Phytophthora mediterranea: an emerging pest of woody trees
Phytophthora mediterranea is a newly described species of Phytophthora previously associated with collar and root rot of myrtle (Myrtus communis) in Italy (EPPO RS 2021/119). Since 2021, new records of P. mediterranea have been made from North America and Europe as well as in nurseries in Australia suggesting it is polyphagous on a broad range of woody host trees and may be moved in trade:
- In a study conducted between 2015 to 2018, P. mediterranea was identified as the causative agent of chlorotic leaves, defoliation, crown rot and dieback of pistachio trees (Pistacia vera) in pistachio orchards across five counties in southern California, USA.
- In a study conducted from October 2016 to October 2021, P. mediterranea was identified as a causative agent of root rot, cankers and canopy dieback of plane trees (Platanus orientalis) in a public park in Athens, Greece.
- During sampling of crown and trunk cankers of almond (Prunus dulcis) between 2015 and 2024, P. mediterranea was identified as the causative agent of cankers on almond trees from six counties across California, USA. O’Fallon et al. (2025) reported that P. mediterranea was routinely found in summer months when Phytophthora diseases of almond are uncommon.
- During a study on soil samples of trees from nursery stock from five nurseries in the state of New South Wales and one nursery from the state of Victoria, Australia conducted between 2021 and 2023, P. mediterranea was identified in four of the nurseries on 10 woody tree species native to Australia including Melaleuca styphelioides, Lophostemon confertus and Elaeocarpus reticulatus.
- In February 2025, P. mediterranea was identified as the causative agent of branch cankers, collar bark necrosis, root rot and death of cork oak (Quercus suber) in a forest in South Sardinia, Italy.
Phylogenetic analysis indicates P. mediterranea is closely related to P. cinnamomi (EU RNQP). Several reports suggest P. mediterranea may therefore have been present before 2021 but previously misidentified as P. cinnamomi (Bregant et al., 2025; Laurence et al., 2024; O’Fallon et al., 2025).
Sources
Antonelli C, Soulioti N, Linaldeddu BT, Tsopelas P, Biscontri M, Tsoukas C, Paplomatas E, Kuzminsky E, Vettraino AM (2024) Phytophthora nicotianae and Ph. mediterranea: a biosecurity threat to Platanus orientalis and P. x acerifolia in urban green areas in Greece. Urban Forestry & Urban Greening 95, 128281 https://doi.org/10.1016/j.ufug.2024.128281
Bregant C, Linaldeddu BT (2025) First report of Phytophthora mediterranea causing root rot, bleeding cankers and sudden death of cork oak (Quercus suber) in Italy. New Disease Reports 52(1), e70060 https://doi.org/10.1002/ndr2.70060
Laurence MH, Mertin AA, Scarlett K, Pang C, Tabassum S, Leishman MR, Burgess TI, Guest DI, Summerell BA (2024) Phytophthora in urban tree planting stock: are we managing the risk to the urban forest and natural ecosystems? Plant Pathology 73(8), 2030-2042 https://doi.org/10.1111/ppa.13960
O'Fallon C, Belisle WH, Browne GT, Forster H, Adaskaveg J (2025) Toxicity of registered and new fungicides to current species of Phytophthora infecting almond in California and their fungicidal properties. Plant Disease (early view).
Trouillas FP, Nouri MT, Bourret TB (2022) Identification and characterization of Phytophthora species associated with crown and root rot of pistachio trees in California. Plant Disease, 106, 197–206. https://doi.org/10.1094/PDIS-05-21-1064-RE