First report of Austropuccinia psidii in the EPPO region
Austropuccinia psidii (EPPO Alert List) is reported for the first time in Switzerland. The fungus was first observed to cause bright yellow pustules on a bonsai of Syzygium buxifolium, in a garden centre in May 2024. Many Syzygium species have already been reported as hosts, but this is a first report for S. buxifolium. Further surveys at four other garden centres, from the same European chain, in Switzerland found S. buxifolium infected by A. psidii. At each site the presence was confirmed by molecular tests. The strains were further identified as belonging to the pandemic biotype. Inoculation tests fulfilling Koch’s postulates confirmed that A. psidii is pathogenic to S. buxifolium and common myrtle (Myrtus communis).
The infected bonsai plants were traced back to a nursery in the Netherlands that had imported plants from China (EPPO RS 2024/212).
All infected plants were destroyed. However the pest status of A. psidii in Switzerland is unclear, as it is not known if infected plants had been distributed within Switzerland before the report and whether the fungus could establish in the country considering its climatic requirements.
This report highlights the risk of introducing A. psidii into the EPPO region via the trade of host plants from areas where the disease occurs. The authors underlined that, as the retailer had a Europe wide distribution network, infected plants may have been distributed in other countries where the climate is more favourable and host plants more widely present than in Switzerland.
Sources
Ruffner B, Beenken L, Kupper Q, Mittelstrass J, Schuler P, Stewart JE, Caballero JI, Winiger R, Prospero S (2024) First report of Austropuccinia psidii on Syzygium buxifolium grown as indoor bonsai in Europe. New Disease Reports 50 (2), e70011. https://doi.org/10.1002/ndr2.70011