Neofusicoccum arbuti : survey of a latent endophytic pathogen reveals widespread infection, broad host range, and a hidden threat. McGregor, Rob Roy
Arbutus menziesii is an iconic tree species of the Pacific Northwest that has been in decline for the past 40 years. Neofusicoccum arbuti, a latent endophytic fungal pathogen in the Botryosphaeriaceae family, has been implicated as the primary cause of disease in A. menziesii, causing wart-like cankers on the stem and branches when the host is stressed. Neofusicoccum arbuti is suspected of causing the symptoms of decline in A. menziesii in Lighthouse Park in West Vancouver, BC. Little is known about the host range of N. arbuti, which has only been reported on A. menziesii, Vaccinium corymbosum, and once from Cytisus scoparius. A survey of Lighthouse Park was carried out to determine the cause and prevalence of cankers on A. menziesii in Lighthouse Park and to identify additional hosts of N. arbuti. Neofusicoccum arbuti was the fungus most commonly associated with cankers on A. menziesii. The pathogen was isolated from 87% of cankers sampled. Cankers were prevalent throughout the park, with at least 75% of arbutus trees having one or more cankers at the majority of sites. Furthermore, the host range of N. arbuti is much broader than previously thought. Seven non-arbutus hosts, spanning four taxonomic orders were identified, including Amelanchier alnifolia, Cytisus scoparius, Gaultheria shallon, Ilex aquifolium, Rosa sp., Sorbus sitchensis, and Spiraea douglasii. These hosts could act as a reservoir providing additional inoculum or may be infected by spores produced on arbutus. The impact of these additional hosts is unknown.
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