Recent studies and reviews involving bacteria associated with acute oak decline
Acute oak decline has been associated with abiotic factors, as well as with the presence of Agrilus biguttatus (Coleoptera: Buprestidae) and a complex of bacterial species, mainly Brenneria goodwinii, Gibbsiella quercinecans and Rahnella victoriana (see EPPO RS 2018/104, RS 2018/126 and RS 2022/134). In the EPPO region, one or more of these bacteria have previously been reported from oak in Latvia, Poland, Portugal, Spain, Switzerland, and the United Kingdom (see RS 2022/134). In addition, a fourth bacterium, Lonsdalea britannica, was also found associated with acute oak decline in the United Kingdom. Recent studies report the bacteria in other countries as follows:
- In France, B. goodwinii, G. quercinecans and R. victoriana were detected in several forests on pedunculate oak (Quercus robur) and sessile oak (Q. petraea) (RS 2024/175).
- In Slovakia, B. goodwinii and G. quercinecans were detected for the first time on Q. robur in the eastern part of the country (RS 2025/014).
- In Serbia, B. goodwinii and G. quercinecans were found on Q. robur in two localities (RS 2025/086).
- In Croatia, B. goodwinii, G. quercinecans and L. britannica were detected in 2021 on holm oak Q. ilex on the Pelegrin peninsula (Hvar Island) where decline symptoms had been observed (Pernek, 2022).
- In Italy, a study on the possible biotic causes of the decline of Q. ilex in the Salento peninsula (Puglia region, south-eastern Italy) detected B. goodwinii, G. quercinecans and R. victoriana in all 7 sampling sites in rural areas (small woods), in respectively, 82 %, 64 % and 62 % of samples collected from symptomatic Q. ilex trees in 2022-2023. The three bacteria were not detected in symptomatic urban trees (roadside and parks) (Carluccio et al., 2024). In further studies, B. goodwinii and G. quercinecans were detected in samples from symptomatic kermes oaks (Q. coccifera) from Bosco dei Romani, Salento peninsula, while R. victoriana was not found (Carluccio et al., 2025).
In addition, two recent reviews, Gosling et al. (2024) and Bene et al. (2025) provide details on acute oak decline.
It is worth noting that B. goodwinii, G. quercinecans and R. victoriana have been found associated with several oak species. In addition, a few recent studies reported them on other trees : G. quercinecans on Tilia cordata in Poland (Tkaczyk et al., 2024), B. goodwinii (and other Brenneria spp.) and R. victoriana on Carpinus betulus in Iran (Moradi-Amirabad et al., 2019), G. quercinecans (and several Brenneria spp.) on Juglans regia in Iran (Allahverdipour et al., 2020; Firouzianbandpey & Khodaygan, 2024) and G. quercinecans on Elaeagnus angustifolia in Iran (Basavand et al., 2021).
Data on the distribution and hosts of Gibbsiella quercinecans have been added to EPPO Global Database at: https://gd.eppo.int/taxon/GIBSQU.
Sources
Allahverdipour T, Shahryari F, Falahi Charkhabi N (2020) First report of walnut bacterial canker caused by Gibbsiella quercinecans and Brenneria roseae subsp. roseae in Iran. New Disease Reports 41(1), 12.
Basavand E, Khodaygan P, Doonan JM, Rahimian H (2021) Gibbsiella quercinecans as new pathogen involved in bacterial canker of Russian olive. 3 Biotech 11(6), 286.
Bene A, Vergine M, Carluccio G, Portaccio L, Delle Donne AG, De Bellis L, Luvisi A (2025) Acute oak decline-associated bacteria: an emerging worldwide threat to forests. Microorganisms 13, 1127. 16 pp. https://doi.org/10.3390/microorganisms13051127
Carluccio G, Sabella E, Greco D, Vergine M, Delle Donne AG, Nutricati E, Aprile A, De Bellis L, Luvisi A (2024) Acute and Chronic Oak Decline in urban and forest ecosystems in Southern Italy. Forestry: An International Journal of Forest Research 97, 739-749.
Carluccio G, Vergine M, De Pascali M, Bene A, Portaccio L, Delle Donne A, De Bellis L, Luvisi A (2025) Brenneria goodwinii and Gibbsiella quercinecans as a Threat to Quercus coccifera L. Forests 16, 789.
Firouzianbandpey S, Khodaygan P (2024) Gibbsiella quercinecans, a pathogen with an increasing prevalence: A study on the causative agents of bacterial canker of Persian walnut and oak trees in central provinces of Iran. Plant Pathology 73(1), 198-212.
Gosling RH, Jackson RW, Elliot M, Nichols CP (2024) Oak declines: Reviewing the evidence for causes, management implications and research gaps. Ecological Solutions and Evidence 5(4), e12395.
Moradi-Amirabad Y, Rahimian H, Babaeizad V, Denman S (2019) Brenneria spp. and Rahnella victoriana associated with acute oak decline symptoms on oak and hornbeam in Iran. Forest Pathology 49(4), e12535. 14 pp. https://doi.org/10.1111/efp.12535.
Pernek M, Kovač M, Jukić A, Dubravac T, Lacković N, Brady C (2022) Akutno odumiranje hrastova (AOH) - nova kompleksna bolest na hrastu crniki (Quercus ilex L.) i mogućnost širenja na ostale vrste hrastova U Hrvatskoj. Šumarski list 9-10, 439-446. doi: 10.31298/sl.146.9-10.5
Tkaczyk M, Sikora K, Plewa R (2024) Dieback of small-leaved lime trees (Tilia cordata Mill.) caused by Gibsiella quercinecans in urban areas in Poland. Forest Pathology 54(3), e12861.