TREES AND TIMBER 431 



Mistletoe (Phoradendron flavescens Nutt). — While not 

 generally considered a pest, this parasite under favorable 

 weather conditions may become so, especially upon 

 trees in lawns and parks. It usually attacks the smaller 

 branches of the trees, and thus cuts off the nourishment 

 from their tips and eventually causes this portion to 

 die. The general effect is to spoil the beauty of the tree. 

 About thirty different kinds of trees are attacked, and the 

 parasite can be carried easily from one host to another. 



To destroy mistletoe the infected branches should all be 

 cut from the trees and no berries allowed to mature, thus 

 preventing dissemination of the pest by birds. 



Special Hosts 

 ASH 



White rot {Polyporus fraxinophilus Peck). — In Missouri, 

 Nebraska, and Kansas in some localities this disease 

 affects 90 per cent of the trees. It prevails in the 

 Mississippi valley and east to the Atlantic. The heairt- 

 wood first darkens, and later becomes soft, pulpy, and yel- 

 lowish. The shelving, pored sporophores, 5-10 cm. long 

 and nearly triangular in section, are numerous, chiefly 

 near stubs or wounds, appearing soon after infection. The 

 old upper surface is bro\vn or black, and very hard. Trees 

 of any age are susceptible, but those over 10 cm. in diameter 

 are most subject to attack. Diseased trees should be cut 

 down, or excision practiced, and the hole filled with tar. 



Rust {Puccinia fraxini (Link) Arthur). — This is a rust 

 which may be recognized by the orange-colored cluster 

 cups upon the much-swollen parts of the leaves and petioles 



