A NATIONAL PLAN FOB AMERICAN FORESTRY 601 



FOREST TREE DISEASES 



The chestnut blight, which in the space of a few years killed nearly 

 all the chestnut timber in the Atlantic Coast States, is evidence of 

 what a forest tree disease can do. The productivity of the national 

 forests in the Appalachians, measured -in terms of value of product, 

 has been substantially decreased by the virtual elimination of chest- 

 nut. Unhappily no means of control has yet been found. The 

 only present hope for the return of chestnut lies in the possibility of 

 the natural development of a blight-resistant variety among the young 

 growth slowly coming back in spots. 



There are other troublesome tree diseases which, though not of 

 major consequence, constitute a certain degree of handicap in timber 

 growing, and, in the case of two important species, may contain the 

 making of a real menace in the future. Of these, the various trunk 

 rots which infect trees injured by fire, logging, or other means, cause 

 a large annual loss of wood by their destruction of part of the mer- 

 chantable portion of the tree. The amount of material which has to 

 be discarded because of rot when timber is cut often runs as much as 

 10 per cent of the total volume of the mature stand, and occasionally 

 amounts to a third or more of the volume. Until the present mature 

 and overmature stands are cut and the forests placed under more 

 intensive management which will cut trees before ovennaturity 

 occurs and allows decay to become measurable, there will continue 

 to be a large aggregate loss of volume by the continued encroachment 

 of wood decay. Better fire protection and increased care in logging 

 will minimize the attacks of these wood-rotting fungi in the young 

 stands. 



Damage in the form of retarded tree growth is caused by mistletoe, 

 abundant in some pine stands in the West. The only practical con- 

 trol measures lie in cutting infected trees as much as possible in timber- 

 sale operations. A form of rust has damaged some of the ponderosa- 

 pine plantations, but not to a serious extent in the aggregate. More 

 serious have been the losses of nursery stock from the " damping-off " 

 fungus, but effective control measures for this fungus have been 

 developed. 



The possible menace lies in the potentialities of the larch canker, 

 which has appeared in the eastern larch stands but has apparently 

 been controlled, should it get into the more extensive western larch 

 forests, and in a Douglas fir canker, quite troublesome in introduced 

 stands of this species in Europe, but not yet found in the great Douglas 

 fir forests of the West. Constant watchfulness is required to prevent 

 these fungi from gaining a hold where they might cause extensive 

 destruction. 



The tree disease of an immediately alarming nature is the white- 

 pine blister rust, which is rapidly gaining a strong foothold in the 

 western white-pine forests of north Idaho, northeastern Washington, 

 and western Montana, and is spreading steadily toward the sugar- 

 pine stands in California. Both of these high-value species mean a 

 great deal in the economic life of the regions where they are found in 

 abundance, especially in north Idaho, where the entire lumber 

 industry rests chiefly on the white-pine forests. Likewise, the lumber 

 of these species is an important, widely used commodity. 



There is a big task on the national forests to eradicate this 

 menace. Part of the job of control is a joint one between Federal, 



