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Spruce Cone Rusts
Chrysomyxa pirolata (Kőrn.) G. Wint
Rossmanomyces monesis (Ziller) Aime & McTaggart
Host(s) in Alaska:
Spruce (Picea spp.)
Alternate hosts Pyrola spp. and Monesis uniflora
Habitat(s): spruce cones and leaves of alternate host plants
Current Status & Distribution in Alaska (2023 Update)
Inland and coastal spruce cones rust diseases are caused by Chrysomyxa pirolata and Rossmanomyces monesis, respectively. Leaves of the alternate host plants, Pyrola spp. and Moneses uniflora, are often covered in rust infection in spring. Rust on the cones is less frequently observed because of their position high in the tree crown. In 2023, cone rust was observed on white spruce in Interior Alaska near Stevens Village. In Southcentral, the Chugach National Forest mounted a spruce cone collection effort on the Kenai Peninsula to take advantage of abundant cone production this year. In the process, spruce cone rust was detected on more than 30 Lutz spruce trees. Diseased specimens were sent to Oregon State University Plant Clinic for DNA identification of the causal organism. Six research grade observations of R. monesis on the understory host Moneses uniflora were submitted to iNaturalist near Anchorage. Cone rusts can cause losses in spruce seed orchards and wild stands, especially where both disease hosts are prevalent and climate conditions favor disease development.
Survey Method
Spruce cone rust damage is observed through ground detection surveys.
Links to Resources & Publications
Cone and seed diseases of North American conifers. North American forestry Commission Publication Number 1. 1987. Sutherland, J.R.; Miller, T.; Quinard, R.S., Editors. Forestry Canada, Pacific and Yukon Region, Victoria, BC. 77 p. Available here.
Spruce cone rust damage is observed through ground detection surveys.Spruce cone rusts. Forest Disease Management Notes. Pacific Northwest Region. Available here.
Content prepared by Robin Mulvey, Forest Health Protection, robin.mulvey@usda.gov.
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