Western redcedar — natural history and pathosystems, with emphasis on cedar leaf blight

Abstract The wood properties of western redcedar (Thuja plicata) (WRC) are revered in traditional practices by Pacific Coast First Nations and valued for speciality commercial purposes. In the near future, WRC harvesting will shift to second growth from old-growth, however, its cultural significance will persist, and the superior physical and chemical properties of the wood mean that it will remain in high demand. Investigating and understanding the adaptations of the species to environmental and pathogen stress in the face of changing climates can assure a sustainable supply of WRC. Of the pathogens affecting WRC, cedar leaf blight (Didymascella thujina) (CLB) is the most severe. This foliar disease infects the leaflets of seedlings and mature trees, causing a loss of photosynthetic area resulting in decreased growth or mortality. The disease is more severe on nursery seedlings than mature trees. Future projected climates in WRC’s native range are expected to increase the prevalence of, and damage from CLB. This review summarizes the state of knowledge and emphasizes recent advances in the understanding of the Thuja – Didymascella pathosystem.