Molecular Identification and Detection of Phytophthora ramorum

The genus Phytophthora comprises over 70 described species, however many new species have been reported recently as a result of the discovery of previously undetected species or by the hybridization of known species. Phytophthora ramorum, one of the new Phytophthora species, is considered a high phytosanitary risk because it is currently responsible for largescale oak mortality in coastal California forests. In Europe, the disease occurs mainly in nurseries on Rhododendron, Viburnum and Camellia. However, in landscapes, infected trees of Quercus rubra, Q falcata, Q. ilex, Aesculus hippocastanum and Fagus sylvatica were reported recently on sites previously identified with infected Rhododendron plants. In addition, numerous nurseries in the U. S. have recently been diagnosed with infected Rhododendron and Camellia spp.