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Title: Prevalence, distribution and identification of Phytophthora species from bleeding canker on European beech

Author
item NELSON, ANGELA - Cornell University - New York
item Weiland, Jerry
item HUDLER, GEORGE - Cornell University - New York

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2010
Publication Date: 9/1/2010
Citation: Nelson, A., Weiland, G.E., Hudler, G. 2010. Prevalence, distribution and identification of Phytophthora species from bleeding canker on European beech. Phytopathology. 28(3):150-158.

Interpretive Summary: Bleeding canker is a serious disease of historic European beech in the northeastern United States. An investigation was conducted in order to: 1) survey for disease prevalence, 2) identify the pathogens involved, 3) prove pathogenicity, 4) compare protocols for pathogen detection, and 5) survey for the pathogen in the soils surrounding European beech. The survey found that approximately 40% of the European beech in five U.S. states were affected by the disease. Five species of Phytophthora were associated with the disease and included P. cactorum, P. gonapodyides, P. cambivora, and two distinct types of P. citricola (P. citricola A and B). Phytophthora cactorum and P. citricola were found the most frequently. All five Phytophthora species caused disease when inoculated into European beech saplings, though isolates of P. cactorum and P. citricola A and B caused the most damage. Phytophthora species were most easily isolated onto selective media in the fall and allowed the identification of the pathogen to species. A Phytophthora test kit worked regardless of season, and had a higher success rate of detection than the selective medium, but was unable to provide information on which Phytophthora species was involved in causing the disease. Therefore, detection and identification with a selective medium is preferred. All five Phytophthora species were found in soils surrounding European beech trees. However, in contrast to the most common species identified from cankers, P. cambivora was more prevalent in the soil. These results act as a foundation for building management strategies to protect valuable specimens of European beech.

Technical Abstract: While bleeding canker of European beech (Fagus sylvatica) has long been recognized as a problem, the cause in the northeastern United States has not been clear. To resolve this, we surveyed for disease prevalence, identified the pathogens involved, proved their pathogenicity, compared protocols for pathogen detection, and conducted a soil assay to determine pathogen presence in soil surrounding European beech. Approximately 40% of surveyed trees in five U.S. states had bleeding cankers. Five pathogens were found to be involved: Phytophthora cactorum, P. gonapodyides, P. cambivora and two distinct clades of P. citricola (P. citricola A and B). Phytophthora citricola A and P. cactorum were most prevalent. All were found to cause 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, which was significantly higher in the fall, was preferred although ELISA detection was more successful and worked regardless of season. All five Phytophthora species were found in soil surveys; P. cambivora was most common, followed by P. cactorum and P. citricola A. These results act as the foundation for building management strategies to protect valuable specimens of European beech.