488 Forestry Quarterly 



nursery diseases. In order to do this, chemical treatment of 

 the seed beds is necessary and a judicial application of water. 

 Here there is a close analogy to horticultural methods or as we 

 might say in human medicine, therapeutical, the application 

 of remedies. A method of this kind can no more be gen- 

 erally applied in the treatment of forest tree diseases than in 

 combating epidemics of human disease. The forest must be 

 considered as a whole. Seldom can attention at the present 

 time be directed to individual trees. Much can be accom- 

 plished, however, in small holdings and eventually, after a more 

 thorough organization, in larger forests by the destruction or 

 removal of diseased trees. My observations in the forest lands 

 of Europe illustrate this point. It is the custom of the authori- 

 ties in many of the large woodlands and parks near the cities, 

 for economic purposes, to scrape up the leaves and fallen branches 

 in the fall of the year and remove the material from the forest. 

 Numerous leaf diseases which pass the winter on fallen leaves 

 are common in these forests. The regular destruction of this 

 debris has practically removed all parasitic leaf diseases from the 

 parks where this is practised. On the other hand, in the wood- 

 lands in the same region in question where the removal of debris 

 was not practised, parasitic leaf diseases are prevalent and cause 

 much injury to the forest growth. Whatever might be said 

 against the method of robbing the forest of this much needed 

 humus material, it is not to be compared with the destructive 

 effect of some leaf blights when they assume, as they often do, 

 the nature of an epidemic. 



Unfortunately in the northwestern United States, a region 

 now being carefully surveyed for serious tree diseases, a great 

 many virulent needle diseases are present. These may become 

 serious or unimportant in forest and nursery according to the 

 conditions under which they appear or the length of time they 

 may continue. There is usually a far greater assimilatory sur- 

 face when large trees are in full leaf than is really necessary, 

 consequently if the ravages of a leaf disease are confined to one 

 year, the injury to the tree is slight, but if repeated year after 

 year the food stored in the roots and the trunk is exhausted 

 and the tree dies. Likewise the northwestern forests are filled 

 with all sorts of wood-destroying fungi, rotting the wood of the 

 living tree and continuing its destruction after the tree has sue- 



