92 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 





Pady, S. M. Further notes on the witches'-brooms and the sub- 

 stomatal pycnia of Melampsorella. Kans. Acad. Sci. Trans. 44: 

 190-201. 1941. 



Peterson, R. S. Host alteration of spruce broom rust. Science 134 

 (3477) :468-469. 1961. 



Comandra Blister Rust 



J. L. MlELKE 



Forest Service, U.S. Department of Agriculture, 

 Logan, Utah 



Cronartium comandrae Pk. (Syn. : C. pyriforme Hedg. & Long) 

 is a disease of hard pines in North America. It is perennial in the 

 living bark of the pine hosts: develops annually on false toadflaxes, 

 the alternate hosts. First conspicuous symptom of the disease on pines 

 is a spindle-shaped swelling of the bark on branches and on stems of 

 small trees. Cankered bark is usually constricted on main stem or 

 trunk of large or mature trees. Generally, there is copious resin 

 exudation from trunk cankers, especially in Pinus contorta. Rodents, 

 mainly porcupines and squirrels, often feed on the infected bark. 

 Wounds inflicted by them may increase resin flow. Dead and dying 

 tops and branches are conspicuous symptoms of this rust in invaded 

 pine stands. Cankers originate on needle-bearing twigs and stems. 



Large, reddish-orange pycnial drops (4-8 mm. diam.) appear on 

 swollen bark 2 to 3 years after initial infection. Aecia are pro- 

 duced the following spring and summer. Aeciospores pyrif orm ; this 

 character readily separates this blister rust from all others on pines. 

 Tiny pycniospores have the same general shape. The life cycle and 

 character of attack on pines are very similar to that of the well- 

 known white pine blister rust (0. ribicola Fischer). Aeciospores 

 are wind disseminated to alternate host plants. Uredia appear about 

 10 days after infection; telia begin to develop about 15 days later. 

 Airborne basidiospores infect pines in late summer and fall, thus 

 completing the life cycle. 



Comandra blister rust is a very destructive disease in Western 

 United States. Pinus contorta, P. ponderosa, and P. pungens are 

 highly susceptible to the fungus. The degree of susceptibility of other 

 reported pine hosts is not precisely known. Infected trees are killed 

 by girdling. Seedlings are killed in a few years; 25 years or more 

 may elapse between initial infection and death of mature pines. 



No method of control has yet been developed. Grubbing out of al- 

 ternate host plants is not feasible as a control measure. Herbicides 

 are not effective on Comandra umbellata, a xerophilous plant inhabit- 

 ing open rangeland and of practically no forage value. C. livida 

 occurs on wet sites; rare in U.S., but fairly common in Canada. 

 Buchleya distichophylla (Nutt.) Torr., was • erroneously reported as 

 an alternate host by J. C. Arthur. 



Range : North America. New Brunswick to the Yukon and British 

 Columbia in Canada and southward to northern Mississippi, 

 New Mexico, and California in U.S. 





