Chrysomyxa pirolata

The spruce cone rust, caused by the rust fungus Chrysomyxa pirolata Wint., affects spruces in 3 continents, including white spruce in Canada (Hiratsuka 1987).^[1] Alternate hosts of the fungus are several species among 3 genera of wintergreen: Pyrola spp., Orthilia spp., and Moneses spp. (Ziller 1974, Sutherland et al. 1984).^[2][3] Diseased cones open prematurely and orange-yellow aeciospores are sometimes produced in such quantity as to color the forest floor and lake surfaces. Up to half of a cone crop can be affected, and most of the affected cones do not produce viable seed. Some localities commonly experience damage to 20% to 30% of cone crops (Hiratsuka 1987),^[1] a factor to be considered in the siting of seed orchards.

References

1. 1 2 Hiratsuka, Y. 1987. Forest tree diseases of the prairie provinces. Gov’t Can., Can. For. Serv., Edmonton AB, Inf. Rep. NOR-X-286. 142 p.
2. ↑ Ziller, W.G. 1974. The tree rusts of western Canada. Environ. Can., Can. For. Serv., Ottawa ON, Publ. 1329. 272 p.
3. ↑ Sutherland, J.R.; Woods, T.A.D.; Miller, G.E. 1984. Effect of selected insecticides and fungicides on germination of Douglas-fir and white spruce pollen. USDA, For. Serv., Tree Plant. Notes 35(1):22–24. (Cited in Coates et al. 1994).