CHAPTER XIX. 
TREE INSECTS AND THEIR CONTROL 
T REES have several insect enemies. In a single season, 
if allowed to work unchecked, an able-bodied colony 
of these pests can undo the efforts of years on the part of 
man and nature. Fortunately for the welfare of the shade 
tree, most of the damage may be prevented or cured, and 
it is to the ways and means of achieving one or the other 
of these results that the tree lover will find he must give 
careful attention. 
Because trees in the forest generally thrive in spite of 
their insect enemies, it must not be figured that the 
shade tree may be trusted to care for itself. The two situ¬ 
ations are so different as to have little in common. In the 
forest the tree has nature’s equipment for defense, such 
as ideal conditions for growth and for the development of 
power of resistance to attacks, and birds and insects of 
many kinds to destroy the pests and thus help keep them 
under control. In the artificial environment of the town 
or city the tree is at a disadvantage. In many situations 
its life is a struggle for existence. It must overcome the 
handicaps of packed soil, uncertain water supply, crowded 
conditions, poisonous gases and the injuries of traffic and 
lack of bird and insect protectors. Thus hampered, it is 
not strange that the tree lacks the rugged vitality of its 
forest kinsmen, and it is not surprising that it should be 
less sturdy in its resistance to the attacks of insects. 
Damage by these natural enemies affects the tree in 
different ways, ranging from injuries so slight as to call 
for no attention, to the severe forms which prove fatal. 
To combat the ravages of the insects requires watchful- 
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