28 BULLETIN 152, U. S. DEPARTMENT OF AGRICULTURE. 
a large amount of hemlock timber throughout the Appalachian and 
Northeastern States. It mines the bark on living, injured, and dying 
trees and kills them outright or hastens their death." Whenever 
large quantities of hemlock are found to be dying, search should be 
made for the work of this insect, and, if found, special advice in 
regard to combating it should be obtained from the Bureau of Ento- 
mology, Division of Forest Insects. 
Hemlock is comparatively free from serious parasitic fungous 
diseases. Damping-off, the great enemy of many conifers in the 
seedling stage, is almost unknown with this species. While there 
are several diseases of the living tree, they seem never to occur in 
serious epidemics. This is no doubt largely due to the fact that the 
tree usually grows in mixed stands. The timber when cut is very sus- 
ceptible to decay, and a large number of saprophytic fungi attack it. 1 
The shallow-rootedness of hemlock makes it very susceptible to 
fire. A ground fire which burns through the humus will usually kill 
hemlock trees, though deeper-rooted species may escape with slight 
injury. Even a severe surface fire may dry out the humus or damage 
the roots sufficiently to kill the tree outright, or at least to lay it open 
to attack by fungi and insects. Severe crown fires are invariably 
fatal. Fires of all kinds are most to be feared after logging opera- 
tions in adjacent timber, when the ground is covered with the dry 
and highly inflammable tree tops and branches. The best safe- 
guard is to burn this debris under conditions making it impossible 
for the fire to escape. The danger can be lessened by lopping away 
all branches from the tops, and either piling them or scattering them 
close to the ground. 
Because of its relatively short, stout, tapering trunk, hemlock is 
less subject to windfall than its shallow root system would lead one to 
expect. Where it grows as an understory among taller neighbors it 
is rarely thrown except by winds strong enough to overthrow all 
species alike. Severe damage is often done, however, to stands con- 
sisting principally of hemlock, especially when located on shallow 
soil and in situations exposed to the wind. In September, 1896, a 
heavy storm near Wilkes-Barre, Pa., blew down over 6,000,000 feet 
of hemlock in one tract, and similar cases are not uncommon. Where 
the roots are fairly secure, the trunk or the crown may be snapped 
off by severe winds. 
The most common and in the aggregate the worst injury to hem- 
lock from wind is the so-called " wind-shake, " which is a separation 
of the rings of wood caused by the tree being rocked back and forth. 
Wind-shake is always found in the butt, which is thereby rendered 
1 This paragraph regarding diseases was prepared by Perley Spaulding, pathologist, Investigations in 
Forest Pathology, Bureau of Plant Industry. Further information on fungous injury to hemlock is con- 
tained in "Diseases of the eastern hemlock," by Dr. Spaulding, in Proc. Society of American Foresters 
Vol. IX, No. 2, pp. 245-256. 
