SILVICULTURAL MANAGEMENT OF BLACK SPRUCE IN MINNESOTA 35 



(Epinotia nanana) at times has made black spruce unfit for use as 

 Christmas trees. 23 Thus, it is of some economic importance. 



The principal diseases affecting growth of black spruce are dwarf 

 mistletoe and the wood rots mentioned earlier. The main harm caused 

 by the wood rots is the weakening of the stems and roots which makes 

 the trees susceptible to breaking and uprooting. They cause a limited 

 amount of direct loss, also, through thgir destruction of merchantable 

 wood. The dwarf mistletoe has caused great damage in some localities 

 by deforming and stunting the trees (fig 22). Since it infests small 



Figure 22. — (A), Typical forking and brooming caused by dwarf mistletoe on 

 black spruce. (Picture is property of and used witb permission of E. L. 

 Mowat,) (B), Close-up of mistletoe plants on an infested black spruce twig. 

 Tbe inconspicuous plants, wbicb are greenish yellow or greenish brown in color, 

 seldom attain a height of more than y 2 inch. 



seedlings as well as larger trees, it is difficult to eradicate once it has 

 become established. Suggestions for its control are given in a later 

 section. 



Aside from the heart rots and dwarf mistletoe, black spruce has 

 few common diseases. The most conspicuous one is spruce leaf rust 



a HODSOX, A. C. MINNESOTA FOREST INSECT SURVEY FOR 1940. Minn. Agl\ Expt. 



Sta. Paper 448, Misc. Journal Series, 8 pp. [No date, mimeographed.] 



