297 MISC: PUBLICATION 290, U. S. DEPARTMENT OF AGRICULTURE 
beetles and defoliating insects. Among: the first group are the west- 
ern pine beetle, the mountain pine beetle, the Black Hills beetle, the 
Engelmann spruce beetle, the southern pine beetle, and the eastern 
spruce beetle. The gypsy moth, the spruce budworm, and the larch 
sawfly are serious defoliating insects. Beetle outbreaks frequently 
follow forest fires when, because of damage by burning, the trees’ 
powers of resistance are low. 
Where insect attacks reach epidemic proportions on the national 
forests, control measures are undertaken in cooperation with the 
Bureau of Entomology and Plant Quarantine. Experimental work 
in insect control also is carried on in cooperation with this bureau. 
TREE DISEASES 
Tremendous losses of timber and young growth are caused by 
tree diseases, such as the white-pine blister rust. Some of the most 
destructive tree diseases have been imported from other countries 
on planting stock. Efforts are now being made to combat those 
already imported and to prevent, by quarantine, the importation of 
new diseases. 
In its control work against tree diseases in the national forests, 
the Forest Service is aided by the Division of Forest Pathology, 
Bureau of Plant Industry, and the Division of Plant Disease Con- 
trol, Bureau of Entomology and Plant Quarantine, Department of 
Agriculture. The Division of Forest Pathology maintains patholo- 
gists in several of the regional offices and forest experiment stations 
of the Forest Service. 
STATE AND PRIVATE COOPERATION 
Paralleling in importance the administration of the national 
forests is the work being done by the Forest Service in cooperation 
with State and private forest-land owners toward better manage- 
ment of American forests as a whole. The importance and extent 
of such operations is clearly seen in the fact that there are in the 
United States more than 426,000,000 acres of land under State and 
private ownership, chiefly valuable for the growing of timber. It is 
apparent that the manner of utilization of these areas profoundly 
affects the social and economic conditions of a large percentage of 
American citizens and communities. The Forest Service, through its 
branch of State and private forestry cooperation, is endeavoring to 
bring about on these lands the sort of utilization that will have the 
most favorable effect on the public welfare. 
BETTER MANAGEMENT OF PRIVATE FORESTS 
Management under the principle of sustained yield, which en- 
ables forest lands to produce tree crops indefintely, is necessary if 
the social and economic values of our forest lands are to be perma- 
nent. That this principle is workable has been proved in the man- 
agement of the national forests. Extending it to all American for- 
ests and woodlands is the logical goal. In the interests of American 
democracy, of which the free and independent ownership of land is 
so much a part, the extension of management designed to perpetuate 
the means by which such ownership can be maintained is a vital 
necessity. 
