New Plant Disease article August 2018

First Report of Phytophthora ramorum Causing Japanese Larch Dieback in France.

N. Schenck, C. Saurat, C. Guinet, C. Fourrier-Jeandel, L. Roche, A. Bouvet, C. Husson, F.-X. Saintonge, C. Contal, and R. Ioos

Plant Disease 0 0:0, PDIS-02-18-0288-PDN

Phytophthora ramorum Werres, De Cock & Man in’t Veld, an oomycete known in the United States as the causal agent of sudden oak death, has spread across Europe since the early 2000s. It is responsible for damage and death to a wide range of plant species, including mature trees. In 2009 it was identified on Japanese larch (Larix kaempferi) in southwest England (Webber et al. 2010), and since then it has caused severe damage and losses to Larix spp. in the United Kingdom and the Republic of Ireland. There are two lineages of the oomycete, EU1 and EU2, found in Europe (King et al. 2015), EU2 being the more aggressive. The symptoms on larch include necrosis and loss of needles, wilting of shoots, dieback of branches, and death, often with abundant resin bleeding on trunks and branches. As sporulating hosts, Larix spp. may disperse P. ramorum over long distances. In May 2017, wilting, yellowing/reddening needles, and branch mortality were observed on mature Larix kaempferi (about 50 years old) in the forest of Saint-Cadou, Finistère, in the far northwestern part of France (3°59′49.2″ W; 48°22′22.4″ N)....

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