68 NEW YORK STATE MUSEUM 
important effect upon many trees, lowering their vitality and pre- 
sumably making conditions more favorable for insect attack. This 
unfortunate condition may be accentuated in certain localities as, 
for example, in southeastern Westchester county, by the abund- 
ance of canker worms or other leaf feeders, since repeated destruc- 
tion of the foliage would weaken the trees and, in the case of 
developing leaves, might cause serious injury without attracting 
much attention. Mr Henry Bird believes that he has detected a 
connection between successive attacks by canker worms and in- 
jury by the hickory bark beetle. 
Another factor which may be more important than many realize, 
is forest fires or burnings. It is unfortunately the practice in 
some communities to burn over pasture and woodlands rather 
freely in the mistaken notion that benefit accrues. It is true that 
such procedure is followed by a more vigorous growth of grass 
and is generally accompanied by the destruction of leaf mold or 
humus, not to mention the killing of numerous small trees and 
injuring some of the larger ones. Moreover, this humus is a most 
important ingredient in maintaining the fertility of the soil and 
also of much service in protecting the roots of trees from ex- 
cessively low temperatures, and by conserving moisture mitigates 
in considerable measure, the severity of droughts. The greater 
exposure to extreme temperatures and the additional severity of 
droughts following the annual practice of burning, may well re- 
sult in reducing the vitality of the trees and bringing about a 
condition favorable to attack by borers. Such procedure is at 
least indefensible from the standpoint of the forester and should 
be condemned and avoided wherever possible. 
Generally speaking, we may expect the least trouble from in- 
jurious insects where normal forest conditions prevail and the 
trees as a whole are in a thriving condition. All practical measures 
which result in the removal of sickly and dying trees and provide 
better conditions for those allowed to remain will, in a general 
way, reduce the lability of serious injury by insects. 
Remedial measures. A serious infestation, indicated by dying 
trees or branches, can be controlled only by cutting out all badly 
infested trees or portions of the same and destroying the bark 
before the following June in order to prevent the grubs then in 
the trees from maturing and changing to beetles which might an- 
other season continue the work in previously uninfested trees. It 
is particularly important to locate hickories which have died 
