INSECT ENEMIES OF EASTERN FORESTS 1s 
broods, and the progeny they produce under such circumstances sel- 
dom cause any trouble in neighboring forests or to the reserve stand, 
especially where logging operations are continuous (Patterson, 345). 
The engraver beetles and twig beetles, which breed in the smaller pieces 
of slash, frequently emerge in such enormous numbers as to kill larger 
patches of reproduction and sometimes the tops of older trees. 
The wood-boring species which breed in slash must be considered 
generally beneficial, as they help to decompose the wood and reduce 
the fire hazard that accompanies a large quantity of slash. Occa- 
sionally they may become injurious, however, and in order to reduce 
or avoid the menace from slash- breeding insects, special thoroughness 
in slash disposal is sometimes necessary. When a logging operation 
is continuous, and a fresh supply of slash is furnished throughout the 
period of attack, the emerging progeny are repeatedly absorbed in the 
slash and in the logs removed to the mill, and no special precautions 
need be taken. But if a cutting operation ceases or is intermittent, 
as in the case of road and power- ‘line development or forest thinnings, 
then some damage to adjacent trees from insects attracted into the 
area can be expected and should be prevented if possible. 
Burning the slash is beneficial, provided the large limbs, cull logs, 
and stumps are included and the burning is done before the adults 
emerge. In many cases this means that the burning must be done in 
the middle of the summer or early in the fall, and this may not be 
safe. Spreading the slash so that it will receive the direct rays of 
the sun will dispose of a high percentage of the insects, especially in 
the more southern latitudes where high bark temperatures can be 
obtained in this way. Normally in the East, losses in standing timber 
from the influence of slash occur only in very dry weather. In. general 
the only precaution necessary is to avoid cutting green timber and 
creating slash at a time when a deficiency in rainfall has existed for 
a month or more. The United States Bureau of Entomology and 
Plant Quarantine (4/5) has issued a circular on the slash problem. 
EFFECT OF DEFOLIATION 
Defolation is a common and widespread factor in the weakening 
of both hardwood and coniferous trees, making them readily STEea es 
tible to attack by bark beetles and borers. Where the line of demare: 
tion between fatal injury by defoliation and the possibility of recovery 
occurs, seems impossible to determine. One defoliation of 75 to 100 
percent will kill most conifers, except larch, regardless of subsequent 
insect attack, but the more thrifty trees are more resistant, and many 
might recover were it not for bark beetles or borers, which almost in- 
variably enter such material. 
Many years’ observations on various hardwoods have shown that 
deciduous trees can stand as many as 5 to 10 years’ defoliation, de- 
pending on site and previous vigor, before they succumb. Secondary 
borers and root fungi (especially Armillaria) often enter into the final 
picture. Dry summers and severe winters also play a part. 
Late spring frost is a common defoliator of new growth, particu- 
larly on oaks in the southern Appalachians. Such defoliations are 
especially damaging and invariably are followed by a high mortality 
of the trees from 1 to 3 years later. Conclusions based on general 
observations and Ee records on thousands of numbered trees lead 
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