A NEW LEAF AND TWIG DISEASE OF 

 PICEA ENGELMANNI 



[a preliminary report] 



By James R. Weir, 



Forest Pathologist, Investigations in Forest Pathology, 



Bureau of Plant Industry 



The doubt expressed by some mycologists that Herpotrichia nigra 

 Hartig and Neopeckia coulteri (Pk.) Sacc. are distinct species should be 

 entirely dispelled by the recent article by Sturgis.^ 



These species are chiefly distinguished by the color and form of 

 their spores. The spores of N. coulteri when mature are blunt-elliptical, 

 dark-brown, i -septate, conspicuously constricted at the septa, measuring 

 from material at hand 19.8 to 28.9 by 9.5 to lOfi. (PI. XXXIV, 

 fig. I, A). Those of H. nigra when mature are elliptical, "pale to darker 

 olivaceous-brown," 3-septate. They are not so dark in color, nor are 

 they so conspicuously constricted at the septa as those of the former 

 species. These spores measure from material at hand 21.8 to 31.8 

 by 7.2 to 9.0/1 (PI. XXXIV, fig. 1,5). 



The microscopical characters of the spores of these species are seen 

 to be quite distinct. Throughout the examination of a large amount 

 of material from all parts of the Northwest and from many hosts these 

 characters were found to be constant. It is practically impossible to 

 distinguish the two species by their gross appearance in nature. The 

 mycelium of both involves the leaves and stems of their hosts in a 

 felt-like mass, resulting in the death of the parts infected. Occa- 

 sionally the mycelium of N. coulteri has a lighter color than that of 

 H. nigra when in mass, but either species may vary in this respect with 

 age and long exposure. As a rule, the species may be readily recog- 

 nized by their choice of hosts. When not in contact or intermingled 

 with others, the host plants selected by H. nigra invariably belong 

 to some species of the genera Abies, Juniperus, Picea, Libocedrus, or 

 Tsuga.^ The writer has collected specimens on the above genera and 

 also on Thuya and Taxus. Hartig ^ reports H. nigra on Pinus montana 

 in Europe. With the exception of very special instances A^. coulteri 

 is always found associated with the genus Pinus. Occasionally both 



•Sturgis. W. C. Herpotrichia and Neopeckia on conifers. In Phytopathology, v. 3, no. 3, p. 152-138, 

 pi. 12-13. 1913- 



' Hedgcock, G. G. Notes on some diseases of -trees in our national forests. In Phytopathology, v. 4, 

 no. 3, p. 181-188. 1914. 



* Hartig, Robert. Trichosphaeria parasitica und Herpotrichia nigra. In Hedwigia. Bd. 27, Heft i, 

 p. 12-1S. 1888. 



Journal of Agricultural Research, Vol. IV, No. 3 



Dept. of Agriculture, Washington, D. C. June 15, 1915 



G— 48 



(251) 



