chemical control and movement restrictions on citrus plants. In 2022–2023, further outbreaks were detected in São Miguel, Faial and São Maria islands, affecting C. aurantiifolia, C. aurantium, C. deliciosa, C. limon, C. reticulata, C. sinensis, C. × clementina and C. × limonia. Thanks to Leonor Viveiros, Fábio Carvalho, Hilário Arruda, and Vitor Vicente (DSADA), and Isabel Rodrigues (INIAV). JH and ED were partiality supported by UID/04046/2025 (BioISI), and EA and HB by UIDP/04551/2020, and UIDB/04046/2020 (GREEN‑IT).