10 MISC. PUBLICATION 278, U. S. DEPT. OF AGRICULTURE 
self, Fires as well as insects and disease outbreaks developed, spread 
destruction, and ran their course. The whole process was very waste- 
ful but seldom resulted in the permanent destruction of the forests 
over any large areas. Natural checks were imposed and the processes 
of regeneration were brought into play. 
With the development of the country and a corresponding increase 
in values came the necessity for better protection and management. 
The first step in stopping Nature’s wasteful processes was the con- 
trol of forest fires. Later, with more intensive forest management 
and the development of control methods, attention was turned to the 
prevention of losses from forest insects and disease. As time goes 
on and forest values increase, more and more attention will be given 
to preventing or controlling forest-insect damage, and a greater re- 
finement in methods will become economically justifiable. 
In a managed forest the first objective of forest-insect control is 
to so regulate conditions as to maintain a natural balance between 
the insect population that is destructive and the beneficial predacious 
forms, as well as between the insects and their food supply, so as to 
prevent the development of destructive insect outbreaks. This ob- 
jective will be attained more fully in the future through silvicultural 
practices applied to growing stands whereby unfavorable conditions 
for the development of insects are maintained and a greater resist- 
ance of the stand to insect attacks is developed. This may involve 
such measures as prompt disposal of slash and correction of other 
insect-breeding conditions, the regulation of stand density and com- 
position, the regulation of environmental factors through drainage 
or other methods, and the selection of insect-resistant varieties and 
species of trees. 
When preventive methods fail to avert insect outbreaks, direct con- 
trol measures must be considered. The total elimination of a forest 
insect is quite impractical, but fortunately this need not be attempted. 
Instead, the objective of direct control is the restoration of the natural 
balance in which the destructive insects are not greatly out of propor- 
tion to their natural enemies. In such proportions the destructive 
species are relatively harmless, and the damage they do is insig- 
nificant. 
In view of present forest values it is hardly practical to attempt 
to control all insect outbreaks. Much of the insect damage to forest 
trees of low value will have to be allowed to run its course, for if a 
policy of combating all threatening insect outbreaks were adopted 
the cost would be enormous and in many cases would exceed the 
damage probable if Nature were allowed to control the epidemic in 
her own way. The older forests, as they stand today, are ripe and 
an easy prey to bark-beetle attack, and if we are not prepared to 
utilize such timber and are willing to wait for Nature to replace any 
losses by the slow process of growing a new crop of trees, no further 
consideration need be given to control. On the other hand, in the 
many cases in which timber is in demand and satisfactory control 
measures are available, failure to take the necessary protective meas- 
ures should be viewed in the same light as failure to control forest 
fires, 
