Prevalence, Distribution and Identification of Phytophthora Species from Bleeding Canker on European Beech

Abstract

Abstract While bleeding canker of European beech trees (Fagus sylvatica) has long been recognized as a problem in Europe and North America, the cause in the northeastern United States has not been clear. To resolve this, we surveyed for disease prevalence on European beech, identified the pathogens involved, proved their pathogenicity, compared protocols for pathogen detection, and conducted a soil assay to determine pathogen presence in soil surrounding established trees in residential and commercial landscapes in New York, Pennsylvania, Maryland, Connecticut and Massachusetts. Approximately 40% of surveyed trees had bleeding cankers. While Phytophthora cactorum, P. gonapodyides, P. cambivora and two newly described species, P. citricola I and P. plurivora, were recovered from symptomatic tissue, P. citricola I and P. cactorum were most prevalent. All caused disease when artificially inoculated into European beech sapling stems, although P. cambivora and P. gonapodyides produced significantly smaller lesions. Recovery of the pathogen from symptomatic tissue using selective media, the preferred method of diagnosis, was significantly higher in the fall. ELISA detection was more successful and worked regardless of season, but did not allow identification to the species level. All five Phytophthora species were found in soil surveys; P. cambivora was most common, followed by P. cactorum and P. citricola I. These results provide a foundation for building management strategies to protect valuable specimens of European beech.