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

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.

Bleeding Canker of European Beech in Southeastern New York State: Phytophthora Species, Spatial Analysis of Disease, and Periodic Growth of Affected Trees

“…Isolates were also compared to Phytopththora spp. previously delineated to species using molecular analysis of rDNA (Nelson et al 2010). Formation of sporangia for each isolate/species was stimulated by collecting fi ve 5-mm (0.2 in) diameter agar plugs from the edge of a 5-7-d-old culture grown on cV8A.…”

“…Integration of taxonomic work by colleagues with our own fi eld and laboratory observations (Nelson et al 2010, leave us to conclude that the species of Phytophthora most often associated with bleeding cankers on European beech in the northeastern U.S. are P. pini (65% recovery) followed by P. cactorum (28% recovery) and occasionally other species. One concern among the tree care community, that the seemingly rapid escalation in bleeding canker incidence since the mid-1990s was due to the ap-pearance of a new exotic pathogen, perhaps P. ramorum (Rizzo et al 2002(Rizzo et al , 2005Grünwald et al 2012), was allayed as hundreds of microscopic examinations of cultures and analyses of defi nitive nucleic acid sequences failed to support said concerns.…”

“…Jung et al (2005) then found that a putative pathogen, tentatively identifi ed as P. infl ata Caroselli & Tucker [perhaps part of the P. citricola complex (Kong et al 2003)] was also associated with declining trees in sites throughout NYS. A more thorough survey by Nelson et al (2010) in NYS and adjacent states revealed that at least one symptomatic tree could be found in every site where ten trees were visible from an at-grade vantage point, and in some sites, the incidence of symptomatic trees was as high as 50%. Following attempts to grow the pathogen from diseased bark onto selective media (Nelson et al 2010), two-thirds of the cankers yielded isolates in the genus Phytophthora, but confi rmation of the identity of one or more putative pathogens was confounded by newly emerging nucleic acid sequence data that challenged previous assumptions about individual species and species complexes.…”

“…A more thorough survey by Nelson et al (2010) in NYS and adjacent states revealed that at least one symptomatic tree could be found in every site where ten trees were visible from an at-grade vantage point, and in some sites, the incidence of symptomatic trees was as high as 50%. Following attempts to grow the pathogen from diseased bark onto selective media (Nelson et al 2010), two-thirds of the cankers yielded isolates in the genus Phytophthora, but confi rmation of the identity of one or more putative pathogens was confounded by newly emerging nucleic acid sequence data that challenged previous assumptions about individual species and species complexes. Oudemans et al (1994) concluded that P. citricola, in particular, was actually a species complex consisting of as many as fi ve distinct taxa.…”

Phytophthora × cambivora as a Major Factor Inciting the Decline of European Beech in a Stand within the Southernmost Limit of Its Natural Range in Europe

“…A similar decline of European beech in central Europe was imputed to the combined effect of climatic extremes and infections by Phytophthora species [3]. The hybrid species Phytophthora × cambivora (formerly P. cambivora) and other soil-borne Phytophthora species were reported to be associated with decline and bleeding stem cankers of European beech in Europe and the USA [4][5][6][7][8][9]. A recent study provided circumstantial evidence the infections by Phytophthora species are a major factor inciting the decline of European beech stands in Austria [10].…”