SPRUCE DISEASES 315 



fungus over the winter. The spores seem to be able to Infect 

 only the young succulent growth, since no new infections occur 

 after the shoots have attained full growth. The mycelium 

 invades the tissues of the twig and leaves. 



Control. 



No definite measures of control are suggested. It would be 

 difficult to keep the new growth covered with any spray mixture 

 during its susceptible period, since the rapid growth that is 

 made in early spring would expose much new tissue between 

 applications. However, some benefit may be derived from 

 pulling and burning immediately all diseased trees in the seed- 

 bed, as soon as they are noticed. This would prevent to a 

 large measure the further spread that season and would eliminate 

 the material which would otherwise harbor the fungus until 

 the next season. 



References 



Graves, A. H. Notes on diseases of trees in the southern Appalachians 

 III. Phytopathology 4 : 63-72, pi. 5. 1914. 



Hartig, R. Septoria parasitica, the spruoe-shoot disease. In Text- 

 book of the diseases of trees, pp. 143-146, figs. 81-82. 1894. 



Leaf Blister-Rusts 



Caused by Melampsoropsis cassandrm (Peck and Clinton) Arthur, 

 M. abietina (Alb. and Schw.) Arthur, and M. ledicola (Peck) Arthur 



The leaves of red, black, white, Engelmann and Sitka spruce 

 throughout the range of these trees in the United States are 

 commonly affected by one or more of three very similar needle 

 blister-rust diseases. All three of the causal rust-fungi have 

 the alternate stages of their life history on plants of the heath 

 family, principally on Labrador tea, bog rosemary and leather- 

 leaf. The whitish blisters formed on the under, sides of the 

 spruce needles shed spores (seciospores) which infect the heaths. 

 On these plants, small reddish or yellowish pustules bearing the 



