Chrysomyxa pirolata explained

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), a factor to be considered in the siting of seed orchards.

Notes and References

1. 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).