PINE DISEASES 



277 



The covering of the blisters breaks and a fine yellow powder 

 of thousands of spores dusts out and is blown away by the 

 wind. The blister stage on the pine is formed in early spring 

 and by midsummer the white 

 coverings of the blisters disap- 

 pear and only rounded depres- 

 sions remain in the bark to mark 

 their location. The area of bark 

 from which the blisters are pro- 

 duced usually dies but the my- 

 celium extends into the surround- 

 ing healthy bark. The yellow 

 blisters are produced year after 

 year from the newly invaded 

 bark until on older trees cankers 

 several feet long are sometimes 

 formed. Usually the branch or 

 trunk is soon girdled and the 

 parts of the tree beyond the 

 girdled point die. The fungus 

 cannot exist except in living 

 tissue and, therefore, is not har- 

 bored after the affected part of 

 the tree is killed. Young trees 

 with the trunk affected show a 

 stunted and compact growth and 

 a slight yellowish color instead 

 of the normal green. 



Infected currant and goose- 

 berry leaves show slightly yellow- 

 ish spots which are more distinct 

 on the under surface. Small 

 yellowish blisters are pushed out ,, c, ,,,. ^ ^ ^ ■, . 



J . , . J! IG. 53. — Blister-rust on trunk 01 



from the lower epidermis and young white pine. 



