EFFECTS OF BROOM RUSTS ON SPRUCE AND FIR 



RogerS. Peterson 1 



"How significant is broom rust damage 9 " is a common question among western 

 foresters who work with spruce and fir. This paper reviews the evidence and reports 

 new data. 



Broom rusts attack most species of spruce and fir throughout North America, but 

 are particularly abundant in the West. • Their most conspicuous symptoms are branch 

 proliferations called witches ' -brooms , which produce annual crops of yellow needles. 

 Other symptoms are branch and trunk swellings and cankers. Broom rust of spruce is 

 caused by Chrysomyxa arctostaphyli , a fungus that completes its life cycle on bear- 

 berry and other Arctostaphylos species. Melampsorella caryophyllacearum causes the 

 similar disease of true firs; it alternates in its life cycle to chickweeds and their 

 relatives in Cerastium and Stellaria. 



REVIEW 

 Spruce Broom Rust 



Spruce broom rust occurs only in North America. The most concentrated out- 

 breaks are in northern Arizona and southern Colorado on Engelmann and blue spruce 

 and in Alaska on black and white spruce, with local epidemics scattered over the 2,000 

 miles between these areas. The rust is missing where Arctostaphylos does not grow, 

 for instance in southeastern Idaho. 



Spruce brooms are associated with bole deformation, loss of increment, spike- 

 tops, and mortality (Bourchier 1953; Foster and Ziller 1952; Kimmey and Stevenson 

 1957; Thomas 1953). Brooms also serve as infection courts for decay fungi such as 

 Fomes pini and Lentinus lepideus, and thereby increase cull (Hedgcock 1912; Mielke 

 and Davidson 1947). A survey in Colorado determined that heart rot was associated 

 with 68 percent of dead rust brooms on trunks of sampled Engelmann spruce (U.S. 

 Forest Service 1959). Wind breakage at rust trunk infections has been reported by 

 Alexander (1957) and Pady (1942). No comprehensive study of economic effects of 

 spruce broom rust has been made, and there has been no large-scale control work. 



1 Plant pathologist. Data from Colorado were obtained while the writer was with 

 the Rocky Mountain Forest and Range Experiment Station at Fort Collins, Colorado. 

 Work was completed at headquarters in Logan, Utah, maintained in cooperation with 

 Utah State University. 



