6 



BULLETIN 212;, U. S. DEPARTMENT OF AGRICULTURE. 



species of Quercus 1 should be of much siguificence in control work. 

 Quercus velutina and Q. coccinea are two scrub oaks frequently form- 

 ing a conspicuous part of the jack-pine type, particularly in Michigan. 

 Methods could be devised for the eradication of these worthless 

 species, thus removing the alternate host of the fungus. However 

 impracticable this may be on a large scale, in wood lots and small 



holdings this would not be a very difficult 

 matter. The removal of infected branches of 

 young growth could be done in the orchard- 

 like stands of jack pine on the more sandy 

 soils, thus saving many young trees from early 

 suppression. 



In a few instances, in the region studied, 

 young jack pine was found to be diseased by 

 Peridermium comjrtoniae (Arthur) Orton and 

 Adams (Cronartium. comptoniae Arthur). 

 (Fig. 4.) In the experience of the writer this 

 fungus was not common. The secial stage of 

 the fungus is chiefly characterized by a slight 

 fusiform swelling, seldom forming the spheri- 

 cal galls so characteristic for P. cerebrum. The 

 peridia rupture with a sharply serrate or 

 spiny margin. The fungus is further dis- 

 tinguished from P. cerebrum by attacking 

 principally young seedlings (PL I, fig. 3) and 

 causing excessive brooming of the branches. 

 It was not found on more mature growth. 

 P. cerebrum attacks both young and old trees. 

 P. comptoniae has its alternate stage on sweet 

 fern 2 (Comptonia peregrina and Myrica gale) . 

 Without the production of the teliospores on 

 these plants the fungus can not reproduce 

 itself on the jack pine. 



As a precaution agains tthese Peridermiums 

 entering the forest nursery and the possibility 

 of their transportation to other regions, all 

 alternate hosts, such as species of oaks and 

 sweet ferns, should be removed from the 

 vicinity of the nursery. This immunity zone 

 should be extended as far back from the nursery as time and means 

 will allow. Before new nurseries are established a pathological sur- 

 vey of the immediate region should be made as to the presence of 

 these hetercecious pine rusts. Much attention should also be given 



Fig. 4. — Young j ack pine infected 

 with Peridermium comptoniae. 

 Note the ruptured peridia with 

 their serrate margins. 



1 Demonstrated by Dr. C. L. Shear, Jour. Myc, vol. 12, p. 89, 1906. 



5 Demonstrated by G. P. Clinton, Conn. Agr. Exp. Sta. Rept., 1907, pp. 380-383, 1908. 



