xii TREE WOUNDS AND DISEASES 



and warns us that damage caused by the ac- 

 cidental breaking of a branch, even near the 

 tree top, should receive prompt and careful 

 attention. Root fungi are difficult to detect, 

 and attack healthy and diseased trees alike ; but, 

 where no visible signs of the pest are traceable 

 on branch or stem, a careful examination of 

 the roots is recommended. 



Though insect attacks are in the main con- 

 fined to unhealthy trees, yet this is not always 

 the case, as instance the widespread depreda- 

 tions of the pine beetle and pine weevil and 

 the goat and wood leopard moths. On the 

 other hand, the elm bark beetle attacks un- 

 healthy trees, while many pests of the orchard 

 can only gain a footing when damage to the 

 bark or stem has been brought about by 

 accident or otherwise. 



Hollow-stem usually accompanies old age 

 or the natural decline of a tree, though in 

 some instances it may be directly traceable 

 to disease brought about by unsuitable soil 

 conditions, as in the case of " pumping " or 

 heart-rot in the larch when grown on gravel. 



These include a few of the many wounds and 



