Canadian Journal of Plant Pathology (2022) 44, 549-558

Nicolas Feau, Mark Mcdonald, Berni Van Der Meer, Yishan Zhang, Padmini Herath and Richard C. Hamelin (2022)
Phytophthora species associated with red alder dieback in British Columbia, Canada
Canadian Journal of Plant Pathology 44 (4), 549-558
Abstract: Red alder (Alnus rubra) trees form an essential component of the communities along coastal streams in the Pacific Northwest. However, canopy dieback has been observed in red alder for several years. Symptomatic trees found at two sites in the greater Vancouver area, British Columbia, Canada, were investigated for disease-causing organisms. We investigated the presence of causal agents by isolating potential pathogens using direct plating of root samples on Petri dishes and by baiting for oomycetes in soil and root samples, followed by DNA barcoding. We identified three pathogenic Phytophthora species: Phytophthora cambivora, P. syringae and P. pseudosyringae. Controlled inoculations of all three on red alder leaves indicated that only P. pseudosyringae has the potential to cause both stem canker and aerial symptoms. This is the first isolation of the tree pathogen P. pseudosyringae in Canada. Additionally, the inoculation experiments revealed that P. gonapodyides, a species that is frequently detected in riparian ecosystems with diseased alders in Oregon but not directly associated with tree mortality, was more aggressive than the three pathogenic Phytophthora species tested. Our results reveal a greater complexity than previously suspected in red alder decline.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Richard C. Hamelin

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora pseudosyringae	Alder (Alnus)	Canada (west)