428 PROTECTION AGAINST PLANTS. 



are induced by certain conditions of soil and weather, the 

 whole of a wood almost simultaneously shows symptoms of 

 disease. An attack by fungi, on the contrary, is propagated by 

 infection from one or a few individuals which are first attacked, 

 and therefore starts from a centre, spreading generally in a 

 centrifugal manner, like the fairy-rings in a meadow due to 

 Marasmius oreades. 



5. Protective Measures against Fungi. 



In order to prevent the attacks of fungi, good sylvicultural 

 rules must be observed as regards the regeneration and 

 tending of the crops of trees. 



The most important of these are : to grow species suitable 

 to the locality ; to cultivate the plants scientifically, and to 

 plant strong plants and in suitable mixtures, especially of 

 broadleaved trees with conifers ; early cleanings ; timely 

 thinnings ; pruning from November till January ; avoidance 

 of injuries to standing trees during fellings; tarring wounds. 



To combat the individual fungi successfully, their life- 

 history must be known. Special rules are : 



Isolation of attacked plants by trenches ; removal of 

 diseased plants ; pruning attacked branches ; destruction of 

 weeds that serve as hosts for injurious fungi ; spraying 

 diseased plants with fungicides * ; removal of infected 

 fallen needles or leaves. All infected material should be at 

 once burned in situ. 



SECTION II. FUNGI ATTACKING CONIFERS. 



The next two sections give a list of the fungi which experi- 

 ence has shown to be injurious to forest trees, with a short 

 description of their external appearance, the classes of woods 

 and localities liable to be infected, and the distribution-areas 

 of the fungi ; also an account of the damage done and the 

 means for combating it. The most injurious species are 

 marked with an asterisk. For a full description of the 

 pathology of each disease induced by fungi, reference is 



* Cf. Lodeman, " The Spraying of Plants." New York : The Macmillan Co. ; 

 London, Macmillan & Co., 1903. 



