2 7 6 



PROTECTION AGAINST TREE DISEASES 



to determine than for forest insects and published figures 

 mainly refer to losses for single species and specified regions. 

 Estimates of the loss on individual areas are already being made 

 with reasonable accuracy 8 by forest pathologists. Weir, 4 in 

 1909, estimated the loss to the merchantable stand of western 

 white pine alone to be in excess of $7,000,000 annually. 



The injury (as with insects) may be : either, of a physio- 

 logical nature, resulting in interference with the life processes 

 of the tree and the death or deformation of a part or the whole 

 tree; or of a technical character resulting in injury to the 

 commercial products in the tree, but not necessarily inter- 

 fering with the life processes, at least until the technical value 

 of the tree is practically destroyed. All parts of the tree 

 may be attacked both above and below the ground by one or 

 more of the numerous species of fungi. Rankin 3 divides 

 tree diseases into: 



Seedling diseases and injuries, 



Leaf diseases and injuries, 



Body and Branch diseases and injuries, and 



Root diseases and injuries. 



The seriousness of the damage varies greatly with the type 

 of fungus. "Of most consequence are those epidemic dis- 

 eases of fungoid origin which cause rapid death of their host, 

 and spread with great rapidity over wide areas. Such, through 

 repeated attacks, may render the cultivation of certain plants 

 impossible in a locality." This quotation from Tubeuf 9 indi- 

 cates his judgment as to the most destructive type of fungi. 

 Wood destroying fungi he classes as nearly equal in the losses 

 caused. 



The destructiveness of the former classes of diseases 10 lies 

 in the fact that they may kill outright trees of all ages com- 

 mercially exterminating a species. Where the species ex- 



