INSECT ENEMIES OF EASTERN FORESTS 7 
increases, the spruce budworm may attack, killing much fir and some 
spruce and bringing about a higher percentage of spruce. Ultimately, 
when the spruce Bacomes Tatuce. the spruce bark beetle may attack 
and again alter the picture. In those areas where white pine is an 
important species of the mixture, all these factors work toward the 
survival of the dominant white pime and no doubt were important 
aids in the pr oduction of the pine stands of early logging days—giant 
pines from 300 to 500 years of age overtopping a fir- hardwood mixture 
beneath. 
EFFECT OF INSECTS ON FOREST PLANTATIONS 
Forest plantations are particularly subject to the destructive activi- 
ties of insects, chiefly because a plantation is usually made up of a 
single species and is even-aged. Many plantations are established 
on soils not especially suitable for the tree species used; therefore the 
growth is slower and the trees are predisposed to insect attack. Soil- 
infesting insects, such as white grubs, make difficult the establishment 
of plantations in some regions. Bud and twig moths, tip weevils, 
and twig beetles not only damage and deform the terminal shoots of 
young trees but at times become so numerous as to kill out or badl: y 
set back the stands over large areas. Often young pines near logging 
operations are severely damaged by infestations of engraver beetles 
and the Pales weevil.  Sawflies in the Northeast and Lake States and 
Colaspis beetles in the Gulf States cause serious defoliation and death 
of small trees. 
INTERRELATIONS BETWEEN INSECTS AND FIRES 
When extensive outbreaks of insects develop in forest types com- 
posed chiefly of one species of tree, a high percentage of the stand 
may be killed. These standing dead trees go down “after a period 
ot years, making an almost impenetr able tangle of logs and tops which 
may be set afire by lightning and result in a widespread conflagra- 
tion almost impossible to fight. Past experience has shown that 
epidemics of the mountain pine beetle in lodgepole pine have been 
followed by fires more often than not. Similar fires have followed 
spruce budworm damage in the Northeast. 
The old snags of insect-killed trees scattered throughout our mature 
forests greatly increase the cost, difficulty, and danger in fire control. 
Snag felling is required in the terms of many sales of national-forest 
timber, and many private operators have already adopted this as a 
practice. The increased cost of combating fires that have spread from 
burning snags within fire lines would alone justify insect control even 
at a high cost. 
Trees scorched or recently killed by forest fires are particularly 
attractive to many species of forest msects which may be drawn to 
them from a radius of several miles. Subsequent imsect damage 
augments the fire losses, as bark beetles often kill many trees which 
otherwise might have survived. Wood-boring species enter beneath 
the bark of scorched trees and riddle the sapwood so that within a 
short time it may become degraded or valueless for lumber purposes, 
thus limiting salvage operations on burns. 
