Phytophthora ramorum detected in Picea sitchensis in Ireland
In Ireland, Phytophthora ramorum (EPPO Alert List) has been detected in a single Picea sitchensis (Sitka spruce) growing in a forest. Although P. sitchensis has been shown to be susceptible to P. ramorum in laboratory trials, this is the first time that a natural infection has been detected on this tree species. Sitka spruce is a very important commercial forest species in Ireland. The infected P. sitchensis was a young tree of approximately 2 m high. It was growing underneath the canopy of a large bush of wild Rhododendron ponticum which was also found to be infected by P. ramorum. It is very likely that this infected rhododendron was the source of the infection. The symptoms observed on P. sitchensis were mainly characterized by shoot tip dieback that was largely confined to the leading shoot. This finding was made during a follow up survey carried out by the Forest Service, approximately 0.5 km from where P. ramorum had previously been detected on rhododendron, Japanese larch (Larix kaempferi) and noble fir (Abies procera). The area around the infected tree has been quarantined and monitoring will continue. P. sitchensis trees growing in the immediate vicinity of Japanese larch stands which had previously been found infected were also surveyed. No further P. ramorum infections have been found but monitoring of P. sitchensis trees will continue as part of the ongoing P. ramorum surveys.
Sources
NPPO of Ireland (2011-04).