Spruce Cone Rusts

Rust on the cones is less frequently observed because of their position high in the tree crown, but some disease was detected on fallen cones this year.

Ground Detection Survey Observations in 2024: 2 on white spruce cones near Anchorage, 1 from wintergreen along the Portage Glacier Highway. 

iNaturalist Observations in 2024: 7 observations of R. pyrolae on wintergreen near Healy, Denali National Park, Anchorage, Kodiak Island, McCarthy, and Juneau. 

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. 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. 

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.

Spruce cone rust damage is observed through ground detection surveys.

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.