Occurrence of Phytophthora ramorum and Other Phytophthora Species on Woody Ornamentals in Public Gardens and Parks in Northwestern Spain

Abstract

Phytophthora ramorum is a harmful pathogen of ornamental and forest trees in Europe and North America. This pathogen has been recovered from nursery plants in Galicia (northwestern Spain) since 2003 and, despite carrying out the measures implemented by Commission Decision 2002/757/CE, including the eradication of infected plants and periodic inspections in nurseries, it is likely that P. ramorum has spread in landscaped green areas through planting of infected nursery stock. The aim of this work was to survey woody ornamental plants in public parks and gardens in Galicia for the presence of P. ramorum from 2011 to 2018 and to identify and characterize any other species of the genus found. Samples of leaves, twigs, and rhizosphere soil of symptomatic ornamental trees and shrubs were analyzed. Morphological, physiological, and molecular characteristics of 93 collect isolates enabled the identification of 13 species of Phytophthora. The greatest diversity of Phytophthora species was detected on Rhododendron and Camellia. P. ramorum was isolated from leaf samples of Camellia sp., Rhododendron sp ., and Viburnum tinus grown in three sites. To our knowledge, this is the first time that P. ramorum has been detected in landscaped green areas in Spain. These results suggest that regular inspections of symptomatic ornamental woody plants are necessary to control the spread of P. ramorum and other Phytophthora species.