Further findings of Phytophthora lateralis and first record of Phytophthora austrocedrae in Scotland (GB)
In the United Kingdom, the presence of Phytophthora lateralis (EPPO A1 List) was recorded for the first time in Scotland (EPPO RS 2011/026) in October 2010, at the Balloch Castle Country Park. In March 2011, P. lateralis was reported from two other sites in Scotland. In addition, in one of these sites, the presence of Phytophthora austrocedrae was detected on one Chamaecyparis nootkatensis tree. P. austrocedrae is a newly described species which was isolated from necrotic lesions of stem and roots of dying trees of Austrocedrus chilensis (Cupressaceae) in Patagonia, Argentina (Greslebin et al., 2007 – see also EPPO RS 2009/007). So far, P. austrocedrae had not been reported outside Argentina, or on another conifer species such as C. nootkatensis.
Site 1: dieback and mortality were noticed on 21 trees of Chamaecyparis lawsoniana in a public park near Greenock (Inverclyde). Affected trees showed similar symptoms to the initial finding of P. lateralis in Scotland, and the identity of the pathogen was confirmed (PCR, sequencing) on bark samples from 3 trees. The ITS sequences for the 3 P. lateralis isolates from Greenock were found to be distinctly different from those of the initial finding, thus suggesting that this might be an independent introduction of P. lateralis. All infected trees were destroyed by April 2011.
Site 2: in another public park in East Renfrewshire, dieback and mortality were also noticed on 3 C. lawsoniana and 2 C. nootkatensis trees. Similarly, the identity of the pathogen was confirmed by molecular tests. On this site, two other Phytophthora species were also detected: P. cambivora on C. lawsoniana and P. austrocedrae on C. nootkatensis. All infected trees were destroyed by May 2011.
It has not yet been possible to identify the source of introduction of P. lateralis or P. austrocedrae on either site and both pathogens could have been present for more than 1 year. Introduction of nursery stock has probably played an important role but tracing-back studies are under way to verify this assumption. It was also noticed that both sites have a high level of public access. In addition to tree destruction, phytosanitary measures were put into place to avoid any further spread of P. lateralis or P. austrocedra, such as: prohibition to remove plant material from infected sites (including composted material), thorough cleaning and disinfection of all machinery and equipment used to fell and dispose of the infected material, warning notices for members of the public and disinfectant foot mats placed at all exit points.
Sources
NPPO of the United Kingdom (2011-05).
Greslebin AG, Hansen EM, Sutton W (2007) Phytophthora austrocedrae sp. nov., a new species associated with Austrocedrus chilensis mortality in Patagonia (Argentina). Mycological Research 111(3), 308-316.