6o 



FORESTRY AND IRRIGATION. 



February, 



DISEASES OF TIMBER. 

 By Hermann von Schrenk, 



Bureau of Plant Industry. 



WITH the awakening of interest in 

 our forests, a number of ques- 

 tions are beginning to receive attention, 

 both at the hands of the practical for- 

 ester and the scientific man. One of 

 these problems deals with the diseases 

 of timber and timber trees. The pres- 

 ence of a dead tree in the forest, or the 

 rotting of structural timber, was a mat- 

 ter of small moment to the past genera- 

 tion, for with such a large supply to 

 draw upon, the dead trees could be 

 ignored and the rotten bridge timber 

 could be quickly replaced. 



FIG. I. POtVPORUS PINICOI^A GROWING ON 

 DEAD TRUNK OF WESTERN HEMI,OCK. 



At the present time, however, when 

 we no longer can count on the supply of 

 fifty years ago, it is a matter of some 

 concern where the great quantities of 

 timber are to come from in the future, 

 especially when we reflect that the rail- 

 roads alone use every year 100,000,000 

 ties and the telegraph and telephone 

 companies several million poles. We 

 are not yet face to face with a timber 

 famine, nor are we likely to be there for 



many years, but it behooves us to con- 

 sider what is coming, for no country, 

 however large its reserve ma}^ be, can 

 look with impunity on the withdrawal 

 of such amounts as indicated above 

 without taking active steps toward con- 

 servation. 



How to best conserve the existing 

 supply is the problem with which the 

 forestry of today has to deal. It will 

 develop in several directions. In the 

 first place, it will be the endeavor to 

 establish ways and means for cutting 

 the existing supply upon a more rational 

 and economic basis; a second line of 

 work will deal with the reforesting of 

 denuded areas and the planting of tree- 

 less districts, while a third will turn its 

 attention toward getting an increased 

 service out of the timber after it is cut. 

 Wood, when cut from the tree, decays 

 in the course of time and has to be re- 

 placed. By increasing the length of life, 

 so called, of a piece of wood, correspond- 

 ingly less timber will be cut, and in that 

 way the existing supply will be con- 

 served. 



Decay of wood, whether it be in the 

 live tree or the dead wood, is caused by 

 the growth in the wood of various low 

 plants called fungi. The fruiting bodies 

 of these fungi are the familiar toad- 

 stools, frogstools, punks, or mushrooms 

 found on trees. The punks liberate mil- 

 lions of minute spores, which germi- 

 nate or sprout in some old knothole, or, 

 in the case of dead timber, on its surface 

 and grow into the sound wood, thereby 

 causing it to deca5^ When enough food 

 has been extracted from the wood, one 

 or more new punks form on the outside. 

 (See Fig. i.) 



There are a great many different 

 kinds of fungi growing on trees. Some 

 grow only in the live parts, w^here they 

 may kill the leaves, the living wood, or 

 the roots. Fig. 2 shows the work of a 

 destructive fungus which destroys many 



