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UMR 1332 - Equipe Mollicutes; Stolbur is a phytoplasma disease affecting crops worldwide. The planthopper Hyalesthes obsoletus is the main natural vector of ‘Candidatus Phytoplasma solani’ responsible of stolbur. In France, lavender (Lavandula angustifolia) and lavandin (Lavandula × intermedia) are strongly affected by this phytoplasma. These plant species are both hosts for the phytoplasma and its insect vector. In 2011, catches of adults were exceptionally sizable on one of the clones of lavandin most tolerant to lavender decline. A high population level of ‘Ca. P. solani’ vector was also observed on the adjacent plot of clary sage, Salvia sclarea. In order to clarify the potential role of S. sclarea as a host plant for H. obsoletus and ‘Ca. P. solani,’ we conducted field surveys and laboratory experiments. The uprooting of clary sage and root examination showed the presence of nymphs during winter. Harvested nymphs have been reared on S. sclarea from seedlings in a greenhouse for many generations. By performing its whole lifecycle on clary sage, we demonstrated for the first time that S. sclarea is a host plant of H. obsoletus and could be a source of stolbur vector. Nevertheless, status of clary sage as host plant of phytoplasma in the field up to now is not so clear. On 42 Q-PCR runs done on S. sclarea, 41 were negative to the phytoplasma, and one positive. Experimental transmission with infected H. obsoletus sampled on infected lavender showed that clary sage plant could be infected, expressed symptoms and multiplied ‘Ca. P. solani.’

The Panel on Plant Health performed a pest categorisation of potato stolbur mycoplasma, recently renamed Candidatus Phytoplasma solani (CPs), for the European Union (EU) territory. CPs is a well‐defined species of the genus Candidatus Phytoplasma, for which molecular detection assays are available. It is a regulated harmful organism in the EU, and is listed as potato stolbur mycoplasma in Annex II, Part A, Section II of Council Directive 2000/29/EC. Although CPs can infect a wide range of host plants, this listing concerns only Solanaceae plants for planting. CPs is transmitted by grafting and vegetative propagation of infected hosts, and by several insect vector species including Hyalesthes obsoletus, Reptalus panzeri, Pentastiridius leporinus and possibly others. The geographical distributions and population densities of these vectors govern the spread of CPs. CPs can infect a wide range of host plants and has been reported in 14 EU Member States (MSs). CPs can cause yield losses in potato and other solanaceous crops, in grapevine, strawberry, maize and lavender. Because host plants, wild or cultivated, are widely distributed throughout the EU, the distribution of vector populations is the main determinant of CPs establishment and spread; therefore, CPs has the potential to establish and spread in unaffected parts of the EU with the extension of the distribution range of its vectors. There are high annual fluctuations in the impact of CPs, and this is mostly affected by the prevalence of plant reservoirs for CPs and by the size of local vector populations, which cannot easily be controlled. There are uncertainties regarding the precise distribution of CPs and its vectors, the evolution of vector distribution, the long‐term impact of emerging CPs genotypes and the extent of impact on the various susceptible crops grown in the EU.