Other Phytophthora species recently described on forest or ornamental species
During studies done on Phytophthora ramorum (EPPO Alert List) either in forests or nurseries, 3 new Phytophthora species have recently been described: Phytophthora nemorosa (Hansen et al., 2003), Phytophthora pseudosyringae (Jung et al., 2003), and Phytophthora hedraiandra (de Cock & Lévesque, 2004).
So far, P. nemorosa has only been reported from USA in California and Oregon. It is associated with stem cankers on Lithocarpus densiflorus and Quercus agrifolia, and foliar lesions on Umbellularia californica, Sequoia sempervirens and Arctostaphylos spp. Lethal cankers have been observed but usually occur on isolated trees.
P. pseudosyringae was first isolated and described from forest soils around mature Q. petraea, Q. robur, and Q. cerris in Europe. It was also isolated from necrotic roots and necrotic bark at the stem base of Fagus sylvatica, and from necrotic bark and rhizosphere soil of Alnus glutinosa. In USA, P. pseudosyringae was isolated from Umbellularia californica and Q. agrifolia. So far, P. pseudosyringae is reported in Europe (Italy, France and Germany) and from USA (California, Oregon).
Host range and symptoms of P. nemorosa and P. pseudosyringae are similar to those of P. ramorum but apparently, they seem less virulent. In California where the 3 species occur, P. nemorosa and P. pseudosyringae do not cause severe mortality on oaks and tanoaks (Lithocarpus densiflorus). In Europe, P. pseudosyringae is not reported to cause widespread mortality on oak or other tree species.
P. hedraiandra was described as a new species in 2004. It had been isolated in the Netherlands in 2001 from Viburnum plants showing leaf spots, but its pathogenicity and geographic distribution were unknown. Interestingly, recent records of this new species have been made from other countries. In Spain, during surveys on P. ramorum done at garden centres in Majorca (Baleares), several potted plants of Viburnum tinus showing branch dieback and basal stem cankers were observed. The causal agent was identified as P. hedraiandra (Moralejo et al., 2005). In Italy in spring 2004, several cases of decline and mortality of Viburnum tinus were observed in nurseries in Toscana (particularly in the province of Pistoia). Symptoms were characterized by collar and root rot. Affected plants showed wilting of leaves and shoots. The causal agent was also identified as P. hedraiandra (Belisario et al., 2005). Finally in Minnesota (US), surveys on the
possible presence of P. ramorum revealed the presence of P. hedraiandra on Rhododendron plants showing leaf lesions and shoot dieback (Schwingle et al., 2006).
Belisario A, Gilli G, Maccaroni M (2005) First report of Phytophthora hedraiandra on Viburnum tinus in Italy. New Disease Report, Volume 12: August 2005 - January 2006. http://www.bspp.org.uk/ndr/jan2006/2005-85.asp
De Cock AWAM, Lévesque CA (2004) New species of Pythium and Phytophthora. Studies in Mycology, 50, 481-487.
Fleischmann F, Gottlein A, Rodenkirchen H, Lutz C, Osswald W (2004) Biomass, nutrient and pigment content of beech (Fagus sylvatica) saplings infected with Phytophthora citricola, P. cambivora, P. pseudosyringae and P. undulata. Forest Pathology 34(2), 79-92.
Hansen EM, Reeser P, Davidson JN, Garbelotto M, Ivors K, Douhan L, Rizzo DM, (2003) Phytophthora nemorosa, a new species causing cankers and leaf blight of forest trees in California and Oregon, USA. Mycotaxon 88, 129-138.
Jung T, Nechwatal J, Cooke DEL, Hartmann G, Blaschke M, Osswald WF, Duncan JM, Delatour C (2003) Phytophthora pseudosyringae sp. nov., a new species causing root and collar rot of deciduous tree species in Europe. Mycological Research 107(7), 772-789.
Martin FN, Tooley PW (2003) Phylogenetic relationships of Phytophthora ramorum, P. nemorosa, and P. pseudosyringae, three species recovered from areas in California with sudden oak death. Mycological Research 107(12), 1379-1391.
Moralejo E, Belbahri L, Calmin G., Lefort F, García JA, Descals E (2005) First report of Phytophthora hedraiandra on Viburnum tinus in Spain. New Disease Report, Volume 12: August 2005 - January 2006. http://www.bspp.org.uk/ndr/jan2006/2005-90.asp
Motta E, Annesi T, Pane A, Cooke DEL, Cacciola SO (2003) A new Phytophthora sp. causing a basal canker on beech in Italy. Plant Disease 87(8), p 1005.
Schwingle BW, Smith JA, Blanchette RA, Gould S, Blanchette L, Pokorny J, Cohen SD (2006) First report of dieback and leaf lesions on Rhododendron sp. caused by Phytophthora hedraiandra in the United States. Plant Disease 90(1), p 109.