28 BULLETIN 152, IT. 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 tire 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. 



