324 MANUAL OF TREE DISEASES 



stimulus which the parasite causes in the tissues. For a 

 further discussion of the mistletoes which grow parasitic on 

 trees, see page 54. 



References 



Schrenk, Hermann von. Notes on Arceuthobium pusillum. Rhodora 



2 : 2^, pi. 12. 1900. 

 Jack, J. G. Arceuthobium pnsilhim in Massachusetts. Rhodora 



2 : 6-8, pi. 13. 1900. 

 Jones, L. R. Arceuthobium pusillum on a new host in Vermont. 



Rhodora 2 : 8-9, pi. 14. 1900. 



Peckt Wood-Rot 



Caused by Trametes pini Fries 



Spruce is commonly affected by pecky wood-rot or ring- 

 shake. This disease is the most destructive wood-rot of coni- 

 fers in the United States. It has been reported in larch, pine, 

 spruce, hemlock, fir and arbor-vitse. Practically all conifers 

 seem to be susceptible except the junipers. In Europe, pine, 

 larch, fir and spruce are attacked. The usual common name 

 for this disease is ring-shake, because a few annual rings are often 

 destroyed, a part of the distance or entirely around the tnmk, 

 causing a shake in the timber. This symptom is not so com- 

 mon in those conifers with a low resin-content, however, and 

 the name pecky wood-rot seems more appropriate. It is by 

 far the most destructive disease of conifers in the forest and 

 by some is believed to equal in importance all other wood- 

 rots. The sapwood and bark as well as the heartwood are 

 invaded and decayed. 



Symptoms. 



The appearance of spruce heartwood when decayed by this 

 fungus is characteristic and the rot may be identified without 

 the accompanying sporophores. Around the decayed area, the 

 spruce wood is stained a purplish tinge. In cross-section when 



