First confirmed report of ‘Candidatus Phytoplasma ulmi’ in the Czech Republic
The NPPO of the Czech Republic recently confirmed to the EPPO Secretariat the occurrence of ‘Candidatus Phytoplasma ulmi’ (EPPO A1 List, initially listed as ‘Elm phloem necrosis’*) on its territory. This finding resulted from a pest specific survey carried out by the Czech NPPO. In June 2015, the pathogen was identified (PCR, sequencing) in a sample (a branch) taken from one tree of Ulmus minor showing suspicious symptoms. On two branches of this tree, leaves had not sprouted and the bark was necrotic. This infected tree was part of a group of 3 elm trees (U. minor) growing in a forest in the Hradec Králové region. In Europe, it has been shown that this phytoplasma disease can be transmitted by Macropsis glandacea (=M. mendax – Hemiptera: Cicadellidae) and Philaenus spumarius (Hemiptera: Aphrophoridae), the latter being very common in the Czech Republic. In 2015, both the host plants and P. spumarius will be surveyed for the presence of ‘Ca. P. ulmi’ to better define the infested area.
The NPPO considers that this is the first confirmed report of ‘Ca. P. ulmi’ in the Czech Republic. Earlier records published in the 1960s (Bojňanský, 1969) or earlier (Klášterský, 1951) were only based on the observation of symptoms (elm yellows) on elm trees. More recently, Navrátil et al. (2009) isolated a phytoplasma belonging to the Elm yellows group and closely related to ‘Ca. P. ulmi’ (EPPO RS 2009/217), but some differences in the oligonucleotide sequences meant that the authors could not assign the Czech isolate to ‘Ca. P. ulmi’.
The pest status of ‘Candidatus Phytoplasma ulmi’ in the Czech Republic is officially declared as: Present, found only in one area; previous records are considered uncertain.
* Note: Although phytoplasma diseases observed in elms in North America (elm phloem necrosis) and in several European countries (elm yellows) have different symptomatology, the phytoplasmas associated with them are very closely related if not belonging to the same species ‘Candidatus Phytoplasma ulmi’. The inclusion of this pathogen on the A1 List (absent from the EPPO region) might need to be reconsidered. However, EFSA performed a pest categorisation study of ‘Ca. P. ulmi’ in 2014 and concluded that the currently available data on its distribution, insect vectors, elm species susceptibility and impacts was not sufficient to reach a conclusion.
NPPO of the Czech Republic (2015-08).
Bojňanský V (1969) Elm witches’-broom, a new disease in Czechoslovakia. In C. Blattný (ed.) Proceedings of the 6th Conference of the Czechoslovak Plant Virologists, Olomouc 1967. Academia, Praha, pp. 211-213.
EFSA (2014) Scientific Opinion on the pest categorisation of Elm phloem necrosis mycoplasma. EFSA Journal 12(7), 34 pp.
Klášterský I (1951) A cowl-forming virosis in roses, lime-trees and elm-trees. Studia Botanica Čechoslovaca 12, 73–171.
Navrátil M, Šafářová D, Válová P, Fránová J, Šimková M (2009) Phytoplasma associated with witches’-broom disease of Ulmus minor Mill. in the Czech Republic: electron microscopy and molecular characterization. Folia Microbiologica 54(1), 37–42.