On 26 December 2017, the French Directorate General for Food (DGAL) made a formal request to ANSES for an expert appraisal on host species in the context of control of Phytophthora ramorum.

BACKGROUND AND PURPOSE OF THE REQUEST

 Since the early 2000s in Europe, the pathogen Phytophthora ramorum (a "pseudo-fungus" belonging to the class Oomycetes, within the Stramenopile lineage) has been known to cause leaf necrosis on ornamental plants, mainly rhododendron and viburnum, in nurseries and semi-natural areas (Werres et al., 2001, Appiah et al., 2004, Xu et al., 2009). At about the same time, it was described as the agent of sudden oak death in California (Garbelotto et al., 2001, Rizzo et al., 2002), where some highly susceptible oak species have developed trunk cankers and died. The situation in Europe changed abruptly in 2009, when an outbreak of P. ramorum was described on Japanese larch plantations in Great Britain, associated with needle loss, branch dieback, resin cankers and lastly, massive tree mortality (Brasier and Webber, 2010). This formal request follows the detection of P. ramorum for the first time in France, on Japanese larch (Larix kaempferi) in Finistère in May 2017 (Schenck et al., 2018), which was officially notified. P. ramorum is classified as a Category 1 health hazard for plant species under French regulations (Ministerial Order of 15 December 2014), and is therefore subject to mandatory control measures.