34 Atmospheric Influence. 



either in their wood, bark, branches, or leaves, 

 and by reducing the vigour of the plant 

 predispose it to disease and decay. 



It is not my intention to dwell minutely 

 upon these individual pests, for a know- 

 ledge of forest entomology, though deeply 

 interesting, cannot be followed far in such 

 limited space. 



As a rule insect attack is favoured and 

 controlled by atmospheric influences, and 

 the forester has but little control over it, 

 nevertheless if he knows from what source 

 and under what conditions the attack may be 

 expected he may exert such influence as lies 

 within his means. How many of us have 

 noted the white wool-like substance upon the 

 young leaves and stems of the larch (indicative 

 of the presence of aphidae), the perforation of 

 the leaves of the limes, the destruction of 

 the leaves of the oak, the black fungoid 

 spots upon the leaves of the sycamores and 

 maples, and the diseased state of the bark, 

 without giving a thought to the cause ! 

 Here again the trained observer will score a 

 point on the non-observer or careless forester. 



