First finding of ‘Candidatus Phytoplasma ulmi’ in Switzerland
In October 2021, in the framework of research activities focused on Grapevine flavescence dorée phytoplasma (EPPO A2 List), one specimen of Orientus ishidae (Hemiptera: Cicadellidae) was found to be infected by ‘Candidatus Phytoplasma. ulmi’ (EPPO A1 List*) in Canton Ticino (Southern Switzerland). O. ishidae is a leafhopper that was identified as an alternative vector of flavescence dorée phytoplasma (EPPO RS 2015/098). Only one specimen of O. ishidae tested positive among the 6 specimens trapped in the same location, and the 283 specimens caught in total in the surveyed area in 2021 and 2022. No phytoplasmas were detected in plant samples taken from the same location.
This is the first report of ‘Ca. P. ulmi’ in Switzerland, as well as in O. ishidae. The authors note that ‘Ca. P. ulmi’ may potentially be present in wild habitats of the Swiss Pre-alpine and Alpine range, but no dedicated surveys have been conducted so far.
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* Note: Although phytoplasma diseases observed in elms in North America (elm phloem necrosis) and in several European countries (elm yellows) have different symptomatologies, the phytoplasmas associated with them are either belonging to the same species ‘Ca. Phytoplasma ulmi’ or very closely related. Therefore, the inclusion of this pathogen on the A1 List (absent from the EPPO region) might need to be reconsidered.
Sources
Oggier A, Debonneville C, Conedera M, Schumpp O, Rizzoli A (2024) First detection of ‘Candidatus Phytoplasma ulmi’ in Switzerland and in Orientus ishidae Matsumura, 1902. Alpine Entomology 8, 29-34. https://zoobank.org/44820AB3-6D26-43D4-91D1-3F5B2143E69A