72 THE LARCH CANKER 



continued, and the trees have now grown too tall to be 

 suitable for further work of this kind. But it is observable 

 that those parts of the stems from which living branches 

 have been removed are much less attacked by canker than 

 the remainder of the trunks, and none of the wounds that 

 were made while the work was in progress have become 

 a source of infection. 



Since the cut branches form a suitable breeding-ground 

 for the fungus, they should not be allowed to lie on the 

 ground, but should be collected and burnt. This will 

 reduce the number of fructifications in the neighbourhood 

 of the trees, and will probably assist in lessening the chance 

 of infection. 



Special treatment of individual trees must nevertheless 

 be avoided as far as possible. It involves labour which is 

 now a serious expense, and this is incurred early in the 

 rotation, so that, with compound interest, it must deplete 

 the already slender profits of forests. The chief of pro- 

 phylactic measures .will always be the correct sylvicultural 

 treatment of the tree. Maintain the general health of the 

 trees and canker will not be a serious pest. The point of 

 first importance is to plant larch in mixtures, which main- 

 tain the soil in better condition than pure larch woods and 

 stimulate better development of roots. Forbes 's views on 

 this subject have already been quoted, and Schotte (1917), 

 after a careful survey of the larch woods of Sweden, adopts 

 a very similar standpoint. The most suitable tree for 

 mixture with larch is probably the beech, but where beech - 

 growing is unprofitable other trees, such as hornbeam and 

 chestnut, may be tried. Among conifers Scots pine can, 

 according to Schotte, ' be unreservedly recommended ' ; but 

 woods of larch and Scots pine in this country are apt to 

 open out in later life and need to be underplanted either 

 with beech or with that most promising of shade-bearers, 

 the western hemlock. Spruce should be avoided in mixture 

 with larch on account of Chermes dbietis, which has alternate 

 generations on the two species, and Schotte states that in 

 Sweden spruce is apt to shade the larch overmuch, and 



