UNITED STATES DEPARTMENT OF AGRICULTURE 

 FOREST SERVICE 



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OCDEN UTAH 



No. hi June 19^7 



THE YELLOW WITCHES' BROOM OF SUBALFINE FIR 

 IN THE INTEKIOUNTAIN REGION 



James L. Mielke 

 Division of Forest Disease Research 



The yellow witches' broom disease of true firs is caused by the 

 rust fungus Melampsorella caryophyllacearum Schroet. This fungus is 

 native to North America (1) and also Europe and Asia (5) • It has been 

 known in Europe for about iSO years and approximately half that long in 

 this country (l) . 



The pathogen is not particularly destructive in Europe ( 5j 3) j and 

 there is no record in the literature of it causing serious damage and 

 losses in any of the true fir species in North America. The purpose of 

 the present paper is to report an epidemic of the rust in subalpine fir 

 ( Abies lasiocarpa (Hook.) Nutt.) on several areas in the southern portion 

 of the Inteimountain Region. 



RANGE OF THE RUST 



In North America, Melampsorella caryophyllacearum is known from 

 Labrador and Newfoundland west to Alaska; south through Canada to the 

 northern United States, and still farther south in the western United 

 States to California and Mexico (2). It has been reported on Abies spp. 

 in all of the western states except Arizona and Nevada (1). 



HOSTS 



The fungus is one of the heteroecious rusts, i.e., it evidently 

 requires an alternate host for the completion of its life cycle (3, 5j 

 9, 10). The alternate hosts are species of Cerastium and Stellaria X2) , 

 coinmonly called chickweeds in this region. Some species within each 

 genus are annual and the others perennial. 



